W inter Meeting 20 11...CPS/CAPnet Winter Meeting 2011 Directions Hotel Information Hotel Mont...

Physiologicalmechanisms

of perception

cognitionand action

February10 - 12

2011

Physiologicalmechanisms

of perception

cognitionand action

February10 - 12

2011

Winter Meeting 2011

Hotel Mont GabrielSainte-Adèle, Quebechttp://www.montgabriel.com/

Department of Physiology

Center for Neuroscience Studies

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CPS/CAPnet Winter Meeting 2011 Directions

Hotel Information

Hotel Mont Gabriel1699 Chemin du Mont GabrielSainte-Adèle, Quebec J8B 1A5Canada

www.montgabriel.com

[email protected]

Phone: (800) 668-5253(450) 229-3547

Location: 65 km North of MontrealHwy 15 N to exit 64Left on Chemin du Mont-GabrielFollow signs to top of Mount Gabriel

Autoroute 15 N

Exit 64 - Chemin du Mont-Gabriel

Montreal

HotelMontGabriel

Page 2

CPS/CAPnet Winter Meeting 2011 Sponsors

Meeting Sponsors

Applied Scientific Laboratories 175 Middlesex TurnpikeBedford, MA 01730 USAPhone:Tel: +1 (781) 275-4000Fax: +1 (781) 275-3388

e-mail: [email protected]

HEKA Electronics Incorporated 47 Keddy Bridge RoadR.R. #2Mahone Bay, NS B0J 2E0CanadaPhone:Main: +1 902 624 0606Fax: +1 902 624 0310

e-mail: [email protected], [email protected]

Northern Digital 103 Randall DriveWaterloo, Ontario CanadaN2V 1C5Phone:Main: +1 (519) 884 5142Toll-Free: +1 (877) 634 6340Fax: +1 (519) 884 5184

e-mail:General Enquiries: [email protected] Enquiries: [email protected]: [email protected]

www.ndigital.comSensoMotoric Instruments, Inc. 28 Atlantic Avenue

236 Lewis WharfBoston, MA 02110USAPhone:Main: +1 617 557 0010Toll-Free: +1 888 SMI USA1Fax: +1 617 507 8319

e-mail [email protected]

Page 3

CPS/CAPnet Winter Meeting 2011 Sponsors

SR Research Ltd. 150 - A1 Terence MatthewsKanata, Ontario, CanadaK2M 1X4Phone:Phone: 613-271-8686Toll Free: 1-866-821-0731Fax: 613-482-4866

e-mail:General Enquiry: [email protected]: [email protected] Support: [email protected]

www.sr-research.comVPixx 1494 Montarville, suite 206

Saint-Bruno, Quebec, J3V 3T5CanadaPhone: 514-328-7499 ( 514-32VPIXX )e-mail:Sales/General Inquiries: [email protected]: [email protected]

www.vpixx.com

Institutional Sponsors

McGill University, Office VP Research (http://www.mcgill.ca/research/about/vp/)Montreal Neurological Institute (http://www.mni.mcgill.ca/)Department of Physiology, McGill University (http://www.medicine.mcgill.ca/physio/)Center for Applied Mathematics in Bioscience and Medicine (http://www.mcgill.ca/cambam/)Center for Neuroscience Studies, Queen’s University (http://www.queensu.ca/neuroscience/index.html)York University, Office of VP Research & Innovation (http://www.yorku.ca/research/)Center for Brain and Mind, University of Western Ontario (http://www.uwo.ca/its/brain/)FRSQ Vision Research Network, Quebec (http://www.reseauvision.ca/)Faculty of Medicine, University of Montreal (http://www.med.umontreal.ca/)

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CPS/CAPnet Winter Meeting 2011 Invited Speakers

Special Lectures

12:00 - 12:45 PM Thursday Feb 10 Grand SalonTHE NATURE OF DECISION RELATED ACTIVITY IN SENSORY NEURONSBruce CummingLaboratory of Sensorimotor ResearchNational Eye Institute

3:30 - 4:15 PM Thursday Feb 10 Grand SalonMERGING THE SENSES: MULTISENSORY INTEGRATION IMPROVES SPATIAL PERCEP-TIONDora AngelakiDepartments of Anatomy & Neurobiology and Biomedical EngineeringWashington University

12:00 - 12:45 PM Friday Feb 11 Grand SalonSarrazin Award LecturePATHOGENESIS OF ENTEROVIRAL HEART DISEASEBruce McManusDepartment of Pathology & Laboratory MedicineUniversity of British Columbia

3:30 - 4:15 PM Friday Feb 11 Grand SalonNEURAL BASIS OF PERCEPTUAL MODULATIONS DURING SACCADESMichael IbbotsonVision SciencesAustralian National University

12:00 - 12:45 PM Saturday Feb 12 Grand SalonREWARD, IMPULSIVITY AND CONTROL OF MOVEMENTSReza ShadmehrDepartments of Neuroscience and Biomedical EngineeringJohns Hopkins University

8:30 - 9:15 PM Saturday Feb 12 Saint AndrewsKeynote LectureTHE POWER OF STUDYING EYE MOVEMENTS TO LEARN ABOUT BRAIN FUNCTIONDoug MunozCentre for Neuroscience StudiesQueen’s University

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Oral Presentation Schedule

CPS/CAPnet Winter Meeting 2011 Oral Presentations

Neuroscience A Thursday Feb 10, 9AM - 12PM Grand Salon

09:00 THE OPTIMALLY SHAPED FIXATION TARGET (p.20)Lore Thaler, A.C. Schütz, M.A. Goodale, K.R. Gegenfurtner

09:15 GAZE SIGNALS IN TACTILE-VISUAL TRANSFORMATIONS (p.21)L.M. Pritchett, L.R. Harris

09:30 THE ROLE OF VISION IN DETECTING AND CORRECTING FINGERTIP FORCE ER-RORS (p.22)Gavin Buckingham, Melvyn A. Goodale

09:45 THE SHAPE OF VISUAL REMAPPING RESPONSES (p.23)Tomas HJ Knapen, Jascha D. Swisher, Frank Tong, Patrick Cavanagh

10:00 GLUTAMATE SPILLOVER AND CROSSTALK BETWEEN IMMATURE EXCITATORYAND INHIBITORY CIRCUITS IN RAT AUDITORY BRAINSTEM (p.24)Javier F. Alamilla, Deda C. Gillespie

10:15 FMRI REVEALS GREATER ACTIVATION IN DORSAL VISUAL STREAM REGIONSFOR GRASPING IN THE LOWER VISUAL FIELD (p.25)Stephanie Rossit, T.D. McAdam, D.A. Mclean, M.A. Goodale, J.C. Culham

10:30 Coffee Break

10:45 SINGLE PRIMARY MOTOR CORTEX NEURONES CONTRIBUTE TO A WIDE RANGEOF MOTOR SKILLS (p.26)Touria Addou, N. Krouchev, J. Kalaska

11:00 THE EFFECT OF HAND POSITION ON VISUAL RESPONSES IN AREAS V2 AND V4(p.27)Carolyn J. Perry, Sarah M. Jones, J. Douglas Crawford, Mazyar Fallah

11:15 SCANNING OF FACE-SCENE OR OBJECT-SCENE PAIRS REVEALS IMPLICIT RELA-TIONAL MEMORY (p.28)Leora R. Branfield Day, Adrian M. Bartlett, Timothy K. Leonard, Kari L. Hoffman

11:30 THE INFLUENCE OF BIOMECHANICAL ANISOTROPIES IN DECISION-MAKING(p.29)Ignasi Cos, Farid Medleg, Paul Cisek

11:45 NEURAL CORRELATES OF PREDICTIVE SACCADES IN YOUNG HEALTHY ADULTS(p.30)Stephen Lee, D. C. Brien, B. C. Coe, I. S. Johnsrude, D. P. Munoz

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Neuroscience B Thursday Feb 10, 4:30 - 6:30 PM Grand Salon

04:30 DYNAMICS OF VISUAL PERFORMANCE AND PERCEIVED CONTRAST AT THETARGETS OF SACCADES (p.31)Martin Rolfs, Marisa Carrasco

04:45 LOCAL TISSUE OXYGENATION IN THE POSTERIOR PARIETAL CORTEX (p.32)Rishi Rajalingham, Sam Musallam

05:00 OBJECT CONNECTEDNESS INFLUENCES PERCEPTUAL COMPARISONS BUT NOTTHE PLANNING OR CONTROL OF RAPID REACHES TO MULTIPLE GOALS (p.33)Jennifer L. Milne, Craig S. Chapman, Jason P. Gallivan, Daniel K. Wood, Jody C. Culham,Melvyn A. Goodale

05:15 MECHANISMS OF FMRI-BASED DECODING OF ORIENTED GRATING STIMULI(p.34)Zeshan Yao, Martin Villeneuve, Pascal Kropf, Javeed Shaikh, Chang’an Zhan, Curtis Baker,Amir Shmuel

05:30 POSSIBLE ROLES OF PMD, M1 AND DLPFC IN DECISION MAKING (p.35)Émilie Coallier, Thomas Michelet, David Thura, John F. Kalaska

05:45 MAPPING THE DISTRIBUTION OF HCN1 ON NECK MOTONEURONS (p.36)Ethan .Y. Zhao, K.K. Fenrich, M. Neuber-Hess, R. Maratta, P.K. Rose

06:00 THE ROLE OF CORTICAL AREA MT+/V5 IN SPATIAL ASPECTS OF MANUAL IN-TERCEPTION: AN RTMS STUDY (p.37)Joost C. Dessing, Michael Vesia, Xiaogang G. Yan, J. Douglas Crawford

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Neuroscience C Friday Feb 11, 9AM - 12PM Grand Salon

09:00 BINOCULAR RIVALRY, MONOCULAR RIVALRY AND DEPTH PERCEPTION COM-PARED WITH FMRI (p.38)Janine D. Mendola, Athena Buckthought

