Visual function and dysfunction at higher cortical areas

Question 1

Experiment that demonstrates the ventral stream?

Answer 1

Temporal lobe lesions interfered
with “object discrimination”
*Trained task:
–monkey had to pick familiar
object and not some new
object (to get food reward
–easy for normal monkey

Question 2

Experiment that demonstrates the dorsal stream?

Answer 2

parietal lobe lesions interfered with
“landmark discrimination”
– Trained task:
* monkey had to pick the object
(left circle) closer to a
previously established
“landmark object (cylinder) to
get food reward
* easy for normal monkeys
– Parietal lobe lesioned monkeys
could not do this task well
* temporal lesion monkeys
performed task satisfactorily

Question 3

What happens with some lesions of the ventral stream?

Answer 3

Visual agnosia. Can see objects but can’t identify what they are.

Question 4

What happens with some lesions of the dorsal stream?

Answer 4

Optic Ataxia: A patient with a lesion in the right posterior parietal cortex makes mostly spatial errors (C) and fewer orientation errors (B).

Question 5

Lesions in dorsal regions

Answer 5

Spatial errors. Putting hand in sldot incorrectly.

Question 6

Ventral stream lesions result in what type of lesions?

Answer 6

They result in orientation lesions. In experiments, they are unable to to prient their hand towards the slot easily.

Question 7

what is the function of the parietal cortex?

Answer 7

• plays a central role in directing attention to
  spatial locations
  *helping to bind different attributes of an object
  together
  As a result it can it help you to
  bind the attributes of attributes of an object together because
  with this kind of spot of attention, you’re able to
  concentrate on one object at a time, and which means
  that that way you can gate what goes through the
  stream
• gating inputs into ventral stream
• important for reading? [link to dyslexia]

Question 8

What does lesion in right parietal cortex result?

Answer 8

Visual neglect. Neglect 1 side of their vision. Usually left.

Question 9

what are the different ways MT gets input?

Answer 9

Sometimes, input can come form konio pathway from LGN bypassing V1.
Can recieve input from V2, AND V3 can also get input directly from primary visual cortex.

Question 10

Blindsight

Answer 10

In cases such as carbon monoxide poisonign where V1 is damaged, one will be able to detect motion, but will not be able to see. Mediated by inputs to MT that
bypass V1.

Question 11

What are mirror Neurons?

Answer 11

respond to action either done by oneself or by another person. Experiment demonstrated this through the action of grasping. Could be the basis of empathy (eg, for instance feeling in pain when someone else is feeling it) Theory that people with autism lack mirror neurons as they lack empathy. (Theory of mind (being able to have perception about other people’s thought and emotions) relates to prescence of mirror neurons).

Question 12

a

Basis of visual hallucinations?

Answer 12

• Predictive hypotheses not
  being vetoed by afferent
  inputs, due to loss of the
  normal visual signals?
• Perception probably works top down, that is, it originally started the helm. Who said All our perception is unconscious influences, but later on the idea has been developed further.
  The perception starts as perceptual hypothesis.
  You make hypothesis, and the more recent name for that
  is predictive coding. Incoming input just just vetoes it
  or supports it.
• The primary visual cortex actually lights up on FMRI
  when you imagine hallucination, all this
  actually activate the primary visual cortex.
  There’s another evidence for things.