Neural circuits for visual perception

Question 1

What is transmission?

Answer 1

Occurs when signals travel from the receptors to the brain.

Question 2

What is processing?

Answer 2

Occurs as a result of interactions amongst neurons.

Question 3

What are the processes of transduction, transmission and processing?

Answer 3

The electricity created from a stimulus, one neuron activates another, interactions between neurons.

Question 4

What do Receptive fields do?

Answer 4

Link sensations and perceptions.

Question 5

What happens when neighbouring neurons are connected in a circuit?

Answer 5

The firing rate will increase as there will be more stimulation to reach the threshold due to convergence.

Question 6

What are the receptive fields of a neuron?

Answer 6

Visual neuron receptor fields are the small area on the retina which when stimulated influences the firing rate of this visual neuron.

Question 7

What are on centre ganglion cells?

Answer 7

Cells that action potential will be stimulated only if the light is in the centre of the retinal surface. If both centre and surround are stimulated the cell will be activated just not as much as if only in the centre.

Question 8

What are off centre ganglion cells?

Answer 8

Cells that action potential will be stimulated only if the light is hitting the surrounding area of the retinal surface, not if the light is only on the centre.

Question 9

How would a centre ganglion cell be shown on a graph of firing rate and receptors stimulated?

Answer 9

It would have a bell hump then trail off as the optimum firing rate is not when all of the receptors are stimulated but only the centre ones therefore the firing rate would decrease past the optimum as the off-centre receptors began to be stimulated.

Question 10

Why are the receptive fields of retinal ganglion cells so important?

Answer 10

All visual information that the eye sends to the brain must be encoded in the responses of retinal ganglion cells.

Question 11

What are the fundamental roles of the RFs of retinal ganglion cells?

Answer 11

understanding the perception of colour, luminance contrast, and darkness.
Capturing and enhancing certain features of the retinal image.

Question 12

Why do off and on centre cells have an optimum light area?

Answer 12

In a centre cell, the centre has excitatory neurons and the outside has inhibitory neurons therefore when both are stimulated the response only happens if there are more centres than off centre neurons. Vice versa.

Question 13

What cant the receptive fields do without the visual cortex?

Answer 13

Capture orientations of lines and edges.

Question 14

Where does the information received by the optic nerve go to via neurons?

Answer 14

The visual cortex with an intermediate stop at the LGN in the thalamus as a relay station.

Question 15

What are the LGN receptors like?

Answer 15

They are identical to the spatial organisation of the receptive field of the retinal ganglion cells.

Question 16

What are complex cells?

Answer 16

Respond to bars of light of a particular orientation (like simple cells)
Respond to movement of bars of light in specific direction. (unlike simple cells)

Question 17

What do end stopped cells respond to?

Answer 17

Moving lines of specific length, moving corners or angles.

Question 18

What don’t end stopped cells respond to?

Answer 18

Stimuli that are too long/large.

Question 19

What are examples of cells that resemble feature detectors and what do they respond to?

Answer 19

Simple cortical cells (orientation and width)
Complex cortical cell (orientated movement)
End stopping cortical cells (oriented moving corner of a particular size)

Question 20

What are the characteristics of the receptive field of an optic nerve cell/ganglion cell?

Answer 20

Center-surrounded, responds best to small spots but also responds to other stimuli.

Question 21

What are the characteristics of the receptive field of a lateral geniculate?

Answer 21

Center-surrounded receptive fields very similar to ganglion cell.

Question 22

What are the characteristics of the receptive fields of a simple cortical?

Answer 22

Excitatory and inhibitory areas arranged side by side. Responds best to bars of a particular oreintation.

Question 23

What are the characteristics of the receptive fields of complex cortical cells?

Answer 23

Responds best to movement of a correctly oriented bar across the receptive field. Many cells respond best to a particular direction of movement.

Question 24

What are the characteristics of the receptive fields of the end-stopped cortical?

Answer 24

responds to corners, angles, or bars of a particular length moving in a particular direction.

Question 25

What responsibility do other stimulus areas have?

Answer 25

capturing depth, motion and the colour of a stimuli.

Question 26

How is stimulus orientation coded?

Answer 26

They are coded alongside surrounding context, causing high er order effect and interactions.

Question 27

What is retinal disparity?

Answer 27

The idea that the two eyes have slight angle differences due to the location of the retinas being slightly different.

Question 28

What was DeAngelis et al experiment in 1998?

Answer 28

Monkey was trained to indicate depth from disparate images. Disparity-selective neurons were activated by this process. Experimenter used microstimulation to activate different disparity-selective neurons. The monkey shifted judgement to the artificially stimulated disparity.

Question 29

What were the findings of DeAngelis' study?

Answer 29

That when the neurons were stimulated the depth was perceived in a different place, changing the disparity.

Question 30

How are simple orientation cells stimulated?

Answer 30

They have to be stimulated right to left in order to get enough activity to be excitatory.

Question 31

What is V1-5?

Answer 31

The different brain areas that are linked by neural circuits of vision.

Question 32

Do single areas produce singular functions?

Answer 32

No the full range of stimulus specificities is found in all areas, though relative proportions vary from area to area.

Question 33

Why can the total percentage in area function exceed 100%?

Answer 33

Because they are responding to multiple attributes and multiple stimuli.

Question 34

What are the two interrelated areas in the second level of the visual association cortex?

Answer 34

Parietal lobe and temporal lobe.

Question 35

What is the pathway from the retinal cortex through V1?

Answer 35

Lateral geniculate nucleus (LGN). Primary visual receiving area in the occipital lobe. (the striate cortex) And then through two pathways to the temporal lobe and the parietal lobe. Finally arriving at the frontal lobe.

Question 36

What are the two visual routes from the visual cortex?

Answer 36

The dorsal stream and the ventral stream.

Question 37

What is the analysis pathway for visual information up the visual cortex?

Answer 37

Eye, thalamus, primary visual cortex.

Question 38

What is the first level of association cortex in occipital lobe?

Answer 38

Visual scene is broken into modules, information is analysed in terms of orientation, Movement, information from both eyes, orientation and widths of lines and colour.

Question 39

What is the difference in the two second level pathways?

Answer 39

Parietal lobe focuses on perception of location and movement. temporal lobe focuses on three-dimensional form perception.