The cerebral basis of time perception: A fMRI Study

In this study we have addressed the issue of the structures involved in time estimation using fMRI. Five right handed male subjects were trained to perform three tasks. 1) Working memory: an array of five digits was displayed. After a 1300 delay a single digit probe appeared and the subject was to signal whether or not the probe was included in the array; 2) Temporal production: an array of five digits was displayed, the probe appeared immediately afterwards but the subject was to provide his response only after a delay of 1500 ms; 3) Control: the subject was to respond depending on the side of a capital X in an array of lower case x. For each subject, a total of 720 volumes were acquired during 12 consecutive scans with a gradient echo EPI sequence (TR=3 s, TE=40, 64x64 matrix) on a GE Signa 1.5 T machine. Data were analyzed using SPM95 software. Temporal production was associated in 4/5 subjects with bilateral activation in the middle and in the inferior occipital gyrus (BA 18, 19). In one subject the same areas were activated only on the left side. Inferior parietal lobule (BA 40) and prefrontal areas (BA 10) were bilaterally activated in four subjects. We hypothesize that extrastriatc cortex and inferior parietal cortex can monitor the duration of visual stimuli. We suggest thai the physiological correlates of prospective time estimation might relay on different areas depending on stimulus characteristic and response modality