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.

Cerebral cortex and autonomic nervous system responses during emotional memory processing

“…The mean power spectra PS k were normalized to the power spectra values from the Control period, to get relative power spectrum density ratios rPS (Fig 2(C)). We calculated the relative power spectra rPS in the theta 1 (4-6 Hz), theta 2 (6-8 Hz), alpha 1 (8-10 Hz), alpha 2 (10-12 Hz), alpha 3 (12-14 Hz), beta 1 (14-16 Hz), beta 2 (16)(17)(18), and beta 3 (18-20 Hz) bands in 57 (114.688-174.080 s) or 58 (116.736-176.128 s) segments, to obtain a time series of relative EEG power spectra in all epochs. X E was defined as a time series of relative EEG power spectra (Fig 2(C)).…”

“…In this study, TLs between X E from EEG recordings of each electrode and X C from the ECG were only calculated if WCC was greater than or equal to the threshold value 0.8 [15,16]. As an exception, if all WCC values in a subject were less than 0.8, a threshold of 0.7 or 0.75 was used for this subject's analysis.…”

“…In our previous research, we showed that simultaneous recordings of EEGs and ECGs are helpful to clarify the relationship between the brain and the ANS [15]. We examined time lag (TL) changes between EEG and activation of the parasympathetic nervous system in response to emotional memory recall [16]. The ANS consists of sympathetic and parasympathetic nerves, which often but not always exert antagonistic functions [17].…”