Neural mechanisms of vibrotactile categorization

Abstract

The grouping of sensory stimuli into categories is fundamental to cognition. Previous research in the visual and auditory systems supports a two‐stage processing hierarchy that underlies perceptual categorization: (a) a “bottom‐up” perceptual stage in sensory cortices where neurons show selectivity for stimulus features and (b) a “top‐down” second stage in higher level cortical areas that categorizes the stimulus‐selective input from the first stage. In order to test the hypothesis that the two‐stage model applies to the somatosensory system, 14 human participants were trained to categorize vibrotactile stimuli presented to their right forearm. Then, during an fMRI scan, participants actively categorized the stimuli. Representational similarity analysis revealed stimulus selectivity in areas including the left precentral and postcentral gyri, the supramarginal gyrus, and the posterior middle temporal gyrus. Crucially, we identified a single category‐selective region in the left ventral precentral gyrus. Furthermore, an estimation of directed functional connectivity delivered evidence for robust top‐down connectivity from the second to first stage. These results support the validity of the two‐stage model of perceptual categorization for the somatosensory system, suggesting common computational principles and a unified theory of perceptual categorization across the visual, auditory, and somatosensory systems.

From descriptive connectome to mechanistic connectome: Generative modeling in functional magnetic resonance imaging analysis

“…The first stage is a “bottom-up” stage where neurons in the sensory cortices learn to respond to stimulus features while the second stage is a “top-down” stage where neurons in higher cortical areas learn to classify the stimulus-selective inputs from the first stage. To investigate whether the two-stage processing hierarchy also exists in the somatosensory system, Malone et al (2019) designed an experiment where human participants, after training to label vibrotactile stimuli presented to their right forearm, underwent an fMRI scan while actively engaging in categorizing the stimuli. The authors first applied representational similarity analysis to identify the stimulus- and category- selective areas.…”

Metamodal Coupling of Vibrotactile and Auditory Speech Processing Systems Through Matched Stimulus Representations

“…1A) used a frequency-to-place mapping algorithm: The energy passed by each filter of the vocoder was used to modulate the vibration of a specific MRI-compatible transducer on the 16-channel VT device (Fig. 1A and 1C) placed on the volar forearm (Malone et al, 2019). Low frequencies mapped to transducers near the wrist, and higher frequencies mapped to transducers near the elbow.…”

Investigating cortical networks from vibrotactile stimulation in young adults using independent component analysis: an fMRI study

“…Recent studies using vibrotactile stimuli to examine cognitive processes have proven reliable in eliciting responses from somatosensory areas. The vibrotactile stimuli have been applied to young adults in areas such as bilateral fingertips (Chung et al, 2013;Goltz et al, 2013;Puckett et al, 2017;Seri et al, 2019Seri et al, , 2020, digits fingertips (Francis et al, 2000;Pfannmöller et al, 2016;Schweisfurth et al, 2011Schweisfurth et al, , 2014Schweisfurth et al, , 2015, right forearms (Malone et al, 2019), breast (Beugels et al, 2020), leg and foot (Akselrod et al, 2017), sole of the right foot (Siedentopf et al, 2008), and the chest, chin and arm (Jung et al, 2018). Similarly, it was observed that the vibrotactile stimulation using a piezoelectric stimulation system shows good congruency in the S1 cortex using fMRI (functional magnetic resonance imaging) response location (Jaatela et al, 2022), thus proving the reliability of vibrotactile as a stimulus to evoke responses in the somatosensory areas.…”