Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S155

Figure 1. Extreme delta brush-like pattern. Rhythmic delta activity (1–1.5 Hz) withbeta activity (13–14 Hz) superimposed in the negative deflection of the delta wavelocalized in the frontal left hemisphere regions.

enhancement of gamma frequency oscillations and an attenuation of thetaactivity. We hypothesize that the pattern observed in our patient will bethe reflection of the ketamine anti-NMDAR effect.

P395Switching from bimanual to unimanual tapping reveals two distinctpost-switching beta synchronization processes

E. Sallard1, J. Tallet2, G. Thut3, M.-P. Deiber4, J. Barral11Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland;2UPS, PRISSMH-LAPMA, University of Toulouse, Toulouse, France; 3Centre forCognitive Neuroimaging (CCNi), Institute of Neuroscience and Psychology,University of Glasgow, Glasgow, United Kingdom; 4Clinical Neurophysiologyand Neuroimaging Unit, Division of Neuropsychiatry, University Hospitals ofGeneva, Department of Psychiatry, Geneva, Switzerland

Question: Post-movement beta synchronization is involved in severalmechanisms, such as the deactivation of motor execution, the processing ofsensory reafferences or the active inhibition preventing movements fromother body parts. These phenomenons have still not been investigated inrelation to the selective inhibition during multi-limb coordination task. Inthis study, we investigated post-switching beta synchronization (PSBS) dur-ing a switching from bimanual to unimanual finger tapping. We computedsource estimation to discriminate the implication of PSBS in inhibitory andsensory reafferences processing.Methods: Participants (n=17) initiated a 2 Hz auditory-paced bimanual tap-ping. After a 1500 ms preparatory period, an imperative stimulus requiredto either selectively stop the left while maintaining the right uniman-ual tapping (SWIT) or to continue the bimanual tapping (CONT). Pairedt-tests were performed between SWIT and CONT conditions on 14-30

Hz time-frequency data from the switching period (epoch duration: 2500ms).Results: PSBS significantly increased in SWIT compared to CONT withmaximal difference within right central region in 14–30 Hz and withinleft central region in ∼22–26 Hz. Source estimations localized these effectswithin the right pre-frontal cortex (superior frontal gyrus) and within theleft parietal cortex (superior and inferior parietal lobules).Conclusion: This study shows for the first time simultaneous PSBS withdistinct functions in different brain regions and frequency ranges during aswitching task. The left parietal PSBS restricted to ∼22–26 Hz could reflectthe sensory reafferences of the right hand tapping. In contrast, the rightfrontal PSBS in a large 14-30 Hz frequency band is likely reflecting theactive inhibition of the left hand. Switching was revealed to be a suitableparadigm to evidence distinct functional aspects of post-movement betasynchronization.

P396Analysis of event related beta and gamma oscillations in perception ofaffective pictures

B. Guentekin, E. Tuelay, B. Turp Goelbası, E. BasarIstanbul Kueltuer University, Brain Dynamics, Cognition and Complex SystemsResearch Center, Istanbul, Turkey

Question: The previous literature showed that unpleasant stimuli of affec-tive pictures (IAPS) elicited higher beta and gamma oscillatory responsesthan neutral and/or pleasant stimuli. However, it was not clear yet howthe stimulation design would affect the oscillatory responses. The presentstudy analyzed event related beta and gamma oscillatory responses uponpresentation of unpleasant, neutral, pleasant pictures, which were shownto the subjects in block or random design.Methods: EEG of 22 healthy subjects were recorded at 32 locations. Theparticipants passively viewed 120 emotional pictures (10X4 unpleasant,10X4 pleasant, 10X4 neutral) in a block and random design. The phaselocking and power of event related beta (15-27 Hz) and gamma (28-48 Hz)oscillations were analyzed in two different time windows (0-200 ms and200-400 ms).Results: Statistical analyze showed that in the first time window duringthe block design unpleasant stimulation elicited higher beta phase lockingand beta power than the pleasant and neutral stimulation (p<0.05).Inthe second time window during the block design over occipital electrodesunpleasant stimulation elicited higher gamma response power than thepleasant stimulation and neutral stimulation (p<0.05). Unpleasant stimu-lation did not elicited higher beta or gamma responses in random design.Conclusions: The present study showed that design matters in perceptionof IAPS pictures. Unpleasant stimulation elicited higher event related betaand gamma phase locking and power only in block design but not inrandom design. It seems that continuous observation of unpleasant stimuliaffects the brain more than random observation.

P397Fast automated detection of inter-ictal epileptiform discharges usingsmart templates and iterative reviewing

S. Lodder, M.J.A. van PuttenUniversity of Twente, Clinical Neurophysiology, Enschede, Netherlands

Question: Automated detection of Inter-ictal epileptiform discharges (IEDs)may assist clinicians in reviewing EEGs faster and more efficiently. Althoughmany algorithms exist, all of them face a similar problem: to achieve highsensitivities, false positive rates remain high, making the manual search forIEDs faster than reviewing all detected events. Our objective was to find asolution that will make automated detection faster and more efficient thanconventional methods.Methods: Using an automated detection algorithm described in Lodderand van Putten (Inter-Ictal Spike Detection using a Database of SmartTemplates. Clin Neurophysiol; 2013), IEDs are detected using a database oftrained templates each representing an IED waveform. During a detectionphase, templates nominate IEDs with high correlations to themselves andpair them with detection certainty values. During the review phase, theten most likely nominations based on certainty values are presented to thereviewer, which either confirms or rejects them as IEDs. After ten eventsare reviewed, certainty values of the remaining nominations are updatedbased on the reviewer feedback, and iteratively another ten nominations

