Chapter 3

Question 1

lateral inhibition

Answer 1

inhibition transmitted across the retina (limulus experiment - crabs - can stimulate individual receptors - a light in A produced a large response, a light in B diminished response in A due to inhibition transmitted across lateral plexus)

Question 2

ommatidia

Answer 2

limullus eye made up of hundres of ommatidia, each has a small lense on surface of they eye directly over a receptor

Question 3

lightness

Answer 3

proportino of shades ranging from white to black

Question 4

The Herman Grid

Answer 4

3 x 3 black boxes with gray ‘ghost’ spots that are not physically present. DIAGRAM FOR INHIBITION EXPLANATION

Question 5

simultaneous contrast

Answer 5

perception of brightness/colour of one area is affected by presence of an adjacent/surrounding area (identical grey looks different surrounded by lighter and darker colours - lighter background = more lateral inhibition making grey look darker - dark background causes less firing of neurons and therefore less inhibition)

Question 6

White’s illusion

Answer 6

Not explained by lateral inhibition, example of belongingness- appearance is influenced by the area to which it appears to belong. In white’s illusion, A appears to be behind the bars and B appears on them DIAGRAM

Question 7

optic nerve

Answer 7

made up of axons of retinal ganglion cells

Question 8

Receptive field

Answer 8

Region of retina over which a cell in the visual system can be influenced by light (excitation/ihibition) as demonstrated by Hartline - isolated single fibre in the optic nerve in open eye cup of frog by teasing it apart where it leaves the eye and recorded from this nerve while shining light on the retina - it responded only to a small area

Question 9

centre surround organization

Answer 9

study of response in optic nerve fibres in cats found that receptive fields are organized in a centre-surround organization (centre responds differently than surround), shows that neurons may respond best to particular patterns of illumination

Question 10

excitatory area

Answer 10

spot of light increases firing

Question 11

inhibitory area

Answer 11

spot of light decreases firing

Question 12

centre surround antagonism

Answer 12

neuron responds best to light the size of excitatory centre, larger light decreases firing as it enters inhibitory portion

Question 13

Lateral geniculate nucleus

Answer 13

oval body located at the termination of optic tract on each side of the brain and acts as the primary relay center for visual information received from the retina of the eye, also receives feedback that helps determine input

Question 14

Hubel and Wiesel’s research on receptive fields

Answer 14

found that neurons at higher levels of visual system become more tuned to respond best to more and more specific stimuli (anaesthetized animal’s eyes focused on a screen w glasses so that image on screen would be on back of eye, eyes stayed stationary, found that points on screen correspond to points on retina)

Question 15

visual receiving area

Answer 15

occipital lobe where signals from retina first reach cortex - also called striate cortex due to striped appearance in cross section

Question 16

superior colliculus

Answer 16

receives some signals from eye (10%, 90 % to LGN) and plays role in movement of eyes

Question 17

simple cortical cells

Answer 17

cells in striate cortex with excitatory and inhibitory fields side by side

Question 18

orientation tuning curve

Answer 18

relationship between orientation and firing determined by measuring responses of simple cortical cells to bars of light with different orientations

Question 19

complex cells

Answer 19

respond best to moving, bar like stimuli with specific orientation (across entire field)

Question 20

end stopped cells

Answer 20

fire to moving lines of specific length or moving corners/angles

Question 21

feature detectors

Answer 21

simple, complex and end stopped cells

Question 22

stimulus physiology relationship

Answer 22

neurons respond to oriented lines

Question 23

physiology perception relationship

Answer 23

link between physiology and perception

Question 24

selective adaptation

Answer 24

neurons tuned to a specific property fire- causes fatigue and adaptation causing decreased rate of firing and reduced reaction when stimulus immediately presented again; selective because only neurons tuned to fire adapt

Question 25

contrast threshold

Answer 25

minimum intensity difference between two adjacent bars that can just be detected - to measure, determine contrast threshold, adapt person to one orientation by having them view high contrast adapting stimulus and remeasure (should be more difficult to see dim grating)

Question 26

selective rearing

Answer 26

animals reared in environment with only certain types of stimuli - neurons that respond to this stimuli more prevalent

Question 27

neural plasticity/experience dependent plasticity

Answer 27

response properties of neurons can be shaped by perceptual experience (long term as opposed to selective adaptation which is short term) - kitten stripes experiment

Question 28

Inferotemporal cortex

Answer 28

Gross - removing parts of IT in monkeys affected their ability to recognize objects - recorded from single neuron in IT and presented various stimuli over 3-4 day periods, found neurons that respond only to complex stimuli

Question 29

prosopagnosia

Answer 29

Humans with IT damage unable to recognize faces

Question 30

fusiform face area

Answer 30

underside of temporal lobe in humans, responds to faces

Question 31

sensory coding

Answer 31

how firing of neurons represents various characteristics of the environment (1 neuron - specificity coding, groups - group coding)

Question 32

specificity coding

Answer 32

proposes a particular object is represented by firing of a neurone that responds only to that and no other object(s)

Question 33

grandmother cell

Answer 33

neuron that fires to one specific stimulus (unlikely)

Question 34

distributed coding

Answer 34

representation by patterns of firing in a large number of neuron (evidence in all senses but usually large numbers are unneccesary)

Question 35

sparse coding

Answer 35

representation by patterns of firing by small group of neurons with majority remaining silent