Individual Differences in Autonomic Response: Conditioned Association or Conditioned Fear?

Abstract

Cluster analysis was used to define three groups of subjects whose conditioned heart rate response emphasized either acceleration, deceleration, or moderate deceleration. A subject pool (N = 148) was generated from four separate studies of differential classical conditioning in which colored slides served as conditioned stimuli (CSs) and the unconditioned stimulus (UCS) was aversive auditory noise. Both the statistically generated Accelerator and Decelerator groups responded with a significant late interval deceleration to CS+. However, only Accelerators also displayed a significant mid‐interval heart rate increase to CS+. Conditioned electrodermal responses were significantly more resistant to extinction for Accelerators than for the other two cluster groups. Accelerators also differed from Decelerators in that their affective judgments of the slide stimuli became less positively valent and less dominant from pre‐ to post‐conditioning, effects not found for Decelerators. Moderate Decelerators produced mixed results across the several psychophysiological and verbal measures of conditioning, resembling Accelerators in their verbal report change, and Decelerators in their rapid electrodermal extinction. It is suggested that cluster assignment may reflect subjects' pre‐conditioning learning set. All successfully conditioned subjects appear to learn a relationship between stimuli such that the appearance of the CS+ prompts an anticipatory orienting response (late interval heart rate deceleration). Accelerators differ from the other two groups in that they also condition a defensive response which is associated with a change in emotional judgments of the stimuli and may represent covert preparation for avoidance. The relationships between defensive responding, avoidance, and the concept of fear are considered, and the problem of desynchrony in emotional change (i.e., the Moderate Decelerators) is addressed. Finally, parallels are drawn between results from classical conditioning and clinical studies of fear and phobia, and further suggestions are made for utilizing the conditioning paradigm in the study of emotion.

Neurobiological Mechanisms Underlying the Blocking Effect in Aversive Learning

“…Another autonomic measure of learning, HR acceleration, did, however, show significantly stronger responses to the nonblocked stimulus (CSY) than to the blocked stimulus (CSX). This is especially relevant, because conditioned HR acceleration is a sensitive index of the affective component in aversive learning (Ö hman, 2009), as it has been selectively associated with an increased state of fear, as represented for example by emotional ratings (Hodes et al, 1985;Hamm and Vaitl, 1996) and fearpotentiated startle (Hamm and Vaitl, 1996), and can also occur without awareness of the CS-US relationship (Hamm and Vaitl, 1996). A post hoc analysis of deceleratory HR responses did not show a blocking effect, but also failed to show a basic effect of conditioning.…”

“…Similar to the SCR analysis, we then compared the maximum in the CS interval to the response during the prestimulus baseline (i.e., 1 s before CS onset) and averaged the responses for each condition. Note that although conditioned HR responses can be both deceleratory and acceleratory, we were specifically interested in the latter as only these have been associated with an increased state of fear (Hodes et al, 1985;Hamm and Vaitl, 1996). Since acceleratory responses have been shown to grow stronger over the course of acquisition (Hare and Blevings, 1975;Fredrikson, 1981), we investigated not only the first 10 trials of acquisition, but also the second 10 trials, where such an effect would be expected to occur.…”

Emotional scenes and facial expressions elicit different psychophysiological responses

“…The EMG response was baseline-corrected by subtracting data from a 100 ms baseline preceding the trial in 100 ms steps, and an average for the first three seconds of each trial was calculated. 4 For the heart rate response, R-spikes were marked in the EKG and inter-beat-intervals were calculated and transformed into beats per minute, in one second bins (see Bradley et al, 2001;Gatchel and Lang, 1974;Hodes et al, 1985). To determine initial heart rate deceleration as the orienting response (Bradley et al, 2001), changed scores were calculated with mean beats per minute for the first three seconds of picture presentation relative to a three second baseline period directly preceding stimulus onset.…”

Neural responses to salient visual stimuli

“…This type of conditioning has been demonstrated across the phylogenetic scale from gastropod molluscs (Hawkins et al 1983) to humans (Hodes et al 1985), and the synaptic changes involved (Kandel & Schwartz 1982) represent one of the simplest forms of value-dependent neural plasticity (Friston et al 1994). In mammals, this plasticity of neural response appears to involve neuromodulatory cholinergic projections, predominantly from the nucleus basalis of Meynert in the basal forebrain (Pirch et al 1992 ;Hars et al 1993 ;Acquas et al 1996).…”