Awareness of physiological responding under stress and nonstress conditions in temporomandibular disorders.

To test the hypothesis that individuals with temporomandibular disorders (TMD) have deficits in proprioceptive awareness, 20 TMD patients were compared with 20 nonpain individuals matched to the TMD patients on age and gender. Left and right frontalis, masseter, and temporalis were monitored, as were forearm extensor, heart rate, and skin conductance while the participants viewed a nonstressful film segment. Following the film segment, participants provided self-reports of these physiological responses. This sequence was repeated for a second, stressful film segment and for a third, non-stressful film segment. Correlations between physiological activity and self-report were used as measures of proprioceptive awareness. The results indicated that TMD subjects were most accurate in their awareness of facial muscle activity during the stress condition and least accurate in the two nonstress periods. Control subjects increased their accuracy of awareness at each time period, showing significantly greater accuracy than the TMD group in the last, nonstress period. TMD subjects more accurately perceived activity of the nonfacial muscle variables in the two nonstress periods than during the stress period. These findings may provide a mechanism for understanding clinical observations showing that TMD patients with myofascial pain engage in high levels of parafunctional oral activity without awareness.