title: Effects of Anodal Transcranial Direct Current Stimulation and Serotonergic Enhancement on Memory Performance in Young and Older Adults.
abstract: In the absence of effective therapies for dementia and its precursors, enhancing neuroplasticity by means of non-invasive brain stimulation such as anodal transcranial direct current stimulation (atDCS) might be a promising approach to counteract or delay the onset of cognitive decline, but effect sizes have been moderate so far. Previous reports indicate that increasing serotonin levels may enhance atDCS-induced neuroplasticity. However, evidence for serotonergic modulation of atDCS effects on memory is still lacking. Here, we conducted a double-blind, randomized, sham-/placebo-controlled trial to investigate the impact of a selective serotonin reuptake inhibitor (SSRI; single dose of 20 mg citalopram) and atDCS over the right temporoparietal cortex (1 mA, 20 min) on memory formation. Twenty young and 20 older subjects completed an object-location learning task in each of the four conditions: sham+placebo, sham+SSRI, atDCS+placebo, and atDCS+SSRI. Outcome measures were performance in immediate (primary outcome) and delayed cued recall. While we found an SSRI effect, but no statistically significant effect of atDCS on immediate recall scores, young and older adults benefited most from the combined application (comparisons: atDCS+SSRI>atDCS+placebo and atDCS+SSRI>sham+placebo). Thus, our data provide evidence that atDCS improves memory formation if serotonergic neurotransmission is enhanced simultaneously. Further studies are needed to assess whether these findings extend to clinical populations with memory impairment and translate into clinically relevant improvements after long-term serotonergic enhancement and repeated stimulation.
authors.affiliation: Department of Neurology and NeuroCure Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Kristin
authors.identifier: 0000-0002-0656-5323
authors.initials: K
authors.lastname: Prehn
authors.affiliation: Department of Neurology and NeuroCure Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Stengl
authors.affiliation: Department of Biostatistics and Clinical Epidemiology, Charité Universitätsmedizin Berlin, Berlin, Germany.|Center for Stroke Research, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Grittner
authors.affiliation: Department of Neurology and NeuroCure Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: René
authors.initials: R
authors.lastname: Kosiolek
authors.affiliation: Department of Neurology and NeuroCure Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Ölschläger
authors.affiliation: Department of Neurology and NeuroCure Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Weidemann
authors.affiliation: Department of Neurology and NeuroCure Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany.|Center for Stroke Research, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Agnes
authors.initials: A
authors.lastname: Flöel
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000187:drug effects* / Q000502:physiology*; D015283:Citalopram / Q000008:administration & dosage*; D004311:Double-Blind Method; D006801:Humans; D008568:Memory / Q000187:drug effects* / Q000502:physiology*; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D010296:Parietal Lobe / Q000187:drug effects / Q000502:physiology; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage*; D065853:Spatial Learning / Q000187:drug effects / Q000502:physiology; D013702:Temporal Lobe / Q000187:drug effects / Q000502:physiology; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
chemical_list: D015283:Citalopram; D017367:Selective Serotonin Reuptake Inhibitors