Biology subjects

Wessberg, J.

Publications and source records attributed to Wessberg, J..

3 recordsLinked to original sources

bioRxiv2025

Single human fingertip mechanoreceptive afferents simultaneously encode multidimensional aspects of touch

Touch using the hands is essential for recognizing surface features and manipulating objects, where different aspects are encoded by four main types of low-threshold mechanoreceptors (LTMs) in glabrous skin. Although factors such as movement, vibration, and pressure are often studied individually, touch requires their integration to produce complex sensations. We investigated these processes jointly by recording single-unit activity via microneurography from human LTM afferents in the median nerve as periodic gratings slid across their receptive fields, varying the normal force and sliding velocity per trial. Mixed-effects models revealed that fast-adapting type 1 (FA-1) afferent firing was influenced by all three parameters--force, velocity, and spatial period. Slowly-adapting type 1 (SA-1) afferent firing was primarily driven by force, and to a lesser extent, velocity. These findings support the view that FA-1 afferents encode stimulus intensity in an approximately linear manner, while SA-1 afferents function mainly as force detectors, demonstrating that mechanoreceptive afferents provide a complementary and multidimensional representation of texture during sliding contact. This distributed encoding challenges the notion that LTMs are dedicated to single stimulus features, suggesting that tactile information is represented across LTM populations where each class contributes differently-weighted inputs to capture skin-object interactions.

physiology↗

bioRxiv2021

A topographical and physiological exploration of C-tactile afferents and their response to menthol and histamine.

Numerous microneurography studies in the human peroneal nerve have suggested that CT afferents are lacking in the more distal parts of the limbs. Here we recorded from unmyelinated low-threshold mechanosensitive afferents in the peroneal and radial nerves, with the most distal receptive fields located on the proximal phalanx of the third finger for the superficial branch of the radial nerve, and near the lateral malleolus for the peroneal nerve. We found that the physiological properties with regard to conduction velocity and mechanical threshold, as well as their tuning to brush velocity, were similar in CT units across the antebrachial, radial and peroneal nerves. Moreover, we found that while CT afferents are readily found during microneurography of the arm nerves, they appear to be much more sparse in the lower leg compared to C nociceptors. We continued to explore CT afferents with regard to their chemical sensitivity and found that they could not be activated by topical application to their receptive field of either the cooling agent menthol or the pruritogen histamine. In light of previous studies showing the combined effects that temperature and mechanical stimuli have on these neurons, including a lack of responsiveness to heat, these findings add to the growing body of research suggesting that CT afferents constitute a unique class of sensory afferents with highly specialized mechanisms for transducing gentle touch.

neuroscience↗

bioRxiv2018

Imaging human cortical responses to intraneural microstimulation using magnetoencephalography

The sensation of touch in the glabrous skin of the human hand is conveyed by thousands of fast-conducting mechanoreceptive afferents, which can be categorised into four distinct types. The spiking properties of these afferents in the periphery in response to varied tactile stimuli are well-characterised, but relatively little is known about the spatiotemporal properties of the neural representations of these different receptor types in the human cortex. Here, we use the novel methodological combination of single-unit intraneural microstimulation (INMS) with magnetoencephalography (MEG) to localise cortical representations of individual touch afferents in humans, by measuring the extracranial magnetic fields from neural currents. We found that by assessing the modulation of the beta (13-30 Hz) rhythm during single-unit INMS, significant changes in oscillatory amplitude occur in the contralateral primary somatosensory cortex within and across a group of fast adapting type I mechanoreceptive 20 afferents, which corresponded well to the induced response from matched vibrotactile stimulation. Combining the spatiotemporal specificity of MEG with the selective single-unit stimulation of INMS enables the interrogation of the central representations of different aspects of tactile afferent signalling within the human cortices. The fundamental finding that single-unit INMS ERD responses are robust and consistent with natural somatosensory stimuli will permit us to more dynamically probe the central nervous system responses in humans, to address questions about the processing of touch from the different classes of mechanoreceptive afferents and the effects of varying the stimulus frequency and patterning.

neuroscience↗