Age-related differences in activation-performance relations in delayed-response tasks: a multiple component analysis.
We used event-related functional magnetic resonance imaging (fMRI) to measure prefrontal cortex (PFC) activity while younger and older adults performed an item-recognition task in which the memory-set size varied between 1 and 8 letters. Each trial was composed of a 4-sec encoding period in which subjects viewed random letter strings, a 12-sec retention period and a 2-sec retrieval period in which subjects decided whether a single probe letter was or was not part of the memory set. For both groups, reaction-time (RT) increased and accuracy decreased with increasing memory set-size. Analyses of individual subjects' performance and cortical activity indicated that speed and accuracy accounted for variance in different task periods in dorsal and ventral PFC. Age-related differences in accuracy-activation relations were observed in dorsal PFC during encoding and ventral PFC during maintenance. Age-related differences in RT-activation relations were observed in dorsal PFC during retrieval. These results and additional fMRI data we have collected during performance of a speeded processing task, directly support a model of cognitive slowing in which processing rate is related to neural efficiency.
Rypma
Bart
B
Rutgers University, USA. bart.rypma@utdallas.edu
Eldreth
Dana A
DA
Rebbechi
Donovan
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001931:Brain Mapping; D003071:Cognition / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D008959:Models, Neurological; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology*; D012016:Reference Values; D018709:Statistics, Nonparametric