title: Reduced prefrontal oxygenation in mild cognitive impairment during memory retrieval.
abstract: BACKGROUND
  Memory impairment is considered a hallmark of amnestic mild cognitive impairment (aMCI) and dementia. Emerging evidence suggests that the prefrontal lobe is required to maintain memory functions. The purpose of this study was to clarify whether older adults with aMCI have decreased prefrontal oxygenation during memory encoding and retrieval compared with age-matched healthy older adults, using multi-channel near-infrared spectroscopy.
  
  
  METHODS
  We examined 64 older adults with aMCI (mean 71.8 years) and 66 cognitively healthy control subjects comparable in age and gender (mean 71.7 years). The concentration of oxy-hemoglobin, which is a reliable biomarker of changes in regional cerebral blood flow, was measured in the prefrontal cortex during encoding and delayed retrieval of a list of 10 target words. Task performance was evaluated as average number of correct answers in the retrieval task.
  
  
  RESULTS
  Subjects with aMCI showed reduced activation in the bilateral dorsolateral cortex (approximately Brodmann area 9) and provided fewer correct answers in the retrieval period than control subjects. There were no significant differences during encoding.
  
  
  CONCLUSIONS
  Reduced activation in the dorsolateral cortex during retrieval may cause deficits in memory performance, which may be used as a marker of aMCI. Further studies are required to examine the predictive validity of this decreased activation pattern for the incidence of Alzheimer's disease.
authors.affiliation: Institute of Innovation for Future Society, Nagoya University, Nagoya, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Uemura
authors.affiliation: Department of Functioning Activation, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shimada
authors.affiliation: Department of Functioning Activation, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Japan.|Research Fellow of the Japan Society for the Promotion of Science, Tokyo, Japan.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Doi
authors.affiliation: Department of Functioning Activation, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Japan.
authors.forename: Hyuma
authors.initials: H
authors.lastname: Makizako
authors.affiliation: Department of Functioning Activation, Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Tsutsumimoto
authors.affiliation: National Center for Geriatrics and Gerontology, Obu, Japan.|Department of Medicinal Biotechnology, Dong-A University, Busan, Korea.
authors.forename: Hyuntae
authors.initials: H
authors.lastname: Park
authors.affiliation: National Center for Geriatrics and Gerontology, Obu, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D001931:Brain Mapping / Q000379:methods; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D017397:Prefrontal Cortex / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D019265:Spectroscopy, Near-Infrared
chemical_list: D015415:Biomarkers; D010108:Oxyhemoglobins
keywords: NIRS; brain aging; cognition; dementia; neuroimaging