Cerebral responses evoked by electrical stimulation of the esophagus in normal subjects

Cerebral responses to electrical stimulation of the esophagus were investigated in 11 healthy male volunteers, 20-40 yr old. The stimulus was applied via a probe equipped with bipolar ring electrodes. It was positioned in the middle and distal esophagus at 20 and 37 cm from the incisors, respectively, and sucked to the mucosa. Electrical stimuli (0.1-ms duration, different stimulus voltages) were applied at frequencies of 0.1-1.0 Hz or in randomized order. Cerebral responses to electrical stimulation were recorded after 20-40 stimulations and averaged on a time base of 1000 ms. Evoked potentials consisted of successive peaks and troughs in the averaged electroencephalogram with good reproducibility within and between subjects. Amplitudes of evoked potentials showed a significant reduction with electrical stimulation at 37 cm compared with 20 cm, and with stimulation frequencies of 0.5 and 1.0 Hz compared with 0.2 and 0.1 Hz. Evoked potentials from 37 cm showed longer latencies compared with those from 20 cm. Irregular stimulation and stimulation during mental distraction did not alter these responses. It is concluded that reproducible evoked potentials can be recorded from the scalp after electrical stimulation of the esophagus and that these are transferred centrally via vagal afferents. The technique may become a useful tool in the study of visceral nervous connections to the brain in health and disease.