title: Under-recruitment and nonselective recruitment: dissociable neural mechanisms associated with aging.
abstract: Frontal contributions to cognitive decline in aging were explored using functional MRI. Frontal regions active in younger adults during self-initiated (intentional) memory encoding were under-recruited in older adults. Older adults showed less activity in anterior-ventral regions associated with controlled use of semantic information. Under-recruitment was reversed by requiring semantic elaboration suggesting it stemmed from difficulty in spontaneous recruitment of available frontal resources. In addition, older adults recruited multiple frontal regions in a nonselective manner for both verbal and nonverbal materials. Lack of selectivity was not reversed during semantically directed encoding even when under-recruitment was diminished. These findings suggest two separate forms of age-associated change in frontal cortex: under-recruitment and nonselective recruitment. The former is reversible and potentially amenable to cognitive training; the latter may reflect a less malleable change associated with cognitive decline in advanced aging.
authors.affiliation: Department of Psychology, Washington University, St. Louis, MO 63130, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Logan
authors.forename: Amy L
authors.initials: AL
authors.lastname: Sanders
authors.forename: Abraham Z
authors.initials: AZ
authors.lastname: Snyder
authors.forename: John C
authors.initials: JC
authors.lastname: Morris
authors.forename: Randy L
authors.initials: RL
authors.lastname: Buckner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D003071:Cognition / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011999:Recruitment, Neurophysiological; D013997:Time Factors; D014705:Verbal Behavior