title: Thinking of the future and past: the roles of the frontal pole and the medial temporal lobes.
abstract: Human lesion data have indicated that the frontal polar area might be critically involved in having an insight into one's future. Retrospective memory mediated by medial temporal lobes and related structures, on the other hand, could be used to extract one's future prospects efficiently. In the present study, we investigated the roles of these two brain structures in thinking of the future and past by using positron emission tomography (PET) and a naturalistic task setting. We measured regional cerebral blood flow (rCBF) in healthy subjects while they were talking about their future prospects or past experiences, with regard to two different temporal windows (in years or days). Many areas in the frontal and the medial temporal lobes were activated during the future and past tasks compared with a control task requiring semantic retrieval. Among these, areas in anteromedial frontal pole showed greater activation during the future tasks than during the past tasks, showing significant effect of temporal distance from the present. Most areas in the medial temporal lobes showed greater or equivalent level of activations during the future tasks compared with the past tasks. The present results suggest that thinking of the future is closely related to retrospective memory, but that specific areas in the frontal pole and the medial temporal lobes are more involved with thinking of the future than that of the past.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK. j.okuda@ucl.ac.uk
authors.forename: Jiro
authors.initials: J
authors.lastname: Okuda
authors.forename: Toshikatsu
authors.initials: T
authors.lastname: Fujii
authors.forename: Hiroya
authors.initials: H
authors.lastname: Ohtake
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsukiura
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Tanji
authors.forename: Kyoko
authors.initials: K
authors.lastname: Suzuki
authors.forename: Ryuta
authors.initials: R
authors.lastname: Kawashima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukuda
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Itoh
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yamadori
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D001364:Awareness / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology; D003657:Decision Making / Q000502:physiology; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D011340:Problem Solving / Q000502:physiology; D011859:Radiography; D012039:Regional Blood Flow / Q000502:physiology; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*; D014055:Tomography, Emission-Computed