Visual Processing Flashcards
Visual Processing objectives
- Identify and describe different levels of hierarchical processing in thalamus
- Identify and describe different levels of hierarchical processing in primary visual cortex
- Know the difference between dorsal vs ventral streams of information processing
- Compare how damage to different areas of cortex involved in vision produce different visual disorders
Pathways from retina to primary visual cortex
Primary Visual Cortex V1
location and organization
Located in occipital lobe
• Organization for:
• L vs R eye
• Location
• Color vs movement
• (we won’t go over in
this class)
• Shape/orientation
Organization:
L vs R eye
Location
Shape/orientation
L vs R eye:
Connects to adjacent strips of cortex forming striations (zebralike stripes) called ocular dominance columns
Location:
V1 is organized retinotopically. Neighboring regions of visual space are represented by neighboring neurons. More space for fovea.
Shape/Orientation:
Orientation selectivity - neurons in V1 respond best to bars of light that are oriented in a particular direction. Different neurons have different preferences. Vertical bar is closest to actual image.
Damage to Visual Cortex results in ?
Damage to Ventral Stream results in ?
Damage to Dorsal Stream results in ?
Visual cortex damage = cortical blindness (loss of vision on side opposite of damage)
Ventral Stream damage = visual agnosia (visual recognition of objects) OR prosopagnosia (inability to recognize faces)
- Difference in symptoms derives from the fact that different categories of objects are segregated in different locations in the ventral visual stream
Dorsal stream damage = Deficits in spatial abilities and hand-eye coordination
- Visual Neglect - inability to perceive regions of space
- Optic Ataxia - Inability to guide movements based on vision
- Motion Blindness (akinetopsia) - The inability to perceive motion. Strobe light effect.
