A systematic review of the effects of low-frequency repetitive transcranial magnetic stimulation on cognition

Abstract

rTMS is increasingly used for a variety of neuropsychiatric conditions. There are data to support ‘fast’ rTMS (≥10 Hz) having some positive effects on cognitive functioning, but a dearth of research looking at any such effects of ‘slow’ rTMS. This question is important as cognitive dysfunction accompanies many neuropsychiatric conditions and neuromodulation that potentially enhances or hinders such functioning has important clinical consequences. To determine cognitive effects of slow (≤1 Hz) rTMS, a systematic review of randomized control trials assayed cognition in neurological, psychiatric, and healthy volunteer ≤1 Hz rTMS paradigms. Both active (fast rTMS) and placebo comparators were included. 497 Records were initially obtained; 20 met inclusion criteria for evaluation. Four major categories emerged: mood disorders; psychotic disorders; cerebrovascular accidents; and ‘other’ (PTSD, OCD, epilepsy, anxiety, and tinnitus). Cognitive effects were measured across several domains: attention, executive functioning, learning, and psychomotor speed. Variability of study paradigms and reporting precluded meta-analytical analysis. No statistically significant improvement or deterioration was consistently found in any cognitive domain or illness category. These data support the overall safety of rTMS in not adversely affecting cognitive functioning. There are some data indicating that rTMS might have cognitive enhancing potential, but these are too limited at this time to make any firm conclusions, and the literature is marked by considerable heterogeneity in study parameters that hinder interpretation. Greater consensus is required in future studies in cognitive markers, and particularly in reporting of protocols. Future work should evaluate the effects of rTMS on cognitive training.

Neuromodulation Using Transcranial Magnetic Stimulation (TMS)

“…From the data behavior observed, it is possible to infer that if the sample were to be expanded, the other subtests would also be statistically significant. Improvement in memory-related functions corroborates findings of previous studies 13,14,18 .…”

“…Studies have already demonstrated the positive effects of highfrequency TMS (10 hz) over cognitive functions, but yet there are not enough studies yet showing this type of improvement with low-frequency TMS 13 . In a randomized assay, in which the effect of the TMS over refractory depression was investigated, significant improvement in the performance of patients assessed with regards to immediate verbal memory and verbal fluency was noted.…”

The physiological effects of noninvasive brain stimulation fundamentally differ across the human cortex

“…Neuromodulation with TMS has attracted much attention as it would offer an elegant way to noninvasively treat aberrant brain Reports about low outcome and replicability, however, have partly compromised this method (9,34). We here propose that a target region's connectivity profile fundamentally affects the direction of modulation.…”

The physiological effects of non-invasive brain stimulation fundamentally differ across the human cortex

“…Neuromodulation with TMS has attracted attention as it potentially offers an elegant way to non-invasively treat aberrant brain activity in neuropsychiatric disorders. Reports about low outcome and replicability, however, have partly compromised this method (Lage et al 2016;Martin et al 2003;Wilson et al 2018). We hypothesized that the key assumption about a frequency-dependent effect of rTMS does not generalize across the entire cortex and could be responsible for inconsistent reports.…”