SCHEDULE-INDUCED MASSETER EMG IN FACIAL-PAIN SUBJECTS VS NO-PAIN CONTROLS

Empirical reports suggest that oral habits (e.g., teeth clenching) may be behavioral mediators linking stress to muscle hyperreactivity and the development of facial pain. Another report suggests that excessive behavioral adjuncts develop in conjunction with fixed-time stimulus p resentation. The present study assessed the extent to which the oral h abits exhibited by facial pain patients are schedule-induced. Subjects with Temporomandibular Disorder (TMD) symptomatology (n = 15) and pai n-free controls (n = 15) participated in a 4-phase experiment (adaptat ion, baseline, task, recovery) designed to elicit schedule-induced beh aviors. Self-report of oral habits and negative affect were recorded a fter each phase. Objective measures of oral habits were obtained via b ehavioral observation and masseter EMG recordings. Results revealed th at negative arousal significantly increased during the fixed-time (FT) task and was also associated with increased oral habits among the TMD subjects. Moreover, 40% of the TMD subjects and none of the controls exhibited a pattern of EMG elevations in the early part of the inter-s timulus interval that met a strict criteria for scheduled-induced beha vior per se. Taken together, these results suggest that the TMD subjec ts were engaging in schedule-induced oral habits. The adjunctive behav ior literature seems to provide a plausible explanation as to how oral habits develop and are maintained in TMD patients, despite their pain ful consequences. Copyright (C) 1997 Elsevier Science Inc.