How do the parasympathetic nervous system and EEG respond to emotional memory recall?

Abstract

An emotional event can provoke somatic symptoms as a consequence of brain responses accompanying reactions of the autonomic nervous system (ANS). ANS consists of the sympathetic nervous system and the parasympathetic nervous system, and their anatomical and physiological mechanisms are different. The aim of this study was to evaluate the time lag between the responses of electroencephalography (EEG) and the parasympathetic nervous system (from electrocardiography; ECG) during emotional recall. EEG and ECG of healthy young adults were simultaneously recorded during the recall of emotionally pleasant and unpleasant audiovisual stimuli, with three repetitions. A time series (TS) of relative power spectra from EEG and a TS of power spectral values in high frequency (HF) of RR intervals in ECG were obtained using fast Fourier transform. The time lag between the TS of EEG and HF was calculated using wavelet cross‐correlation analysis. The results indicated that the cerebral cortex responded earlier than the parasympathetic nervous system to the pleasant stimuli. In contrast, the parasympathetic nervous system responded earlier than the cerebral cortex to the unpleasant stimuli. These events constantly appeared in both unfamiliar and familiar situations. This study quantitatively shows that the parasympathetic nervous system quickly and constantly reacts to emotionally unpleasant stimuli. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.