09:15 OCULOMOTOR INFLUENCES ON VISUAL RESPONSES IN MACAQUE CORTICALAREA V4 (p.39)Jachin A. Monteon, T. Zanos, P. Mineault, D. Guitton, C.C. Pack

09:30 INFLUENCE OF DIURNAL SLEEP (NAP) ON CEREBRAL CORRELATES OF CONSOL-IDATION OF DIFFERENT REPRESENTATIONS OF MOTOR SEQUENCE LEARNING,ASSESSED BY FMRI. (p.40)Genevieve Albouy, Stuart Fogel, Vo An Nguyen, Amel Bouyoucef, Frederic Jeay, EdwinRobertson, Julien Doyon

09:45 RAPID MOTOR RESPONSES DURING REACHING ARE SENSITIVE TO TARGETSHAPE AND OBJECTS IN THE ENVIRONMENT (p.42)Joseph Nashed, Stephen H. Scott

10:00 A NOVEL TECHNIQUE FOR INVESTIGATING NEUROVASCULAR COUPLING: SI-MULTANEOUS OPTICAL IMAGING OF BLOOD-OXYGENATION AND MEMBRANEPOTENTIAL (p.43)James McNicol, Amir Shmuel

10:15 RELATIVE ENCODING OF REWARD IN THE REACH SYSTEM. (p.44)Georgios Tsoulfas, Sam Musallam

10:30 Coffee Break

10:45 DEFICITS IN MIRROR SACCADE PRODUCTION IN PARIETAL DAMAGED PA-TIENTS (p.45)Aarlenne Z. Khan, Annabelle Blangero, Laure Pisella, Douglas P. Munoz

11:00 STOCHASTIC REFERENCE FRAME TRANSFORMATIONS ALTER MULTI-SENSORYPERCEPTION AND ACTION (p.46)Jessica Burns, Joseph Nashed, Gunnar Blohm

11:15 BEHAVIORAL AND STIMULUS CORRELATIONS OF NEURAL ACTIVITY IN AREAMT IN AN OMITTED STIMULUS DETECTION TASK (p.47)Navid G. Sadeghi, Erik P. Cook

11:30 FUNCTIONAL CONNECTIVITY IN MACAQUE CORTICAL AREA V4 (p.48)Theodoros P. Zanos, Jachin A. Monteon, Patrick J. Mineault, Christopher C. Pack

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11:45 INSTRUCTION-RELATED SACCADE AND HEAD MOVEMENT ACTIVITY INSUPERIOR COLLICULUS UNITS DURING PLANNED SEQUENCES OF HEAD-UNRESTRAINED GAZE SHIFTS IN THE MONKEY (p.49)Xiogang Yan, Marie Avillac, Jachin Ascencio-Monteon, Hongying Wang, John Douglas Craw-ford

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Sensorimotor Friday Feb 11, 4:30 - 6:30 PM Grand Salon

04:30 PREDICTIVE FINGERTIP FORCE APPLICATION IN THE ABSENCE OF VISUALCUES FOR WEIGHT (p.50)Daniel K. Wood, Gavin Buckingham, Aizaan Anwar, Melvyn A. Goodale

04:45 NEURONAL ACTIVITY IN SOMATOSENSORY CORTEX (S1) AND PRIMARY MOTORCORTEX (M1) DURING TACTILE EXPLORATION IN THE MONKEY. (p.51)Pascal Fortier-Poisson, Allan M. Smith

05:00 HIGHER INTEGRATION OF A CORTICO-STRIATAL FUNCTIONAL NETWORK FOL-LOWING THE CONSOLIDATION OF A MOTOR SEQUENCE LEARNING TASK (p.52)Karen Debas, Julie Carrier, Pierre Orban, Marc Barakat, Abdallah Hadj Tahar, Avi Karni,Leslie G. Ungerleider, Habib Benali, Julien Doyon

05:15 SENSITIVITY OF RAPID MOTOR RESPONSES TO SMALL PERTURBATIONS DUR-ING POSTURAL CONTROL AND REACHING (p.54)Frederic Crevecoeur, Isaac Kurtzer, Stephen H. Scott

05:30 THE DISTRIBUTION OF SEROTONERGIC, NORADRANERGIC AND DOPAMINER-GICSYNAPSES ON FLEXOR MOTONEURONS (p.55)R Maratta, M. Neuber-Hess, K.K. Fenrich, E.Y. Zhao, P.K. Rose

05:45 A DIFFERENTIAL BENEFIT TO MOTOR SEQUENCE LEARNING FOLLOWING ADAYTIME NAP IN YOUNG AND ELDERLY ADULTS (p.56)S. Fogel, G. Vien, C. Popovicci, R. Hoge, S. Jbabdi, S. Benali, H. Karni, A. Maquet, J.Carrier, J. Doyon

06:00 RAPID, INTELLIGENT ADAPTATION OF REACTIVE FORCE CONTROL WHENLIFTING OBJECTS (p.57)Simona Markovik, Lee A. Baugh, J. Randall Flanagan

06:15 CROSS-VALIDATED MODELS OF THE RELATIONSHIPS BETWEEN NECK ELEC-TROMYOGRAPHY (EMG) AND HEAD KINEMATICS EVOKED BY STIMULATIONOF THE INTERSTITIAL NUCLEUS OF CAJAL (INC) (p.58)Farshad Farshadmanesh, Patrick Byrne, Xiaogang Yan, Hongying Wang, Brian D. Corneil,J. Douglas Crawford

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General Physiology Friday Feb 11, 9AM - 12PM Nicklaus Palmer Watson (N-P-W)

09:00 H2S AS A NOVEL BIOMARKER AND THERAPEUTIC TARGET FOR ASTHMA (p.59)Peipei Wang, Qiuhui Cao, Guangdong Yang, Rui Wang

09:15 JUNCTIONAL TACHYCARDIA IN THE MOUSE CAN BE PREVENTED BY PACE-MAKER CHANNEL (If) BLOCKADE (p.60)Jari M. Tuomi, Douglas L. Jones

09:30 INTERACTION OF HYDROGEN SULFIDE AND ESTROGEN ON THE PROLIFERA-TION OF VASCULAR SMOOTH MUSCLE CELLS (p.61)Hongzhu Li, Sarathi Mani, Guangdong Yang, Rui Wang

09:45 CYSTATHIONINE GAMMA-LYASE EXPRESSION AND H2S PRODUCTION IN MICEHEART (p.62)Ming Fu, Weihua Zhang, Guangdong Yang, Rui Wang

10:00 A CRITICAL LIFE-SUPPORTING ROLE OF CYSTATHIONINE GAMMA-LYASE IN THEABSENCE OF DIETARY CYSTEINE SUPPLY (p.63)Sarathi Mani, Guangdong Yang, Rui Wang

10:15 EFFECT OF H2S ON MEMBRANE POTENTIAL OF VASCULAR SMOOTH MUSCLESIN SITU AND THE UNDERLYING MECHANISMS (p.64)Guanghua Tang, Lingyun Wu, Rui Wang

10:30 Coffee Break

10:45 H2S IMPAIRS INSULIN-STIMULATED GLUCOSE UTILIZATION AND INCREASESGLUCONEOGENESIS IN HEPG2 HEPATOMA CELLS (p.65)Ling Zhang, Guangdong Yang, Lingyun Wu, Rui Wang

11:00 SATURATED FREE FATTY ACIDS DECREASE PROINSULIN PROCESSING VIA UCP2(p.66)Catherine B. Chan, N. Kashemsant

11:15 HYDROGEN SULFIDE DECREASES HYPOXIA-INDUCED ACCUMULATION OF HY-POXIA INDUCIBLE FACTOR 1α IN HEP3B CELLS (p.67)Bo Wu, Huajian Teng, Guangdong Yang, Rui Wang

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Sensory & Perception Friday Feb 11, 4:30 - 6:30 PM Nicklaus Palmer Watson (N-P-W)

04:30 EXPANSION OF SPATIOTEMPORAL RECEPTIVE FIELD PROFILES OF MACAQUEMT NEURONS DURING ATTENTIVE TRACKING (p.68)Robert Niebergall, Paul Khayat, Stefan Treue, Julio Martinez-Trujillo

04:45 SACCADE TARGET SELECTION BASED ON SINGLE OR MULTIPLE REMEMBEREDVISUAL FEATURES (p.69)David C. Cappadocia, Mike Vesia, Patrick A. Byrne, Xiaogang Yan, J. Douglas Crawford

05:00 USING REWARD TO CHANGE POPULATION TUNING TO IMPROVE DECODE PER-FORMANCE FOR USE IN NEURAL PROSTHETIC SYSTEMS. (p.70)Caitlin Wharin, Sam Musallam

05:15 CONTRAST SENSITIVITY OF MT RECEPTIVE FIELD CENTERS AND SURROUNDS(p.71)James M.G. Tsui, Christopher C. Pack

05:30 DECODING VISUAL OBJECTS IN SOMATO-SENSORY CORTEX (p.72)F.W. Smith, M.A. Goodale

05:45 INVESTIGATING A VISUOTACTILE ILLUSION INDUCED BY MONOCULAR OCCLU-SION WITH A BLACK CONTACT LENS: QUANTITATIVE ANALYSES (p.73)Paula M. Di Noto, Joseph F.X. DeSouza

06:00 THE PERSISTENCE OF GLOBAL FORM IN V1 (p.74)Lars Strother, Cheryl Lavell, P.S. Mathuranath, Adrian Aldcroft, Melvyn A. Goodale, TutisVilis

06:15 RECEPTIVE FIELD SUBSTRUCTURE OF V4 NEURONS (p.75)Patrick J Mineault, Theodoros P. Zanos, Jachin A. Monteon, Christopher C. Pack

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Neuroscience D Saturday Feb 12, 9AM - 12PM Grand Salon

09:00 A RIGHT HEMISPHERE DOMINANCE FOR BIMANUAL GRASPS (p.76)Ada Le, Michael Vesia, Xiaogang Yan, J. Douglas Crawford, Matthiasé Niemeier