S156 Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339

are presented for review. Confirmed events are stored and marked asdetected IEDs.Results: Evaluation was performed on a test set of 15 EEGs (306 min, 244IEDs marked by an experienced reviewer). A total of 8426 events werenominated as epileptiform events, and 241 of the 244 IEDs were detected(25.8 fp/min over all certainty levels). Using the described method, 15iterations (10 events reviewed per iteration) were performed on each EEG,and the number of confirmed IEDs was counted after each iteration. Resultsshow that 74% of all marked IEDs were found after five iterations, 90% afterten iterations, and 95% after fifteen iterations. The review time for eachiteration was on average twenty seconds, resulting in a total review time offive minutes per EEG.Conclusions: The use of automated IED detection algorithms are limitedby their high number of false detections. The proposed method shows howautomated detection can be used to find IEDs in a fast and efficient man-ner, regardless of a high false detection rates. Compared to conventionalmethods, it can improve review times significantly and make long-termrecordings for epilepsy diagnosis more feasible.

P399EEG independent component analysis and 3D localization of brainpathological areas

A. IvanovNeurosoft Ltd., Software, Ivanovo, Russian Federation

Independent Component Analysis (ICA) is a computational method widelyused in practice for EEG artifact removal. ICA can be also used for theimproving of 3D dipole localization method. ICA decomposition of an EEGallows to separate independent components containing paroxysmal activity.Independent components without paroxysmal activity are to be excludedfrom analysis. The target trace processed with ICA contains only fragmentswith paroxysmal activity. This technique provides clear visualization ofparoxysmal events on trace and improves results of 3D dipole localization.The validity and performance of the approach were confirmed by medicaltrial. A total of 8 patients aged from 13 to 58 year with clinically provenepilepsy were examined. Long-term EEG was recorded from all the patients.Recorded EEG traces were processed using ICA method. Raw EEG tracesand traces obtained after ICA processing were exposed to 3D localizationby dipole model using BrainLoc 6.0 software for 3D dipole localization(Neurosoft, Russia).Research shows that the graphic representation of paroxysmal events ontrace is denser for ICA-processed EEG trace than for raw trace. So, the 3Ddipole localization of ICA-processed EEG traces is far more efficient than 3Dlocalization of raw EEG traces.Conclusion: This composite method helps to reduce redundant data forbetter feature extraction. The efficacy of the combined algorithm wasproven during medical trial.

P400Home Video Telemetry vs Inpatient Telemetry – an evaluativecomparison

S. Biswas, R. Luz, F. BrunnhuberKing’s College Hospital NHS Trust, Clinical Neurophysiology, London, UnitedKingdom

Objective: Evaluation of current attended Home VT practice, looking atvideo quality.Is video quality in Home Video Telemetry worse than Inpatient Telemetry?Method: One of the first studies completed to assess our Home VideoTelemetry (HVT) practice, which commenced in 2012, was to retrospec-tively compare the video quality against Inpatient Video Recording, consid-ering the latter as the gold standard. A pilot study was conducted in 2008using the Test-Re-Test design on 5 paediatric patients.Patients (n=28) referred for diagnostic or presurgical evaluation wereincluded in each group over a period of one year.Data were collected from referral spreadsheets, King’s ePR and telemetryarchive.Consensus scoring, by 2 scorers were carried out of the events only. Clustersof events were considered as one event.Variables compared included - visibility of body part of interest; visibilityof eyes; time of event; lighting; contrast; sound quality; quality of picturewhen amplified to 200%

Data were quantified and statistical evaluation carried out using Shapiro-Wilk and Chi-square tests. P-value of ≤0.05 was considered statisticallysignificant.Results:• Significant differences were demonstrated in - Lighting and Contrastbetween the two groups (Home VT performed better in both).

• Quality of Picture When Amplified was slightly better on the HVT group.Conclusion: HVT is not inferior to IPT; in fact it surpasses IPT in certainaspects like lighting and contrast. Results reconfirmed in a larger sample ofpatients with more variables.

P401A new approach for analysis of gamma event-related oscillatoryresponses in Alzheimer’s disease

G. Yener1,2,3,4, D.D. Emek-Savas1, B. Guentekin1, E. Basar11Istanbul Kultur University, Brain Dynamics, Cognition and Complex SystemsResearch Center, Istanbul, Turkey; 2Dokuz Eylul University, Brain DynamicsMultidisciplinary Research Center, Izmir, Turkey; 3Dokuz Eylul University,Department of Neurosciences, Izmir, Turkey; 4Dokuz Eylul University MedicalSchool, Department of Neurology, Izmir, Turkey

Background: The changes in brain dynamics of Alzheimer’s disease (AD)can be detected by brain event-related oscillations (ERO). Gamma oscil-latory responses were explored in many neuropsychiatric conditions andreported to be related to cognition.Methods: In this preliminary study, we explored ERO target gamma re-sponses of AD subjects (n=12) and healthy elderly controls (HC) (n=13)in four time frames of post-stimulus 0-200, 200-400, 400-600, 600-800ms and a wide window of 0-800 ms. We calculated event-related spectralpower (ERSP) in two frequency bands (28-39 Hz and 40-48 Hz). Repeatedmeasures of ANOVA was performed for 4× anteriorposterior, 3× coronal,2× frequency bands.Results: The group difference of gamma ERO responses was not evident,however there was a significant frequency × coronal × group effect(p<0.002) in 0-200 ms time window, showing lower amplitudes at 28-39Hz over right sided electrodes in AD. In 600-800 ms time interval, anterior-posterior x group effect was significant (p<0.044), indicating late responsesover frontal regions in AD. These significant findings disappeared whenanalysis was done in 0-800 msec time block. Analyses in time intervals of200-400 ms and 400-600 ms did not show any significant group effect.

Figure 1