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Lab write up due this Friday

Proposal due Monday March 6

Late reports, one mark out of 20 for each

day late.

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Ch. 11

Vision - central processes

Ultimately visual perception

Also:

Adjust size of the pupil

Direct eyes to the targets of interes

Regulate homeostatic behaviors to L/D cycle

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Primary Visual Pathway

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Primary Visual Cortex

AKA

Striate cortex

Brodmanns area 17 or VI

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Optic Disc

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Blind Spot:

Test your blind spot.

Optic disc is located on the nasal side of theretina.

With both eyes open, information about thecorresponding region of visual space comes

from the temporal side of the contralateralretina.

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Blind Spot

With one eye, blind spot is undetected.

Why?

Visual cortex receptive fields fill in with

cortical mechanisms that integrate

information from the visual field

(somehow).

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Optic Disc

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Optic Chiasm

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x

O ti T t

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Optic Tract

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Decussation

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Ganglion cell axons to lateral geniculate nucleus

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Another target of ganglion cells:

Pretectum co-ordinates pupillary light reflex

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Another target of ganglion cells:

suprachiasmatic nucleus

(Retino-hypothalamic pathway)

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Suprachiasmatic nucleus

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Another target for ganglion cells:

superior colliculus

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Another target for ganglion cells:

superior colliculus

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RETINOTOPIC REPRESENTATION OF

THE VISUAL FIELD

Each eye sees a part of the visual

space that defines its visual field

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VISUAL FIELD

Temporal visual fields are more

extensive than the nasal visual fields

Vision in the peripheral field is mono-

ocular

Most of the rest of the visual field is

seen by both eyes.

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Map is maintained in the LGN

Maintained by the visual cortex

Fovea is in the back of the visual cortex

Peripheral is progressively more anterior

Sensory surface reflects density of

receptors

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Upper visual field

Calcarine

sulcus

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Hubel and Weisel

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Hubel and Weisel

Visual cortex responses using micro-electrodes

Respond ot light/dark bars or edges Only if in a particular orientation

Peak frequency depends on angle,preferred orientation

All edges representations were equallyrepresented

Orientation selective neurons

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Visual Cortex

Simple cells - Spatially distinct on and offzones

Complex cells - receptive field has a mixtureof on and off zones

Length cells - respond to length of a bar thatwas moved across a receptive field

Direction cells - respond to direction of a barmoving across the receptive field.

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Still do not understand the mechanisms

responsible for generating these

selective responses.

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Complex cell

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Complex

Cell

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Binocular vision

Individual LGN neurons are mono-ocular

driven.

How are neurons with different receptivefields arranged within the striate cortex?

A column of cells has similar response

properties

Adjacent columns have similar response

properties.

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Visual Cortex

Composed of repeating units that

contain all the neuronal machinery

necessary to analyze a small region ofvisual space for a variety of different

stimulus attributes.