Frequency-specific insight into short-term memory capacity.
The digit span is one of the most widely used memory tests in clinical and experimental neuropsychology for reliably measuring short-term memory capacity. In the forward version, sequences of digits of increasing length have to be reproduced in the order in which they are presented, whereas in the backward version items must be reproduced in the reversed order. Here, we assessed whether transcranial alternating current stimulation (tACS) increases the memory span for digits of young and midlife adults. Imperceptibly weak electrical currents in the alpha (10 Hz), beta (20 Hz), theta (5 Hz), and gamma (40 Hz) range, as well as a sham stimulation, were delivered over the left posterior parietal cortex, a cortical region thought to sustain maintenance processes in short-term memory through oscillatory brain activity in the beta range. We showed a frequency-specific effect of beta-tACS that robustly increased the forward memory span of young, but not middle-aged, healthy individuals. The effect correlated with age: the younger the subjects, the greater the benefit arising from parietal beta stimulation. Our results provide evidence of a short-term memory capacity improvement in young adults by online frequency-specific tACS application.
Department of Medicine, Surgery and Neuroscience, Unit of Neurology and Clinical Neurophysiology, Brain Investigation and Neuromodulation Laboratory (Si-BIN Lab), Azienda Ospedaliera Universitaria of Siena, Policlinico Le Scotte, Siena, Italy; School of Psychology, Centre for Cognition and Decision Making, National Research University Higher School of Economics, Russian Federation, Moscow, Russia; mfeurra@hse.ru.
Matteo
M
Feurra
Department of Medicine, Surgery and Neuroscience, Unit of Neurology and Clinical Neurophysiology, Brain Investigation and Neuromodulation Laboratory (Si-BIN Lab), Azienda Ospedaliera Universitaria of Siena, Policlinico Le Scotte, Siena, Italy; Department of Psychology, Faculty of Arts and Social Sciences, Kingston University, Kingston Upon Thames, United Kingdom; and.
Giulia
G
Galli
Department of Medicine, Surgery and Neuroscience, Unit of Neurology and Clinical Neurophysiology, Brain Investigation and Neuromodulation Laboratory (Si-BIN Lab), Azienda Ospedaliera Universitaria of Siena, Policlinico Le Scotte, Siena, Italy; Department of Psychology, Sapienza University of Rome, Rome, Italy.
Enea Francesco
EF
Pavone
Department of Medicine, Surgery and Neuroscience, Unit of Neurology and Clinical Neurophysiology, Brain Investigation and Neuromodulation Laboratory (Si-BIN Lab), Azienda Ospedaliera Universitaria of Siena, Policlinico Le Scotte, Siena, Italy;
Alessandro
A
Rossi
Department of Medicine, Surgery and Neuroscience, Unit of Neurology and Clinical Neurophysiology, Brain Investigation and Neuromodulation Laboratory (Si-BIN Lab), Azienda Ospedaliera Universitaria of Siena, Policlinico Le Scotte, Siena, Italy;
Simone
S
Rossi
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology* / Q000523:psychology*; D000704:Analysis of Variance; D001611:Beta Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D010296:Parietal Lobe / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
beta frequency; digit span; posterior parietal lobe; short-term memory; transcranial alternating current stimulation