Changes in cognition, affect, and brain function combine to promote a shift in the nature of mentation in older adulthood, favoring exploitation of prior knowledge over exploratory search as the starting point for thought and action.
In humans, the exploration versus exploitation trade-off has been extensively studied in young adults. Yet there is growing evidence that the determinants and criteria governing decisions to explore versus exploit are altered over the adult life span, with direct implications for mentation and real-world functioning in later life.
Age-related exploitation biases result from the accumulation of prior knowledge, reduced cognitive control, and a shift toward affective goals. These are accompanied by changes in cortical networks, as well as attention and reward circuits. By incorporating these factors into a unified account, the exploration-to-exploitation shift offers an integrative model of cognitive, affective, and brain aging.
- Exploration- and exploitation-based search processes underlie goal-directed cognition.
- Older adults rely more on exploitation-based search during goal-directed tasks.
- Emergence of an exploitation-biased mental mode is coincident with declining cognitive control, knowledge accumulation, altered motivational drives, and brain network changes in older adulthood.
- The exploitative mental mode hypothesis may offer a more unitary account of mental functions in late-life development.
- The age-related shift in mental mode has both adaptive and maladaptive implications for performance on laboratory-based tasks, as well as real-world functioning in later life.
Panel A. Reward and motivation circuit.
The AIM framework proposes three processes (affective, integrative, motivational) that shape exploitation and exploration decisions. Age-related changes to these circuits provide a mechanism for the emergence of an exploitation biased mental mode. At the Affective level, reduced sensitivity to predicted negative choice
outcomes in older adulthood, increases positive reward expectancies, leading to increased DA signaling to attention modulation circuits (Panel C, and see below). At the integration level, greater integration of positively-valenced affective information and prior knowledge coded in medial prefrontal cortex (mPFC) regions, reduces uncertainty of known choice options, increasing the relative risk of information seeking (i.e., exploration) behaviors, motivating an exploitation-biased choice. We propose that prior knowledge and affective information are integrated in Schema and instantiated in mPFC. Note that the Motivation level of the hierarchy is dotted, reflecting our lack of specific predictions regarding age-related changes to this circuit.
Panel B. Putative brain systems.
Medial prefrontal cortex, a core node of the default network, integrates prior knowledge (via connections to default network regions) and affective value information (via dopaminergic inputs from nucleus accumbens into schema. Positive signaling from mPFC to the attention modulation circuit (anterior cingulate cortex (ACC), locus coeruleus (LC)) within the salience network biases noradrenergic functioning, promoting phasic attention.
Panel C. Attention modulation circuit.
This model describes an integrated neural system for the adaptive regulation of performance. Increased dopaminergic reward signaling from mPFC and associated with positively-valenced outcome expectations and value-based enhances noradrenergic signaling from ACC to LC . Increased noradrenergic signaling leads to sustained phasic firing in LC. According to Adaptive Gain Theory, phasic LC signaling promotes focused attention and a sustained bias towards exploitation-biased choice. Abbreviations: dopamine (DA), norepinephrine (NE).
There is – according to the review – emerging evidence that the shifting architecture of cognition, affect, and brain function leads to the emergence of an exploitation-biased mental mode in later life; one that favors the exploitation of prior knowledge over exploratory search for novel information, solutions, associations, and experiences. This shift in the exploration and exploitation trade-off reflects reduced cognitive control in the context of growing stores (and influence) of prior knowledge, as well as a shift toward affective goals, and parallels age-related changes to cortical brain networks, attention, and reward circuits.
By encapsulating the dual trajectories of aging cognition (reduced control and increased prior knowledge), as well as shifts in affectively driven motivations, age-related changes in the exploitation–exploration trade-off provide a more integrative marker, capturing multiple dimensions of aging mentation in a single behavioral outcome.
More importantly, reframing these changes in cognitive, affective, and brain architectures as resulting in a fundamentally altered mode of mentation, highlights the possibility, perhaps even the probability, that older adults approach all volitional mentation and action from a different starting position than younger adults; one that carries both the weight and the wisdom from decades of lived experience with evidence of both positive and negative outcomes.
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