Ch 12: identifying stimuli and stimulus objects

Question 1

Grandmother cell coding scheme vs population coding scheme

Answer 1

1. Grandmother cell coding scheme:
   - there is one neuron dedicated to identifying each possible stimulus object.
2. Population coding scheme:
   - seeing an object activates a specific COMBINATION of neurons that collectively represent the object.
   - some of these neurons might also be active when you see a different stimulus.
   - the code does not reside in the activity of the individual neurons but in their combination.

Question 2

____ ___ is the pathway that uses spatial information to guide eye, head, and hand movements.
____ ___ is the pathway concerned primarily with object identification

Answer 2

DORSAL STREAM is the pathway that uses spatial information to guide eye, head, and hand movements.
VENTRAL STREAM is the pathway concerned primarily with object identification

Question 3

dorsal and ventral streams both originate from ___

Answer 3

V1

Question 4

The dorsal stream originates in the ___ of the ___ lobe and then passes through the ___ ___ ___ to the ___ and __ cortices

Answer 4

The dorsal stream originates in the V1 of the OCCIPITAL lobe and then passes through the POSTERIOR PARIETAL CORTEX to the PREMOTOR and MOTOR cortices

Question 5

The ventral stream proceeds from __ to the inferior portion of the ___ ___

Answer 5

The ventral stream proceeds from V1 to the inferior portion of the TEMPORAL LOBE

Question 6

how do on-center retinal ganglion cells respond to bright spots presented at the center of their spatial receptive field?

Answer 6

by increasing in firing rate

Question 7

How do on-center retinal ganglion cells respond when they are stimulated with a ring of light surrounding the center of their receptive field?

Answer 7

they lower their firing rates

Question 8

stimulating on-center retinal ganglion cells with uniform light yields what response?

Answer 8

no response (no change in firing rate)

Question 9

off-center retinal ganglion cells respond with increased firing rates to:

Answer 9

dark spots in the receptive field’s center

Question 10

on- and off-center ganglion cells receive input from:

Answer 10

ON and OFF bipolar cells

Question 11

surround cone inhibitory influence is due primarily to retinal ____ cells

Answer 11

surround cone inhibitory influence is due primarily to retinal HORIZONTAL cells

Question 12

the input from photoreceptors onto horizontal cells is _____, whereas the output of horizontal cells back onto photoreceptors is ______

Answer 12

the input from photoreceptors onto horizontal cells is EXCITATORY, whereas the output of horizontal cells back onto photoreceptors is INHIBITORY

Question 13

What generates the center-surround organization and what is its purpose?

Answer 13

LATERAL INHIBITION (surround inhibition) through HORIZONTAL CELLS generates the center-surround organization.
It SHARPENS LOCAL STIMULUS CONTRAST

Question 14

Our visual system is more sensitive to ___ luminance contrast than to ___ luminance

Answer 14

Our visual system is more sensitive to LOCAL luminance contrast than to ABSOLUTE luminance

Question 15

Significance of Mach bands

Answer 15

-at the boundary between luminance intensites, the lighter coloured square seems to be even brighter and the darker square seems to be darker in colour.
-this is because lateral inhibition enhances the contrast when there are zones of different intensities
(light edge on dark square, dark edge on light square)

Question 16

which brain region provides the major visual input to V1?

Answer 16

Lateral geniculate nucleus (LGN)

Question 17

The LGN has ___ distinct layers

Answer 17

6

Question 18

Do V1 neurons respond better to lines and edges or to circular spots?

Answer 18

lines and edges

Question 19

V1 simple cells respond best to lines presented at a ___ ____ and in a ____ ____

Answer 19

V1 simple cells respond best to lines presented at a SPECFIC LOCATION and in a PARTICULAR ORIENTATION

Question 20

What did Hubel and Wiesel hypothesize what the reason V1 cells become sensitive to lines rather than spots?

Answer 20

They hypothesized that each simple cell receives CONVERGING INPUT from multiple geniculate neurons whose receptive field centers are ALL THE SAME TYPE and ARRANGED IN A LINE

Question 21

If the receptive fields of the geniculate neurons converging on a V1 neuron are all of the ON-CENTER type, then…

Answer 21

the V1 simple cell should respond to a BRIGHT line that falls across those on-centers

Question 22

If the receptive fields of the geniculate neurons converging on a V1 neuron are all of the OFF-CENTER type, then…

Answer 22

the V1 simple cell should respond best to a DARK line tht covers those off-centers

Question 23

direction sensitivity is generated mainly in the __ __

Answer 23

visual cortex

Question 24

V1 Simple vs complex cells

Answer 24

• both respond preferentially to bright or dark lines and edges in a particular orientation
• complex cells receive converging input from multiple V1 simple cells
• complex cells respond to activity in any of their converging input lines, whereas simple cells fire only when a particular combination of geniculate neurons is excited

Question 25

Sine-wave grating

Answer 25

a series of parallel bands varying continuously in brightness according to a sine-wave function, along a line perpendicular to their lengths

Question 26

Spatial frequency

Answer 26

the relative width of the bands in a sine-wave grating, measured in cycles per degree of visual angle

Question 27

the visual angle between adjacent sine waves is ___ when the waves are closer together

Answer 27

smaller

Question 28

Although Hubel and Wiesel's studies suggested that neurons in V1 detected lines and edges, subsequent research found that they actually responded best to ________

Answer 28

sine-wave gratings

Question 29

what is the spatial frequency of a sine-wave grating?

