Right Inferior Parietal Lobule Causally Contributes to Stimulus Encoding for Temporal Order and Duration Perception: Evidence from Stimulus–Stimulant Transcranial Magnetic Stimulation

Abstract

Temporal-order judgment (TOJ) and duration perception are fundamental aspects of subjective time experience. Previous research indicates that both may involve the inferior parietal lobe (IPL), yet the two have been studied in different contexts. This study sought to determine whether the IPL causally contributes to the temporal stimulus encoding process in TOJ and duration perception. To this end, we utilized single-pulse transcranial magnetic stimulation (TMS) as both a task stimulus and a disruptive stimulant. We combined the two tasks into an adaptive staircase method and measured both discrimination thresholds and reaction times. In a 2 × 2 within-subjects design, 24 participants performed the two tasks over two separate days (left or right IPL). Discrimination thresholds during both tasks were significantly higher in right IPL than left IPL conditions, without significant reaction time differences between the conditions. We thus provide a shared neural substrate within the right IPL, which subserves both temporal-order judgment and duration perception by encoding temporal representations. Our novel use of single-pulse TMS would be useful for other TMS studies in terms of the ability to selectively disrupt the stimulus encoding process and experimental efficiency.