21 Cortical Vision

Question 1

conclusion of a study on Single cell recordings in area MT(V5)

Answer 1

the activity of a single neuron in area MT was recorded while a white bar passed through the neuron receptive field in varying directions

Results: neuron fired vigorously when the bar moved downward toward the left and opposite movement elicited the least activity

concussion: neurons in area MT are selective for the direction of motion

follow-up study?: neurons in area MT are selective for the speed of motion

Question 2

Study on PET activation during a visual stimulation in macaque monkeys? What was the conclusion.

Answer 2

the specialisation of function in the human visual cortex was investigated using positron emission tomography.

method: positron emission tomography was used to measure regional cerebral blood flow in order to identify which parts of the brain are involved in the perception of different types of visual stimuli

results: relative location of the region activated by coloured stimuli and the region activated by moving stimuli.

Conclusion: this data shows that, as in macaque monkeys, different areas of the human extrastriate visual cortex are involved in processing different attributions of vision.

Question 3

what are the two main projection routes from primary visual cortex (V1) to extrastraite visual cortex?

Answer 3

dorsal steam
ventral stream

Question 4

what does the dorsal stream code

Answer 4

motion and location

Question 5

what does the ventral stream code

Answer 5

processes detailed stimulus features and object identity.

Question 6

Dorsal vs ventral pathways

Answer 6

PET study that we just considered demonstrated functional differences in the dorsal and ventral pathways.

Question 7

what is the extrastriate cortex?

Answer 7

The extrastriate cortex is the region of the occipital cortex of the mammalian brain located next to the primary visual cortex. Primary visual cortex (V1) is also named striate cortex because of its striped appearance in the microscope

Question 8

Communication in visual cortex?

Answer 8

complex but not random. not every area is connected with every other.
numbering scheme should not be taken to mean that the synapses proceed sequentially from one area to the next.
boundaries are mapped by topographic discontinuities

Question 9

What do we know happenss in V4, where is it located?

Answer 9

V4 is located along the ventral stream
observations of neruons in V4 reveal they were selective for colour, and it was thought they distringused colour.
We now know that some cells in V4 respond to combinations of colour and form

Question 10

What do we know happens in area v5 and where is it located.

Answer 10

located in the dorsal stream
neurons here are selective for the direction of motion and speed of motion
damage to V5 can disrupt motor perception