The optimal method and parameter to quantify emotion-modulated startle EMG in schizophrenic patients.

In electromyographic (EMG) research, different parameters and signal conditioning methods are used to quantify the EMG signal. In the present study, several methods (integration, smoothing, envelope) and parameters (magnitude, relative amplitude, blink area, onset latency, amplitude latency, response duration) were investigated by means of startle eyeblink EMG. Because previous studies have shown schizophrenic patients to have a disturbed emotional modulation of the startle reflex, 38 schizophrenics and 53 controls were subjected to an emotion-modulated startle paradigm, in which sudden noisebursts were presented while pictures with emotional content (negative, neutral, positive) were viewed. The results revealed that optimal discrimination between response patterns of patients and controls was obtained with the combination of the envelope method and the relative amplitude parameter. The present results are of great value for future studies in this area, offering new directions for the use of EMG in psychophysiological research.