Bilateral auditory-evoked potentials in conditions of hypnosis and focused attention

Brain event-related potentials (ERPs) evoked by auditory stimulation were used to study cerebral hemispheric activity during hypnosis. ERPs were recorded from bilateral central (C3 and C4) and temporal (T3 and T4) scalp locations in response to tone pips in 6 medium-high and 6 low-susceptible subjects in three conditions: baseline (tones only), hypnosis (tones plus hypnotic induction), and a focused attention control (tones plus a newspaper story read by the hypnotist). Task asymmetries were individually adjusted for baseline asymmetries. Responses from central locations did not differentiate hypnosis from focused attention for either group. The same was true of temporal locations for the low-susceptible group. The predominant temporal lobe pattern for both conditions and groups was larger left than right responses. The exception was the hypnosis condition for the medium-high susceptible group where there was an increase in responses in the right temporal lobe.