Abstract:
Reduced capacity for executive cognitive function and for the autonomic control
of cardiac responsivity are both concomitants of the aging process. These may be linked
through their mutual dependence on medial prefrontal function, but the specifics ofthat
linkage have not been well explored. Executive functions associated with medial
prefrontal cortex involve various aspects ofperformance monitoring, whereas centrally
mediated autonomic functions can be observed as heart rate variability (HRV), i.e.,
variability in the length of intervals between heart beats. The focus for this thesis was to
examine the degree to which the capacity for phasic autonomic adjustments to heart rate
relates to performance monitoring in younger and older adults, using measures of
electrocortical and autonomic activity.
Behavioural performance and attention allocation during two age-sensitive tasks
could be predicted by various aspects of autonomic control. For young adults, greater
influence of the parasympathetic system on HRV was beneficial for learning unfamiliar
maze paths; for older adults, greater sympathetic influence was detrimental to these
functions. Further, these relationships were primarily evoked when the task required the
construction and use of internalized representations of mazes rather than passive
responses to feedback. When memory for source was required, older adults made three
times as many source errors as young adults. However, greater parasympathetic influence
on HRV in the older group was conducive to avoiding source errors and to reduced
electrocortical responses to irrelevant information. Higher sympathetic predominance, in
contrast, was associated with higher rates of source error and greater electrocortical
responses tq non-target information in both groups. These relations were not seen for
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errors associated with a speeded perceptual task, irrespective of its difficulty level.
Overall, autonomic modulation of cardiac activity was associated with higher levels of
performance monitoring, but differentially across tasks and age groups. With respect to
age, those older adults who had maintained higher levels of autonomic cardiac regulation
appeared to have also maintained higher levels of executive control over task
performance.
