Lecture 4: Visual System

Question 1

Retina

Answer 1

Sheet of cells along your eyeball, composed of the ganglion cell layer, bipolar cell layer, and photoreceptor layer

Question 2

Ganglion Cell Layer

Answer 2

Composed of ganglion cells, send information to the brain via optic nerve (ganglion cell axons)

Question 2

Photoreceptor laye

Answer 2

Made up of Rods and Cones

Question 3

Rods

Answer 3

Detect brightness, concentrated in periphery

Question 4

Cones

Answer 4

Detects color, concentrated in fovea. Not ass sensitive to light as rods

Question 5

Neuron

Answer 5

Composed of the dendrites, soma, and axon

Question 6

Dendrites

Answer 6

Where information comes into the neuron

Question 7

Soma

Answer 7

Cell body, contains the innerworkings of the cell

Question 8

Axon

Answer 8

Output process of the neuron

Question 9

Action Potential

Answer 9

Difference in charge between the inside and outside of the cell when the neuron fires

Question 9

Resting Potential

Answer 9

Difference in charge between the inside and outside of the axon at rest (-70mV when neuron is not firing)

Question 10

Threshold

Answer 10

Potential needs to cross this threshold to fire an action potential

Question 11

All-or-None

Answer 11

Action potential always has same strength, either you get all of it or none of it

Question 12

Propagation

Answer 12

Once past threshold, active process (ion pumping) propagates action potential down axon

Question 13

Refractory Period

Answer 13

Short period after firing before the neuron can fire again

Question 14

Neurotransmitters

Answer 14

Neurons communicate by sending these chemicals across very small gaps, synapses, between the cells

Question 15

Electrochemical Transmission

Answer 15

Involves an electrical action potential within cells, which releases chemical neurotransmitters into the synapse

Question 16

Summation

Answer 16

The sum of inhibitory and excitatory neurotransmitters, whichever is greater is expressed

Question 17

Excitatory

Answer 17

Increase the potential and make it more likely to pass the threshold

Question 18

Inhibitory

Answer 18

Decrease the potential and make it less likely to pass the threshold

Question 19

Center-Surround

Answer 19

Ganglion cells are either on-center off-surround, or off-center on-surround. This means that the cells are responsible for exiting action potentials when the “on” section receives light, and inhibits them when the “off” section is stimulated

Question 19

M-Cells

Answer 19

Project to magocelluar layers of LGN

Question 19

P-Cell

Answer 19

Projects to parvocellular layer of LGN

Question 20

Thalamus

Answer 20

Where most sensory input goes in the brain

Question 21

Lateral Geniculate Nucleus

Answer 21

Part of thalamus responsible for vision

Question 21

Magnocellular Layers

Answer 21

Neurons here have a transient (short burst) response, larger receptive fields, process movement and location

Question 22

Parvocellular Layers

Answer 22

Sustained response, small receptive field, processes patterns, colors, and form

Question 23

Cerebral Cortex

Answer 23

Sheet of grey matter outside of the brain, divided into 4 lobes, frontal, parietal, temporal, and occipital

Question 24

Simple cell

Answer 24

Likes a bar of light, specific orientation and retinal position

Question 25

Complex Cell

Answer 25

Likes edges/movement

Question 26

Hypercomplex Cells

Answer 26

Recognized very specific shapes, corners, and gaps

Question 27

Positron Emission Tomography (PET scanning)

Answer 27

Injection of a radioactive tracer, goes into the blood supply and emits positrons in the brain, which is scanned by a PET scanner to figure out neural activity

Question 28

Kohler Experiment

Answer 28

• Had people do a where task and a what task to see what would be activated
• Had people answer questions, either if objects are in the same spots or are the objects the same

Question 29

Population coding

Answer 29

We use populations of neurons to represent any stimulus or idea via patterns of fired neurons

Question 30

Identification

Answer 30

The ability to recognize what a stimulus is

Question 31

Localization

Answer 31

The ability to determine physical position or spatial location of a stimulus

Question 32

Patient A.H.

Answer 32

○ Modality specific impairment (visual)
○ Had trouble identifying where an object is based on vision alone, but could locate objects based on audio and/or touch

Question 32

Modality Specific Impairment

Answer 32

Problems specific to one sense or area of the brain (ex. vision but not hearing)