title: Aging changes and gender differences in response to median nerve stimulation measured with MEG.
abstract: OBJECTIVE
  The current study uses magnetoencephalography (MEG) to characterize age-related changes and gender differences in the amplitudes and timing of cortical sources evoked by median nerve stimulation.
  
  
  METHODS
  Thirty-four healthy subjects from two age groups: 20-29 and >64 years of age were examined. After measuring the MEG responses, we modeled the data using a spatio-temporal multi-dipole modeling approach to determine the source locations and their associated timecourses.
  
  
  RESULTS
  We found early, large amplitude responses in the elderly in primary somatosensory (approximately 20 ms) and pre-central sulcus timecourses (approximately 22 ms) and lower amplitude responses in the elderly later in primary somatosensory (approximately 32 ms) and contralateral secondary somatosensory timecourses (approximately 90 ms). In addition, females had larger peak amplitude responses than males in the contralateral secondary somatosensory timecourse (approximately 28 and 51 ms).
  
  
  CONCLUSIONS
  These results show that the median nerve stimulation paradigm provides considerable sensitivity to age- and gender-related differences. The results are consistent with the theory that increased amplitudes identified in the elderly may be associated with decreased inhibition.
  
  
  CONCLUSIONS
  The results emphasize that an examination of two discrete age groups, collapsed across gender, cannot provide a complete understanding of the fundamental changes that occur in the brain across the lifetime.
authors.affiliation: Department of Radiology, MSC10 5530, 1 University of New Mexico SOM, Albuquerque, NM 87131, USA. jstephen@unm.edu
authors.forename: Julia M
authors.initials: JM
authors.lastname: Stephen
authors.forename: Doug
authors.initials: D
authors.lastname: Ranken
authors.forename: Elaine
authors.initials: E
authors.lastname: Best
authors.forename: John
authors.initials: J
authors.lastname: Adair
authors.forename: Janice
authors.initials: J
authors.lastname: Knoefel
authors.forename: Sanja
authors.initials: S
authors.lastname: Kovacevic
authors.forename: Denise
authors.initials: D
authors.lastname: Padilla
authors.forename: Blaine
authors.initials: B
authors.lastname: Hart
authors.forename: Cheryl J
authors.initials: CJ
authors.lastname: Aine
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology / Q000528:radiation effects*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D008959:Models, Neurological; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D012727:Sex Characteristics