Neurodevelopment across the lifespan 2

Question 1

What is sexual differentiation?

Answer 1

Females have 2 x chromosomes, males have an x and y chromosome.

Question 2

What happens during prenatal development in terms of sexual differentiation?

Answer 2

During prenatal development the male and the female anatomy is the same - biopotential (has both possibilities).

Question 3

With ducts do males and females carry?

Answer 3

Both carry a set of Müllerian ducts (female) and Wolffian ducts (males) and primitive gonads (testes or ovaries).

Question 4

What happens in male sexual differentiation?

Answer 4

SRY = sex-determining region of the y chromosome, causes the primitive gonads to turn into testes. Testosterone causes the development of the Wollfian ducts to develop into seminal vesicles and vas deferens.

Question 5

What is the Müllerian Inhibiting hormone (MIH)?

Answer 5

Causes degeneration of the M. ducts (oviducts, uterus, upper vagina).

Question 6

What are gonadal hormones?

Answer 6

If male, have a large amount of androgens and not a lot of estrogens. Reversed in females. In females, androgens are associated with sexual pleasure.

Question 7

What are organising effects of sex hormones?

Answer 7

Sensitive stage of development, produces long-lasting effects. In humans happens before birth (3rd and 4th month) but also at puberty.

Question 8

What are activating effects of sex hormones?

Answer 8

Can occur at any time in life when a hormone temporarily activates a particular response (only when the hormone is present).

Question 9

What are brain sex differences?

Answer 9

Males have more dendritic branching in the visual cortex. Females have more dendritic branching in the motor cortex. The corpus callous (bundle of fibres that go from one hemisphere to the other) is slightly thicker in females.

Question 10

Can neurogenesis happen postnatally?

Answer 10

Neurogenesis is completed by 7 months of gestation. However, new neurons can be born in adult brains.

Question 11

What is evidence for neurogenesis happening postnatally?

Answer 11

In songbirds - there is a steady replacement of neurons in the singing area.
Olfactory bulb - olfactory receptors continually replace dying ones.
Hippocampus - great deal of neurogenesis. Neurogenesis in adult mammals facilitates learning.

Question 12

What brain area is it difficult to get neurogenesis?

Answer 12

The cerebral cortex - may be exceptions following injury or stroke. Recovery may involve branching of axons and dendrites. Much more difficult to get neurogenesis in the cerebral cortex.

Question 13

Can there be a regrowth of axons.

Answer 13

Yes - better in young brains and in the periphery (this is to do with glia). Damaged axons can grow back. Recovery involves collateral sprouting.

Question 14

What is collateral sprouting?

Answer 14

New branches formed by non-damaged axons that attach to vacant spots on dendrites and cell bodies. The cells secrete neurotrophins that allow collateral sprouting to occur. After injury there is empty space - axon will take over empty space and strengthen it connection with this particular neuron. Shows the brain can change depending on our experiences.

Question 15

What is brain plasticity?

Answer 15

Our experiences of our environment are reflected in our brain because they are malleable. This is due to the brain forming new synapses and pruning others - “use it or lose it”.

Question 16

What is evidence for the environment changing our brain?

Answer 16

D.O.Hebb (1947) - rats at home vs. laboratory environment and ability to solve mazes. Rosenzweig & Bennet (1980) - rats raised in an enriched environment develop a thicker cortex and have increased dendritic branching (correlated with better ability to learn).

Question 17

How does the brain adapt?

Answer 17

In people blind since infancy there is enhanced tactile (finger sensitivity) and auditory ability. Deaf people have a better sense of touch and vision.

Question 18

Evidence for brain adaptions in blind people?

Answer 18

Burton et al. (2002). Asked sighted and blind people to feel braille letter and say whether they were the same or different, blind people performed better. PET & fMRI scans showed substantial activity in the occipital cortex of blind people when they performed these tasks. Occipital lobe controls vision - example of the brain reorganising itself to adapt to a new environment.

Question 19

Evidence for brain adaptions in music training?

Answer 19

Musicians have larger brain areas responsible for hearing and finger control. Have thicker grey matter in the part of the brain responsible for hand control and vision of professional keyboard players.

Question 20

What is a critical period?

Answer 20

A period where the brain is most sensitive to a specific experience. Important for the development of a particular skill. Lorenz - imprinting behaviour has a critical period. Richard Tees - we develop certain skills to enable us to survive later on. Senses have an early critical period. Have the capacity to develop language, but only if in an environment exposed to linguistics.

Question 21

How is the adolescent brain different?

Answer 21

Adolescents tend to be more impulsive & seek immediate pleasure. However when allowed time to make decision they do well, and presence of peers affects this ability. The prefrontal cortex is immature: this affects decision making tasks, but mid-brain is well developed (pleasure centre). Antisaccade task (looking away from a powerful attention-getter) - adolescents perform well but have to put in lots of effort. Jay Giedd - brain scans of 3-25 year olds - revealed grey matter thickens in childhood but things out gradually.

Question 22

What are memory related impairments seen in aging?

Answer 22

Alzheimer’s disease (severe and rapid dementia, genetic component). Age-asscoated memory impairment (AAMI) - less severe cognitive decline, seen in general population.

Question 23

In normal aging, what are there no deficits in?

Answer 23

1. Implicit memory tasks - stimuli present and on further presentations there is a change in behaviour (even through the subject is not aware that they have previously experienced the stimuli).
2. Short-term memory tasks - Repeating a short list of numbers or words
3. Recognition memory tasks - Subject is shown a series of pictures (e.g. faces). In the test phase they have to say which faces they recognise from a larger set of stimuli.

Question 24

In normal aging, what are there deficits in?

Answer 24

1. Free or cued recall - e.g. inability to recall a particular word.
2. Recollection of original context in which an event occured.
3. Prospective memory tasks - remembering to carry out a task in the future.
4. Working memory tasks - presented with a list of words and need to recall the words in alphabetical order.