Neuromodulation of the right inferior frontal gyrus in bipolar disorder to target response inhibition: a proof-of-concept study.

OBJECTIVE

Bipolar disorder (BD) affects over 1% of the population and is characterized by deficits in response inhibition. Response inhibition, a crucial component of executive functions, involves the ability to suppress or withhold a planned or ongoing response that is no longer required or appropriate in a given context. Response inhibition may be dissociated into three subcomponents: interference inhibition, action withholding, and action cancellation. These subcomponents are assessed using the hybrid response inhibition (HRI) task. Previous research has shown that inhibitory control is strongly lateralized to the right hemisphere. Specifically, the right inferior frontal gyrus (rIFG) is a key node underpinning response inhibition and might be amenable to neuromodulation using repetitive transcranial magnetic stimulation (rTMS). This proof-of-concept study aimed to investigate the effects of rTMS targeting the rIFG on response inhibition in individuals with BD and controls.

METHODS

We investigated HRI performance scores in individuals with BD (n = 12) and sex-/age-matched controls (n = 12) immediately before and after intermittent theta-burst stimulation (iTBS) and continuous TBS to modulate cortical excitability of the rIFG.

RESULTS

The response inhibition subcomponent "action withholding" was significantly improved in the HRI task following iTBS in the BD group. No other significant effects were observed in the results.

CONCLUSIONS

Our study is the first to show that iTBS to the rIFG neuromodulated a specific subcomponent of response inhibition in BD. Further research investigating the potential therapeutic effect of neuromodulation of the rIFG in BD is warranted.