The role of the human amygdala in the production of conditioned fear responses
Section snippets
Participants
Nine healthy right-handed volunteers [5 female and 4 male; age (mean ± SEM): 28.33 ± 1.65 years; age range: 23 to 39 years] participated in this study. All subjects provided written informed consent in compliance with the National Institute of Mental Health Institutional Review Board.
Conditioning procedure
Two pure tones (700 and 1300 Hz) were presented as CSs (10 s duration) during the training session. The CS+ (30 trials) co-terminated with a 500-ms loud (100 dB) white-noise (UCS) on 80% of the trials and 20% of
SCR
Comparison of SCRs elicited by CS+ and CS− presentations indicates that the procedure used in this study supports excitatory conditioning. SCRs were separated into first interval response (FIR: SCRs that occur within the first 5 s following CS onset) and second interval response (SIR: SCRs that occur within seconds 6–10 following CS onset) SCRs. The FIRs and SIRs produced during CS+ (mean ± SEM: FIR = 0.14 ± 0.05, SIR = 0.14 ± 0.06) presentations were larger than those elicited by CS− (mean ±
Discussion
Large fMRI signal changes were observed within a number of brain areas during the production of conditioned, orienting, nonspecific, and unconditioned skin conductance responses. These regions included the anterior cingulate, insula, basal ganglia, cerebellum, thalamus, and areas of the prefrontal, temporal, and parietal cortices (see Fig. 4 and Table 1a). Previous studies exploring the neural mechanisms of SCR production have observed activations within many of these areas (Critchley et al.,
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