Answer to Question 1
Plasticity in the brain refers to its ability to change in structure and function as a relation of the brain's interaction with the environment. Plasticity refers to brain change or flexibility over time. The fact that research documents that older adults can improve their memories by being trained to use certain strategies in certain circumstances speaks to the brain's ongoing plasticity. Evidence for plasticity is also seen when older adults use bilateral activation. While younger adults use more unilateral activation when working on specific tasks, older adults use more bilateral activation. It appears they are working harder and utilizing more brain structures to optimize their thinking and performance. Finally, it was believed that neurogenesis (the proliferation of neural cells) dwindled with the embryonic period. The finding that neural stem cells exist in adult brains and can generate new neurons throughout the life span speaks to the plasticity of the human brain.
Answer to Question 2
The default network of the brain refers to the areas of the brain that are most active when one is at rest and not engaged in any cognitive task. Older individuals have more problems than younger people suppressing this default network. For example, when a younger begins an engaging and challenging cognitive task, the default network is suppressed. Older adults show less suppression, resulting in poorer performance overall. Increased frontal activity in older adults may be one way they work around this lack of suppression.
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