title: Age-related decline in differentiated neural responses to rare target versus frequent standard stimuli.
abstract: One mechanism hypothesized to contribute to cognitive aging is the failure to recruit specialized neural modules and generate differentiated neural responses to various classes of stimuli. Here, ERPs were used to examine the extent to which target and standard stimulus types were processed differently by well-matched adults ages 19-99. Subjects responded to designated visual target letters under low and high load conditions. Temporospatial PCA was used to parse the P3b component, an index of categorization/memory updating. The P3b amplitude difference between targets and standards decreased substantially as a function of age. Dedifferentiation began in middle age, and continued into old-old age. The reduced differentiation of neural responses was driven by an age-related decline in the size of the P3b to targets and an age-related increase in the P3b to standards. Larger P3b amplitude to standards among older subjects was associated with higher executive capacity and better task performance. In summary, dedifferentiation begins relatively early in adulthood and progresses in a linear fashion throughout the lifespan. The age-related augmentation of the P3b to standards appears to reflect a compensatory mechanism that helps maintain task performance.
authors.affiliation: Center for Brain/Mind Medicine, Division of Cognitive and Behavioral Neurology, Department of Neurology, Brigham and Women׳s Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA. Electronic address: kmott@partners.org.
authors.forename: Katherine K
authors.initials: KK
authors.lastname: Mott
authors.affiliation: Center for Brain/Mind Medicine, Division of Cognitive and Behavioral Neurology, Department of Neurology, Brigham and Women׳s Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA. Electronic address: balperin@partners.org.
authors.forename: Brittany R
authors.initials: BR
authors.lastname: Alperin
authors.affiliation: Department of Psychology, Tufts University, 490 Boston Avenue, Medford, MA 02155, USA. Electronic address: pholcomb@tufts.edu.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Holcomb
authors.affiliation: Center for Brain/Mind Medicine, Division of Cognitive and Behavioral Neurology, Department of Neurology, Brigham and Women׳s Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA. Electronic address: kdaffner@partners.org.
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Daffner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology* / Q000523:psychology; D003118:Color Perception / Q000502:physiology; D003463:Cues; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D056344:Executive Function / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D013037:Spatial Behavior / Q000502:physiology; D055815:Young Adult
keywords: Cognitive aging; Compensatory activity; Dedifferentiation; ERPs; P3b; Temporospatial PCA