title: Feedback-Controlled Transcranial Alternating Current Stimulation Reveals a Functional Role of Sleep Spindles in Motor Memory Consolidation.
abstract: Transient episodes of brain oscillations are a common feature of both the waking and the sleeping brain. Sleep spindles represent a prominent example of a poorly understood transient brain oscillation that is impaired in disorders such as Alzheimer's disease and schizophrenia. However, the causal role of these bouts of thalamo-cortical oscillations remains unknown. Demonstrating a functional role of sleep spindles in cognitive processes has, so far, been hindered by the lack of a tool to target transient brain oscillations in real time. Here, we show, for the first time, selective enhancement of sleep spindles with non-invasive brain stimulation in humans. We developed a system that detects sleep spindles in real time and applies oscillatory stimulation. Our stimulation selectively enhanced spindle activity as determined by increased sigma activity after transcranial alternating current stimulation (tACS) application. This targeted modulation caused significant enhancement of motor memory consolidation that correlated with the stimulation-induced change in fast spindle activity. Strikingly, we found a similar correlation between motor memory and spindle characteristics during the sham night for the same spindle frequencies and electrode locations. Therefore, our results directly demonstrate a functional relationship between oscillatory spindle activity and cognition.
authors.affiliation: Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Caroline
authors.initials: C
authors.lastname: Lustenberger
authors.affiliation: Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Boyle
authors.affiliation: Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Sankaraleengam
authors.initials: S
authors.lastname: Alagapan
authors.affiliation: Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Juliann M
authors.initials: JM
authors.lastname: Mellin
authors.affiliation: Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA.
authors.forename: Bradley V
authors.initials: BV
authors.lastname: Vaughn
authors.affiliation: Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA; Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Electronic address: flavio_frohlich@med.unc.edu.
authors.forename: Flavio
authors.initials: F
authors.lastname: Fröhlich
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D025461:Feedback, Physiological; D005260:Female; D006801:Humans; D000069077:Memory Consolidation; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult