title: Effects of aging and dopamine genotypes on the emergence of explicit memory during sequence learning.
abstract: The striatum and medial temporal lobe play important roles in implicit and explicit memory, respectively. Furthermore, recent studies have linked striatal dopamine modulation to both implicit as well as explicit sequence learning and suggested a potential role of the striatum in the emergence of explicit memory during sequence learning. With respect to aging, previous findings indicated that implicit memory is less impaired than explicit memory in older adults and that genetic effects on cognition are magnified by aging. To understand the links between these findings, we investigated effects of aging and genotypes relevant for striatal dopamine on the implicit and explicit components of sequence learning. Reaction time (RT) and error data from 80 younger (20-30 years) and 70 older adults (60-71 years) during a serial reaction time task showed that age differences in learning-related reduction of RTs emerged gradually over the course of learning. Verbal recall and measures derived from the process-dissociation procedure revealed that younger adults acquired more explicit memory about the sequence than older adults, potentially causing age differences in RT gains in later stages of learning. Of specific interest, polymorphisms of the dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32, rs907094) and dopamine transporter (DAT, VNTR) genes showed interactive effects on overall RTs and verbal recall of the sequence in older but not in younger adults. Together our findings show that variations in genotypes relevant for dopamine functions are associated more with aging-related impairments in the explicit than the implicit component of sequence learning, providing support for theories emphasizing the role of dopaminergic modulation in cognitive aging and the magnification of genetic effects in human aging.
authors.affiliation: Max Planck Institute for Human Development, Center for Lifespan Psychology, Lentzealle 94, 14195 Berlin, Germany; Humboldt-Universität zu Berlin, Department of Psychology, Unter den Linden 6, 10099 Berlin, Germany. Electronic address: nschuck@princeton.edu.
authors.forename: Nicolas W
authors.initials: NW
authors.lastname: Schuck
authors.forename: Peter A
authors.initials: PA
authors.lastname: Frensch
authors.forename: Brit-Maren M
authors.initials: BM
authors.lastname: Schjeide
authors.forename: Julia
authors.initials: J
authors.lastname: Schröder
authors.forename: Lars
authors.initials: L
authors.lastname: Bertram
authors.forename: Shu-Chen
authors.initials: SC
authors.lastname: Li
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000235:genetics*; D004298:Dopamine / Q000235:genetics; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32 / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011930:Reaction Time / Q000235:genetics; D012691:Serial Learning / Q000502:physiology*; D011795:Surveys and Questionnaires; D014706:Verbal Learning; D055815:Young Adult
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; C497928:PPP1R1B protein, human; D004298:Dopamine
keywords: Aging; DARPP-32; DAT; Dopamine; Implicit and Explicit Memory; Sequence Learning; Serial Reaction Time Task