title: Pre-task prefrontal activation during cognitive processes in aging: a near-infrared spectroscopy study.
abstract: OBJECTIVE
  Cognitive processing generally deteriorates as people age. Recent neuroimaging studies have shown that the prefrontal cortex (PFC) is involved in human-specific behavior, such as preparing for future actions and prospective memory; hence, the PFC may be voluntarily activated even during the "resting" condition that precedes task execution. The purpose of the present study was to investigate changes in voluntary pre-task activation as a result of aging using a paradigm that includes a longer intertrial interval (e.g., 30 sec) than has been used in previous studies.
  
  
  METHODS
  A total of 120 cognitively normal adults (young: 60, old: 60) participated in this near-infrared spectroscopy (NIRS) study. All subjects performed 6 repetitions of the working memory task, which included a 30 sec resting period and a 28.8 sec task period. The resting period was divided into baseline and pre-task (preT) periods, and the task period was divided into early easy task (eT) and late difficult task (dT) periods. We then normalized the data, analyzed the magnitude of task-related NIRS responses in each period and compared the results between groups using an analysis of variance test.
  
  
  RESULTS
  Statistical analyses revealed a significant interaction between group × optode location × period, in which hemodynamic responses in the PFC during the preT period were smaller in the elderly in than young adults. By contrast, during the task period, the hemodynamic responses were higher in the lateral PFC in the elderly than in young adults. Spearman's rank correlation analysis showed a positive correlation between hemodynamic changes during the preT period in the PFC and correct answer ratios in both groups.
  
  
  CONCLUSIONS
  These findings suggest that more pre-task activation in the anterior PFC is related to better cognitive performance in humans. Thus, a reduction in this activation might partly explain cognitive decline in the elderly.
authors.affiliation: Department of Biofunctional Imaging, Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan; Department of Occupational Therapy, Faculty of Health and Medical Sciences, Tokoha University, Hamamatsu, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Oboshi
authors.affiliation: Research Center for Child Mental Development, Kanazawa University, Kanazawa, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Kikuchi
authors.affiliation: Department of Biofunctional Imaging, Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan; Central Research Laboratory, Hamamatsu Photonics KK, Hamamatsu, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Research Center for Child Mental Development, Kanazawa University, Kanazawa, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Yoshimura
authors.affiliation: Research Center for Child Mental Development, Kanazawa University, Kanazawa, Japan.
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Hiraishi
authors.affiliation: Department of Biofunctional Imaging, Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan; Central Research Laboratory, Hamamatsu Photonics KK, Hamamatsu, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okada
authors.affiliation: Department of Molecular Imaging, Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Magata
authors.affiliation: Department of Biofunctional Imaging, Medical Photonics Research Center, Hamamatsu University School of Medicine, Hamamatsu, Japan.
authors.forename: Yasuomi
authors.initials: Y
authors.lastname: Ouchi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D000704:Analysis of Variance; D001931:Brain Mapping; D003071:Cognition; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult