Occipital and temporal lobes

Question 1

hierarchy and functional differentiation

Answer 1

• complexity of visual representation increasing for retina to visual association cortices
• functional differentiation - different neuron types processing visual stimuli

Question 2

simple features

Answer 2

• light intensity and wavelength
• 2d position in visual field
  >
• combination via parallel channels
  >
• complex visual representations
• integrated info, surface, spatial relationships and movement
• integration with sensory modalities

Question 3

visual processing in extrastriate cortex

Answer 3

neurons signal global properties of visual scenes and objects

Question 4

global colour vs component wavelength

Answer 4

• perceived colours depend on wavelength reflected by objects and surroundings
• some V4 are colour sensitive vs neurons in visual pathway and V2 wavelength sensitive

Question 5

two visual processing streams

Answer 5

V1 > visual info processing mediated by 2 streams anatomically different
- dorsal and ventral stream
visual streams
inferior temporal lobe - lesions in macaques impair discrimination not location
posterior parietal lobe - impair location not discrimination

Question 6

visual streams - Milner and Goodale

Answer 6

• ventral streams process visual into for object perception
• dorsal stream process for visuo-spatial guided action
• patients with occipito-temporal brain damage show visual agnosia but intact guided actions
• posterior parietal lobe lesions show optic ataxia

Question 7

patient DF

Answer 7

bilateral ventral stream lesions has visual agnosia but guided reaching: act on visual stimulus, unable to make perceptual judgement

Question 8

visual perception and memory inferior temporal cortex

Answer 8

• receive inputs from extrastriate cortex and forms final stage in visual processing hierarchy of ventral stream
• neurons inferior temporal cortex respond selectively
  responses show:
• invariance in size, orientation etc,
• sustained activity in absence of visual object, STM

Question 9

face cells

Answer 9

highly selective response to faces
- compared to ‘gnostic units’
- areas showing selective responses to faces identified in inferior temporal love using FMRI

Question 10

medial temporal lobe

Answer 10

• end of visual processing hierarchy, combine inputs from ventral and dorsal streams, output from sensory modalities
• elaborate visual representations further and generate multi-modal representations

HM
- severe deficits in memory
- other cognitive functions intact
hippocampal face cells
- rats
- humans hippocampus during virtual navigation