title: Brain stimulation during an afternoon nap boosts slow oscillatory activity and memory consolidation in older adults.
abstract: Sleep-related consolidation of declarative memories, as well as associated neurophysiological events such as slow oscillatory and spindle activity, deteriorate in the course of aging. This process is accelerated in neurodegenerative disease. Transcranial slow oscillatory stimulation (so-tDCS) during sleep has been shown to enhance slow oscillatory brain activity and thereby improve memory consolidation in young subjects. Here, we investigated whether so-tDCS applied to older adults during an afternoon nap exerts similar effects. Eighteen older human subjects were assessed using visuo-spatial (picture memory, primary, and location memory) and verbal memory tasks before and after a 90-min nap either comprising weak so-tDCS at 0.75Hz over fronto-central location or sham (no) stimulation in a within-subject design. Electroencephalographic activity was recorded throughout the naps and immediate effects of stimulation on brain activity were evaluated. Here, spectral power within three frequency bands of interest were computed, i.e., slow oscillatory activity, slow spindle and fast spindle activity; in 1-min stimulation-free intervals following 5 stimulation blocks. So-tDCS significantly increased frontal slow oscillatory activity as well as fast spindle activity, and significantly improved picture memory retention after sleep. Retention in the location memory subtask and in the verbal memory task was not affected. These findings may indicate a novel strategy to counteract cognitive decline in aging in a convenient manner during brief daytime naps.
authors.affiliation: Department of Neurology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany. Electronic address: Julia.Ladenbauer@charite.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Ladenbauer
authors.affiliation: Department of Neurology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany. Electronic address: Nadine.Kuelzow@charite.de.
authors.forename: Nadine
authors.initials: N
authors.lastname: Külzow
authors.affiliation: Department of Neurology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany. Electronic address: Sven.Passmann@charite.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Passmann
authors.affiliation: Department of Neurology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany. Electronic address: Daria.Antonenko@charite.de.
authors.forename: Daria
authors.initials: D
authors.lastname: Antonenko
authors.affiliation: Biostatistics and Clinical Epidemiology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany. Electronic address: Ulrike.Grittner@charite.de.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Grittner
authors.affiliation: Department of Psychology, Freie Universität Berlin, 14195 Berlin, Germany. Electronic address: Tamm@zedat.fu-berlin.de.
authors.forename: Sascha
authors.initials: S
authors.lastname: Tamm
authors.affiliation: Department of Neurology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany. Electronic address: Agnes.Floeel@charite.de.
authors.forename: Agnes
authors.initials: A
authors.lastname: Flöel
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D058256:Brain Waves / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D000069077:Memory Consolidation / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D008875:Middle Aged; D012890:Sleep / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*
keywords: Aging; Declarative memory; Sleep; Sleep spindles; Slow oscillations; tDCS