Lecture 9 - Cortical Maps and Plasticity

Question 1

What is a map?

Answer 1

• Representation

Question 2

Where are maps in the brain?

Answer 2

• Rodents use whiskers to explore the world
• Rodents have representations of their whiskers with their somatosensory cortex also known as the barrel cortex
• Info about the world is transmitted to the brain through the stimulation of each whisker
• At each level of the brain, the spatial relationship between 2 whiskers is sustained
• Barrel cortex is a map of spatial organisation of the rodent’s whiskers in the periphery

Question 3

Why are maps not limited to touch?

Answer 3

• Visual space is mapped in a similar fashion
• The mapping links a location on the retina with groups of neurons within the lateral geniculate nucleus and primary visual cortex
• Called retinotopic map

Question 4

Describe neurones in V1

Answer 4

• Particular neurons will fire more when stimuli are orientated specifically
• Tuning is not absolute e.g 45 degrees = most firing but 40 degrees = slightly less firing
• When we combine neurons, we get an orientation selective map in V1

Question 5

What is a feature space?

Answer 5

• Neurons have receptive fields
• receptive field of neuron = region of feature space that it responds strongest to
• Can be location e.g whisker or orientation e.g angle
• Seen throughout species

Question 6

How do maps link structure and function by their relative sizes/specialisations?

Answer 6

e.g blind mole map
- Skin has grown over eyes
- Visual system is used for circadian functions
- They still have a V1 and a retino-pathway
- However visual cortex has been co-opted by auditory system

Question 7

What are the differences in cortical maps within species?

Answer 7

• Plasticity

Question 8

Can brain function be changed by experience in development?

Answer 8

• Capacity for big change happens in post natal life - critical period
  e.g Lorenz and Geese
• Complex cognitive abilities can be effected by experience e.g language acquisition and for bilingualism to be fluent = before 12

Question 9

What is an example of extreme plasticity of sensory maps during critical period?

Answer 9

• Kittens only see horizontal/vertical lines (not even body)
• If raised horizontally, cells do not develop true vertical representation and vice versa

Question 10

Can you remold beyond the critical period?

Answer 10

• We can learn and acquire new skills = cannot be encoded in genes = brains and nervous system needs to be flexible

Question 11

What does the central somatotopical organisation look like?

Answer 11

• Map does not represent the spatial size of a skin area BUT the density of receptors in it

Question 12

What did we see from map plasticity int he primate somatosensory system?

Answer 12

• Found there are two topographic representations of the body surface within cytoarchitectinic areas in adult monkeys (able to distinguish cells by features of cells in area)
• If monkeys lost a finger = map looked different = plotted baseline, removed finger and remapped
• Found that area that responded before to the finger removed would respond on digits on either side = adult plasticity
• Then stuck 2 fingers together = received more input = looked at how map changed and found areas worked together when stroking the finger