09:15 RAPID IMPLEMENTATION OF EYE AND HAND FORAGING STRATEGY IN A NOVELFREE-CHOICE MOVEMENT TASK (p.77)Jonathan S. Diamond, Michael C. Dorris, J. Randall Flanagan

09:30 REWARD AND UNCERTAINTY ENCODING IN THE MEDIAL INTRAPARIETAL SUL-CUS (p.79)Richard G Stacey, Sam Musallam

09:45 ROLE OF THE FRONTAL EYE FIELD IN CHOOSING MIXED STRATEGY SACCADES(p.80)Abdullahi Abunafeesa, Michael Dorris

10:00 HOW MUTUAL GAZE ALTERS THE FACE-VIEWING PATTERNS OF MACAQUES.(p.81)Timothy K. Leonard, Galit Blumenthal, Katalin M. Gothard, Kari L. Hoffman

10:15 REWARD-INDUCED TUNING CURVE SHIFT MECHANISM AND DYNAMIC, PREDIC-TIONS FROM MODELING (p.82)Frederic Simard, Sam Musallam

10:30 Coffee Break

10:45 STRENGTH OF RESPONSE SUPPRESSION TO DISTRACTER STIMULI DETER-MINES ATTENTIONAL FILTERING PERFORMANCE BY PRIMATE PREFRONTALNEURONS (p.83)Therese Lennert, Julio C. Martinez-Trujillo

11:00 MONKEY FRONTAL CORTEX REFLECTS THE TIME COURSE OF CHANGING EVI-DENCE FOR REACH DECISIONS (p.84)David Thura, Paul Cisek

11:15 INVESTIGATING COGNITIVE DEFICITS IN AMYOTROPHIC LATERAL SCLEROSISUSING EYE MOVEMENTS AND FMRI (p.86)Kelsey LM Witiuk, Ryan McKee, Nadia Alahyane, Brian C Coe, Don Brien, Michel Melanson,Douglas P. Munoz

11:30 WORKING MEMORY REPRESENTATIONS OF VISUAL MOTION DIRECTION AREENCODED IN THE FIRING PATTERNS OF NEURONS IN DORSOLATERAL PRE-FRONTAL CORTEX, BUT NOT IN AREA MT (p.88)Diego Mendoza, Julio Martinez-Trujillo

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11:45 IS LOCATING AN OCCLUDED MOVING TARGET USING INDIRECT INFORMATIONA STATISTICALLY OPTIMAL PROCESS? (p.89)Patrick Byrne, J. Douglas Crawford

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Neuroscience E Saturday Feb 12, 4:30 - 6:15 PM Grand Salon

04:30 THE CHARACTERISTICS OF ANALGESIA-WITHHOLDING IN ANIMAL-BASED SCI-ENTIFIC PROTOCOLS IN CANADA (p.90)Gilly Griffin, C. Tellier, N. Fenwick

04:45 PREVENTVE ANALGESIC EFFECTS OF PROPENTOFYLLINE, ALONE AND IN COM-BINATION WITH MORPHINE AND AMITRIPTYLINE, IN THE RAT SPARED NERVEINJURY MODEL (p.91)Shannon E.G. Duffus, Gary V. Allen, Jana Sawynok

05:00 DECODING EFFECTOR-SPECIFIC AND EFFECTOR-INDEPENDENT MOVEMENTINTENTIONS FROM HUMAN PARIETO-FRONTAL BRAIN ACTIVITY (p.92)Jason P. Gallivan, D.A. McLean, F.W. Smith, J.C. Culham

05:15 MODELING SACCADE CONTROL IN THE SUPERIOR COLLICULUS USING INPUTSFROM THE CORTEX AND BASAL GANGLIA (p.93)Brian C. Coe, Thomas Trappenberg, Douglas P. Munoz

05:30 PRE-SACCADIC (PREDICTIVE) VISUAL RESPONSES IN SUPERIOR COLLICULUSNEURONS ACROSS PURSUIT EYE MOVEMENTS (p.94)Suryadeep Dash, Hongying Wang, Xiaogang Yan, J. Douglas Crawford

05:45 VARIABLE VS CONSTANT THRESHOLD FOR SACCADE INITIATON IN THEFRONTAL EYE FIELD AND SUPERIOR COLLICULUS (p.95)Jay Jantz, Masayuki Watanabe, Stefan Everling, Douglas Munoz

06:00 PERTURBATION-RELATED ACTIVITY OF PRIMARY MOTOR CORTEX NEURONSIS ALTERED BY BEHAVIOURAL CONTEXT (p.96)Mohsen Omrani, Andrew J. Pruszynski, H. Scott Stephen

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Abstracts

CPS/CAPnet Winter Meeting 2011 Abstracts

Neuroscience A 09:00 AM, Thursday Feb 10 Grand Salon

THE OPTIMALLY SHAPED FIXATION TARGET

Lore Thaler[1] A.C. Schütz[2] M.A. Goodale[1] K.R. Gegenfurtner[2][1] Department of Psychology, University of Western Ontario[2] Department of Psychology, Giessen University

People can direct their gaze at a visual target for extended periods of time. Yet, even duringfixation the eyes make small, involuntary movements (e.g. tremor, drift, micro saccades). This canbe a problem during experiments that require stable fixation. Thus, it would be good if one couldminimize eye movements during fixation without interfering with the experimental paradigm. Theshape of a fixation target can be easily manipulated in the context of many experimental paradigms.Thus, the current experiments tested if the shape of a target affects eye movements during fixation.On each trial (17 sec), subjects were asked to direct their gaze at a fixation target, while theireye movements were measured (Eyelink 2, 250 Hz, monocular). The shape of the fixation targetvaried from trial to trial and was drawn from a set of seven shapes: (1) 0.2◦ circle (2) 1.5◦ circle(3) 1.5◦ cross (4) 0.2◦ circle + 1.5◦ circle (5) 0.2◦ circle + 1.5◦ cross (6) 1.5◦ circle + 1.5◦ cross(7) 1.5◦ circle + 1.5◦ cross + 0.2◦ circle. To determine stability of fixation we computed spatialdispersion (2D-SD) and micro saccade frequency for each target shape. Two observers participatedin 4 separate sessions (total of 36 trials per shape). 10 observers participated in a single session(total of 12 trials per shape). We found that only target shape 7, which looks like a combination ofbulls eye and cross hair, resulted in combined low 2D-SD and micro saccade frequency. Specifically,we found that this shape reduced both 2D-SD and micro saccade frequency by at least 50%, wherethe reduction (%) was relative to the highest average 2D-SD and micro saccade frequency for eachobserver. We conclude that the combination of bulls eye and cross hair (target shape 7) minimizeseye movements during fixation, and we recommend it as fixation target shape for experiments thatrequire stable fixation.

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GAZE SIGNALS IN TACTILE-VISUAL TRANSFORMATIONS

L.M. Pritchett, L.R. HarrisYork University

The location of a touch to the skin, first coded in body coordinates, is subsequently recodedinto an external, likely visual, reference frame. In order for the touch location to be transformedinto a visual reference frame the location of the eyes and head must be taken into account. Sys-tematic errors in tactile localization related to eye and head position can be utilized to elucidatethe neural code used in the body-to-visual coordinate transformation. First we investigated thecombined effects of head and eye position on perceived touch location. Subjects were instructedto position their head to the left, right, or centred on their body while also positioning their eyesto the left, right or centred in their head. We found that eye and head position have equivalenteffects and combine linearly. These results could indicate a parallel process where eye and headposition is combined into a gaze signal that can then be used to code the touch in a visual refer-ence frame. Alternatively, the eye and head position information could be kept separate but causeequivalent amounts of error in the coordinate transformation. Experiments using larger eye andhead movements suggested that the effects of eye and head position might not be linear across thefull range; errors in tactile localization appeared to saturate beyond 30 degrees of eccentricity. Thisfinding may allow for a disambiguation of the gaze signal (eye and head in serial or parallel) usedin tactile-to-visual transformations.

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THE ROLE OF VISION IN DETECTING AND CORRECTING FINGERTIP FORCE ERRORS

Gavin Buckingham, Melvyn A. GoodaleCentre for Brain and Mind, University of Western Ontario

Our expectations of an object’s heaviness not only determine how much force we will useto lift it, but also influence our perception of heaviness. This effect is highlighted by the classicsize-weight illusion (SWI), where identically-weighted objects that vary in sizes feel as if they weighdifferent amounts. Here, we examined whether our expectations of how heavy an object will be aresufficient to induce the SWI in a single wooden cube. This cube was lifted without vision, followinga brief preview period where participants saw an object that was either larger or smaller than theone they would eventually lift. Participants (who were expecting to lift the larger or smaller objectthat they had just seen), reported that the weight of the single cube varied as a function of the sizeof object they thought that they were lifting. Seeing the small object before the lift made the cubefeel heavier than it did after seeing the large object. Lifting the object without vision, however,had a surprising impact upon the pre-liftoff fingertip force rates. On initial lifts, participants madeerrors that tallied with their expectations of heaviness - with a greater rate of force used to lift afterpreviewing the larger cube than previewing the smaller cube. These expectation-driven errors werenot, however, corrected with repeated lifting; participants failed to adapt their grip and load forcerates from the expected weight to the object’s actual mass in the same way that they could whenlifting with vision. Unexpectedly, vision appears to be crucial for the detection and correction ofthe ostensibly haptic grip and load force errors. Expectations of heaviness are not only powerfulenough to alter the perception of a single object’s weight, but also continually drive the forces weuse to lift the object, when vision is unavailable during the lift.

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THE SHAPE OF VISUAL REMAPPING RESPONSES

Tomas HJ Knapen[1] Jascha D. Swisher[2] Frank Tong[2] Patrick Cavanagh[3][1] University of Amsterdam[2] Vanderbilt University[3] Université Paris Descartes

In order to maintain visual stability in the face of continuous saccadic eye movements, thebrain has to incorporate the motor commands for upcoming saccades into visual processing. Theprocess by which saccadic motor commands impinge on retinal processing is called remapping. Inremapping, neurons with receptive fields sensitive to the post-saccadic retinotopic location of thestimulus preactivate before the saccade, and thus, before they receive visual input. Evidence forremapping responses has been found in areas ranging down to the lowest levels of visual cortex.

We investigated whether remapping responses at the fovea encode the shape of the saccadetarget by using phase-encoded signals in a functional imaging experiment. A wedge was presentedin the periphery and extinguished before saccades to the point of the wedge. While subjects weremaking repeated saccades at a rate of one per second, the intermittently presented wedge rotatedaround the saccade target every 32 seconds. This slow rotation generated phase-encoded remappingresponses in foveal areas that were not visually stimulated.

We show that information about the position of the wedge in its rotational trajectory can befound near the fovea, revealing the remapping response’s shape.

Our results indicate that remapping responses transfer position and shape information acrossthe retinotopic maps involved in visual processing.

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GLUTAMATE SPILLOVER AND CROSSTALK BETWEEN IMMATURE EXCITATORY ANDINHIBITORY CIRCUITS IN RAT AUDITORY BRAINSTEM

Javier F. Alamilla, Deda C. GillespieDepartment Psychology Neuroscience Behaviour, McMaster University

The lateral superior olive (LSO) of the auditory brainstem computes interaural intensity bycomparing glutamatergic input from the ipsilateral anteroventral cochlear nucleus (aVCN), withfrequency-matched inhibitory glycinergic input from the ipsilateral medial nucleus of the trapezoidbody (MNTB). Before hearing onset in rodents, MNTB terminals release glutamate onto functionalNMDA receptors (NMDARs). We asked whether it might be possible for spillover of glutamatefrom one pathway to activate postsynaptic NMDARs under the opposite pathway, a situation thatcould allow for synaptic crosstalk.

We used whole cell voltage clamp in acute brainstem slices from rat pups age postnatal day 0- 12 (P0 - 12). After patching an LSO principal cell with inputs from both aVCN and MNTB path-ways, we isolated the NMDAR component pharmacologically. Baseline responses to stimulation inboth aVCN and MNTB pathways were collected, the use-dependent open-channel blocker MK-801was applied for 10 minutes, and then stimulation was delivered to one pathway to decrement theresponse. Subsequently, stimulation was delivered to the second, previously un-stimulated, pathwayand the amplitude of the first NMDAR-mediated response in this second pathway was measured.Previous stimulation in one pathway caused a significant reduction in the amplitude of responsesin the opposite, second pathway (percent baseline: 84± 3% first pathway; 35± 3% second pathway,P=0.0002, W=136.0, N=16, Wilcoxon test). To control for the possibility that longer periods ofMK-801 exposure in the second pathway had allowed additional non-specific activation and blockof NMDAR receptors, we used a longer initial incubation (15 minutes), followed by interleavedstimulation of the two pathways. The 50% longer incubation period did not significantly affectfirst-response amplitudes in the first pathway (83 ± 3%, N=20, 10 min; 84 ± 4%, N=10, 15 min,P=0.9120, U=97, Mann-Whitney U test). Response amplitudes in the second pathway were how-ever significantly reduced relative to the first pathway (82 ± 5% first path; 47 ± 4% second path).Finally, we obtained synaptically connected MNTB-LSO pairs and attempted to replicate theseexperiments, using direct stimulation of the MNTB neuron for the first pathway and electricalstimulation in the aVCN-LSO for the second pathway. First response amplitude in the aVCN-LSOpathway after full decrement in the MNTB-LSO pair was significantly reduced (2 pairs).

These data indicate that nascent excitatory and inhibitory synapses in the immature LSOare sufficiently near one another to allow glutamate spillover, and further suggest that glutamatespillover and activation of postsynaptic NMDARs could allow bidirectional crosstalk between imma-ture excitatory and inhibitory synapses during a period characterized by major circuit refinement.Sponsored by a CIHR operating grant (DCG) and a CONACyT postdoctoral fellowship (JFA).

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FMRI REVEALS GREATER ACTIVATION IN DORSAL VISUAL STREAM REGIONS FORGRASPING IN THE LOWER VISUAL FIELD

Stephanie Rossit, T.D. McAdam, D.A. Mclean, M.A. Goodale, J.C. CulhamThe Centre for Brain and Mind, University of Western Ontario

Humans have been shown to be more efficient when reaching or grasping stimuli in the lowervisual field than in the upper visual field. This suggests that the dorsal ‘action’ visual stream isbiased towards processing information in the lower visual field. In line with this, several neurophys-iological studies in the monkey have reported that neurons within the dorsal stream over-representthe lower visual field relative to the upper visual field. The present study used slow event-relatedfunctional magnetic resonance imaging (fMRI) to examine whether human brain areas implicatedin action would show such visual field preferences. We asked ten participants to fixate one of fourLEDs positioned in a square such that each LED was at 13◦ (visual angle) from a centrally presentedobject. Thus the objects could appear in the upper left, upper right, lower left or lower right visualfield with respect to the fixation points. On some trials, participants reached to grasp the objectwith the right hand and on other trials they passively viewed the object. At the beginning of eachtrial, participants had to saccade to one of the fixation points and to maintain fixation there forthe duration of the trial. By manipulating the position of the LEDs rather than the position of theobjects, we ensured that the biomechanics of the movements did not differ across conditions. Thesuperior parieto-occipital cortex and the anterior intraparietal area, brain areas implicated in thecontrol of hand actions, showed significantly higher activation when participants grasped objectspresented in the lower visual field than in the upper visual field. However, no visual field prefer-ences were observed in these regions during passive viewing. These findings suggest that the neuralresponses within dorsal visual stream regions may reflect a lower visual field advantage specific tovisually guided actions.

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SINGLE PRIMARY MOTOR CORTEX NEURONES CONTRIBUTE TO A WIDE RANGE OFMOTOR SKILLS

Touria Addou, N. Krouchev, J. KalaskaDépartement de Physiologie Université de Montréal

Recent primate neural recording studies have examined the possible mechanisms of motorlearning and adaptation to dynamic force fields in primary motor cortex (MI) (Li et al, 2001).Their results show that directional tuning of M1 neurons changes under viscous curl field taskdynamics in a manner that would compensate for the effect of the external field on the limb tra-jectory. That study implicated M1 in the adaptation to a single external force field. Sergio et al(2005) showed that many M1 neurons provide clear signals about the differences in the time courseof motor output dynamics between an isometric output force-ramp task and a reaching task withan inertial load. To elucidate how M1 contributes to the performance of a larger range of differ-ent and even incompatible motor skills, we trained 2 monkeys to perform single degree-of-freedomelbow movements that could be perturbed by a variety of externally-generated force fields. Fieldswere presented in a pseudo-random sequence of short 8-trial blocks. Different computer monitorbackground colors signalled the nature of the field throughout each 8-trial block. There were fivedifferent force fields: baseline null field without perturbing torque (N; black screen color), assistive(V-) and resistive (V+) fields proportional to velocity (green and red respectively), elastic force field(E+) proportional to position (blue) and a visco-elastic field (VE+) which is the linear combinationof V+ and E+ (magenta). The color associations were kept constant for the whole period of train-ing. Neural recordings were subsequently made over many weeks in MI contralateral to the trainedarm. EMG activity was chronically recorded from 8 arm muscles in each arm. The EMG activitypatterns were clearly directional and showed strong modulations in the different fields. Here weshow that many MI cells alter their activity systematically across most or all of the force fields in amanner that is appropriate to contribute to the compensation for each of the fields. The net activityof the entire sample population likewise provided a signal about the differences in the time course ofexternal forces across all force conditions. If separate neural “modules” exist that are preferentiallyresponsible for compensation for different specific environmental dynamics (e.g., MOSAIC model),they must exist outside of M1, while M1 neurons are implicated in the compensation for a broadrange of environmental dynamics.Supported by CIHR, FRSQ

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THE EFFECT OF HAND POSITION ON VISUAL RESPONSES IN AREAS V2 AND V4

Carolyn J. Perry[1, 2] Sarah M. Jones[1, 3, 4] J. Douglas Crawford[1, 3, 4]Mazyar Fallah[1, 2, 4][1] Centre for Vision Research, York University[2] School of Kinesiology and Health Science, York University[3] Department of Psychology, York University[4] Canadian Action and Perception Network

Visual spatial attention is described as enhanced processing of visual information at an at-tended location. It has been shown that the oculomotor system which guides eye movements candeploy spatial attention and more recently, that the presence of a hand also enhances visual pro-cessing in the space near it. An object in peripersonal space has different functional applicationsthan one out of reach. Thus, peripersonal space requires extra monitoring. This extra monitoringmay take the form of attentional selection near the hand. We investigated whether the presence ofa hand would enhance visual processing. Areas V2 and V4 are intermediate stages in visual pro-cessing that exhibit orientation (V2) and color (V4) selectivity. Importantly, they have repeatedlybeen shown to be modulated by visual spatial attention. We recorded from V2 and V4 neuronsin one animal. The animal fixated on a central point while a series of oriented bars (V2) or acolored square (V4) was presented in the receptive field (RF). In area V4, responses to the pre-ferred color were increased when the hand was passively placed near the RF. Next, the animal wastrained to reach to a touch bar and hold it while the oriented bars were presented. In area V2,orientation tuning curves were determined with and without the hand on the touch bar. Responserates increased when the hand was present near the RF. Some cells also showed a sharpening of ori-entation tuning. These results are discussed in relation to vision for action and the grasping system.

