architecture, such as processing speed, working memory, and episodic memory, tend to decline across the adult lifespan (i.e. life‐long decline). Other well‐practised abilities and tasks that involve knowledge, like semantic memory and vocabulary, exhibit little or no decline until very late in life (i.e. late‐life decline). Finally, several cognitive competencies such as autobiographical memory, emotional processing, and automatic memory remain substantially unchanged throughout life (i.e. life‐long stability). Such heterogeneity in the patterns of cognitive change over the lifespan has been recognized in the constructs of crystallized and fluid abilities.69,71 Crystallized abilities, like vocabulary and general knowledge, are skills that are overlearned, well‐practised, and familiar and tend to remain stable (or even improve) over time. On the other hand, fluid abilities encompass functions involving problem‐solving and reasoning about things that are less familiar and less influenced by what one has learned in life. These skills, including processing speed, executive functions, and episodic memory, peak in early adult life and gradually decline over time. The most commonly observed age‐related changes in attention and memory functions are listed in Table 6.3.
Key points
Ageing is associated with structural and functional changes in the nervous system.
Neurodegenerative conditions share some pathophysiological processes, neuropathological modifications, and phenotypic manifestations with the physiological ageing process.
A neurological examination of the ageing individual commonly reveals clinical abnormalities.
Age‐related changes in cognition are not uniform across all older individuals and mostly occur in specific cognitive domains.
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