title: Relation between working memory performance and evoked cerebral blood oxygenation changes in the prefrontal cortex evaluated by quantitative time-resolved near-infrared spectroscopy.
abstract: OBJECTIVE
  The lateral prefrontal cortex (LPFC) plays a central role in working memory (WM). In the present study, we employed quantitative, near-infrared time-resolved spectroscopy (TRS) to evaluate the relation between LPFC activity during WM and the task  performance in 19 healthy, middle-aged, female subjects (mean age of 46·8±2·1 years).
  
  
  METHODS
  Concentration changes of oxyhemoglobin (oxy-Hb), deoxyhemoglobin, and total hemoglobin in the bilateral LPFC were measured by means of TRS during performance of Sternberg  tests (ST) of one digit and six digits. The oxy-Hb changes were compared to performance in ST. In addition, we evaluated whether pathlength of the forehead and baseline concentration of oxy-Hb influenced WM performance.
  
  
  RESULTS
  TRS revealed increases in oxy-Hb in association with  a decrease in deoxy-Hb during ST. We found a significant negative correlation between the reaction time of six-digit ST and oxy-Hb changes in the bilateral LPFC (left, P = 0·0061; right, P = 0·0029); however, no significant correlation was observed  with one-digit ST. In contrast, accuracy of ST did not correlate with the oxy-Hb changes in the prefrontal cortex. The optical pathlength of the forehead and concentration of oxy-Hb at rest in the LPFC did not correlate with either reaction time or accuracy in ST.
  
  
  CONCLUSIONS
  The  present results indicate that oxy-Hb changes in the LPFC during a WM task, as measured by TRS, correlated with WM performance. TRS is compact and less expensive than functional magnetic resonance imaging, and may be a useful tool to evaluate neural correlates of WM in normal adults.
authors.affiliation: Shiseido Research Center, Yokohama, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tanida
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sakatani
authors.forename: Takeo
authors.initials: T
authors.lastname: Tsujii
mesh_terms: D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006454:Hemoglobins / Q000032:analysis / Q000378:metabolism; D006801:Humans; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D010108:Oxyhemoglobins / Q000032:analysis / Q000378:metabolism; D017397:Prefrontal Cortex / Q000098:blood supply / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin