title: Disrupting the ipsilateral motor cortex interferes with training of a complex motor task in older adults.
abstract: Performance of unimanual movements is associated with bihemispheric activity in the motor cortex in old adults. However, the causal functional role of the ipsilateral MC (iMC) for motor control is still not completely known. Here, the behavioral consequences of interference of the iMC during training of a complex motor skill were tested. Healthy old (58-85 years) and young volunteers (22-35 years) were tested in a double-blind, cross-over, sham-controlled design. Participants attended 2 different study arms with either cathodal transcranial direct current stimulation (ctDCS) or sham concurrent with training. Motor performance was evaluated before, during, 90 min, and 24 h after training. During training, a reduced slope of performance with ctDCS relative to sham was observed in old compared with young (F = 5.8, P = 0.02), with a decrease of correctly rehearsed sequences, an effect that was evident even after 2 consecutive retraining periods without intervention. Furthermore, the older the subject, the more prominent was the disruptive effect of ctDCS (R(2) = 0.50, P = 0.01). These data provide direct evidence for a causal functional link between the iMC and motor skill acquisition in old subjects pointing toward the concept that the recruitment of iMC in old is an adaptive process in response to age-related declines in motor functions.
authors.affiliation: Brain Imaging and Neurostimulation (BINS) Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany and.
authors.forename: Máximo
authors.initials: M
authors.lastname: Zimerman
authors.forename: Kirstin-F
authors.initials: KF
authors.lastname: Heise
authors.forename: Christian
authors.initials: C
authors.lastname: Gerloff
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Cohen
authors.forename: Friedhelm C
authors.initials: FC
authors.lastname: Hummel
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D001288:Attention; D005221:Fatigue; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D012153:Retention, Psychology; D011795:Surveys and Questionnaires; D013663:Teaching; D050781:Transcranial Magnetic Stimulation; D064232:Visual Analog Scale; D055815:Young Adult