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SCANNINGOF FACE-SCENE OROBJECT-SCENE PAIRS REVEALS IMPLICIT RELATIONALMEMORY

Leora R. Branfield Day[1]Adrian M. Bartlett[2]Timothy K. Leonard[2]Kari L. Hoffman[2][1] Queen’s University[2] York University

The hippocampus is thought to play a role in the formation of memories of arbitrary relationsamong items in a scene (Cohen and Eichenbaum, 1993). Recently, we described a change detectiontask in which visual scanning of objects in a scene indicated explicit memory for those objects, andis thought to require hippocampal function (Chau, Murphy, Rosenbaum, Ryan, & Hoffman, 2010).In contrast, a task pairing faces and scenes revealed that the scanning of faces can be used as ameasure of implicit memory, yet it, too, is associated with hippocampal function (Hannula & Ran-ganath, 2009). One difference between tasks is that the latter was never tested with object-scenepairs. In this study, we replicated the face-scene pair task, and added an object-scene condition todetermine if the difference in scanning of previously shown pairs exists also for objects-scene pairsand if, as with faces, this bias exists even in the absence of explicit recall. Participants studied facespresented on scenes, and then viewed three faces superimposed on a scene that had been previouslypaired with only one of the faces in the array. In a second block, objects were used in place offaces. Participants were not informed that their memory for the pair was being examined, and theywere asked questions in debriefing to assess whether they had been aware of this memory test ornot. Consistent with previous reports, paired items were viewed preferentially, whether the itemswere faces or objects, and irrespective of whether recall was implicit or explicit. The bias towardsthe paired image emerged within the first 500ms of viewing for all but explicitly recalled face-scenepairs, and the protracted response was stronger for explicit than implicit faces. Taken together, theresults suggest that this task is effective whether using face or object stimuli, and could be used totease apart the role of the hippocampus in explicit and implicit memory formation. Furthermore,its use of non-verbal measurements makes it amenable for use in animal models.

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THE INFLUENCE OF BIOMECHANICAL ANISOTROPIES IN DECISION-MAKING

Ignasi Cos, Farid Medleg, Paul CisekUniversite de Montreal

Previous studies have suggested that while planning a movement, humans take into accountthe biomechanics of the motor apparatus. In particular, the path around an obstacle is influencedby the biomechanical properties of the arm in such a way as to minimize the probability of collision(Sabes & Jordan, 1997). Here, we investigate whether decisions between different reaching move-ments also take factors of biomechanical anisotropies into account, and whether this takes placeprior to movement onset. In particular, we investigated how humans make a free choice betweentwo potential trajectories where the options vary in path distance as well as biomechanical factorssuch as arm inertial load and stiffness anisotropy. Target and via-point placements were designed toequalize arm biomechanical factors during the launching phase and to maximise their difference atthe end of movement. Our results show that, given approximately equal kinematic factors, subjectschose movements that optimized aiming precision and stability. Because these decisions had to bemade prior to movement onset, they had to be presumably driven by predicted arm biomechanicsassociated with the potential trajectories. This suggests that we do not make decisions simply onthe basis of purely abstract criteria and only take knowledge of biomechanics into account whenplanning and executing the chosen movement. Instead, we are able to predict the biomechanics ofdifferent options and select the one that best optimizes precision and stability.

Furthermore, we investigated the influence on subjects’ choices of three biomechanical factors- Transport energy (TE); difficulty of stopping (DS), and difficulty of aiming (DA) - which areknown to influence end-point kinematic errors at the end of straight trajectories (Flash and Hogan,1985; Flanagan and Lolley, 2001). Loosely speaking, DS reflects the arm’s inertial load along thedirection of movement, while DA reflects end-point control along the direction perpendicular to themovement. To assess the effect of these additional factors, we had subjects perform the task indifferent blocks, with different target widths and with or without the requirement of stopping in thetarget. The results reveal that the relaxation of the aiming and/or stopping requirements does notreverse the movement preferences expressed during the first set of experiments, but rather exagger-ates the influence of biomechanics. This demonstrates that factors of biomechanical anisotropiesrelated to the stopping and aiming factors also play a role in the process of selection between move-ments. We suggest that parts of the brain involved in predicting the dynamics of movement and inthe control of the end-point, putatively including the cerebellum, may contribute to the process ofselecting between potential motor actions.

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NEURAL CORRELATES OF PREDICTIVE SACCADES IN YOUNG HEALTHY ADULTS

Stephen Lee, D. C. Brien, B. C. Coe, I. S. Johnsrude, D. P. MunozQueen’s University

The predictive saccade paradigm is a valuable tool that uses eye movements to measure thecontrol of anticipatory behaviour. In this task, subjects follow a visual target that alternates be-tween two fixed locations at a predictable inter-stimulus time interval (ISI). In our study, we alsoincluded a modified version of this task using auditory cues (i.e., white noise bursts), such that sub-jects generated saccades toward the direction of the sound. When the ISI is predictable, saccadicreaction times (SRT) become predictive (SRT 100ms). The goal of our study was to contrast areasin the brain that are active for predictive versus reactive saccades in young healthy adults (N = 18,ages 19 - 29 yrs) using BOLD fMRI.

In the visual and auditory predictive tasks (PRED Vis, PRED Aud) the ISI was fixed at750ms and subjects predominantly generated predictive saccades (69.4%, 84.5% respectively). Inthe visual and auditory reactive saccade tasks (REACT Vis, REACT Aud), the ISI varied randomlyfor each target step (500, 625, 750, 875, 1000ms) and SRTs remained reactive (11.7%, 16.3% predic-tive saccades). We used a blocked-design in which the four experimental blocks were presented inan order that was pseudorandom and counterbalanced across subjects. Experimental blocks wereall separated by periods of fixation. An eye tracker (Eyelink 1000) was used to measure saccadesfrom the right eye of each subject.

fMRI analysis revealed similar patterns of activation when comparing PRED and REACTconditions for both the auditory and visual tasks. We found greater activation in the medial pre-frontal and posterior cingulate cortex, medial temporal lobe and hippocampus for PRED versusREACT conditions. When we compared REACT versus PRED, we found greater activation inbrain areas known to be involved with the oculomotor network, including the frontal, supplemen-tary, and parietal eye fields, dorsolateral prefrontal cortex, putamen, and thalamus.

Our findings suggest that anticipatory behaviour in the PRED task recruits neural struc-tures that support internally-guided responses while the REACT task recruits structures that driveexternally-generated responses.

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Neuroscience B 04:30 PM, Thursday Feb 10 Grand Salon

DYNAMICS OF VISUAL PERFORMANCE AND PERCEIVED CONTRAST AT THE TAR-GETS OF SACCADES

Martin Rolfs, Marisa CarrascoDepartment of Psychology, New York University

Spatial attention shifts to the targets of saccades some time before the eyes move, specificallyalerting their locations in early visual cortices and locally improving visual performance as timeprogresses towards the movement. We now show that saccade preparation is also accompanied by aremarkable change in the visual appearance of stimuli presented at the movement goal. In a seriesof experiments, participants fixated a central spot while two standard stimuli (Gabor patches) wereflashed in the visual periphery, left and right of fixation. Shortly afterwards, a central movement cueinstructed participants to quickly generate a saccade to one of the two stimulus locations. Duringthe latency of the saccade, that is, after the movement cue but before the saccade was actuallyexecuted, a test stimulus was flashed at the movement goal. The test stimulus differed from thestandard both in contrast and orientation and, after the execution of the saccade, participantsjudged these differences in a combined two by two alternative forced-choice task. This procedureallowed for the concurrent assessment of changes in visual performance (tilt discrimination) andperceived contrast across the time course of saccade preparation. We find that, as time approachedthe saccade, tilt discrimination performance increased, and the test contrast necessary to equate thestandard (point of subjective equality) decreased substantially. Our results suggest that saccadepreparation, like covert attention, alters early visual processing in a way that is similar to changingthe signal strength, and uncover perceptual correlates of feedback signals from eye-movement con-trol areas to visual cortex.

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LOCAL TISSUE OXYGENATION IN THE POSTERIOR PARIETAL CORTEX

Rishi Rajalingham, Sam MusallamMcGill University

Functional magnetic resonance imaging (fMRI) couples large-scale changes in cortical oxygen,via the blood oxygen level dependent (BOLD) signal, to changes in neural activity. Thus, currentmodels of the hemodynamic response relate increases in neural activity to an eventual increasein cortical oxygen, often passing through an initial decrease. This study focuses on the hemody-namic response, based on local (micro-electrode) cortical oxygenation. We recorded local tissueoxygenation and single-unit neural activity simultaneously in the posterior parietal cortex of rhesusmonkeys. Local O2 was measured using a fluorescence-quenching optical oxygen sensor, while singleunit activity was recorded with a micro-electrode. Throughout the recordings, monkeys performeda delayed memory reach task to targets on the 2D fronto-parallel plane. Results show that increasesin spiking activity during the motion period coincided with an immediate and persistent decrease intissue oxygenation. The relative size of this “dip” was strongly linked to the increase in firing rate.Interestingly, local oxygen increased from baseline prior to this, during the memory period, whenno or little significant change was observed in neuronal activity. Furthermore, the rate of increaseduring this period of anticipation correlated significantly (r > 0.3) with the rate of consumptionof oxygen during the “dip”. The hemodynamic response could possibly be dynamic, i.e. corticaloxygen could be recruited dynamically to optimally meet neuronal requirements.

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OBJECT CONNECTEDNESS INFLUENCES PERCEPTUAL COMPARISONS BUT NOT THEPLANNING OR CONTROL OF RAPID REACHES TO MULTIPLE GOALS

Jennifer L. Milne, Craig S. Chapman, Jason P. Gallivan, Daniel K. Wood, Jody C.Culham, Melvyn A. GoodaleUniversity of Western Ontario

We developed a rapid reaching paradigm in which we require participants to make speededreaches toward ambiguous target displays, with a goal target filling-in only after movement onset.In our previous work, we have found that initial reaches extend toward the averaged spatial locationof the presented targets. Our aim for the current study was to determine if object connectedness- a strong perceptual illusion in which two connected objects appear as one - could influence thestrategic reaching behaviour. Even though there was a powerful effect of the illusion on perception,the visuomotor system was able to utilize the true target information and continue to plan reachesbased on the number and distribution of targets presented. These results resonate with the idea of adivision of labour between vision-for-perception and vision-for-action - but extend this dissociation(with respect to the action system) into the realm of motor planning.

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MECHANISMS OF FMRI-BASED DECODING OF ORIENTED GRATING STIMULI

Zeshan Yao, Martin Villeneuve, Pascal Kropf, Javeed Shaikh, Chang’an Zhan, CurtisBaker, Amir ShmuelMontreal Neurological Institute, McGill University

Orientation stimuli were accurately decoded from evoked fMRI responses in human V1 usingmultivariate pattern analysis. The size of fMRI voxels (3 by 3 by 3 mm) was large relative tothe mean cycle length (2 mm) of orientation maps. The mechanisms of this decoding of informa-tion conveyed in fine-scale organization by coarse voxels remains unknown. Here we investigatedtwo mechanisms that have been proposed to play a role: (I) irregularities of the orientation mapsthat bring about biased sampling of orientation columns, and (II) orientation selective responses ofdraining vein that may drain blood from regions with imbalanced orientation preference.

Optical imaging of intrinsic signals was pursued in cat area 18, while the animal viewed mov-ing gratings of 8 different orientations. We evaluated the contrast to noise ratio obtained fromdifferential cortical responses to orthogonal stimuli. In addition, we evaluated the performance ofa classifier (linear support vector machine) with bin-size scaled to mimic the conditions of fMRI inhumans.

We found that the power-spectrum of orientation maps is broad, including power in frequen-cies lower than the main frequency of the organization that can be captured by fMRI-like voxels.Small blood vessels (diameter < 0.2mm) show orientation selectivity similar to the columns theydrain. Medium size (diameter 0.3 - 0.4 mm) showed reduced orientation selectivity, while bloodvessels wider than 0.5 mm did not carry information on the stimuli.

We conclude that irregularities in orientation maps and small-to-medium blood vessels con-tribute to decoding with lower performance compared to that reported in human studies. Hence,we expect additional contributions to decoding, of mechanisms not investigated in our current study.

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POSSIBLE ROLES OF PMD, M1 AND DLPFC IN DECISION MAKING

Émilie Coallier, Thomas Michelet, David Thura, John F. KalaskaDépartement de Physiologie Université de Montréal

Decision-making is a neural process that involves several cortical and sub-cortical areas thatsample and integrate sensory evidence for and against different alternatives until the evidence sup-porting one alternative reaches a decision criterion threshold. This predicts that the reaction time(RT) necessary to make a decision depends on the quality of sensory evidence required to makea decision. We presented two potential reach targets (blue, yellow) in opposite spatial locations,and then a central decision stimulus made of 100 squares of the two colors on a red backgroundon a screen to a monkey. The quality of the stimulus (percentage of squares of each color) rangedfrom unambiguous (one color only) to very ambiguous (nearly equal numbers of squares of eachcolor). The physical dimension of the stimuli on which the response choice was based (color ratio)has no spatial or directional property on its own. The monkey had to move a cursor to the correcttarget to obtain a drop of juice reward. A range of decision stimuli were presented: from 100/0(unambiguous: one color) to 52/48 (ambiguous). Subjects could move at any time after the decisioncue appeared (“choose-and-go” task) Psychophysics data in humans and monkeys show that RTand error rates varied with the quality of the sensory evidence, but not with the quantity.

We recorded cells in the dorsal premotor cortex (PMd), the primary motor cortex (M1) andthe dorsolateral prefrontal cortex (DLPF). M1 neuronal activity is relatively time-locked to theonset of movement and relatively independent of the quality of sensory evidence or the durationof the RT, which suggests a primary role in movement execution. PMd neuronal activity oftensuggests an accumulation of evidence across time between the appearance of the decision cue andthe onset of movement. When monkeys choose the wrong target, the neuronal activity reflects itsbehavioural choice not the physical properties of the stimuli. Furthermore, PMd neurons code forspatial/directional information but not usually show little or no color information. In contrast,DLPF cells show neuronal activity correlated with both the color and location of the target, whichsuggests a role in representing and applying the color/location conjunction rule.

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MAPPING THE DISTRIBUTION OF HCN1 ON NECK MOTONEURONS

Ethan .Y. Zhao, K.K. Fenrich, M. Neuber-Hess, R. Maratta, P.K. RoseCIHR Group in Sensory-Motor Integration, Queens University

Over 95% of the synapses on motoneurons are located on the dendritic tree. Thus, the cur-rent generated by these synapses must travel along dendrites that can be over 1000 µm long beforereaching the soma. Dendrites of many neurons are endowed with a wide array of voltage-dependentchannels. These channels can provide additional current that amplifies or dampens synaptic cur-rent en route to the soma. The specific consequences will depend on the properties of the voltage-dependent channels, their density, and their distribution. HCN1 channels are responsible for thecharacteristic membrane potential sag in response to hyperpolarizing current steps. The magnitudeof this sag depends on the size of the motoneuron. Previous immunocytochemical studies have re-ported the presence of HCN1 channels on the somatic membranes of motoneurons. However, thereare no descriptions of the distribution of HCN1 channels on motoneuron dendrites. The goal of thepresent study is to use immunocytochemical, confocal and three-dimensional image analysis tech-niques to map the distribution of HCN1channels on the somatic and dendritic membranes of neckextensor motoneurons in the adult cat. Antidromically identified motoneurons were intracellularlystained in order to visualize the entire dendritic tree. HCN1 channels were labeled with a specificantibody (NeuroMab clone N70/28). Serial optical sections of the intracellular stain and HCN1 la-beling from proximal (0 - 200 µm), intermediate (200 - 800 µm), and distal dendritic regions (>800µm) were acquired using confocal microscopy and rendered into a three-dimensional volume. Theperimeter of the intracellular stain was used to define a three dimensional zone that corresponds tothe region occupied by the dendritic membrane. Analysis of HCN1 labeling was constrained to thisjuxta-membrane zone. This technique provides a means of extracting membrane-associated HCN1channels and therefore the functional distribution of HCN1 channels. Preliminary observations re-veal a distance-dependent distribution of HCN1 on the membrane of dendrites projecting rostrallyand caudally. The density of immunofluorescence on the membranes of distal dendrites was 10-foldlarger than on the membranes of proximal dendrites. Locally, HCN1 channels are organized indiscrete clusters with an area of 0.5 - 3.0 µm2. In addition, the intensity of somatic membranelabeling of HCN1channels varied from motoneuron to motoneuron suggesting that the expressionof HCN1 channels on motoneuron somata is heterogeneous.

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THE ROLE OF CORTICAL AREA MT+/V5 IN SPATIAL ASPECTS OF MANUAL INTER-CEPTION: AN RTMS STUDY

Joost C. Dessing[1, 2, 3]Michael Vesia[4, 5]Xiaogang G. Yan[1] J. Douglas Crawford[1, 3, 6][1] Centre for Vision Research, York University[2] Canadian Action and Perception Network (CAPnet)[3] Departments of Psychology Biology and Kinesiology Health Science, York University[4] Faculty of Applied Health Sciences Department of Kinesiology, University of Waterloo[5] Sunnybrook Research Institute Brain Sciences Research Program[6] Canada Research Chair in Visuomotor Neuroscience

Planning the spatial aspects for manual interception of a moving visual target must incor-porate visual signals about target motion. Currently, it is unknown how this is exactly achieved.Nevertheless, cortical area MT+/V5 is known to process visual motion and indeed is involved in thetemporal control of interception; this role extends to online visual guidance. We hypothesized thatMT+/V5 would also be involved in online spatial control (i.e., motion extrapolation); we examinedthis using TMS to MT+/V5 (MRI-guided; control site: CZ on EEG 10 20 cap). Subjects (n =7) were fixating (± 15 deg) while a target moved down on a screen along one of many straightor oblique trajectories, approaching an imaginary horizontal line along which the target had to betouched with the finger. In one condition, the target could change direction shortly after movementonset, requiring updating of finger movement endpoint. In part of the trials, rTMS (3 pulses at10Hz, 110% RMT) was started when the target changed direction. Even though the target wasvisible for only 200 ms after the change, subjects achieved about two thirds of the required changein the movement endpoint. These corrections did not differ significantly for visual target motion inthe left and right visual field. More importantly, TMS did not influence the extent of these spatialcorrections (i.e. no difference between TMS and no TMS trials, nor of between TMS at MT+/V5or at CZ). Interceptive timing was also not affected. These unexpected findings might indicatethat MT+/V5 is not involved in the spatial control in this interceptive task. We hypothesize thatMT+/V5 will play a role in more complex tasks, with less predictable target motion. Follow-upexperiments are underway to functionally confirm the stimulation site (motion direction judgmentsfor random dot kinematograms) and to assess the role of MT+/V5 in variants of the task involvingless predictable target motion.

