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Abstract:
Brain imaging studies on time perception usually report a
pattern of activation including prefrontal, mesial frontocentral,
inferior parietal cortices, striatum, and cerebellar hemispheres.
In order to determine which areas specifically subtend timing
processes, we investigated whether activation within this network
varies with the duration to be estimated. Six previously trained
subjects (20-30 years) participated in an event-related fMRI study
(3T Brucker Scanner, TE = 35ms, TR = 2sec, 3.75x3.75x6mm 18 slices,
whole-brain volumes per subject). They were requested to estimate
either a short (325 to 575 ms) or a long (950 to 1650 ms) interval
separating two LED flashes. Control trials with no estimation were
also included. Data were analyzed with SPM99; single-subject
analyses as well as random-effect group analysis were carried out.
As expected, duration estimation relative to control task activated
prefrontal, cingulate and right inferior parietal cortices,
supplementary motor area (SMA), and striatum for all subjects. More
importantly, the activation in mesial frontocentral cortex (peaking
in either SMA or cingulum depending on subjects) was significantly
greater for long than short duration in all six subjects. This
provides evidence that this region plays a crucial role in time
coding which could be the cumulative function postulated by
pacemaker-accumulator models.
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