S T U A RT R E D

VISUAL PERCEPTION

ANY DIFFERENCE IN THE PICTURES?

WHAT IF THEY ARE RIGHT SIDE UP?

SERENO LAB APPROACHES TO COGNITIVE NEUROSCIENCE

• Behavioral Testing• Eye Movements• Touch Responses

• Monkey Physiology• Computational Modeling• Integration of All Approaches

VISUAL SYSTEM

THE VISUAL SYSTEM IS COMPLICATED

DIFFERENT STREAMS

WHAT AND WHERE PATHWAYS

A LITTLE BIT OF HISTORY

PARIETAL LESIONS CREATED DIFFICULTY WITH LOCALIZING OBJECTS

“… vision was evidently defective… it was able to pick up grains of rice scattered on the floor, but always with uncertainty as to their exact position.”

EARLY VIEW OF PARIETAL LESIONS IN HUMANS

• Sir Gordon Holmes (1918) described bilateral posterior parietal lesion patients with deficits in:• reaching and pointing to visual targets• Avoiding obstacles• Judging distance and size• No issues in object recognition

• W.R. Brain (1941)• Unilateral lesions• Contralateral neglect

A LITTLE BIT OF HISTORY

INABILITY TO DISCRIMINATE BETWEEN OBJECTS

“He appears no longer to discriminate between the different kinds of food ; e.g., he no longer picks out the currants from adish of food…”

KLUVER-BUCY SYNDROME

- Thought hallucinations preceding temporal lobe seizures were similar to mescaline induced hallucinations

- Removed temporal lobes from monkeys and administered mescaline

- No difference in effects of mescaline but…

- When off the drug, these monkeys exhibited “psychic blindness” or “visual agnosia”

- Along with a host of other symptoms…

UNGERLEIDER AND MISHKIN 1982

UNGERLEIDER AND MISHKIN 1982

RESULTS

STARE AT THE CENTER OF THE SCREEN

AKINETOPSIA

JJ, Fig 2.3 (Tanaka, 1991)

Functional Specialization- Ventral

Complex stimuli:

(a) star shape

(b) shape & texture

Fig 6.6

Functional Specialization-Ventral

Complex stimuli: hand

(a) orientation, not important

(b) position, not important

(c) bilateral, near fovea best

WHY ARE EYE MOVEMENTS SO IMPORTANT?

CONES DENSELY PACKED AT FOVEA

HISTORY OF EYE TRACKING

• Edmund Huey (1898)• Used plaster of paris cup molded to fit the cornea with

whole for subject to read through

ALFRED YARBUS (1950S AND 1960S)

MODERN EYE TRACKING

WHAT CAN WE LEARN ABOUT ATTENTION THROUGH EYE MOVEMENTS?

ATTENTION

• Attention filters out irrelevant information

• Reflexive vs voluntary attention• Reflexive attention involves the more

automatic response• Voluntary attention involves more thought

REFLEXIVE VS VOLUNTARY

REFLEXIVE VS VOLUNTARY

REFLEXIVE VS VOLUNTARY

REFLEXIVE VS VOLUNTARY

PROSACCADE AND ANTISACCADE TASK

WHAT’S REQUIRED FOR ANTISACCADE?

• Subject must inhibit the reflexive response and transform the stimulus location into a voluntary movement to look away

• Requires inhibition of saccade producing neurons in SC and FEF

• Where this inhibition is coming from remains a question, could be Basal Ganglia, SEF, or DLPFC

ERROR RATE IS MUCH LARGER FOR ANTISACCADE

PROSACCADE & ANTISACCADE RT