Abstract
Author SummaryWhen we slide our fingertip across a textured surface, small, complex, and high-frequency vibrations are elicited in the skin and our nervous system extracts information about texture from these vibrations. In this study, we investigate how texture-like vibrations are processed in primary somatosensory cortex (S1). First, we show that the time-varying amplitude of skin vibrations is encoded in the time-varying response rates of a subpopulation of S1 neurons. Second, we show that this same subpopulation of S1 neurons produces responses whose timing closely matches that of the vibrations: The frequency composition of the spiking patterns matches that of the stimulus, even for complex vibrations. We demonstrate that this temporal precision is behaviorally relevant by showing that the tactile perception of vibration is better predicted from neuronal responses when spike timing is taken into consideration than when it is not. The activity of S1 neurons is thus multiplexed at different time scales: Stimulus amplitude, which changes relatively slowly, is represented at a relatively coarse temporal resolution, while stimulus frequency is represented by precisely timed action potentials.
Highlights
When we scan our finger across a textured surface, complex, high-frequency vibrations are elicited in the skin, and our ability to acquire information about surface microgeometry relies on the transduction and processing of these vibrations [1,2,3,4]
We found that firing rates increased logarithmically with amplitude over the range tested for all three stimulus sets (Figures 1A, 1B, and S1), as is the case at the somatosensory periphery [5]
When we slide our fingertip across a textured surface, small, complex, and high-frequency vibrations are elicited in the skin and our nervous system extracts information about texture from these vibrations
Summary
When we scan our finger across a textured surface, complex, high-frequency vibrations are elicited in the skin, and our ability to acquire information about surface microgeometry relies on the transduction and processing of these vibrations [1,2,3,4]. The frequency content of skin vibrations, on the other hand, is conveyed through the timing of the response with millisecond precision [7], as illustrated by the well-documented phase-locking of peripheral fibers to sinusoidal stimuli [8,9]. In primary somatosensory cortex (S1), neurons exhibit phase-locked responses to low-frequency sinusoidal stimuli (,100 Hz) [10], but the extent to which this temporal patterning is perceptually relevant is unclear [10,11,12]. Phase locking in S1 responses has been reported to disappear at higher frequencies [10], so the cortical mechanisms that mediate our ability to distinguish the spectral content of highfrequency vibrations remain to be elucidated. Virtually nothing is known about how naturalistic (spectrally complex) vibrations are represented in cortex
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