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

>

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laip

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Regions Of Interest analysis

>n=11

Left hemisphere Right hemisphereaIPS

raip

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FuG

Task-related activation

Action-oriented task Object-oriented task

jartwo

n=11

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Experiment 2 – Object vs. Grasp adaptation effect

time

Object-based Vs. Grasping-based Adaptation

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Regions Of Interest analysis

•Object-based adaptation in ventral ROIs.•Grasping-based adaptation in dorsal ROIs.

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SoSg

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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”