Table 6.3 Age‐related changes in attention and memory functions.
Source: Adapted from Glisky60; Zanto and Gazzaley72.
| Function | Description | Most common age‐related change |
|---|---|---|
| Attention | ||
| Selective attention | Ability to attend to some stimuli while disregarding others that are irrelevant to a given task | Relevant heterogeneity |
| Sustained attention | Maintaining vigilance or concentration on a task over time | Relevant heterogeneity |
| Divided attention Attention switching | Processing two or more sources of information or performing multiple tasks at the same time | Impaired |
| Working memory | Cognitive system that enables temporary storage and manipulation of information | Impaired |
| Long‐term memory | ||
| Episodic memory | Memory for personally experienced events that occurred at a particular time and place | Impaired |
| Semantic memory | Memory of general knowledge about the world and words and concepts | Preserved |
| Autobiographical memory | Memory for one’s personal past (includes both semantic and episodic memories) | Preserved |
| Procedural memory | Knowledge of skills and procedures that are expressed automatically in performance | Preserved |
| Implicit memory | Change in behaviour occurring after a prior experience (not consciously or explicitly recalled) | Preserved |
| Prospective memory | Remembering to perform a planned action at some future point in time | Preserved (frequently with external aids) |
Moreover, the ageing process influences certain cognitive functions disproportionately, and different trajectories of cognitive changes have been described.69,70 Specifically, basic functions in the cognitive information processing 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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