Answer 29

its variation in brightness measured in cycles per degree of visual angle

Question 30

small objects, details within large objects, and large objects with sharp edges provide a signal rich in ___ ______

Answer 30

high frequencies

Question 31

large areas of light and dark are represented by __ ___

Answer 31

low frequencies

Question 32

most important visual information is that contained in ___ spatial frequencies

Answer 32

low

Question 33

how does ISOI work?

Answer 33

Intrinsic signal optical imaging (ISOI) measures changes in tissue oxygenation. Oxygenated and deoxygenated blood absorb light differently. Orange light directed at animal's exposed cortex. ISOI measures dip in blood oxygenation due to neural activity. images are taken

Question 34

aperture problem

Answer 34

- seen in neurons with a SMALL receptive field - When looking at a moving straight line through an aperture, the edge always seems to move at right angles to its long axis, regardless of the underlying object's true direction of motion

Question 35

How can the aperture problem be solved?

Answer 35

by combining info from multiple neurons | ie. multiple edges in multiple apertures

Question 36

Results from the monkey experiment where their MT cells were stimulated

Answer 36

-monkeys failed to identify the movement direction correctly when the preferred direction of the stimulated neurons differed from that of the dots that were presented. THE ELECTRICAL STIMUATION BIASES THE MONKEY'S PERCEPTION OF MOVEMENT DIRECTION IN FAVOR OF THE DIRECTION TO WHICH THE STIMULATED NEURONS ARE TUNED AND AGAINST THE OPPOSITE DIRECTION

Question 37

MT in "MT neurons" stands for

Answer 37

middle temporal

Question 38

Red-green opponent cells compare the activation levels of __ and ___ cones

Answer 38

L- and M-cones

Question 39

blue-yellow opponent cells compare the activity if the __ cones to the combined activity of the __ and __ cones

Answer 39

blue-yellow opponent cells compare the activity if the S-cones to the combined activity of the L- and M-cones

Question 40

bottom-up vs top-down spatial attention

Answer 40

bottom-up: something captures your attention | top-down: looking towards an area to see if something is happening

Question 41

double opponent cells

Answer 41

give opposite responses to opposite wavelengths in center vs. surround

Question 42

the phenomenon that perception of colour barely changes as it gets darker is called

Answer 42

color constancy

Question 43

colour-sensitive patches in the anterior occipital and posterior temporal lobes are called ___

Answer 43

globs

Question 44

what do Face-selective neurons respond to

Answer 44

respond strongly to faces and poorly to scrambles faces or other stimuli. They respond more poorly to faces without eyes than with eyes.

Question 45

What happens when you electrically stimulate face-selective cells?

Answer 45

perception becomes biased in favour of faces

Question 46

What is the name of the largest face-selective patch in the inferior portion of the temporal lobe?

Answer 46

fusiform face area

Question 47

higher neural response for (basic/superordinate) words

Answer 47

basic

Question 48

Category-sensitive neurons can be found in the:

Answer 48

inferior temporal cortex

Question 49

what is agnosia?

Answer 49

deficit in object identification

Question 50

porisipagnosia

Answer 50

inability to identify faces | -problems in conducting in INFERIOR LONGITUDINAL FASCICULUS

Question 51

cell assembly in the olfactory cortex

Answer 51

repeated exposure to a specific olfactory stimulus forges the olfactory cortex neurons activated by that stimulus into a coherent entity (cell assembly)

Question 52

different olfactory cortex nerves converge onto a single ___ ___, which diverges onto ___ ___

Answer 52

different olfactory cortex nerves converge onto a single OLFACTORY GLOMERULUS, which diverges onto OLFACTORY EPITHELIUM

Question 53

the auditory cortex ascends to the neocortex though a series of ___, ____ and ___ nuclei

Answer 53

the auditory cortex ascends to the neocortex though a series of MEDULLARY, MIDBRAIN and THALAMIC nuclei

Question 54

Whee is gthe auditory cortex?

Answer 54

it lies along the superior edge of the temporal lobe

Question 55

auditory cortex is divisible into 3 regions:

Answer 55

core, belt, and parabelt regions

Question 56

What region of the audtory cortex is the primary auditory cortex (A1) part of?

Answer 56

core

Question 57

when the belt area is damaged, what can it produce?

Answer 57

an auditory agnosia

Question 58

damage to the left belt results in __ __ and damage in the right belt results in ___

Answer 58

damage to the left belt results in RECEPTIVE APHASIA (ie. Wernicke's aphasia) and damage in the right belt results in AMUSIA