Time bisection and reproduction: Evidence for a slowdown of the internal clock in right brain damaged patients

Previous studies show that the right hemisphere is involved in time processing, and that damage to the right hemisphere is associated with a tendency to perceive time intervals as shorter than they are, and to reproduce time intervals as longer than they are. Whether time processing deficits following right hemisphere damage are related and what is their neurocognitive basis is unclear. In this study, right brain damaged (RBD) patients, left brain damaged (LBD) patients, and healthy controls underwent a time bisection task and a time reproduction task involving time intervals varying between each other by milliseconds (short durations) or seconds (long durations). The results show that in the time bisection task RBD patients underestimated time intervals compared to LBD patients and healthy controls, while they reproduced time intervals as longer than they are. Time underestimation and over-reproduction in RBD patients applied to short but not long time intervals, and were correlated. Voxel-based lesion-symptom mapping (VLSM) showed that time underestimation was associated with lesions to a right cortico-subcortical network involving the insula and inferior frontal gyrus. A small portion of this network was also associated with time over-reproduction. Our findings are consistent with a slowdown of an 'internal clock' timing mechanism following right brain damage, which likely underlies both the underestimation and the over-reproduction of time intervals, and their (overlapping) neural bases.