Cortical integration of tactile inputs distributed across timescales

Sensory experiences in the real world cut across timescales from milliseconds to seconds. Emerging evidence suggests that somatosensory processing is sensitive to the temporal structure of the stimuli in the sub-second scale, yet only a few select ranges within this scale have been studied. To process real-world information, the integration of tactile inputs must occur over a much broader temporal range. To address temporal integration across timescales, we recorded scalp EEG signals from somatosensory cortex in response to a train of tactile pulses presented to the fingertips with varying inter-stimulus intervals (ISI) spanning 100 to 10,000 ms. To capture a rich variety of influences of the temporal structure on the cortical signals, we used a multi-dimensional event-related potential where the stimulations are separated according to the next interval structure. We tracked cortical tactile processing through its early (<75 ms), intermediate (75 to 150 ms) and late stages (150 to 300 ms). We find that the early and late stages of cortical activity were similarly dominated by the preceding ISI; EEG signals were suppressed with ISIs < 500 ms and enhanced with longer ISIs, with this effect persisting even when ISIs were approximately 8 seconds. The intermediate stage of cortical activity was sensitive to both the previous and the penultimate ISIs. Our findings suggest that the specific somatosensory cortical networks integrate temporal structure across timescales to enable complex sensory experiences.