The effect of acupuncture stimulation of the middle latency auditory evoked potential.

The effects of acupuncture stimulation (AS) on the middle latency auditory evoked potentials (MLAEPs) were studied in 19 normal male volunteers. Scalp recordings were made from 21 points (including Cz) and posterior auricular muscle (PAM) electrodes referenced to the linked mastoid. Four components of MLAEPs (Po, Na, Pa and Nb) and two components of PAM reflex (N12 and P17) were statistically analyzed for changes in latency and amplitude. Wave phase of Po and Na reversed to N12 and P17, respectively, and the peak-to-peak amplitude of Po-Na, Na-Pa, Pa-Nb and N12-P17 showed a marked increase during AS to the ipsilateral side whereas no change in latency was detected. Each component's isovoltage topographic maps and dipole locations were calculated to be near both PAM (Po and Na) and temporal positions (Pa and Nb) during AS. These data showed that AS can promote MLAEPs activity and these signals (Po and Na) may originate from increased activity in N12 and P17 of the PAM reflex, respectively, and that the auditory cortex of the temporal gyrus is the generator substrate of Pa and Nb.