Enhancing working memories using repetitive TMS

Abstract

Working memory, the ability to retain and manipulate information no longer present in the environment, is fundamental for goal-directed behavior (Baddeley, 2012; Baddeley & Hitch, 1974; D'Esposito, 2007; D'Esposito & Postle, 2015). Alpha oscillations (~8-12 Hz) have two apparently contradictory roles in working memory. Alpha activity gates irrelevant information through inhibition, a role causally supported by rhythmic transcranial magnetic stimulation (TMS) of parietal cortex at alpha frequency when a retrospective cue renders a memory item irrelevant (Bonnefond & Jensen, 2012; Riddle et al., 2020). Yet alpha activity also tracks the content of memory and binds the features of memorized objects during maintenance (Foster et al., 2016; Pagnotta et al., 2026). Whether alpha oscillations causally support the fidelity of memory representations during maintenance is untested. Here, 24 participants received short trains of repetitive TMS (rTMS) at theta (6 Hz) or alpha frequency (10 Hz), or in an arrhythmic control pattern, during the second half of the delay of a color working memory task, over the left posterior inferior frontal sulcus or the left intraparietal sulcus. A mixture model separated memory precision from swap errors and guesses. Alpha stimulation of the intraparietal sulcus specifically increased memory precision, whereas rhythmic stimulation of either site reduced response error, guesses and swaps irrespective of frequency. These results provide causal evidence that alpha oscillations support the fidelity of working memory representations during maintenance, and show that rhythmic stimulation at the appropriate frequency, site and time can enhance human working memory.