Social conditioning and extinction paradigm: a translational study in virtual reality

Abstract

In human beings, experiments investigating fear conditioning with social stimuli are rare. The current study aims at translating an animal model for social fear conditioning (SFC) to a human sample using an operant SFC paradigm in virtual reality. Forty participants actively (using a joystick) approached virtual male agents that served as conditioned stimuli (CS). During the acquisition phase, unconditioned stimuli (US), a combination of an air blast (5 bar, 10 ms) and a female scream (95 dB, 40 ms), were presented when participants reached a defined proximity to the agent with a contingency of 75% for CS+ agents and never for CS- agents. During the extinction and the test phases, no US was delivered. Outcome variables were pleasantness ratings and physiological reactions in heart rate (HR) and fear-potentiated startle. Additionally, the influence of social anxiety, which was measured with the Social Phobia Inventory scale, was evaluated. As expected after the acquisition phase the CS+ was rated clearly less pleasant than the CS-. This difference vanished during extinction. Furthermore, the HR remained high for the CS+, while the HR for the CS- was clearly lower after than before the acquisition. Furthermore, a clear difference between CS+ and CS- after the acquisition indicated successful conditioning on this translational measure. Contrariwise no CS+/CS- differences were observed in the physiological variables during extinction. Importantly, at the generalization test, higher socially fearful participants rated pleasantness of all agents as low whereas the lower socially fearful participants rated pleasantness as low only for the CS+. SFC was successfully induced and extinguished confirming operant conditioning in this SFC paradigm. These findings suggest that the paradigm is suitable to expand the knowledge about the learning and unlearning of social fears. Further studies should investigate the operant mechanisms of development and treatment of social anxiety disorder.

Keywords: fear-potentiated startle; heart rate; operant conditioning paradigm; social anxiety; social fear conditioning; virtual reality.

FIGURE 1

Virtual environment. (A) Room where acquisition and extinction phase in VR took place. (B,C) Two of the social stimuli (agents) used for the conditioning. (D) Setting (VR was presented via a head-mounted-display) during the experiment (laboratory room was darkened).

FIGURE 2

Pleasantness ratings (n = 40) for CS+ and CS– pre and post acquisition (A), extinction (B), and test phase (C) as well as the generalization effect (D) for CS+, CS– and CS∼ during test phase for low and high socially fearful participants. Note: CS+, agents with aversive unconditioned stimulus (US); CS–, agents without aversive US; CS∼, new agents on the 2nd day without aversive US; Pre, before each phase; Post, after each phase; Test, test phase. Mean pleasantness ratings (0 = least pleasant to 10 = most pleasant) were given. For the generalization effect (D) mean pleasantness ratings (0 = least pleasant to 10 = most pleasant) for low (Low, n = 21) and for high socially anxious participants (High, n = 19) were given. Anxiety was measured with the German version of the Social Phobia Inventory (SPIN; Stangier and Steffens, 2002), and participants were divided via median split of the SPIN (median = 15) in two groups (low and high socially anxious). Standard errors are presented by error bars.

FIGURE 3

Heart rate (n = 28) for CS+ and CS– pre and post acquisition (A), extinction (B), and test phase (C) as well as the generalization effect (D) for CS+, CS–, and CS∼ during test phase. Note: CS+, agents with aversive unconditioned stimulus (US); CS–, agents without aversive US; CS∼, new agents on the 2nd day without aversive US; Pre, before each phase; Post, after each phase; Test, test phase. Mean heart rate (HR, beats/minute) was given. Standard errors are presented by error bars.

FIGURE 4

Fear-potentiated startle (n = 32) for CS+ and CS– pre and post acquisition (A), extinction (B), and test phase (C) as well as the generalization effect (D) for CS+, CS–, and CS∼ during test phase. Note: CS+, agents with aversive unconditioned stimulus (US); CS–, agents without aversive US; CS∼, new agents on the 2nd day without aversive US; Pre, before each phase; Post, after each phase; Test, test phase. Mean fear-potentiated startle (presented in T-values) was given. Standard errors are presented by error bars.