Watkins, R. H. | bioRxiv Science

bioRxiv2026

A psychophysical characterization of tactile and temperature perception on the human torso

Numerous studies have been conducted to investigate touch on the hand and forearm, but less is known about the rest of the body, particularly the torso and breasts, which play an important role in affective touch. We conducted psychophysical tests on three skin sites on the torso: upper breast, nipple-areola complex (NAC), and under the breast, as well as on two control sites: palm and forearm. We studied touch pleasantness and intensity by applying gentle caress-like strokes using a soft brush, and measured temperature and tactile detection thresholds. The results show an inverted U-shaped relationship for pleasantness over increasing stroking velocity for all skin sites, although we found some differences between sites, particularly at 30 cm.s-1, where participants found stroking on the NAC to be more intense and women additionally found it to be less pleasant. For temperature detection, we found that the NAC was more sensitive in men. For tactile detection, we mainly observed that the areola was far less sensitive than the other areas. Together, these results provide insights into tactile perception in the torso on a fundamental level, which can be applied to understanding how to regain sensations after mastectomy.

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↗