primary visual cortex+beyond

Question 1

Review the origin and cortical targets of magno- and parvocellular visual pathways

Answer 1

parvo:
-origin arises from the reina, whereby midget ganglion cells (P cells) carry info through impulse signals received from visual stimuli (real world)
-passes through layers 3-6 of parvocellular laminae of the LGN
-projects to layers 4CB of striate cortex (V1)
-down the ventral stream to higher centres including IT,V4
-later projections to temporal cortex and prefrontal cortex
-parts of the ‘what’/ object recognition/ vision for perception

magno:
-origin arises from the reina, whereby parasol ganglion cells (M cells) carry info through impulse signals received from visual stimuli (real world)
-passes through layers 1-2 of magnocellular laminae of the LGN
-projects to layers 4CA of striate cortex (V1)
-down the dorsal stream to higher centres including V2,MT
-later projections to parietal cortex and prefrontal cortex
-parts of the ‘where’/ spatial localisation/ vision for action

Question 2

what and where are the output signals from the different layers of V1 go to

Answer 2

layers 2-3-4 go to other cortical areas
layers 5-6 go to deep structures of the brain

Question 3

what are the output layers of p and m pathways in V1 and

Answer 3

As the p and m pathways input layer 4 of striate cortex, their output signals go to other cortical areas.

Question 4

Explain the dual stream hypothesis and the evidence that led to its formulation

Answer 4

-Lesions in ventral stream in monkeys cause problems with object recognition, and lesions in dorsal stream in monkeys lead to problems with spatial localisation

-imaging

-electrophysiology

Question 5

Discuss the evidence that cortical area MT is specialized for visual motion processing

Answer 5

-lesion studies in monkeys where by their MT region was lesioned and led to impairment in motion detection and prolonged time to respond to rapid changes in motion

In the case of LM, they were not able to pour tea from a kettle as she saw it as a solid object rather than a moving one (lesion in MT)

Question 6

what are the functions of motion in the visual
stimulus

Answer 6

draw attention
location and navigation

Question 7

What cortical area is selectively responsive to motion? What are the neurons receptive tissues, and where do they receive input from (which cortical regions)?

Answer 7

MT (V5)
responsive to speed and range of motion.
-inputs from V1, V2, and V3 via M pathway

Question 8

which cortical areas respond to elemental or global motion also explain what those are

Answer 8

elemental: refers to direction of an individual element (V1)

global: refers to the overall superimposed movement of more than one element in the visual scene (MT)