Preliminary study on auditory evoked potentials during qigong meditation

Author: Zhang Wenbin////
Shanghai Qigong Institute, Shanghai, China [1]
Conference/Journal: 3rd Nat Acad Conf on Qigong Science
Date published: 1990
Other: Pages: 4 , Word Count: 525

It has been claimed that during QiGong meditation (QM) the auditory cortex is in an inhibitory state whereas the brainstem appears to be facilitated (Liu, et al.1987). However, with this same method of auditory evoked potentials (AEPs), no consistent changes in the AEP late components were noted when practising transcendental meditation in an earlier report (Barwood, et al. 1979). The present work was undertaken to determine whether the AEPs would be changed and the cerebral cortex should really be in an inhibitory state during QM. The results were as follows:

1. Middle- and long-latency AEPs
The averaged AEP to clicks (50-55dB HL, 0.5Hz) recorded from C2- Al derivative was a composite and polyphasic wave composed of several components labelled Na-Pa-P1-N1-P2-N2. The Na and Pa belonged to the middle-latency components while the Pl, Nl, P2 and N2 were long-latency ones (late components). It was found that the N1 peak latencies were lengthened by 4.2±8.3ms (from 84.3±7.6 to 88.5±7.3ms, P<0.05) and the Pl-N1 amplitudes decreased by l.0±2.1uv (from 7.3±3.3 to 6.3±2.4uv, P<0.05) during QM in the Qigong practising group (n=20). No significant changes in the other components were observed. In the Qigong learning group (n=12) the APEs did not change significantly throughout the experiments. The raw EEGs showed that the alpha rhythms were slightly augmented in most cases and attenuated on rare occasions. Sometimes a few theta waves occurred. The EEG patterns resembled those characterizing the A, even B stage of sleep (Loomis, et al. 1937) when the vigilance level lowered and the AEP late components, N1a, N1b and P2b, amplitudes reduced (Fruhstorfer, et al. 1969). The results of our observation on QM were analogous to these. Hence, the AEP amplitude reduction during QM may also be interpreted as a decline in the activity of certain brain functions which are essential for the maintenance of an efficient subject/environment relation.

2. The recovery functions of AEPs
The AEP late components (R1,R2) to paired clicks (3' interval, 60-65dB HL. O.lHz) were investigated during QM in 12 Qigong practitioners, 15 Qigong learners and 7 controls. In the Qigong practitioners, the R1 amplitudes (N1-P2,P2-N2) decreased and the P2-N2 R2/R1 ratios increased from 85.2±l2.5 to 104.9±l4.9% (P<0.005). There were no significant changes in R1, R2 and R2/R1 in the others. The audible thresholds for the clicks lowered by about 2.5dB on average (P<0.05-0.001) immediately after QM or after rest in all 3 groups. It may be suggested that, therefore, the subnormality of those neurons responsible for the evoked responses is less marked and recovers more rapidly during QM. Evidently the auditory cortex is not in an absolutely inhibitory state during QM as some authors have reported.

3. The brainstem auditory evoked responses (BAERs)
The BAERs to 70 and 40dB SL clicks were measured in 8 and 11 Qigong practitioners respectively. The responses recorded were a relative consistency throughout the experimental sessions. No greater amplitudes were noted during QM than before and after QM. The authors argue that if the BAERs change in amplitude during QM the variation of muscle tone must be considered, because the EMG artifacts interfere with the BAER recording greatly.