Effects of Transcranial Alternating Current Stimulation on Cognitive Functions in Healthy Young and Older Adults.
Recently, transcranial alternating current stimulation (tACS) has emerged as a tool to enhance human cognitive processes. Here, we provide a brief summary of the rationale behind tACS-induced effects on task-relevant brain oscillations and associated cognitive functions and review previous studies in young subjects that have applied tACS in cognitive paradigms. Additionally, we present pilot data where we administered theta-tACS (6 Hz) over the temporoparietal cortex and a supraorbital reference for 20 min during implicit language learning in healthy young (mean/SD age: 22/2) and older (mean/SD age: 66/4) adults, in a sham-controlled crossover design. Linear mixed models revealed significantly increased retrieval accuracy following tACS-accompanied associative learning, after controlling for session order and learning success. These data provide the first implementation of tACS during cognitive performance in older adults and support recent studies suggesting that tACS in the theta frequency range may serve as a tool to enhance cognition, possibly through direct modulation of task-relevant brain oscillations. So far, studies have been heterogeneous in their designs, leaving a number of issues to be addressed in future research, including the setup of electrodes and optimal stimulation frequencies to be employed, as well as the interaction with age and underlying brain pathologies in specific patient populations.
Department of Neurology, NeuroCure Clinical Research Center, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany.
Daria
D
Antonenko
Department of Neurology, NeuroCure Clinical Research Center, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany.
Miriam
M
Faxel
Center for Stroke Research, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany; Department for Biostatistics and Clinical Epidemiology, Charité Universitätsmedizin, 10117 Berlin, Germany.
Ulrike
U
Grittner
Department of Psychology, Bar Ilan University, 52900 Ramat Gan, Israel.
Michal
M
Lavidor
Department of Neurology, NeuroCure Clinical Research Center, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany; Center for Stroke Research, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany; Department for Biostatistics and Clinical Epidemiology, Charité Universitätsmedizin, 10117 Berlin, Germany.
Agnes
A
Flöel
D000161:Acoustic Stimulation / Q000379:methods; D000368:Aged; D000375:Aging / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D018592:Cross-Over Studies; D005260:Female; D006304:Health Status; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000502:physiology; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D010865:Pilot Projects; D016037:Single-Blind Method; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult