Non-invasive brain stimulation for modulating a consolidated fear memory

Introduction Despite the high effectiveness of cognitive behavioural therapy in the treatment of anxiety disorders, not all patients show a satisfactory therapeutic success. Recently, studies have examined the additional benefit of non-invasive brain stimulation (NIBS) in combination with psychotherapy for anxiety disorders. To further optimise the effectiveness of NIBS, it has been suggested that the therapy-relevant learning processes involved should be examined in more detail. The present study, therefore, investigated the enhancing effect of tDCS stimulation of the ventromedial prefrontal cortex (vmPFC) on extinction learning in consolidated fear memory.

Methods In a two-day fear conditioning paradigm with female faces as conditioned stimuli and a 95-dB female scream as the unconditioned stimulus, skin conductance reactions and subjective fear ratings were examined. Sixty-one healthy subjects showed successful fear conditioning and were included in the statistical analyses. Participants were randomly and double-blinded assigned into a sham and verum stimulation group. The day after fear conditioning, brain stimulation and extinction learning took place under the same experimental conditions. The stimulation began ten minutes before extinction learning.

Results Results showed a significant time x condition x group interaction, F(1.59) = 4.35, p < .05. Post-hoc t-tests indicated that active stimulation enhances extinction learning with a significant loss of CS+/CS- discrimination. The discrimination loss was observed by a significant decrease in response to CS+ and an increase in response to CS- in the experimental group. During this period, the control group showed no significant reaction changes.

Conclusion Results showed that the stimulation protocol can be used to modulate a consolidated fear memory and thus to enhance therapy-relevant learning processes. Future studies should investigate the applicability of the paradigm to a clinical sample in the context of exposure therapy.