Effects of Posture and Stimulus Spectral Composition on Peripheral Physiological Responses to Loud Sounds

In the “loud-tone” procedure, a series of brief, loud, pure-tone stimuli are presented in a task-free situation. It is an established paradigm for measuring autonomic sensitization in posttraumatic stress disorder (PTSD). Successful use of this procedure during fMRI requires elicitation of brain responses that have sufficient signal-noise ratios when recorded in a supine, rather than sitting, position. We investigated the modulating effects of posture and stimulus spectral composition on peripheral psychophysiological responses to loud sounds. Healthy subjects (N = 24) weekly engaged in a loud-tone-like procedure that presented 500 msec, 95 dB sound pressure level, pure-tone or white-noise stimuli, either while sitting or supine and while peripheral physiological responses were recorded. Heart rate, skin conductance, and eye blink electromyographic responses were larger to white-noise than pure-tone stimuli (p’s < 0.001, generalized eta squared 0.073–0.076). Psychophysiological responses to the stimuli were similar in the sitting and supine position (p’s ≥ 0.082). Presenting white noise, rather than pure-tone, stimuli may improve the detection sensitivity of the neural concomitants of heightened autonomic responses by generating larger responses. Recording in the supine position appears to have little or no impact on psychophysiological response magnitudes to the auditory stimuli.

强音范式（loud-tone procedure）指在无任务情境下呈现一系列短促、高强度纯音刺激的实验范式，是用于测量创伤后应激障碍（PTSD）患者自主神经敏化的经典范式。在功能磁共振成像（fMRI）中应用该范式时，需保证在仰卧位（而非坐位）记录时，脑响应具备足够的信噪比。本研究探讨了体位与刺激频谱构成对强声诱发的外周心理生理反应的调节效应。共24名健康被试，每周参与一次类强音范式实验：实验呈现500毫秒、95分贝声压级的纯音或白噪音刺激，分别在坐位与仰卧位下进行，同时记录外周生理反应。相较于纯音刺激，白噪音刺激诱发的心率、皮肤电导率及眨眼肌电反应均显著更强（p<0.001，广义η方为0.073~0.076）。坐位与仰卧位下，刺激诱发的心理生理反应无显著差异（p≥0.082）。采用白噪音而非纯音刺激，可通过诱发更强的反应，提升对自主神经反应增强对应的神经关联物的检测灵敏度。仰卧位记录对听觉刺激诱发的心理生理反应强度几乎无影响。