ELECTROPHYSIOLOGICAL STUDY OF SUPERFICIAL ABDOMINAL REFLEXES IN NORMAL MEN

We studied the superficial abdominal reflexes of 83 normal men, using as stimuli a train of electrical pulses or a needle scratch. Electrica l stimulation delivered to the midline of the abdominal wall evoked, a lmost symmetrically on both sides, two reflex discharges: an early res ponse having an oligophasic wave form, and a late response of polyphas ic wave form. The threshold of the early response significantly exceed ed that of the late response. With repetitive stimulation, the late re sponse generally revealed habituation. Electrical stimulation of the u nilateral abdominal wall evoked two responses on the stimulated side, whereas it evoked only the late response on the contralateral side. A needle scratch on the unilateral abdominal wall evoked one reflex disc harge with a long latency and a polyphasic wave form. This response oc curred generally on the stimulated side and became habituated to repea ted scratching. These observations suggest that the superficial abdomi nal reflexes elicited by electrical stimulation are composed of two re flex discharges with a different reflex arc. They appear to closely re semble the blink reflex, The response elicited by needle scratching is thought to correspond to the late response of the electrically elicit ed abdominal reflexes.