Stimulus transformation into motor action: Dynamic graph analysis reveals a posterior‐to‐anterior shift in brain network communication of older subjects

Abstract

Cognitive performance slows down with increasing age. This includes cognitive processes that are essential for the performance of a motor act, such as the slowing down in response to an external stimulus. The objective of this study was to identify aging‐associated functional changes in the brain networks that are involved in the transformation of external stimuli into motor action. To investigate this topic, we employed dynamic graphs based on phase‐locking of Electroencephalography signals recorded from healthy younger and older subjects while performing a simple visually‐cued finger‐tapping task. The network analysis yielded specific age‐related network structures varying in time in the low frequencies (2–7 Hz), which are closely connected to stimulus processing, movement initiation and execution in both age groups. The networks in older subjects, however, contained several additional, particularly interhemispheric, connections and showed an overall increased coupling density. Cluster analyses revealed reduced variability of the subnetworks in older subjects, particularly during movement preparation. In younger subjects, occipital, parietal, sensorimotor and central regions were—temporally arranged in this order—heavily involved in hub nodes. Whereas in older subjects, a hub in frontal regions preceded the noticeably delayed occurrence of sensorimotor hubs, indicating different neural information processing in older subjects. All observed changes in brain network organization, which are based on neural synchronization in the low frequencies, provide a possible neural mechanism underlying previous fMRI data, which report an overactivation, especially in the prefrontal and pre‐motor areas, associated with a loss of hemispheric lateralization in older subjects.

Still Wanting to Win: Reward System Stability in Healthy Aging

“…However, the direct test for hemispheric asymmetry yielded no significant results ( Figure 5B ,b). Hemispheric asymmetry reduction in older adults has been reported during cognitive tasks across studies ( Hogan et al, 2012 ; Learmonth et al, 2017 ; Kenney et al, 2019 ; Rosjat et al, 2021 ). The here presented results do not show an apparent HAROLD effect.…”

“…Due to the close link between reward processing and cognition, we propose the involvement of HAROLD, PASA, and FPCN compensatory mechanisms in preserved reward system function in healthy aging. These compensatory models have been tested successfully with EEG connectivity analyses elsewhere ( Rosjat et al, 2018 ; Rosjat et al, 2021 ).…”

“…Thus, the results show no clear PASA effect. Nevertheless, the higher fronto-occipital coherence modulation in the older group could comply with a PASA effect ( Rosjat et al, 2021 ). The PASA phenomenon has been described during cognitive tasks across studies ( Huizeling et al, 2021 ; Rosjat et al, 2021 ; Seider et al, 2021 ).…”

“…Nevertheless, the higher fronto-occipital coherence modulation in the older group could comply with a PASA effect ( Rosjat et al, 2021 ). The PASA phenomenon has been described during cognitive tasks across studies ( Huizeling et al, 2021 ; Rosjat et al, 2021 ; Seider et al, 2021 ). According to the PASA hypothesis, declined occipital activation is due to older adults’ sensory processing deficits.…”

M/EEG Dynamics Underlying Reserve, Resilience, and Maintenance in Aging: A Review

“…These compensatory phenomena are found not only in cognitive tasks but also in motor tasks. For example, Rosjat et al ( 2021 ) showed increases in delta and theta synchrony (measured by PLV) in healthy elderly in association with sustained motor performance at the same level as in young people (see also Rosjat et al, 2018 ).…”