5.16 - Functional Localisation in Brains I: Topography

Question 1

Name the 4 main approaches for the localisation of brain function.

Answer 1

1. Neuroanatomical tracing
2. Electrophysiology mapping (EEG & ECoG)
3. Imaging (fMRI)
4. Stimulation

Question 2

What does this 3d homunculus tell you about the mapping of the motor and somatosensory cortices?

Answer 2

The homunculus visually displays how the motor and somatosensory cortices are mapped. The larger the body part in the diagram, the more of the cortex is dedicated to its movement or sense of touch.

Note that

• more of your brain is dedicated to the movement and feeling of your face and hands than to the rest of your body combined.
• The two cortices are almost exactly dedicated to the same parts in the body. The same parts of your body you need to have a lot of movement control over tend to also be the most sensitive to touch.

Question 3

What is a retinotopic map?

Answer 3

The primary visual cortex is a retinotopic map. Retinotopy means that spatially close patches of visual cortex respond to spatially close bits of visual input.

Question 4

What are the somatotopic and mototopic map?

Answer 4

The motor and somatosensory cortices are well-mapped, meaning we know exactly which part of each strip connects to each part of the body. A somatotopic map is the projection of the body surface onto the somatosensory cortex.

The projection of the bodily movement onto the primary motor cortex.

Question 5

What is meant by divergence and convergence in the brain?

Answer 5

A single neuron can project to a group of neurons (divergence)

A group of neurons can project to a single neuron (convergence)