visual processing

• What shape are the receptive fields in the retina?

  Circular
• What happens when light is applied across a portion of the retina?

  It evokes a response in a bipolar cell
• What is the area of the retina called that responds to light?

  Receptive field
• How do bipolar cells receive input from photoreceptors?

  They receive direct glutamate input from the receptive field centre
• What role do horizontal cells play in the retina?

  They provide indirect input to bipolar cells from surrounding photoreceptors
• What is the effect of light hitting the receptive field centre compared to the surround?

  They have opposite effects on the bipolar cells
• What is the direct route for activation of bipolar cells?

  Centre illumination
• What is the indirect route for activation of bipolar cells?

  Surround illumination
• What are the two types of retinal bipolar cells?

  On and off bipolar cells
• What happens to glutamate release from photoreceptors in darkness?

  Glutamate is released
• What happens to glutamate release from photoreceptors in light?

  There is less or no glutamate release
• How are on and off ganglion cells related to bipolar cells?

  On bipolar cells synapse with on ganglion cells
• What determines the receptive fields of ganglion cells?

  They are determined by the bipolar cells they are in contact with
• What is the main stimulation in vision?

  Differences
• What does the appearance of an object depend on?

  The contrast between the object and its background
• Why do we not have a precise reproduction of our visual field?

  We only need to know differences, not absolute reality
• What is the lateral geniculate nucleus (LGN) segregated into?

  Layers
• How is input from rods and cones treated in the LGN?

  Input from rods and cones remains separate
• What are the magnocellular (M layer) LGN layers responsible for?

  Input from rods, bipolar, and ganglion cells
• What do the parvocellular (P layer) LGN layers receive input from?

  Input from cones, bipolar, and ganglion cells
• How is input from the two eyes treated in the LGN?

  Input from the two eyes remains separate
• What do koniocellular LGN layers receive input from?

  NonM-nonP types of retinal ganglion cells
• What is Brodmann's area 17 known as?

  The visual cortex
• What is the primary target of geniculo-cortical projection?

  Connections made primarily with layer 4 of the visual cortex
• What is V1 also called?

  Striate cortex
• What is the arrangement of cells in V1 related to?

  Specific orientation of light
• What is orientation selectivity in V1 cells?

  It arises from receptive fields elongated along a particular axis
• What do orientation columns and oculomotor dominance help discriminate?

  Differences from each eye and shape
• What does a 2x2mm area of visual cortex contain?

  Ocular dominance columns and complete sampling of all 180-degree possible orientations
• What are blobs in the visual cortex concerned with?

  Color rather than orientation
• What do complex cells in V1 respond to?

  Edges crossing a receptive field
• How do complex cells differ from simple cells?

  Complex cells are insensitive to the position of the edge
• What do complex cells integrate information from?

  Many simple cells synapse to one complex cell
• What type of responses do complex cells show?

  On or off responses to stimulus onset/offset
• How are cells in V1 arranged?

  In a precise fashion with preferred orientation within a column
• What happens to information from V1?

  It is sent to V2 and V3
• What are the two processing streams in the visual system?

  Dorsal and ventral visual streams
• What does the middle temporal area process?

  Object motion
• What does the medial superior temporal area process?

  Linear, radial, and circular motion
• What does V4 specialize in?

  Orientation and color selectivity