Types in Striate Cortex - Introduction to Sensation and Perception - Lecture Notes, Study notes for Brain and Cognitive Science. Alliance University
nagam-ram
nagam-ram22 November 2012

Types in Striate Cortex - Introduction to Sensation and Perception - Lecture Notes, Study notes for Brain and Cognitive Science. Alliance University

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Types in Striate Cortex, Receptive Field Properties, Neurons in the Visual Cortex, Receptive Field Types, Single Cell Recording, Hubel and Wiesel Hierarchical RF Taxonomy, Mechanism of Cortical Simple Cell, Complex Cell ...
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Types in striate cortex

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1 Receptive field properties of neurons in the visual cortex From eye to brain continued…

2 Neurons in the visual cortex • Nobel Prize for Medicine and Physiology in 1981 for work describing cell properties in

cat primary visual cortex with Roger Sperry

3 Receptive field types 4 Single cell recording 5 Laminar organization, example: LGN input to cortex

6 Hubel and Wiesel’s hierarchical RF taxonomy 1.simple - cells response to stimuli can be understood in terms of “on” and

“off” regions 2.complex 3.hypercomplex ( end-stopped ) 4.hypercomplex of higher order

7 simple cell • Defined ON and OFF regions

• This accounts for responses to bars of specific orientation 8 Simple cell: responses to flashed bar

• Shows orientation and position selectivity • Predicted from the arrangement of ON and OFF areas

9 Simple cell tuning curve 10 Hubel and Wiesel video of cortical simple cell receptive field

• no response to diffuse light • inhibition from dark bar in RF centre • mechanism?

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12 Possible mechanism of cortical simple cell 13 Complex cell

• no response to spots • generalized orientation selectivity over an extended region

14 Plotting a complex cell’s receptive field-- video • excitatory response area is large, not confined • cells respond to stationary and moving targets, bidirectional • cells respond to bright and dark bars

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16 Hubel and Wiesel’s theory of a mechanism for a complex cell

17 hypercomplex (end-stopping) • another stage beyond complex cells ? • length summation properties

– for comparison - standard – end stopping

18 Standard complex cell 19 end stopping hypercomplex cell 20

21 What is the mechanism for hypercomplex end stopping cells?

22 Stages of visual processing 23 Direction selectivity 24 Sample MC test questions:

The proximal stimulus in vision refers to: a) the object outside of the eye

b) the integrating perceptual process in the brain c) a three-dimensional object in the environment

d) the inverted retinal image of an object

An eye that focuses light exactly on the retina is termed: a) myopic

b) hypermetropic

c) hyperopic

d) emmetropic

When the lens thickens or flattens in order to bring an image into focus on the retina, this is called:

a) acomodation

b) accomodation

c) accommodation

d) acommodation

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