The passage of time is sensed, perceived, experienced, but – unlike for touch, vision, hearing, olfaction – there exist no sensory receptors for time. This fact has long tantalized neuroscientists with the possibility that sensing time might “piggyback” on true sensory modalities. New research in fact demonstrates that the percept of time embodied within a tactile experience is rooted in the dual functionality of the somatosensory cortex. Professor Mathew Diamond and his SISSA research team recently published their findings in Nature Communications, shedding light on the intricate interplay between the sense of touch and the sense of time.
As we process stimuli received through the skin, neurons in the somatosensory cortex robustly represent the detailed features of the stimuli, culminating in the subjective experience of touch. However, was the stimulus brief or extended in time? How does the perception of elapsed time emerge? The research team's results indicate how the somatosensory cortex contributes to the perception of time.
Utilizing optogenetics, a technique enabling the modulation of neuronal activity through application of light to the cortex, the study established a connection between two seemingly distinct experiences – the "what" and the "how long" of a stimulus. In rats trained to assess vibration intensity while disregarding duration, optogenetic intervention influenced perceived intensity. Conversely, in animals trained to evaluate vibration duration while disregarding intensity, optogenetic intervention influenced perceived duration. These findings not only affirm the expected function of the somatosensory cortex in constructing the tactile sense but also support the notion that the perception of time is rooted in a widespread network of brain areas with diverse functions, including touch. This research lays the foundation for future studies exploring the intricate relationship between sensory experiences and the perception of time.