The visual pathways
Ventral pathway receptive field properties 0
1
TE receptive fieldV4 receptive field V1 receptive field
“What” and “Where” visual streams
From:Mishkin, Ungerleider& Macko (1983)
Functional organization of the visual systemSegregation of form, color, movement, and depth.
Livingstone & Hubel, 1988
Magno and parvo pathwaysOrigin of visual pathways: The LGN
Contributions of M and P pathways to vision
Schiller & Logothetis, 1990
Discrimination Detection
Which stimulus is the
“odd one out”?
Where is the target stimulus?
Experimental Conditions
Shape perception is impaired at isoluminance
Major Behavioral Major Behavioral Results of Results of
““M” and “P” M” and “P” Lesions in the Lesions in the
LGNLGN
Normal
Normal
Normal
Normal
Normal
Normal
Deficit
Deficit
Deficit
Deficit
Deficit
Deficit
Function Tested Result of“P” Lesion
Result of“M” Lesion
Color vision
Texture Perception
Pattern Perception
Acuity
Contrast Perception
Flicker Perception
The monkey & human cortex
Hierarchy of visual processing stages
Vision for action
Object recognition
Goodale & Milner 1992
Goodale & milner’s Subject DF
A set of 12 asymmetric shapes
Same set was used for:
1) same/different discrimination.
2) Grasping movements
Comparing RV and DFin the same/different task
Points of 2-finger grasping
MRI vs. fMRI
neural activity blood oxygen fMRI signal
MRI fMRI
one image
high resolution(1 mm)
low resolution(3 mm)
fMRI Blood Oxygenation Level Dependent (BOLD) signal
indirect measure of neural activity
…
Source: Jody Culham’s fMRI for Dummies web site
Physiological basis of fMRI
Statistical Mapsuperimposed on
anatomical MRI image
~12s
Functional images
Time
Condition 1
Condition 2 ...
~ 9 min
Time
fMRISignal
(% change)
ROI Time Course
Condition
Activation Statistics
Region of interest (ROI)
Source: Jody Culham’s fMRI for Dummies web site
A Look at D.F.’s brain
Objects> scrambled objects
An event related fMRI of DF’s grasping
The Ebbinghaus illusion
Dissociation of perception and action in the Ebbinghaus illusion
Shmuelof & Zohary, Neuron 2005
fMRI study: Viewing object manipulation clips
• Signa Horizon 1.5T GE scanner.
• Gradient-echo EPI sequence (TR = 3000, TE = 55, flip angle = 90, FOV: 2424 cm2 ).
• 27 nearly-axial slices of 4mm thickness and 1mm gap.
• T1-weighted high resolution (111mm) anatomical images
Hand
Right Left
Experiment 1 – laterality effect
Object
"Name the object”
Action“how many fingers
touch the object”?
Task
Action vs. Object representation
>
-1
0
1
2
-6 -3 0 3 6 9 12 15 18
rfg
0
1
2
lfg
0
1
2FuG
-1
0
1
2
-6 -3 0 3 6 9 12 15 18
*
laip
0
1
2
% s
ign
al
ch
an
ge
-1
0
1
2
-6 -3 0 3 6 9 12 15 18
sec
*
Regions Of Interest analysis
>n=11
Left hemisphere Right hemisphereaIPS
raip
0
1
2
-1
0
1
2
-6 -3 0 3 6 9 12 15 18
**
aIPS
FuG
Task-related activation
Action-oriented task Object-oriented task
jartwo
n=11
<
Experiment 2 – Object vs. Grasp adaptation effect
time
Object-based Vs. Grasping-based Adaptation
0
1
2
Regions Of Interest analysis
•Object-based adaptation in ventral ROIs.•Grasping-based adaptation in dorsal ROIs.
0
1
2
0
1
2
0
1
2
% s
igna
l cha
nge
aIPS
FuG
SoSg
SoDg
DoSg
DoDg
Milner and Goodale’s conceptual novelty
• The division between these streams is task rather than stimulus based.
• Rather than a division of stimulus attributes – the division relates to “how it’s going to be used”