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.
