Interoceptive awareness selectively predicts timing accuracy in irregular contexts.

Awareness of psychophysiological changes has been proposed to play a role in duration perception; however, evidence on whether interoceptive awareness affects timing is mixed, and it is not clear which task features favor the reliance on bodily changes to track time. Here we tested the hypothesis that interoceptive awareness is selectively involved in timing when the context does not provide reliable cues on elapsed time. We developed a novel paradigm assessing interval reproduction in two conditions: 1) with regularly spaced stimuli during the encoding/reproduction phase (regular condition), 2) with irregularly spaced stimuli during the encoding/reproduction phase (irregular condition). Interoceptive awareness was assessed using the "Self-Awareness Questionnaire", investigating the frequency of common bodily sensations. Interoceptive awareness predicted timing accuracy in the irregular, but not in the regular condition; also, the contribution was specifically due to awareness of visceral sensations rather than somatosensory sensations. Overall, results suggest that individual differences in interoception differently affect timing according to contextual features, consistently with evidence that different mechanisms mediate timing in different conditions.

Duration reproduction in regular and irregular contexts after unilateral brain damage: Evidence from voxel-based lesion-symptom mapping and atlas-based hodological analysis.

It has been proposed that not completely overlapping brain networks support interval timing depending on whether or not an external, predictable temporal cue is provided during the task, aiding time estimation. Here we tested this hypothesis in a neuropsychological study, using both a topological approach - through voxel-based lesion-symptom mapping (VLSM), that assesses the relation between continuous behavioral scores and lesion information on a voxel-by-voxel basis - and a hodological approach, using an atlas-based tractography. A group of patients with unilateral focal brain lesions and their matched controls performed a duration reproduction task assessing time processing in two conditions, namely with regularly spaced stimuli during encoding and reproduction (Regular condition), and with irregularly spaced stimuli during the same task (Irregular condition). VLSM analyses showed that scores in the two conditions were associated with lesions involving partly separable clusters of voxels, with lower performance only in the Irregular condition being related to lesions involving the right insular cortex. Performance in both conditions correlated with the probability of disconnection of the right frontal superior longitudinal tract, and of the superior and middle branches of the right superior longitudinal fasciculus. These findings suggest that the dissociation between timing in regular and irregular contexts is not complete, since performance in both conditions relies on the integrity of a common suprasecond timing network. Furthermore, they are consistent with the hypothesis that tracking time without the aid of external cues selectively relies on the integration of psychophysiological changes in the right insula.