Object recognition and localisation

Question 1

Lesions in what part of the brain decrease the ability to recognise objects?

Answer 1

inferior temporal cortex

Question 2

Lateral geniculate nucleus

Answer 2

Has 6 layers and receives monocular input
each layer alternates input from each eye
made up of P and M ganglion cells which are organised retinotopically

Question 3

What is the thalamic relay station?

Answer 3

where ganglion axons make 1 to 1 connections with LGN projection neurons, which have similar receptive fields of retinal ganglion cells

Question 4

Examples of object localisation in the visual system

Answer 4

orienting reflex
smooth persuit
prediction of motion during prey capture
saccadic movements during object inspection

Question 5

Orienting reflex

Answer 5

orientation of head and eyes to focus salient stimulus on the retina

Question 6

Smooth persuit

Answer 6

following a moving object

Question 7

Ablation of what leads to the disappearance of orienting reflex?

Answer 7

optic tectum
superior colliculus in lower vertebrates

Question 8

Important areas in stimulus localisation and motion processing

Answer 8

retina
dorsal stream in cortex
superior and inferior colliculus

Question 9

Superior colliculus

Answer 9

receives input from ganglion cells, auditory and somatosensory systems
integrates info from different sensory modalities and main function is to regulate saccadic movements
consists of several layers

Question 10

Retinotopic map

Answer 10

an organisation whereby neighbouring cells in the retina feed info to neighbouring places in target structures

Question 11

Foveation hypothesis

Answer 11

the interaction between retinotopic and topographic maps is what initiates the orienting reflex

Question 12

What defines direction selectivity?

Answer 12

the ratio between inhibitory and excitatory inputs
motion in one direction causes neurons to spike and motion in the opposite direction does not cuase neuron to spike

Question 13

Columnar organisation in the cortex

Answer 13

ocular dominance column- each one receives input from either contralateral or ipsilateral eye
orientation or direction columns
blobs for different colours

Question 14

Blobs

Answer 14

stained by cytochrome oxidase and process info about colour by receiving input from parvocellular cells of the LGN
not orientation selective

Question 15

What is the difference between simple and complex cells?

Answer 15

complex cells may receive inputs from many simple cells having the same orientation of the receptive field

Question 16

What do simple cells do?

Answer 16

detect orientation of object

Question 17

What do complex cells do?

Answer 17

detect whether an object is moving to the right or the left
fires or inhibits depending on what direction

Question 18

What layers are simple cells localised in?

Answer 18

4 and 6

Question 19

How will simple cells respond to a bar of light?

Answer 19

will only respond to a bar in the centre of the receptive field

Question 20

How will complex cells respond to a bar of light?

Answer 20

will respond to bar anywhere in the receptive field as long as it is in the correct orientation

Question 21

What layers are complex cells localisaed in?

Answer 21

2,3 and 6

Question 22

Hypercomplex or end stopped cell

Answer 22

will respond to bar in any place in the receptive field but if bar crosses out of it inhibitory surround will takeover
if the orientation changes after exiting field it will still respond

Question 23

How do receptive fields change downstream of V1?

Answer 23

get bigger are more complex

Question 24

What do neurons in the temporal lobe respond to?

Answer 24

simple shapes that we may perceive as something else
complex shapes

Question 25

Problems with the jennifer aniston model

Answer 25

still poor in scale and orientation invariance
doesn’t take into account feedback from higher cortical areas
needs experimental validation which is difficult as you need to record pre and post synaptic responses

Question 26

In preferred direction

Answer 26

excitation is larger
inhibition is smaller and delayed

Question 27

In null direction

Answer 27

excitation is smaller and delayed
inhibition is larger

Question 28

Where do dorsal stream cells receive excitation from?

Answer 28

excitation from bipolar cells
inhibition from amacrine cells