Answers: graded potentials and action potentials. Remember that photoreceptors provide gradual responses to light while ganglion cells 'fire' all-or-nothing action potentials.

2. [TRUE or FALSE] Cones respond to light by emitting an increased amount of neurotransmitter.

Answer: False.

3. In 25 words or less, describe what a "concentric" receptive field is.

Answer: a receptive field with opposite center and surround portions; one excitatory, one inhibitory (ON-center/OFF-surround or vice versa).

4. Quickly sketch the receptive field of a simple cell.

Answer: Any receptive field with an oriented bar (+ or -) and opposite "flankers" was fine (see Lecture 3 notes). Several people confused simple cells with retinal ganglion cells and so drew concentric center-surround receptive fields. Simple cells are in V1.

5. [TRUE or FALSE] Outputs from the left half of the right retina (e.g., right visual field in the right eye) cross at the optic chiasm.

Answer: True. Remember, right visual field, left hemisphere. The right visual field in the right eye must therefore make it to the left hemisphere; it does so by crossing at the optic chiasm.

6. [TRUE or FALSE] Magnocellular ("M-pathway") retinal ganglion cells exhibit differential responses to different colors ("color-opponent" responses).

Answer=FALSE. P-pathway cells exhibit this property.

7. Name the 4 lobes of the brain, and underline the lobe in which primary visual cortex lies.

Answer: Frontal, Parietal, Temporal, Occipital.

8. Which of the following is not a possible characteristic of V1 neurons:

a. lateral inhibition

b. direction-selectivity

c. organization into ocular dominance columns

d. "end-stopped" receptive fields

e. none; all of the above are possible characteristics

Answer: e.

9. (2 points) Name the 4 criteria commonly used for separating and defining visual brain areas.

Answer: FACT:

• Function
• Architecture (also accepted: Anatomy)
• Connections
• Topography or Retinotopy