02. Neurodevelopment II - Part 2

Question 1

There is a correlation between myelination and…

Answer 1

… ability to grasp

Question 2

History of neurogenesis in adults

Answer 2

Originally believed that after infancy there was no neurogenesis. Findings in rats contradicted this belief (Altman, 1962; Bayer, 1982; Kaplan, 1981) but were criticised

Question 3

Evidence for neurogenesis (animals)

Answer 3

Rats - earliest evidence
Birds - in songbirds there is a seasonal replacement of neurons in ‘singing’ areas (Nottebohm, 70s and 80s)

Question 4

Evidence for adult neurogenesis (humans)

Answer 4

There are ‘neurogenic’ areas:
- The olfactory epithelium (Bedard & Parent, 2004)
- The subventricular zone (Altman, 1969; Curtis et al 2007)
- The hippocampus (Zhao & van Praag, 2020)
- The cerebral Cortex

Question 5

In the olfactory epithelium…

Answer 5

…cells continuously divide to provide new olfactory sensory neurons, and replace damaged ones (Bedard & Parent, 2004)

Question 6

In the subventricular zone (SVZ)…

Answer 6

…cells are produced. They migrate along the ‘Rostral Migratory Stream’ (Altman, 1969; Curtis et al 2007) towards the olfactory bulb, where they become interneurons.

Question 7

How are cells guided along the Rostral Migratory Stream?

Answer 7

Astrocytes wrap around migrating neurons, creating a ‘pipeline’ that they ‘flow through’

Question 8

In the hippocampus…

Answer 8

…neurogenesis occurs in the dendate gyrus (Altman & Das, 1965) (Zhao & van Praag, 2020)

Question 9

In the cortex…

Answer 9

…there is very little neurogenesis. It often occurs after injury, depending on the extent of the injury

Question 10

Recovery after injury

Answer 10

• Better in younger brains
• Better in the PNS than CNS
• Mostly consists of collateral sprouting

Question 11

What is collateral sprouting?

Answer 11

• A neighbouring neuron to the damaged one grows new axons and connects to the empty space
• This is possible because the cells secrete neurotrophins
• Synapses form very fast, especially in first 2 weeks

Question 12

Brain adaptations

Answer 12

In people blind since infancy, there is enhanced tactile and auditory ability
Deaf people have better tactile and vision ability
If people with a lazy eye wear an eyepatch, it can restore good vision
Losing a finger causes the brain areas for neighbouring digits to grow larger (monkey labs)

Question 13

Monkey finger amputation

Answer 13

If a digit is amputated the cortical area for that digit becomes responsive to the neighbouring digits

Question 14

In blind people’s occipital cortex…

Answer 14

…PET scans indicated substantial activity when they read braille (Sadato et al 1996;1998). There was also activity in visual areas (Burton et al 2002).

Question 15

Blind people also…

Answer 15

…recruit brain areas used for vision for auditory tasks (Weeks et al 2000)

Question 16

More vs fewer experiences (rats)

Answer 16

Rats raised in an enriched environment (more physical activity) have a thicker cortex and increased dendritic branching (Rosenzweig & Bennet 1980; Nithianantharajah & Hannan, 2006). They therefore had improved ability to learn

Question 17

What is a critical period?

Answer 17

A period where the brain is most sensitive to a specific experience (Konrad Lorenz, 1930s) e.g. ducklings follow a person (imprinting) but only at 1 day old

Question 18

‘Train ride’ - Richard Tees

Answer 18

The human brain’s sensitivity to learning has 3 waves. The critical period for senses comes first, then language, then higher cognition.

Question 19

Example of critical periods: Blakemore & Cooper, 1970

Answer 19

Kittens were raised in tubes with vertical stripes during a visual critical period. As a result they could recognise vertical but not horizontal lines

Question 20

Example of critical periods: Genie

Answer 20

Abused child kept in darkness, with no social experience, and little food. She couldn’t speak and had incorrect growth & posture