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Neuroscience C 09:00 AM, Friday Feb 11 Grand Salon

BINOCULAR RIVALRY, MONOCULAR RIVALRY AND DEPTH PERCEPTION COMPAREDWITH FMRI

Janine D. Mendola, Athena BuckthoughtMcGill Vision Reasearch, McGill University

We have recently conducted a series of experiments designed to take advantage of detailedpsychophysical characterization of binocular rivalry and depth so as to ask specific questions aboutpossible neural substrates that can be addressed with fMRI. In the first experiment, human subjectsperformed either a rivalry report task or a depth report task for identical binocular plaid stimuli,indicating alternating percepts by button press. Depth is perceived from the near-vertical com-ponents, while the diagonal components undergo rivalry (Buckthought & Wilson, 2007). In threeconditions the spatial frequencies of the near-vertical and diagonal components were, respectively:2.5 and 6.4 cpd; 6.4 and 2.5 cpd; or 6.4 and 6.4 cpd. Consistent with the observation that binoculardepth and rivalry could be perceived simultaneously in the same location, we obtained evidencethat this may be accomplished in part by depth and rivalry coexisting in different spatial frequencychannels, and distinct visual areas. At the same time, cue invariant activity in the lateral occipitalcortex for depth or rivalry when compared to a fusion control is consistent with a representationat the surface level that might facilitate grouping of features, and accommodate more than onefeature at a spatial location. In the second experiment, subjects performed a rivalry report task forbinocular rivalry grating stimuli or for similar stimuli matched in each eye that produce monocular(pattern) rivalry, a bi-stable perception related to binocular rivalry (O’Shea et al, 2009). By com-paring binocular and monocular rivalry, we showed that the increased perceptual suppression thatdistinguishes binocular from monocular rivalry at higher stimulus contrasts was associated with re-duced activity in specific visual areas (V2, V3). Other areas such the motion sensitive area hMT+showed an overall preference for binocular over monocular rivalry. These results place constraintson models of binocular vision, and contribute to the discovery of neural networks that modulateconscious awareness. In addition, understanding perceptual suppression in normal rivalry workstowards characterization of perceptual suppression in developmental visual disorders such as am-blyopia and strabismus. Supported by a NSERC Discovery Grant, CFI LOF award, and NIH R01EY015219.

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OCULOMOTOR INFLUENCES ON VISUAL RESPONSES IN MACAQUE CORTICAL AREAV4

Jachin A. Monteon, T. Zanos, P. Mineault, D. Guitton, C.C. PackMontreal Neurological Institute, McGill University

The responses of neurons in the primate extrastriate cortex are closely linked to visual percep-tion. In particular, previous experiments have shown selectivity for the complex stimulus featuresthat form the basis for psychophysical judgments. These experiments have usually been conductedduring steady fixation, but during natural vision perception is strongly influenced by movements ofthe eyes and head. We have therefore examined the interaction between visual responses and sac-cadic eye movements, using a paradigm that allows us to map the spatial and temporal structure ofexcitatory and inhibitory visual responses in a population of neurons in cortical area V4. METH-ODS: We recorded simultaneously from 30 - 50 V4 neurons in the alert macaque monkey, usingchronically implanted micro-electrode arrays. A sparse noise stimulus, consisting of a random arrayof 50% black and 50% white squares, presented on a gray background, was used to map the RF ofeach neuron during fixation and perisaccadically. The positions of the black and white squares werechanged randomly at the frame rate of 85 Hz. The monkey made visually guided 20◦ saccades toand fro between two targets which appeared on the flickering background. For most experimentsone of the targets was positioned near the center of the spatial distribution of all receptive fields.To recover the receptive field structure in space and time, we computed spike-triggered averagesof the first- and second-order properties of the stimulus. RESULTS: For most neurons the sparsemapping approach provided receptive fields with strong excitatory and inhibitory spatial compo-nents, as well as temporal impulse response functions. These visual responses were influenced bothby eye position and perisaccadically depending on the planned direction of eye movement. Eyeposition effects were primarily manifested as changes in the gain of the receptive fields, with themost common effect being an inhibitory effect (reduced gain) for eye positions opposite the locationof the ensemble of visual receptive fields. Perisaccadic effects involved changes in the gain, thesize, and the position of receptive fields. Preliminary analysis suggests that the size and positionchanges are related to those reported previously by Tolias et al. (2001) in V4 and by others inLIP and FEF (e.g., Duhamel et al., 1992). CONCLUSION: Neuronal responses in V4 are stronglyinfluenced by oculomotor signals, and these neural properties may help to explain previous percep-tual studies that find large distortions in the perception of visual space around the time of a saccade.

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INFLUENCE OF DIURNAL SLEEP (NAP) ON CEREBRAL CORRELATES OF CONSOLI-DATION OF DIFFERENT REPRESENTATIONS OF MOTOR SEQUENCE LEARNING, AS-SESSED BY FMRI.

Genevieve Albouy[1] Stuart Fogel[1]Vo An Nguyen[1]Amel Bouyoucef[1] Frederic Jeay[1]Edwin Robertson[4] Julien Doyon[1, 2][1] Unité de Neuroimagerie Fonctionnelle Centre de Recherche de l’Institut Universitaire de Gériatriquede l’Université de Montréal[2] Centre de recherche en neuropsychologie et en cognition Département de Psychologie Universitéde Montréal[3] Centre d’étude du sommeil et des rythmes biologiques Hôpital du Sacré-Cœur de Montréal[4] Centre de Stimulation Cérébrale Non-Invasive Beth Isral Deaconess Medical Center Départementde Neurologie

Introduction: The acquisition of a new sequential motor skill requires learning simultaneously al-locentric and egocentric representations of the sequence.By manipulating a digital motor sequencelearning task, we explored the influence of diurnal sleep (nap) on the cerebral correlates of consol-idation of both the allocentric (extrinsic, spatial) and egocentric (intrinsic, motor) representationsof the sequential motor task.Methods: In a first behavioural study, 44 volunteers were trained on a motor sequence learningtask. At the end of training, they were divided in 4 groups according to whether they would betested on the allocentric (ALLO) or egocentric (EGO) representation of the sequence and accord-ing to whether they would be re-tested on this representation after a 90-minutes nap (NAP) orafter quiet wakefulness (NONAP). We then considered 4 groups of subjects: ALLO-NAP, ALLO-NONAP, EGO-NAP and EGO-NONAP (n=11 in each group).

In a second study, this protocol was adapted to fMRI and cerebral activity of 28 new partici-pants was recorded in the ALLO-NAP (n=15) and ALLO-NONAP (n=13) groups while practicingthe motor task. The acquisition of data concerning the EGO groups are still in progress. Nap andno-nap were monitored using polysomnography.Results: Behavioral study: A repeated measure ANOVA performed on speed to perform thetask showed that performance significantly improved during the training session (F(1,13)=29.91,p


left IPS Z=4.36, p



RAPID MOTOR RESPONSES DURING REACHING ARE SENSITIVE TO TARGET SHAPEAND OBJECTS IN THE ENVIRONMENT

Joseph Nashed, Stephen H. ScottCentre for Neuroscience Studies, Queen’s University

An impressive feature of our motor system is the ability to rapidly counter unexpected per-turbations when moving in the environment. For example, when reaching to a cup of coffee, if thehand is perturbed away from its initial trajectory the result is a rapid corrective movement directedtowards the cup. That said, we live in a cluttered environment, so what happens if a glass of juiceis in the way of our typical corrective movement towards the cup? Our interest is to explore theflexibility and sophistication of corrective movements and how they are influenced by the nature ofthe goal and features in the environment.

The first experiment examined the influence of the shape of the spatial goal on feedbackcorrections during reaching. Twelve subjects made planar reaching movements (KINARM, BKINTechnologies) from a start target located close to the body, to one of two types of end goals, a circu-lar dot or a horizontal bar, located 20cm directly in front of the start target. Subjects were requiredto make the reaching movement between the two targets between 700 and 1000 ms. On 20% oftrials, the KINARM robot applied a step torque 5 cm after leaving the start target. Perturbationscaused lateral deviations (either right or left) from the initial trajectories. Unperturbed reachingmovements for both target shapes were directly forward to the same location, the shortest path fromstart target to each goal. For the circular dot, perturbations were overcome with vigorous correctivemovements that directed the hand to the dot. In contrast for the horizontal bar, responses were lessvigorous: corrective movements when perturbed to the right were directed to the right side of thebar. Correspondingly, leftward corrections were directed to the left side of the bar. We recordedthe activity of proximal arm muscles during the two tasks. We found that rapid motor responses(RMRs) were observed starting 60 ms following the perturbation for reaching movements to eithertarget shape. However, these RMRs were significantly larger for the circular dot as compared tothe horizontal bar (p



A NOVEL TECHNIQUE FOR INVESTIGATING NEUROVASCULAR COUPLING: SIMULTA-NEOUS OPTICAL IMAGING OF BLOOD-OXYGENATION AND MEMBRANE POTENTIAL

James McNicol, Amir ShmuelMcGill University MNI

The key to improving quantitative fMRI analysis is to have a comprehensive model of neu-rovascular coupling, one which links oxygen metabolism and blood flow to neuronal activity. Inorder to build such a model, one must be able to record simultaneously, at high temporal and spa-tial resolution and with sufficient spatial coverage, both neurophysiological and blood oxygenationsignals. We have developed a system, based on optical imaging techniques, capable of such record-ings. Optical signals, emanating from voltage sensitive dye-stained cortex, are split spectrally intotwo separate streams: one carrying electrophysiology-related signals, and another carrying bloodoxygenation-related signals. These separate streams are then captured by two distinct cameraCCDs. The optical split is made feasible by choosing a dye whose excitation and emission spectraoverlap minimally with the wavelengths from which the hemodynamic signals are obtained. Thesplit is physically accomplished using a dichroic mirror and series of optical filters with carefully de-signed spectral responses. The system was tested using adult Sprague-Dawley rats, which receivedsmall craniotomies (5 by 5 mm) above area S1, as well as having their dura removed. Subsequentto staining with voltage-sensitive dye (RH-1692), experiments were performed using electrical stim-ulation of the forepaw. We found that the membrane potential signal was highly localized, andpreceded the onset of the hemodynamic response, which had a much slower response and broaderspatial profile. The data captured with this system will allow for a more comprehensive, quantita-tive spatiotemporal model of neurovascular coupling to be developed.

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RELATIVE ENCODING OF REWARD IN THE REACH SYSTEM.

