title: Correlations of striatal dopamine synthesis with default network deactivations during working memory in younger adults.
abstract: Age-related deficits have been demonstrated in working memory performance and in the dopamine system thought to support it. We performed positron emission tomography (PET) scans on 12 younger (mean 22.7 years) and 19 older (mean 65.8 years) adults using the radiotracer 6-[(18)F]-fluoro-L-m-tyrosine (FMT), which measures dopamine synthesis capacity. Subjects also underwent functional magnetic resonance imaging (fMRI) while performing a delayed recognition working memory task. We evaluated age-related fMRI activity differences and examined how they related to FMT signal variations in dorsal caudate within each age group. In posterior cingulate cortex and precuneus (PCC/Pc), older adults showed diminished fMRI deactivations during memory recognition compared with younger adults. Greater task-induced deactivation (in younger adults only) was associated both with higher FMT signal and with worse memory performance. Our results suggest that dopamine synthesis helps modulate default network activity in younger adults and that alterations to the dopamine system may contribute to age-related changes in working memory function.
authors.affiliation: Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA.
authors.forename: Meredith N
authors.initials: MN
authors.lastname: Braskie
authors.forename: Susan M
authors.initials: SM
authors.lastname: Landau
authors.forename: Claire E
authors.initials: CE
authors.lastname: Wilcox
authors.forename: Stephanie D
authors.initials: SD
authors.lastname: Taylor
authors.forename: James P
authors.initials: JP
authors.lastname: O'Neil
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: Baker
authors.forename: Cindee M
authors.initials: CM
authors.lastname: Madison
authors.forename: William J
authors.initials: WJ
authors.lastname: Jagust
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001931:Brain Mapping; D003342:Corpus Striatum / Q000000981:diagnostic imaging* / Q000378:metabolism; D004298:Dopamine / Q000096:biosynthesis*; D005462:Fluorine Radioisotopes; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014443:Tyrosine / Q000031:analogs & derivatives; D055815:Young Adult
chemical_list: C496696:6-fluoro-3-hydroxyphenylalanine; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D014443:Tyrosine; D004298:Dopamine