title: Disinhibitory shift of recovery curve of somatosensory-evoked response in elderly: A magnetoencephalographic study.
abstract: OBJECTIVE
  The aim of the study was to investigate the functional differences between N20m and P30m components of somatosensory-evoked magnetic cortical field (SEF) in young and senior subjects.
  
  
  METHODS
  Twenty-nine healthy subjects, 13 younger (mean age: 21.8years) and 16 senior (63.8 years), participated. Magnetic fields were measured using a 160-channel, whole head MEG. Single- and paired-pulse stimulations of 200 artifact-free MEG signal epochs were averaged separately. We calculated how aging affects recovery function of SEFs.
  
  
  RESULTS
  The senior showed a prolonged N20m peak latency compared to the younger, although the P30m peak latency was not significantly different between groups. The N20m ratios at 60 and 80 ms in the senior were significantly increased compared to the ratios in the younger (60 ms: P<0.05, 80 ms: P<0.001). The P30m ratios at inter-stimulus interval (ISI) of 80 and 100 ms showed even disinhibition in the senior than in the younger (P<0.05). The younger also showed a significantly negative correlation between P30m and N20m components' recovery curves (R=0.72, P<0.05).
  
  
  CONCLUSIONS
  Aging-related changes that occurred in recovery functioning were the decrease in N20m component suppression and the increase in P30m component recovery, indicating that the N20m and P30m components have different functions in aging-related recovery changes.
  
  
  CONCLUSIONS
  Our results show that the N20m ratio at an ISI of 80 ms was significantly increased in the senior group, indicating that the second stimulus-evoked SEF was less inhibited by the initial stimulus at this ISI, suggesting less refractory effect or increased disinhibition.
authors.affiliation: Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Sae
authors.initials: S
authors.lastname: Goto
authors.affiliation: Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Fujisawa
authors.affiliation: Department of Physical and Occupational Therapy, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Uemura
authors.affiliation: Department of Physical and Occupational Therapy, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Department of Physical and Occupational Therapy, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Hoshiyama
authors.affiliation: Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: hirasan@med.nagoya-u.ac.jp.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hirayama
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult
keywords: Aging-related change; Cortical inhibitory neuronal function; Magnetoencephalographic study; Paired-pulse suppression; Recovery function; Somatosensory-evoked response