Relationship between scalp potential and autonomic nervous activity during a mental arithmetic task.

The cerebral cortex had massive bidirectional connections to autonomic nervous system and mental performance can induce change of autonomic activity, but which regions are related to autonomic function is not clear. The study was to analyze the scalp positions which may affect cardiac autonomic nervous activity during a mental arithmetic (MA) task. Forty-three healthy male subjects were voluntarily participated in the study. Sympathetic and parasympathetic activities were estimated with heart rate variability. Scalp potential was determined by the wavelet packet parameters and approximate entropy (ApEn) of Electroencephalogram (EEG). The results showed that heart rate and the normalized low frequency power component were significantly increased (p<0.01) and the high frequency power component was decreased (p<0.01). Meanwhile relative wavelet packet energy in alpha band of EEG at P3, P4, Pz, O1, O2 and Oz electrodes were decreased and the beta band of EEG at the same electrodes were increased significantly (p<0.01). ApEn was significantly increased in MA (p<0.01). Moreover, changes of brain activity were earlier than the changes of autonomic activity and significantly correlations existed between heart rate variability and wavelet packet energy (p<0.05). In addition, a significant positive correlation between HR change and the laterality ratio score of alpha band in P3 v P4 (p<0.05) were observed. It is noted that cerebral conscious activity enhanced with the decrease of parasympathetic activity and increase of sympathetic activity, and the right post-central areas dominated sympathetic activity during stress-inducing mental tasks.