5.16 - Functional Localisation in Brains I: Topography

Question 1

Name scientific paradigms used for the localization of brain function.

Answer 1

1. Lesion studies
2. Neuroanatomical tracing
3. Electrophysiology mapping
4. Imaging
5. 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.

Question 3

What is a retinotopic map?

Answer 3

Retinotopy means that spatially close patches of visual cortex respond to spatially close bits of visual input.

The primary visual cortex has a retinotopic structure.

Question 4

What is a somatotopic map?

Answer 4

Maps are referred to as ‘somatotopic’ when cortical spaces are related to locations on the body, such that adjacent neurons in the neural tissue respond selectively to stimuli presented to adjacent locations on the body.

Question 5

What is meant by divergence and convergence in the brain?

Answer 5

A group of neurons projects to a single neuron (convergence)

A single neuron projects to a group of neurons (divergence)

Question 6

Degeneration of neurons is a type of _______ ______, used to ________

Answer 6

neuroanatomical tracing,

investigate where the neural projections travel

Question 7

Anterograde tracing travels from ______ to _____.

Answer 7

soma …. axon

Question 8

How is the pseudorabies virus used as a method of neuroanatomical tracing?

Answer 8

Pseudorabies is a retrograde tracer that travels from axons to the dendrites. It can bounce from one neuron to another, eventually covering all the cells in an animal body.

Using this method, we can determine how the neurons are connected.

Question 9

How is the herpes virus used in neuroanatomical tracing?

Answer 9

The herpes virus is used as an anterograde tracer (traveling from the cell dendrites to the terminals).

Combined with retrograde viruses, the herpes virus can provide evidence for the visual pathway.

Question 10

Name some of the methods of electrophysiological mapping.

Answer 10

EEG - electroencephalography

ECOG - electrocorticography

Question 11

What is the goal of electrophysiological mapping?

Answer 11

To record from sites of the brain during stimulation or movement in order to map the responsiveness of specific regions.

Question 12

What is the goal of brain stimulation?

Answer 12

To investigate behavioral responses to the activation and inhibition of brain regions.

Question 13

What is the main mechanism underlying the calcium imaging technique?

Answer 13

GCaMP (calcium indicator) becomes fluorescent when bound to calcium (involved in synaptic transmission). GCaMP shows a graded response, proportional to the strength of neuronal activation.

Question 14

Why does topography occur in the brain?

Answer 14

Topography occurs as a result of neural activity (in response to stimuli) together with the genetic underpinnings of the projections of neurons.

Question 15

How is the topographical organization prioritized in the brain?

Answer 15

What takes up more space on the cortex, is more important to feel/control in the body

Question 16

What is the evolutionary underpinning of neuronal diversity in the brain?

Answer 16

Neuronal diversity follows the need. The goal is to solve the problems the neurons need to solve in the most efficient way.

Different types of neurons and receptors are perfectly made to solve the particular problems they encounter.

Question 17

Injection of Pseudorabies virus, Herpes virus, and Cholera toxin into a neuron are methods of________

Answer 17

neuroanatomical tracing

Question 18

How are horizontal cells involved in vision?

Answer 18

Horizontal cells are involved in lateral inhibition;