Fig. 4. Psychophysiological testing at baseline.

(A) During the acquisition (Acq) of fear conditioning, images of a lamp shining a red, blue, or yellow light were shown. The former two (conditioned stimuli; CS+) but not the latter (unconditioned stimuli; CS−) were accompanied by an electric shock. SCR was measured during the trials. During fear extinction (Ext), the CS+ red light and CS− yellow light were presented in the absence of electric shocks. On the following day, participants were exposed to extinction memory recall testing. Nonextinguished stimuli (CS+ NE; blue light), extinguished stimuli (CS+ E; red light), and CS− (yellow light) were shown to the patients and controls (CTL) with no shock pairing. (B) Similar preoperative SCR values were recorded during the acquisition and extinction phases. In contrast, a trend toward higher SCR responses was observed in patients with PTSD during the recall of CS+ E (P = 0.057). (C) SCR measurements during the acquisition and recall of CS+ NE stimuli were similar in patients with PTSD and controls at baseline. μS, microsiemens; §, trend toward significance.