Effects of meditation on brainstem auditory evoked potentials.

Brainstem auditory evoked potentials (BAEPs) were measured in five advanced practitioners of Transcendental Meditation (TM) to determine whether such responses would reflect reported increases in perceptual acuity to auditory stimuli following meditation. The BAEP provides an objective physiological index of auditory function at a subcortical level. Repeated measures of the BAEPs of TM practitioners were taken before and after a period of meditation and were compared with those of age-matched controls. Peak latencies as well as interwave latencies between major BAEP components were evaluated. No pre-postmeditation differences for experimental subjects were observed at low stimulus intensities (0--35 dB). At moderate intensities (40--50 dB), latency of the inferior collicular wave (wave V) increased following meditation, but at higher stimulus intensities (55--70 dB), latency of this wave was slightly decreased. Comparison of slopes and intercepts of stimulus intensity-latency functions indicates a possible effect of meditation on brainstem activity.

Effects of interstimulus interval on latency of the brainstem auditory evoked potential.

Peak latency of the inferior collicular response (wave V) of the brainstem auditory evoked potential (BAEP) increases with decreasing interstimulus interval (ISI). The present research investigated relative peak shifts of major components of the BAEP in an attempt to identify the source of the observed shift in wave V. Peripheral as well as central transmission times (CTT) were computed for 9 young adults between an ISI of 100 msec and an ISI of 10 msec. The results indicate that shifts in wave V latency with changing ISI are due to a combination of central and peripheral processes. The magnitude of the shift observed for wave V was approximately 0.50 msec. This increase in latency was accounted for by an average 0.29 msec increase in peripheral transmission time, a 0.14 msec increase in CTT between waves I and III, and a 0.07 msec increase in CTT between waves III and V. The results suggest a dual process underlying latency changes in wave V of the BAEP as a function of decreasing ISI. These are peripheral adaptation or fatigue and central processes that may include short-term habituation.