title: Spectral Variability in the Aged Brain during Fine Motor Control.
abstract: Physiological aging is paralleled by a decline of fine motor skills accompanied by structural and functional alterations of the underlying brain network. Here, we aim to investigate age-related changes in the spectral distribution of neuronal oscillations during fine skilled motor function. We employ the concept of spectral entropy in order to describe the flatness and peaked-ness of a frequency spectrum to quantify changes in the spectral distribution of the oscillatory motor response in the aged brain. Electroencephalogram was recorded in elderly (n= 32) and young (n= 34) participants who performed either a cued finger movement or a pinch or a whole hand grip task with their dominant right hand. Whereas young participant showed distinct, well-defined movement-related power decreases in the alpha and upper beta band, elderly participants exhibited a flat broadband, frequency-unspecific power desynchronization. This broadband response was reflected by an increase of spectral entropy over sensorimotor and frontal areas in the aged brain. Neuronal activation patterns differed between motor tasks in the young brain, while the aged brain showed a similar activation pattern in all tasks. Moreover, we found a wider recruitment of the cortical motor network in the aged brain. The present study adds to the understanding of age-related changes of neural coding during skilled motor behavior, revealing a less predictable signal with great variability across frequencies in a wide cortical motor network in the aged brain. The increase in entropy in the aged brain could be a reflection of random noise-like activity or could represent a compensatory mechanism that serves a functional role.
authors.affiliation: BrainImaging and NeuroStimulation Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
authors.forename: Fanny
authors.initials: F
authors.lastname: Quandt
authors.affiliation: BrainImaging and NeuroStimulation Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
authors.forename: Marlene
authors.initials: M
authors.lastname: Bönstrup
authors.affiliation: BrainImaging and NeuroStimulation Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Schulz
authors.affiliation: BrainImaging and NeuroStimulation Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
authors.forename: Jan E
authors.initials: JE
authors.lastname: Timmermann
authors.affiliation: Institute of Neuroscience, Favaloro UniversityBuenos Aires, Argentina; Institute of Cognitive NeurologyBuenos Aires, Argentina.
authors.forename: Maximo
authors.initials: M
authors.lastname: Zimerman
authors.affiliation: Department of Neurophysiology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Nolte
authors.affiliation: BrainImaging and NeuroStimulation Laboratory, Department of Neurology, University Medical Center Hamburg-EppendorfHamburg, Germany; Institute of Neuroscience, Favaloro UniversityBuenos Aires, Argentina; Clinical Neuroengineering, Brain Mind Institute and Centre of Neuroprosthetics (CNP), Swiss Federal Institute of Technology (EPFL)Geneva, Switzerland; Clinique Romande de Réadaptation, Swiss Federal Institute of Technology (EPFL Valais)Sion, Switzerland.
authors.forename: Friedhelm C
authors.initials: FC
authors.lastname: Hummel
keywords: EEG; aging; entropy; motor control; oscillations