Relationship between Somatization and Effects of Stress on Electrogastric Waveforms in Humans

Abstract

Electrogastric waveforms of human Ss were examined in relation to conditions oE response contingent avoidance of a noxious tone, altered feedback of successful and unsuccessful avoidance, non-response contingent aversive stimulation and somatization scores on the Mini-Mult Test. Significant differences were observed in eleccrogastric waveform frequency measures between baseline and tone periods. There was a significant difference for amplitude measures between trials based o n presence and absence of tone, and in the inreraction between presence and absence of tones and the personality characteristic of somatization. A trend was observed for amplitude in an interaction effect of successful vs unsuccessful avoidance and high vs low somatization.In research by Brady, et al. ( 1958), rhesus monkeys undergoing avoidance conditioning developed gastric disorders. Post mortem analysis revealed the presence of severe ulceration in all experimental Ss, with no such indication of pathological condition evidenced in yoked control animals. This research suggested that stress produced by response-contingent avoidance situations is manifested in gastrointestinal activity. Brady ( 1963) commented that there is a consistent decrease in gastric acidity during such stress-producing periods. Since gastric acidity and motility usually have a positive association (Stern, 1966), one might expect response-contingent stimulation to produce decreased gastric motility. Such results were obtained by White ( 1964) in a study on humans, where a decrease in amplitude of "20-sec. cycle" gastric activity occurred during an avoidance situation.Other investigations, however, have yielded results different from those of Brady and White. Davis and Berry (1963) found that a noise-avoidance task resulted in more motility than did passive reception of the same noise stimulus. Stern (1966) in a study of gastrointestinal motility amplitude and latency obtained results supporting those of Davis and Berry. Stern's results indicated that, during a response-contingency task, motility amplitude was greater and latency more brief than under random-noise conditions. Fedor and Russell ( 1965) designed an experiment to analyze in greater detail the effect of response-contingent situations and gastric motility. During an avoidance task similar to Davis and Berry's method, Ss could avoid an aversive auditory stimulus if a key was pressed at certain time intervals. This procedure made it possible to analyze different gastrointestinal reactions for successful and unsuccessful trials. In this study, amplitude of gastric motility decreased significantly when avoidance of the noise was successful. These results suggest chat motility increases under stress and that it may be the operation of cognitive feedback in response-contingent or stress situations that affects stomach motility.