Task 4 on columns and pathways

Question 1

Lateral Geniculate Nucleus

Answer 1

o The axons of retinal ganglion cell synapses in the two LGNs, one in each cerebral hemisphere
o Important for connections on the way to the brain, so it can modulate input from the eyes

Question 2

Organisation of LGN

Answer 2

The left LGN receives input from the left side of both eyes ad the right LGN receives input from the right site of both eyes, second each layer of the LGNs receive from one or the other eye
 Layers 1, 4, and 6 of the right LGN receive input from the left eye (contralateral=referring to the opposite site of the body)
 Layers 2, 3, and 5 of the right LGN receive input from the right eye, ipsilateral

Question 3

Topographical mapping/Retinal topic map

Answer 3

The right side of the world falls on the left side of the retina, whose ganglion cells project it to the right. Cells that are close to each other in the LGN are close to each other in the Visual cortex
o Six layered structure

Question 4

Magnocellular layers

Answer 4

(bottom two layers), large, receive input from M ganglion cells in the retina
• Respond to large, fast-moving objects

Question 5

Parvocellular layers

Answer 5

(top four layers), small, receive input from the P ganglion cells in the retina
• Responsible for processing details of stationary objects

Question 6

Koniocellular cell

Answer 6

A neuron located between the magnocellular and the parvocellular layers, involved in different aspects of processing

Question 7

The striate Cortex

Answer 7

(primary visual cortex) receives direct input from the LGN, as well as the feedback from other brain areas
Consists of 6 major layers, some of which have sublayers, LGN projects mainly but not exclusively to the 4th layer, with magnocellular axons coming in to the upper part of Layer 4c (known as 4cα) and pavorcellular axons project to the lower part of layer 4c (known as 4cβ)

Question 8

Cortical magnification

Answer 8

The amount of cortical area devoted to a specific region in the optical field (fovea is dedicated to a bigger part in the striate cortex than the periphery

Question 9

Receptive fields in the striate cortex

Answer 9

respond more to bares, line, edges than to round spots

Question 10

Orientational tuning

Answer 10

The tendency of neurons in the striate cortex to respond optimally to certain orientations and less to others, more response to horizontal and vertical targets

Question 11

Ocular dominance

Answer 11

the property of the receptive fields int the striate cortex that they respond more rapidly to stimuli in the one eye than in the other eye

Question 12

Simple cells

Answer 12

A cortical neuron whose receptive fields have a clearly defined excitatory and inhibitory region
 Edge detector: is most highly exited when there is light on one site and darkness on the other site
 Stripe detectors: reacts best to light that has a particular width, surrounded with darkness on both sides

Question 13

Complex cells

Answer 13

A cortical neuron whose receptive fields does not have clearly defined excitatory and inhibitory regions, it will respond regardless where the stripe is presented

Question 14

End stopping

Answer 14

The process by which a cell in the cortex first increase firing as the bar length increases to fill up it receptive field. And then decreases when the bar goes further than the receptive field
 Important to detect luminance boundaries and discontinuities, responds more when contrast is higher

Question 15

Column

Answer 15

: A vertical arrangement of neurons. Neurons within a single column tend to have similar receptor fields and similar orientation preferences, arises as a consequence of statistical wiring mechanisms combined with evenly spread mosaics of On and Off centre retinal ganglion cells

Question 16

Hypercolumn

Answer 16

A 1-mm block of striate cortex containing two sets of columns, each covering every possible orientation (0-180 degrees) with one set preferring input from the right eye and one set preferring input from the left eye

Question 17

Retinal topic map

Answer 17

Cells that are close to each other in the LGN are close to each other in the Visual cortex

Question 18

Ventral pathway

Answer 18

(what pathway) from the striate cortex to the temporal lobe
o Responsible for determining an objects identity
o Neurons with high-resolution selectivity & sensitivity to form, pattern & colour
o Some cells respond selectively to faces, to hands … and ignore change in detail after optical & viewpoint transformation (can’t generalise recognition across viewing conditions)

Question 19

Dorsal pathway

Answer 19

(where/how pathway) from striate cortex to the parietal lobe, how to direct action/movement
o Strongly linked with the premotor regions in frontal cortex
o Form information: from V3 and or V4, both of which project to MT (V5)
o Motion information: inputs pass through MT and MST, both of which contain cells selective for object motion in different directions (including rotation in motion in depth)
o Receives movement information from the magnocellular cells

Question 20

Optic ataxia

Answer 20

damage to the posterior parietal region results in difficulties in accurate reaching toward objects but not in recognition-problems (dorsal pathway)

Question 21

Visual agnosia

Answer 21

damage in occipitotemporal regions that causes inability to recognise/ describe common objects although they can easily navigate through the everyday world (ventral pathway)
o Scale grip to dimensions of the objects that were about to be picked up even though they can’t “perceive” those dimensions

Question 22

Fusiform face area (FFA)

Answer 22

specialised to respond to faces

 Inferior temporal cortex

Question 23

Parahippocampal place area (PPA)

Answer 23

specialised for places & spatial layout

 Inferior temporal cortex

Question 24

Extrastriate body area (EBA)

Answer 24

specialised for (parts of) bodies
	Inferior temporal cortex

Question 25

Lateral occipital complex (LOC)

Answer 25

specialised for object recognition

Question 26

Visual word form area (VWFA)

Answer 26

specialised for words (reading)

Question 27

V4

Answer 27

specialised for colours

Question 28

V5

Answer 28

specialised for motion

Question 29

Selective adaptation

Answer 29

short term after a longer exposure of an stimuli the firing gets less because of fatigue, elevating threshold

Question 30

Selective riring

Answer 30

Your neurons develop with the environment.

Question 31

Single dissociation

Answer 31

One patient has brain damage and can’t do a certain task. So the researcher reasons that the damaged brain area is responsible for the not doable task

Question 32

Double dissociation

Answer 32

Person 1 can do task 1 but not task 2, person 2 can do not task 1 but task 2 than you can say that this brain region is necessary for a certain task

Question 33

Lateral inhibition

Answer 33

inhibition that is transmitted across the retina

o Horizontal and amacrine cells transmit lateral inhibition in the human eye

Question 34

Hermann Grid

Answer 34

You see the spots in the intersection because higher illumination means higher lateral inhibition so the corridors are surrounded by black fields which reflect less light to the retina → less lateral inhibition so the corridors look white and the intersection where more lateral inhibition is caused by more white fields is seen as grey (inhibition is always 0.1 from the original intensity)

Question 35

Mach Bands

Answer 35

o Lateral inhibition is causing us to see the stripes in different tone but in reality, there are only two tons of grey