Abstract:
In studies of cognitive processing, the allocation of attention has been consistently
linked to subtle, phasic adjustments in autonomic control. Both autonomic control of
heart rate and control of the allocation of attention are known to decline with age. It is not
known, however, whether characteristic individual differences in autonomic control and
the ability to control attention are closely linked. To test this, a measure of
parasympathetic function, vagal tone (VT) was computed from cardiac recordings from
older and younger adults taken before and during performance of two attentiondemanding
tasks - the Eriksen visual flanker task and the source memory task. Both
tasks elicited event-related potentials (ERPs) that accompany errors, i.e., error-related
negativities (ERNs) and error positivities (Pe's). The ERN is a negative deflection in the
ERP signal, time-locked to responses made on incorrect trials, likely generated in the
anterior cingulate. It is followed immediately by the Pe, a broad, positive deflection which
may reflect conscious awareness of having committed an error.
Age-attenuation ofERN amplitude has previously been found in paradigms with
simple stimulus-response mappings, such as the flanker task, but has rarely been
examined in more complex, conceptual tasks. Until now, there have been no reports of
its being investigated in a source monitoring task. Age-attenuation of the ERN
component was observed in both tasks. Results also indicated that the ERNs generated in
these two tasks were generally comparable for young adults. For older adults, however,
the ERN from the source monitoring task was not only shallower, but incorporated more
frontal processing, apparently reflecting task demands. The error positivities elicited by
3
the two tasks were not comparable, however, and age-attenuation of the Pe was seen only
in the more perceptual flanker task. For younger adults, it was Pe scalp topography that
seemed to reflect task demands, being maximal over central parietal areas in the flanker
task, but over very frontal areas in the source monitoring task.
With respect to vagal tone, in the flanker task, neither the number of errors nor
ERP amplitudes were predicted by baseline or on-task vagal tone measures. However, in
the more difficult source memory task, lower VT was marginally associated with greater
numbers of source memory errors in the older group. Thus, for older adults, relatively
low levels of parasympathetic control over cardiac response coincided with poorer source
memory discrimination. In both groups, lower levels of baseline VT were associated with
larger amplitude ERNs, and smaller amplitude Pe's. Thus, low VT was associated in a
conceptual task with a greater "emergency response" to errors, and at the same time,
reduced awareness of having made them. The efficiency of an individual's complex
cognitive processing was therefore associated with the flexibility of parasympathetic
control of heart rate, in response to a cognitively challenging task.
