title: Reduced dorsal premotor cortex and primary motor cortex connectivity in older adults.
abstract: Motor functions decline with increasing age. The underlying mechanisms are still unclear and are likely to be multifactorial. There is evidence for disruption of white matter integrity with age, which affects cortico-cortical connectivity. Studies with transcranial magnetic stimulation found both inhibitory and facilitatory connections from dorsal premotor cortex (PMd) to the ipsilateral primary motor cortex (M1) in young adults. We investigated whether aging affects this connectivity in 15 older and 15 young healthy adults. Transcranial magnetic stimulation in a paired-pulse paradigm was used to test the connectivity between left PMd and M1. Motor evoked potential in the right first dorsal interosseous muscle was recorded. We found that both the inhibitory effect with low intensity PMd stimulation and the facilitatory effect with high intensity PMd stimulation observed in young adults were decreased in older adults. We conclude that the connectivity between PMd and ipsilateral M1 is reduced in older adults.
authors.affiliation: Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Ni
authors.affiliation: Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Reina
authors.initials: R
authors.lastname: Isayama
authors.affiliation: Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Castillo
authors.affiliation: Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Gunraj
authors.affiliation: Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Utpal
authors.initials: U
authors.lastname: Saha
authors.affiliation: Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada. Electronic address: robert.chen@uhn.ca.
authors.forename: Robert
authors.initials: R
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D009435:Synaptic Transmission; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Aging; Dorsal premotor cortex; Motor evoked potential; Primary motor cortex; Transcranial magnetic stimulation