Neural correlates of variable working memory load across adult age and skill: dissociative patterns within the fronto-parietal network.
We examined neural changes related to variations in working memory load by using an n-back task with three levels and functional magnetic resonance imaging. Younger adults were divided into high- and low-performing groups (Young-High; Young-Low) and compared with older adults. Relative to Young-High, capacity-constraints in working memory were apparent between load 1-2 for the elderly and between load 2-3 for Young-Low. Capacity-constraints in neural activity followed this pattern by showing a monotonically increasing response in parietal cortex and thalamus for Young-High, whereas activity leveled off at 1-back for the elderly and at 2-back for Young-Low. The response in dorsal frontal cortex followed a similar pattern with the addition that the magnitude of activation differed within capacity limitations (Old > Young at 1-back; Young-Low > Young-High at 2-back). These findings indicate that an important determinant of WM capacity is the ability to keep the frontal cortex adequately engaged in relation to current task demands.
Nyberg
Lars
L
Integrative Medical Biology (Physiology section), Umeå University, Umeå, Sweden. lars.nyberg@physiol.umu.se
Dahlin
Erika
E
Stigsdotter Neely
Anna
A
Bäckman
Lars
L
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*