Georgios Tsoulfas[1] Sam Musallam[1, 2][1] Department of Physiology, McGill University[2] Department of Electrical and Computer Engineering, McGill University

Previous work has shown that expected value of reward associated with a reach modulatesneural activity in the medial intraparietal cortex (MIP) and that this reward signal can be decoded.In this study, we investigated the reliability of reward coding in MIP by examining whether a certainreward value is encoded in a similar way when presented in different contexts. We are interestedis seeing whether prior knowledge is used to interpret information about the reward in the currenttrial. We recorded from single neurons while two Rhesus macaque monkeys performed a delayedreach task under two conditions. In the first condition, high and low reward values were randomlyinterleaved trial by trial (variable reward schedule) while in the second condition only one of thesereward values was delivered for a block of trials (constant reward schedule). Each recording sessionconsisted of a variable reward schedule as well as a small and large constant reward schedule. Thevalue of the reward was indicated by a cue preceding the delay period of each trial. For the samereward, the firing rate of neurons in the delay period changed significantly between the constant andvariable reward conditions. Our results show that reward conditions from previous trials affects theneural firing frequency within MIP. This suggests that the neural activity within MIP is modulatedby not only expected value of reward but also the reward delivery schedule.

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DEFICITS IN MIRROR SACCADE PRODUCTION IN PARIETAL DAMAGED PATIENTS

Aarlenne Z. Khan[1] Annabelle Blangero[2] Laure Pisella[2] Douglas P. Munoz[1][1] Centre for Neuroscience Studies, Queen’s University[2] Espace et Action, INSERM

Successfully executing a saccade to a different location than the visual target e.g. anti-saccades, involves inhibiting the reflexive saccade to the visual target and computing a new saccadeto the the appropriate location. Recent neurophysiology as well as imaging studies (e.g. Meden-dorp et al., 2005; Zhang & Barash, 2004) have shown the involvement of the parietal cortex in bothinhibition and in producing anti-saccades. Here we tested the involvement of this brain region byinvestigating performance in patients with lesions to the posterior parietal cortex in a saccade taskwith requiring both anti- and orthogonal saccades to mirror locations across and within hemifields.

Two unilateral and one bilateral parietal damaged patient took part, along with 5 neuro-logically intact age-matched controls in a mirror saccade task with three different conditions, i)producing a saccade across the vertical meridian from the target (across the visual hemifield), ii)producing an orthogonal saccade across the horizontal meridian from the target (within the visualhemifield) and iii) producing an anti-saccade. Subjects also performed a baseline condition wherethey produced a reflexive saccade to the target location. Visual targets were randomly presentedbriefly at one of 4 oblique positions at a 7 deg eccentricity from central fixation. All conditions wereperformed in separate blocks.

Patients showed a shifted speed-accuracy tradeoff with respect to correct mirror saccades vs.erroneous reflexive saccades compared to controls; when saccade reaction times matched those ofcontrols, there were many more erroneous saccades to the visual target location, whereas correctmirror saccades had much longer latencies. This suggests that the circuit involving the inhibition ofreflexive saccades includes the parietal cortex. In addition for all 3 conditions, all patients showedincreased variability and required multiple saccades to reach the goal. Finally, saccade endpointswere biased toward the inhibited reflexive saccade goal location. This may be due to the involve-ment of the parietal cortex in computing a new saccade vector; damage to which results in faultyvector calculation.

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STOCHASTIC REFERENCE FRAME TRANSFORMATIONS ALTER MULTI-SENSORY PER-CEPTION AND ACTION

Jessica Burns, Joseph Nashed, Gunnar BlohmCentre for Neuroscience Studies, Queen’s University

In perception and action, multi-sensory integration refers to the statistically optimal com-bination of redundant sensory information. In the brain it is thought that sensory signals fromdifferent sources first need to be converted into matching representation before they can be com-bined. This requires coordinate matching transformations that depend on the relative orientation ofthe different body segments involved. For example, when integrating seen hand position and sensedjoint configuration of the arm into a unified internal belief of where the hand is, visual signalsentering the brain in eye-centered coordinates are combined with proprioceptive signals initially injoint coordinates. To transform those into a common reference frame, the brain has to estimateeye and head orientations relative to the body. Because these estimates of eye and head orientationare affected by signal-dependent noise, we hypothesized that this additional noise in the referenceframe transformations should affect both multi-sensory perception and action.

We tested this hypothesis in two experiments. In the perceptual experiment, participants hadto judge the location of a visual probe relative to their unseen hand. In the reaching experiment,we asked subjects to reach to visual targets while dissociating the visual feedback of initial handposition from the true location of their unseen hand. Both experiments were performed with thehead straight and the head tilted 30deg towards either shoulder. We conjectured that the latterwould introduce additional noise to the reference frame transformation due to signal-dependenthead orientation uncertainty.

A model-based analysis showed that head roll affected both multi-sensory perception and ac-tion. It added noise to the perceptual estimate of relative hand position as well as to the reachingmovements. In addition, multi-sensory weights were affected by head roll such that transformedsensory signals were less reliable due to added noise in the reference frame transformations. Thisdemonstrates that reference frame transformations are stochastic, that the brain knows about thereliability of sensory signals and that we can use this information to adjust multi-sensory weightsin a Bayes optimal fashion.

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BEHAVIORAL AND STIMULUS CORRELATIONS OF NEURAL ACTIVITY IN AREA MT INAN OMITTED STIMULUS DETECTION TASK

Navid G. Sadeghi, Erik P. CookDepartment of Physiology, McGill University

Our ability to predict external events depends on our perception of temporal correlations.In-vitro studies have shown that sensory areas as low as the retina may respond predictively basedon observed temporal correlations (omitted stimulus response). We asked how the visual cortexresponds when temporal correlations are disrupted in awake animals. We used a random dot visualstimulus composed of a series of regularly appearing motion pulses (200 msec 80% coherent) thatwere separated by 350 msec of random motion. We recorded 70 multiunits from the Middle Tem-poral (MT) area of visual cortex of two Macaque monkeys that viewed this rhythmic stimulus andwere trained to release a lever when one of the pulses was omitted (the signal) and shown slightlylater than expected. To provide a good estimate of the regular interpulse interval, the monkeysviewed a minimum of 5 pulses before random occurrence of the signal (non-flat hazard function).Our paradigm had two conditions based on the direction of motion: preferred and null repeats. Tosee whether there was an omitted stimulus response that could be used by higher areas to detectthe omission, we used an ROC analysis to compare the preferred and null responses for each pointin time. This analysis showed no population activity signaling the observed motion direction atthe time of omission for both spike rate and local field potential (LFP) power. We also calculatedthe time course of detect probability (DP) and correlation with reaction time (RTcorr) for spikerate and LFP power. For both conditions, we observed a DP greater than 0.5 and negative RTcorrfor spike rate after signal onset. These behavioral correlations for LFP power were correlated andanticorrelated with those of spike rate for frequencies above and below approximately 50 Hz, respec-tively. Being in the same direction for both conditions, these neural-behavioral correlations are morelikely the result of top-down attention as opposed to being causal for detection of lack of motionat signal onset time. Consistent with attentional gain modulation, we observed weak counterphasemodulations of DP and RTcorr for the two conditions in response to our periodic stimulus for a fewseconds before signal onset. In addition, these typical neural-behavioral correlations were absenton trial start when attentional efforts were presumably less due to the non-flat hazard function ofthe paradigm. In conclusion, our results suggest that temporal correlations are not perceived inlow-level sensory areas. Our results also show that LFPs, which are easier to isolate, may be usedfor behavioral and stimulus correlations.

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FUNCTIONAL CONNECTIVITY IN MACAQUE CORTICAL AREA V4

Theodoros P. Zanos, Jachin A. Monteon, Patrick J. Mineault, Christopher C. PackMontreal Neurological Institute, McGill University

Much of the input to a cortical neuron originates from within the cortex, and corticocorticalconnections are of two main types. Inter-areal connections link distinct cortical areas, either byfeedforward or feedback projections, while intra-areal connections involve neurons within the samecortical area. Most of our understanding of sensory systems is based on models that rely heavilyon inter-areal connectivity, as in the standard hierarchical models of visual processing. However,intra-areal connections tend to be far more common in cortical neurons, and their function is poorlyunderstood. We have therefore sought to develop a method for estimating the contributions of theseconnections to visual processing the macaque cortex. To this end we have analyzed data obtainedfrom 100-electrode Utah arrays chronically implanted into area V4 of the macaque monkey. AreaV4 contains a retinotopic representation of visual space, and individual neurons in this area areselective for complex stimulus features related to the perception of object shape. Based on ourrecordings we are able to estimate the interactions or functional connectivity among V4 neuronsin a variety of contexts, using a method based on the nonlinear Volterra modeling approach. Thisapproach provides estimates of the strength and statistical reliability of connections among neu-rons, including nonlinear interactions and excitatory and inhibitory connections. Our results thusfar reveal a pattern of connectivity within V4 that conforms to the results of previous anatomicalwork: Excitatory connections are far more common than inhibitory connections ( 65%), strongerconnections are found among neurons that are physically near one another, and connections arestronger among neurons with similar receptive field properties. However, this connectivity is ca-pable of reorganizing on short time scales according to the stimulus: Stimuli that evoke strongsuppression at the single-unit level introduce stronger inhibition among V4 neurons, identifyingrecurrent connectivity as the source of the suppression. Our preliminary results also show thatfunctional connectivity depends on the demands of the task, as the connections among V4 neuronsappear to be modulated by the animal’s oculomotor behavior. Overall, these results provide insightinto the dynamic nature of neuronal organization within V4.

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INSTRUCTION-RELATED SACCADE AND HEAD MOVEMENT ACTIVITY IN SUPERIORCOLLICULUS UNITS DURING PLANNED SEQUENCES OF HEAD-UNRESTRAINED GAZESHIFTS IN THE MONKEY

Xiogang Yan[1, 2, 3]Marie Avillac[1, 4] Jachin Ascencio-Monteon[1, 5]Hongying Wang[1, 2, 3]John Douglas Crawford[1, 2, 3][1] Center For Vision Research, York University[2] The Canadian Action and Perception Network (CAPnet)[3] Department of Psychology, York University[4] Neurobiology of Learning Memory and Communication Laboratory, University of Orsay[5] Montreal Neurological Institute and Hospital, McGill University

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