Attempting to counteract vigilance decrement in older adults with brain stimulation

Birte S Löffler; Heiko I Stecher; Arnd Meiser; Sebastian Fudickar; Andreas Hein; Christoph S Herrmann

doi:10.3389/fnrgo.2023.1201702

Attempting to counteract vigilance decrement in older adults with brain stimulation

Front Neuroergon. 2023 Dec 12:4:1201702. doi: 10.3389/fnrgo.2023.1201702. eCollection 2023.

Authors

Birte S Löffler¹, Heiko I Stecher², Arnd Meiser², Sebastian Fudickar¹, Andreas Hein¹, Christoph S Herrmann^{2

3}

Affiliations

¹ Assistance Systems and Medical Device Technology, Department of Health Services Research, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.
² Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster of Excellence "Hearing4all", Carl von Ossietzky University Oldenburg, Oldenburg, Germany.
³ Research Center Neurosensory Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.

Abstract

Introduction: Against the background of demographic change and the need for enhancement techniques for an aging society, we set out to repeat a study that utilized 40-Hz transcranial alternating current stimulation (tACS) to counteract the slowdown of reaction times in a vigilance experiment but with participants aged 65 years and older. On an oscillatory level, vigilance decrement is linked to rising occipital alpha power, which has been shown to be downregulated using gamma-tACS.

Method: We applied tACS on the visual cortex and compared reaction times, error rates, and alpha power of a group stimulated with 40 Hz to a sham and a 5-Hz-stimulated control group. All groups executed two 30-min-long blocks of a visual task and were stimulated according to group in the second block. We hypothesized that the expected increase in reaction times and alpha power would be reduced in the 40-Hz group compared to the control groups in the second block (INTERVENTION).

Results: Statistical analysis with linear mixed models showed that reaction times increased significantly over time in the first block (BASELINE) with approximately 3 ms/min for the SHAM and 2 ms/min for the 5-Hz and 40-Hz groups, with no difference between the groups. The increase was less pronounced in the INTERVENTION block (1 ms/min for SHAM and 5-Hz groups, 3 ms/min for the 40-Hz group). Differences among groups in the INTERVENTION block were not significant if the 5-Hz or the 40-Hz group was used as the base group for the linear mixed model. Statistical analysis with a generalized linear mixed model showed that alpha power was significantly higher after the experiment (1.37 μV²) compared to before (1 μV²). No influence of stimulation (40 Hz, 5 Hz, or sham) could be detected.

Discussion: Although the literature has shown that tACS offers potential for older adults, our results indicate that findings from general studies cannot simply be transferred to an old-aged group. We suggest adjusting stimulation parameters to the neurophysiological features expected in this group. Next to heterogeneity and cognitive fitness, the influence of motivation and medication should be considered.

Keywords: EEG; alpha power; brain stimulation; enhancement; gamma-tACS; older adults; reaction times; vigilance.

Grants and funding

This research has been funded by the Volkswagen Foundation, Ministry of Science and Culture of Lower Saxony as a part of the Interdisciplinary Research Centre on Critical Systems Engineering for Socio-Technical Systems (Grant No.: VWZN2861 VWZN2998) and by own resources of the OFFIS e.V., Institute for Information Technology, Oldenburg, Germany.