Differential behavioral and neural effects of physical and mental fatigue on modality-specific task interference in cognitive-postural dual-task situations in young and old adults

• Applicants: Professor Dr. Urs Granacher, Ph.D.; Professor Dr. Stephan Heinzel; Professor Dr. Michael Rapp; Professorin Dr. Christine Stelzel
• Subject Area: General, Cognitive and Mathematical Psychology
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 274922926

Age-related decrements in postural control and working memory as well as dual-task performance have ample significance for everyday activities and critical outcomes such as falls. Postural control reflects a multimodal system affected by age-related changes in cognition, sensory input, as well as muscular output. Based on models of content-specific interference (i.e. modality compatibility) as well as models of limited central capacities, during the first period of this priority program, we addressed the question whether the compatibility of input and output modality mappings (i.e. that visual input and motor output are deemed compatible, while e.g. auditory input and motor output are deemed incompatible) differentially affect dual-tasks involving postural control. Overall, we were able to show that modality-specific interference affects continuous dual-task performance in young and more so in old adults, and that these age differences are related to compensatory mechanisms in the lateral prefrontal cortex (PFC).In order to investigate the interaction between central processing limitations and effects of modality compatibility, the current proposal will examine the effects of domain-specific resource depletion operationalized as fatigue interventions on modality-specific cognitive-motor dual-task performance. For this purpose, two experimental series with two domain-specific fatigue interventions (physical vs. mental fatigue) will be launched that i) disentangle the effects of physical and mental fatigue on cognitive-postural performance during dual-task stimulus-response modality compatibility conditions in healthy young and old adults and ii) delineate brain mechanisms underlying these effects. We hypothesize that physical fatigue results in similar relative declines in postural control in young and old adults, but we expect greater physical fatigue-related performance declines with increasing modality incompatibility in old age. Mental fatigue should affect relative cognitive performance in both age groups, but we expect selective age-related effects of mental fatigue with increasing modality incompatibility in postural control due to age-related central resource limitations and larger attentional demands.Behavioral cognitive and motor measures will be complemented by neuronal markers (electroencephalography EEG, functional magnetic resonance imaging fMRI) to assess these effects, and we expect fatigue to suppress dual-task related fMRI activity in PFC regions, and increase alpha and theta band power in EEG in young and old adults, with selective effects of physical fatigue in the old age group. In sum, the investigation of the effects of physical vs. mental fatigue and modality compatibility on cognitive-motor dual-task performance in young and old adults may shed further light on the mechanisms underlying age-related decline and compensatory mechanisms in cognitive-motor multitasking and may inform targeted interventions in old age.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1772: Human performance under multiple cognitive task requirements: From basic mechanisms to optimized task scheduling
• Co-Investigators: Professor Reinhold Kliegl, Ph.D.; Professor Dr. Henrik Walter