week 3 - lateral inhibition + receptive fields

Question 1

lateral inhibition

Answer 1

neuron “taking the spotlight” and inhibiting everything around them

Question 2

lateral inhibition in pain receptors

Answer 2

when we stub our toe we usually rub around the painful area, we are laterally inhibiting it

Question 3

Explain the process of lateral inhibition and simultaneous contrast.

Answer 3

• Occurs when our perception of brightness/color of one area is affected by the presence of an adjacent/surrounding area
• People see an illusion of changed brightness or color

Question 4

Explain lateral inhibition in the interior box example.

Answer 4

• Lighter side has higher levels of lateral inhibition in comparison to darker box
• Because the lighter side is receiving more lateral inhibition, the middle box is perceived as darker even though they are the same color

Question 5

What illusion seems to not be affected by lateral inhibition? Why?

Answer 5

• White’s illusion
• Rectangle surrounded by black seems darker than rectangle surrounded by white
• However, lateral inhibition would state that the rectangle surrounded by white would be darker

Question 6

Explain the actual lateral inhibition that occurs in White’s illusion.

Answer 6

• Illusion has to do with the background of rectangle
• A is on white background and B is on black background
• A seems darker and B seems lighter

Question 7

Why is lateral inhibition important?

Answer 7

gives us the ability to perceive objects and define edges and lines, and therefore accurately recognize objects

Question 8

belongingness

Answer 8

an area’s appearance is affected by where we perceive it belongs

Question 9

optic nerve

Answer 9

collection of ganglion cells’ axons

Question 10

processing from retina to visual cortex and beyond

Answer 10

• area of receptors that affect firing rate of a given neuron in the circuit
• receptive fields are determined by monitoring of a single cell response

Question 11

center surround organization

Answer 11

when a spot of light is pointed directly at an excitatory/inhibitory center/surround, there would be an increase/decrease of ganglion cell nerve fiber firing

Question 12

excitatory center and inhibitory surround

Answer 12

• increase of ganglion cell nerve fiber firing if center is stimulated
• If we were to stimulate the negative/inhibitory surround, we would expect a decrease in ganglion cell nerve fiber firing

Question 13

inhibitory center and excitatory surround

Answer 13

• highest degree of firing occurs when surround is activated by illumination
• the focus of illumination on the center decreases the firing

Question 14

What is the center surround organization based on?

Answer 14

based on size of illumination

Question 15

Hubel and Wiesel’s rationale for studying receptive fields

Answer 15

• Had cats look at fixation points on a screen, they are able to record the optic nerve.
• Able to map out the rest of the visual system

Question 16

What is the visual map Hubel and Wiesel discovered?

Answer 16

retina –> optic nerve –> LGN –> visual cortex –> temporal + parietal lobe –> frontal lobe

Question 17

lateral geniculate nucleus

Answer 17

• found in thalamus
• center-surround receptive field
• regulates info from retina

Question 18

feature detectors

Answer 18

• neurons that fire to specific features of a stimulus
• much more complex stimuli that are able to elicit the activation of our visual cortex
• neurons in our visual cortex

Question 19

optic nerve fiber (ganglion cell) receptive field

Answer 19

center surround receptive field

Question 20

LGN receptive field

Answer 20

• center surround receptive fields
• very similar to ganglion cell