Neural Correlates of Aging-Related Differences in Pro-active Control in a Dual Task

Abstract

Background: Multi-tasking is usually impaired in older people. In multi-tasking, a fixed order of sub-tasks can improve performance by promoting a time-structured preparation of sub-tasks. How proactive control prioritizes the pre-activation or inhibition of complex tasks in older people has received no sufficient clarification so far.Objective: To explore the effects of aging on neural proactive control mechanisms in a dual task.Methodology: To address this question, the psychological refractory period (PRP) paradigm was used. Two 2-alternative-forced-choice reaction tasks with a predefined order (T1 and T2) signaled by a cue had to be executed simultaneously or consecutively by young (mean age 25.1 years, n = 36) and old subjects (mean age 70.4 years, n = 118). Performance indices of dual-task preparation were used to assess the focused preparation of T1 and T2. To compare preparatory mechanisms at the neurophysiologic level, multi-channel electroencephalogram (EEG) was recorded and negative slow cortical potentials (SCPs) were analyzed as objective markers of the amount and localization of cortical pre-activation before sub-task presentation.Results: Dual-task performance was significantly slower in old adults. T1 performance was facilitated in both age groups, but T2 processing in old adults was not optimized by the temporal structure as efficiently as in young adults. Also, only young adults manifested a stable pattern of focused of negative slow-wave activity increase at medial frontal and right-hemisphere posterior regions, which was associated with a coordinated preparatory T1 pre-activation and T2 deferment, while old adults manifested a broad topographic distribution of negative SCPs associated with a pre-activation of sensory and motor processes.Conclusions: These observations demonstrate that the proactive preparation for dual tasking is altered with aging. It is suggested that in young adults, attention-based pre-activation of working memory and inhibitory networks in the right hemisphere synchronizes the simultaneous preparation of the two sub-tasks, whereas in old adults, sensory and motor networks appear to be non-specifically pre-activated for subsequent deferred mode of processing.

The assessment of executive function abilities in healthy and neurodegenerative aging—A selective literature review

“…Seventy-two percent of studies reported an age-associated decline (see Supplementary material ), but there was some inconsistency in the outcome measures reported. For example, some studies reported the TMT cost (the difference between RT or error rate in parts A and B; see, for example, Tournier et al, 2014 and Yordanova et al, 2021 ); others reported the measures of TMT parts A and B separately or just the part B measure (the shifting measure of the task without considering the non-shifting condition; see Müller et al, 2014 ); and Rey-Mermet et al ( 2018 ) reported the TMT ratio. Therefore, shifting ability and deficits may not be confidently compared across studies, and it is recommended that researchers should report scores for parts A and B alongside ratio or cost scores.…”