Effects of deep transcranial magnetic stimulation (dTMS) on cognition

Deep transcranial magnetic stimulation (dTMS) is a modern non-invasive brain stimulation method demonstrated as effective in the treatment of major depression and obsessive-compulsive disorder (OCD). This review aims to survey present knowledge concerning the cognitive function changes identified in dTMS research. A systematic literature search in PubMed and Google Scholar was performed and 23 out of 64 studies on dTMS and cognitive functioning were included in the review. Ten studies were conducted with patients with affective disorders, six with healthy participants, two with schizophrenia patients, two with OCD patients, and one study each with patients suffering from central neuropathic pain, autistic disorder, and attention deficit hyperactivity disorder. The best outcomes were obtained after 20 sessions of high-frequency dTMS with OCD patients, where, in addition to clinical improvement, patients showed amelioration of cognitive functions, specifically in cognitive control domains. The studies on patients with depression appear to show inconsistent results, from cognitive improvement in open-label studies to no improvement versus sham dTMS in controlled trials. Experimental research in healthy volunteers suggests an influence of dTMS on memory and self-agency, and also contain contradictory results. Most studies did not demonstrate a significant improvement in cognitive functioning. However, randomized sham-controlled trials with larger groups of medication-free patients and inclusion of functional imaging or electrophysiological recording connected with dTMS application are necessary for more detailed and confident conclusions concerning the effect of dTMS on cognitive functions.