Higher Visual Processing

Question 1

Mishkin, 1986

Answer 1

over half the visual cortex can be stimulated by visual stimuli

Question 2

Evidence for higher visual processing?

Answer 2

Contextual modulation (zapadia et al 1995), similar studies by lamme et al 1999, ungerleider and mishkin, attention modulates vision

Question 3

Ungerleider and Mishkin

Answer 3

Presented monkeys with two tasks – object discrimination (after presentation of an object the monkey must choose the correct object to gain reward) and landmark discrimination (monkey had to pick the food closest to a landmark). Those with temporal lobe removed could not perform object recognition and those with parietal lobe removed could not perform landmark task.
o Led them to identify the dorsal pathway (that leads to parietal) as the where stream and the ventral pathway as the what stream

Question 4

Ventral stream

Answer 4

runs into interior temporal lobe detecting colour and form. the what pathway or vision for perception

Question 5

Dorsal stream

Answer 5

runs into area MT, detects movement, the where pathway or vision for action

Question 6

Milner and Goodale 1995

Answer 6

Patient DF can damage to ventral stream
cannot recognize objects, but can interact with them. E.g. Can post a letter but cannot line the post up with postbox
Patient VK - damage to the parietal stream
can identify objects but cannot interact with them appropriately.
Redefine streams as vision for action and vision for perception

Question 7

Medial temporal cortex (MT)

Answer 7

Recognises movement. E.g. newsome and pare 1988. What percentage has to be moving in unison for you to report any motion in that direction. In a monkey the detection of threshold is about 3% If you take out area MT the monkey needs 100% and even then it struggles to tell you direction. Stimulating MT can make animals response bias to certain direction

Question 8

Evidence for parallel streams

Answer 8

M to dorsal. P to ventral

Question 9

Infero temporal cortex (IT)

Answer 9

As you move further away receptive fields become larger. Responsive to more complex stimuli. Arranged in columns.

Question 10

FFA

Answer 10

fusiform face area. fMRI  Kanwisher et al, 1997 subtracted the brains response to other objects such as houses and scrambled faces from brains response to faces and the area left was the fusiform face area

Question 11

IT neurons, built in or experience?

Answer 11

Logothetsis et al 1994 trained monkey cells to fire to paperclip stimuli. Also evidence for in built face selective neurons

Question 12

Top down processing

Answer 12

evidence for higher processing. Sheinberg and Logothetis (1997). Monkey presented with image to each eye but pulls lever for certain image. shows that the brain selects only one image to be perceived despite the fact they are both seen on the receptive field.

Question 13

Attention can effect vision

Answer 13

In-attentional blindness e.g. Mack & Rock (1998)
The attentional blink
Change blindness e.g. Levin and Simons, 1997, showed a video of a conversation between two women and told to pay close attention. During the video several things change (i.e. plate colour). Only one in ten patients claimed to have seen a change.

Question 14

Binding

Answer 14

binding must occur because we see a complete image. neurons will respond to colour, movement and shape, firing synchronously and indicating that all qualities belong to the corvette (synchronous oscillations). Stryker 1989

Question 15

Cross-correlograms

Answer 15

o Engel et al, 1992, suggested that when an object evokes firing in several different locations, the firing of these locations is synchronised with one another. When a joint bar moved across two receptive fields it evokes synchronous oscillations but when the bar is split and moving in opposite directions there is no synchronised firing