Differential involvement of regions of rostral prefrontal cortex (Brodmann area 10) in time- and event-based prospective memory.
Rostral prefrontal cortex (approximating Brodmann area 10) has been shown repeatedly to have a role in the maintenance and realization of delayed intentions that are triggered by event cues (i.e., event-based prospective memory). The cerebral organization of the processes associated with the use of time cues (time-based prospective memory) has however received less attention. In two positron emission tomography (PET) studies we therefore examined brain activity associated with time- and event-based prospective memory tasks. In the time-based condition of the first study, young healthy volunteers were asked to make a prospective response based on their self-estimation of the passage of time while engaged in an attention-demanding ongoing activity. In the time-based condition of the second study, participants had a clock available in the ongoing task display and did not need to estimate the time for the prospective response. In the event-based condition of both studies, participants were asked to make a prospective response when prospective cues were presented in ongoing trials. Both studies showed activation differences in rostral prefrontal cortex according to whether the task was time- or event-based. In study one, an area of left superior frontal gyrus was more active in the time-based condition. In study two, three rostral prefrontal regions were more active in the time-based condition: right superior frontal gyrus, anterior medial frontal lobe and anterior cingulate gyrus. A region in left superior frontal gyrus, different from the area found in the first study, was more active in the event-based condition. These results indicate involvement of multiple brain regions of rostral prefrontal cortex in time- and event-based prospective memory. The results are interpreted as reflecting the differing processing demands made by event- or time-based prospective memory tasks, and the differing demands of time-based tasks according to whether a clock is present as an aid.
Okuda
Jiro
J
Institute of Cognitive Neuroscience and Psychology Department, University College London, 17 Queen Square, London WC1N 3AR, UK. j.okuda@lab.tamagawa.ac.jp
Fujii
Toshikatsu
T
Ohtake
Hiroya
H
Tsukiura
Takashi
T
Yamadori
Atsushi
A
Frith
Christopher D
CD
Burgess
Paul W
PW
D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D003463:Cues; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D033182:Intention; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D014055:Tomography, Emission-Computed / Q000379:methods