Inhibiting human aversive memory by transcranial theta-burst stimulation to primary sensory cortex

Background
Predicting adverse events from past experience is fundamental for many biological organisms. However, some individuals suffer from maladaptive memories that impair behavioral control and wellbeing, e.g. after psychological trauma. Inhibiting the formation and maintenance of such memories would have high clinical relevance. Previous pre-clinical research has focused on systemically administered pharmacological interventions, which cannot be targeted to specific neural circuits in humans. Here, investigated the potential of non-invasive neural stimulation on human sensory cortex in inhibiting aversive memory in a laboratory threat conditioning model.

Methods
We build on an emerging non-human literature suggesting that primary sensory cortices may be crucially required for threat memory formation and consolidation. Immediately before conditioning innocuous somatosensory stimuli (conditioned stimuli, CS) to aversive electric stimulation, healthy human participants received continuous theta-burst transcranial magnetic stimulation (cTBS) to individually localized primary somatosensory cortex in the CS-contralateral (experimental) or CS-ipsilateral (control) hemisphere. We measured fear-potentiated startle to infer threat memory retention on the next day, as well as skin conductance and pupil size during learning.

Results
After overnight consolidation, threat memory was attenuated in the experimental compared to the control cTBS group. There was no evidence that this differed between simple and complex CS, or that CS identification or initial learning were affected by cTBS.

Conclusions
Our results suggest that cTBS to primary sensory cortex inhibits threat memory, likely by an impact on post-learning consolidation. We propose that non-invasive targeted stimulation of sensory cortex may provide a new avenue for interfering with aversive memories in humans.