Task 4

Question 1

Definition visual acuity

Answer 1

= the smallest spatial detail that can be seen at 100% contrast

Question 2

Retinotopic map

Answer 2

electronic map of the retina on the cortex

Question 3

Cortical magnification

Answer 3

• representation on the cortex is distorted, with more space being allotted to locations near the fovea than location in the peripheral retina

Question 4

Organization of cortex in columns

• orientation columns
• location columns
• hypercolumns

Answer 4

• Orientation columns = each column containing cells that respond best to a particular orientation
• Location columns = all of the neurons within a location column have their receptive fields at the same location on the retina

Question 5

Ventral Pathway / What

Answer 5

= pathway leading from the striate cortex to the temporal lobe
- identifying objects

Question 6

Dorsal Pathway / Where

Answer 6

= pathway leading from the striate cortex to the parietal lobe

• locating objects
• “action pathway”
• can perceive size within an action

Question 7

Retinal Ganglion Cells and Stipes

Answer 7

• retinal ganglion cells: respond vigorously to spots of light
• spatial frequency too high —> ganglion cell responds weakly
• spatial frequency just right —> cell responds vigorously

Question 8

LGN (Lateral Geniculate Nucleus)

• magnocellular layers
• parvocellular layers
• topographical mapping

Answer 8

LGN: structure in the thalamus, part of the midbrain —> receives input from the retinal ganglion cells and has input and output connection to the visual cortex

• axons of retinal ganglion cells synapse in two lateral geniculate nuclei (one each hemisphere)
  
  • magnocellular layers: neurons in bottom layers —> input from M ganglion cells in the retina —> respond to large, fast-moving objects
• parvocellular layers: neurons in top two layers —> input from P ganglion cells —> responsible for processing details of stationary targets
• topographical mapping = orderly mapping of the world in the lateral geniculate nucleus and the visual cortex —> retinotopic-topic map
• LGN as location where various parts of the brain can modulate input from the eyes

Question 9

Striate Cortex

Answer 9

= primary visual cortex (V1)

• area of the cerebral cortex of teh brain that receives direct inputs from the LGN, as well as feedback from other brain areas
• six major layers
• sysgtematic topographical mapping of the visual field
• important features:
  
  • topography
  • magnification

Question 10

Receptive Fields in Striate Cortex

- Orientation tuning

Answer 10

= tendency of neurons in striate cortex to respond optimally to certain orientations and less to others

Question 11

Receptive Fields in Striate Cortex

- receptive-field properties

Answer 11

• cortical cells also respond well to gratings
• striate cortex as a filter
• majority of cells can be influenced by input from both left and right eye

Question 12

Receptive Fields in Striate Cortex

- simple cell

Answer 12

= cortical neuron whose receptive field has clearly defined excitatory or inhibitory regions —> “phase-sensitive”

Question 13

Receptive Fields in Striate Cortex

- complex cell

Answer 13

= cortical neuron whose receptive field does not have clearly defined excitatory and inhibitory regions —> “phase-insensitive”

Question 14

Coding

• specificity coding
• population coding
• sparse coding

Answer 14

• Specificity coding: idea that an object could be represented by the firing of a specialized neuron that responds only to that object
• population coding: representation of a particular object by the pattern of firing of a large number of neurons
• sparse coding: when a particular object is represented by a pattern of firing of only a small group of neurons (majority of neurons being silent)