Cognitive effects of focal neuromodulation in neurological and psychiatric disorders

Focal direct-to-brain neuromodulation approaches, such as repetitive transcranial magnetic stimulation (TMS), deep brain stimulation (DBS) and ablative techniques, hold tremendous therapeutic promise for challenging-to-treat neurological and psychiatric disorders. These interventions modulate brain circuits that contribute to clinical symptoms and overlap with the networks that support cognition. Depending on the reason for the intervention — whether it aims to improve clinical symptoms or cognitive symptoms — focal neuromodulation techniques might indirectly or directly affect cognitive processes. In this Review, we examine the effects of repetitive TMS, DBS and ablative techniques on post-intervention cognition in patients with psychiatric disorders (major depressive disorder, obsessive–compulsive disorder and schizophrenia) and neurological conditions (Parkinson disease, essential tremor and Alzheimer disease). Our findings indicate that focal neuromodulation is generally safe from a cognitive standpoint and, in some cases, can improve aspects of cognition. We conclude with methodological recommendations aimed at advancing our knowledge of the cognitive effects associated with focal neuromodulation approaches.