title: Is better preservation of eccentric strength after stroke due to altered prefrontal function?
abstract: Ventrolateral prefrontal cortex (VLPFC) is part of a network that exerts inhibitory control over the motor cortex (MC). Recently, we demonstrated that VLPFC was more activated during imagined maximum eccentric than during imagined concentric contractions in healthy participants. This was accompanied with lower activation levels within motor regions during imagined eccentric contractions. The aim was to test a novel hypothesis of an involvement of VLPFC in contraction mode-specific modulation of force. Functional magnetic resonance imaging was used to examine differences in VLPFC and motor regions during the concentric and the eccentric phases of imagined maximum contractions in a selected sample of subjects with stroke (n = 4). The subjects were included as they exhibited disturbed modulation of force. The previously demonstrated pattern within VLPFC was evident only on the contralesional hemisphere. On the ipsilesional hemisphere, the recruitment in VLPFC was similar for both modes of contractions. The findings support a hypothesis of the involvement of VLPFC in contraction mode-specific modulation of maximum force production. A disturbance of this system might underlie the lack of contraction mode-specific modulation commonly found among stroke subjects, often expressed as an increased ratio between eccentric and concentric strength.
authors.affiliation: a Department of Community Medicine and Rehabilitation , Umeå University , Umeå , Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Hedlund
authors.affiliation: a Department of Community Medicine and Rehabilitation , Umeå University , Umeå , Sweden.
authors.forename: Britta
authors.initials: B
authors.lastname: Lindström
authors.affiliation: b Department of Health Sciences , Mid-Sweden University , Östersund , Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Sojka
authors.affiliation: c Department of Radiation Sciences, Biomedical Engineering , Umeå University , Umeå , Sweden.
authors.forename: Ronnie
authors.initials: R
authors.lastname: Lundström
authors.affiliation: d CEDAR, Center for Demographic and Aging Research , Umeå University , Umeå , Sweden.|e UFBI, Umeå Centre for Functional Brain Imaging , Umeå University , Umeå , Sweden.
authors.forename: Carl-Johan
authors.initials: CJ
authors.lastname: Boraxbekk
mesh_terms: D000368:Aged; D017352:Echo-Planar Imaging; D004576:Electromyography; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D053580:Muscle Strength / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D017397:Prefrontal Cortex / Q000098:blood supply / Q000503:physiopathology*; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology*
chemical_list: D010100:Oxygen
keywords: Motor imagery; concentric; eccentric; fMRI; inhibition; stroke