Lecture 22 – The Aging Brain (Plasticity)
Structural changes;
- Slow but persistent rate of decline in volume of the brain (Kemper, 1994).
- Loss of brain cells (neurons) in primary aging is less than previously believed.
- But is linked now to the shrinkage of cell bodies and dendritic debranching instead.
- Loss of total number of neurons but not all loss translates to functional decline= Life-
long plasticity (new dendrites and pruning).
- Connectivity is also effect - Slowing of transmission across the synapses between
neurons. The speed at which the action potential travels down the axon impaired?
- Heterogenous = massive individual differences in how this changes occur and what
changes occur.
The Weight of the Human Brain during Development;
- Over production of nerve cell up to adulthood
- By seven new cells added quicker than old ones being
killed
- After this, the total neurons decrease but size and
complexity can increase past ninety.
- No biological causes of why this happens, must be a
mechanism which is linked to the wiring of the neural
brain.
Structural changes;
- Accumulation of chemicals and pathological structures inside and outside neurons.
E.g., lipid lipofuscin (‘wear and tear substance’; fat deposits).
- Frontal cortex, neostriatum (subcortical forebrain) declines
- What about the hippocampus? Hippocampal decline may be more of an indicator of
dementia.
- Some regions of the brain don’t see this decline is psychological
function and biological decline.
- Raz (1997) MRI volumes (picture);
- See the decline in both the frontal and medial lobes, but this may
be greater in the frontal lobe.
Functional changes;
- Neurochemistry, blood flow, take up of oxygen and glucose
- Reduction in receptors, neurotransmitters
- Cholinergic deficits/Memory deficits
The frontal lobes;
- Frontal Ageing Hypothesis;
- Is the age-related deterioration of the frontal lobes responsible for the functional
decline?
- Similarities in the behavioural problems exhibited by frontal lobe patients and older
adults (West, 1996)
- West’s (1996) - “cognitive functions supported by the prefrontal cortex should reveal
declines at an earlier age than those supported by other brain regions”
Structural changes;
- Slow but persistent rate of decline in volume of the brain (Kemper, 1994).
- Loss of brain cells (neurons) in primary aging is less than previously believed.
- But is linked now to the shrinkage of cell bodies and dendritic debranching instead.
- Loss of total number of neurons but not all loss translates to functional decline= Life-
long plasticity (new dendrites and pruning).
- Connectivity is also effect - Slowing of transmission across the synapses between
neurons. The speed at which the action potential travels down the axon impaired?
- Heterogenous = massive individual differences in how this changes occur and what
changes occur.
The Weight of the Human Brain during Development;
- Over production of nerve cell up to adulthood
- By seven new cells added quicker than old ones being
killed
- After this, the total neurons decrease but size and
complexity can increase past ninety.
- No biological causes of why this happens, must be a
mechanism which is linked to the wiring of the neural
brain.
Structural changes;
- Accumulation of chemicals and pathological structures inside and outside neurons.
E.g., lipid lipofuscin (‘wear and tear substance’; fat deposits).
- Frontal cortex, neostriatum (subcortical forebrain) declines
- What about the hippocampus? Hippocampal decline may be more of an indicator of
dementia.
- Some regions of the brain don’t see this decline is psychological
function and biological decline.
- Raz (1997) MRI volumes (picture);
- See the decline in both the frontal and medial lobes, but this may
be greater in the frontal lobe.
Functional changes;
- Neurochemistry, blood flow, take up of oxygen and glucose
- Reduction in receptors, neurotransmitters
- Cholinergic deficits/Memory deficits
The frontal lobes;
- Frontal Ageing Hypothesis;
- Is the age-related deterioration of the frontal lobes responsible for the functional
decline?
- Similarities in the behavioural problems exhibited by frontal lobe patients and older
adults (West, 1996)
- West’s (1996) - “cognitive functions supported by the prefrontal cortex should reveal
declines at an earlier age than those supported by other brain regions”
