title: Regional white matter and neuropsychological functioning across the adult lifespan.
abstract: BACKGROUND
  The current study utilized magnetic resonance imaging (MRI) to more fully elucidate the relationship among age, regional white matter, and neuropsychological functioning.
  
  
  METHODS
  One hundred ninety-nine neurologically healthy adults received MRI and standardized neuropsychological assessment. MR images were spatially normalized and segmented by tissue type; relative white matter values in each of the four cerebral lobes in each hemisphere were computed. Subjects were divided into Younger (ages 21-30), Middle (ages 31-54), and Older (ages 55-79) age groups.
  
  
  RESULTS
  The Older group had significantly less overall relative white matter than the Middle group, who had significantly less overall relative white matter than the Younger participants (F (2, 193) = 5.42, p = 0.005). Differences in frontal lobe white matter were of largest magnitude, followed by temporal lobe (F (6, 579) = 3.32, p = 0.003). Age and frontal and temporal lobe white matter were primarily associated with performance on neuropsychological tests of executive functioning and memory. Mediational analysis suggested that frontal lobe white matter mediated the relationship between age and performance on tasks of executive functioning and memory.
  
  
  CONCLUSIONS
  The results confirm age-associated decline in frontal and temporal white matter, and age-related cognitive decline in several domains. Decline in neuropsychological functioning is, in part, mediated by a relative age-related reduction in frontal white matter.
authors.affiliation: Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, NY 10032, USA. amb2139@columbia.edu
authors.forename: Adam M
authors.initials: AM
authors.lastname: Brickman
authors.forename: Molly E
authors.initials: ME
authors.lastname: Zimmerman
authors.forename: Robert H
authors.initials: RH
authors.lastname: Paul
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Grieve
authors.forename: David F
authors.initials: DF
authors.lastname: Tate
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Cohen
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Williams
authors.forename: C Richard
authors.initials: CR
authors.lastname: Clark
authors.forename: Evian
authors.initials: E
authors.lastname: Gordon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology* / Q000523:psychology; D000704:Analysis of Variance; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology; D003430:Cross-Sectional Studies; D005625:Frontal Lobe / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009186:Myelin Sheath; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D009929:Organ Size; D010296:Parietal Lobe / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D012016:Reference Values; D012737:Sex Factors; D013702:Temporal Lobe / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology