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The link between the sense of touch and perception of time is unknown territory. In this regard, a team of researchers at SISSA published a new theory in PLOS Computational Biology which explains how an individual can sense the passage of time via sensory stimuli. In this study, scientists found that the perceived time span, of a vibration applied to the subject (humans and rats), increases in relation to actual elapsed time and the intensity of the vibration.
How does the brain resemble a stopwatch?
According to Mathew Diamond, director of the Tactile Perception and Learning Lab and senior author of the study, the main challenge that neuroscience researchers face is the lack of dedicated receptors, i.e., an individual can sense the passage of time without having an actual sensor. We can gauge time lapses in our brain similarly to a stopwatch, i.e., the brain can record the start and stop time of an event and compute the total time duration between these two instances. However, even after years of research, scientists have failed to determine a specific brain mechanism resembling a stopwatch. While analyzing this problem, the research team at SISSA wondered if the answer to the problem lies in a better understanding of the sensory system.
How can one sense time?
The researchers trained both humans and rats to compare the durations of tactile vibrations, i.e., vibrations applied to the fingertips of the humans and those applied to the whiskers of rats. They observed that an increase in the stimulus intensity resulted in an increased perceived duration. Additionally, an increase in the duration of vibration led to an increase in perceived intensity. Thus, the perceived period of vibration introduced to the skin (or whisker in the case of rats) increased with respect to a) actual elapsed time; and b) intensity of the vibration. In other words, the subjects felt that a stronger vibration lasted longer.
Subsequently, the research group proposed a model based on the subjects’ experience after encountering a stimulus. The model was tested by analyzing the recordings of spike trains from the vibratory somatosensory cortex, which is a receptor that senses touch after the subjects were introduced to a vibration (touch). The comparable results of both humans and rats validate the model’s prediction of perceived time (neurometric functions) to actual psychophysical functions.
The model proposed by the research team at SISSA could provide neurometric functions, using sensory code from vibratory somatosensory cortex as inputs. These neurometric functions were analogous to the psychophysical functions of rats. This result reveals the viability of the model in deciphering the time elapsed after a touch stimuli. Thereby, this model could be used to assess the sense of time-lapse one feels after experiencing a tactile sensory stimulus.