40 Hz visual and auditory entrainment increases EEG alpha activity and improves cognitive functions of middle-aged healthy controls

Aim: 40 Hz auditory-visual entrainment has a neuroprotective effect and could maintain synaptic integrity and reduce tau phosphorylation levels in Alzheimer’s Disease mouse models. The effect of 40 Hz entrainment on the cognitive functions of healthy controls is unknown. The present study aims to analyze the 40 Hz entrainment on the cognitive functions of healthy middle-aged subjects and compare it with the effect of 40 Hz gamma tACS.Methods: 13 subjects were applied auditory-visual 40 Hz entrainment, nine subjects were applied 40 Hz gamma tACS on the left temporoparietal area for ten days, nine subjects were included as a control group. Spontaneous EEG (eyes closed/eyes open) was recorded three times for each group (baseline,1 hour after entrainment/20 minutes after tACS, and ten days later). Neuropsychological tests for all groups were applied twice at baseline and after ten days. Alpha, beta, and gamma activity were analyzed with FFT.Results: 40 Hz entrainment increased eyes closed alpha (8-13 Hz) activity. ANOVA results showed significant groupXtime interaction (p=0,034), the entrainment group had increased alpha activity after one hour and after ten days of application, on the other hand, this was not the case for the other two groups. Furthermore, there was a significant increase in the neuropsychological test scores of the entrainment group and tACS groups.Conclusions: This study, for the first time in the literature, showed that auditory-visual 40 Hz entrainment increases alpha activity in spontaneous EEG and cognitive functions in healthy subjects.This study was funded by TÜBİTAK (No. 122R056).