In addition to A-beta fibres the human hairy skin has unmyelinated (C) fibres responsive to light touch. Previous functional magnetic resonance imaging (fMRI) studies in a subject with a neuronopathy who specifically lacks A-beta afferents indicated that tactile C afferents (CT) activate insular cortex, whereas no response was seen in somatosensory areas 1 and 2. Psychophysical tests suggested that CT afferents give rise to an inconsistent perception of weak and pleasant touch. By examining two neuronopathy subjects as well as control subjects we have now demonstrated that CT stimulation can elicit a sympathetic skin response. Further, the neuronopathy subjects' ability to localize stimuli which activate CT afferents was very poor but above chance level. The findings support the interpretation that the CT system is well suited to underpin affective rather than discriminative functions of tactile sensations.
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Parkinsonism Relat Disord
January 2025
Human Sensorimotor Control Laboratory, School of Kinesiology, University of Minnesota, USA; Center for Clinical Movement Science, University of Minnesota, USA.
Introduction: Cervical dystonia (CD) is characterized by involuntary neck muscle spasms that lead to abnormal head movements or postures. It is associated with somatosensory (tactile and proprioceptive) dysfunction. Here we tested whether vibro-tactile stimulation (VTS) of the cervical muscles constitutes a non-invasive form of neuromodulation of the somatosensory system that can provide temporary symptom relief for people with CD.
View Article and Find Full Text PDFNeuropsychopharmacology
January 2025
Department of Biomedical and Clinical Sciences, Center for Social and Affective Neuroscience, Linköping University, Linköping, Sweden.
Social relationships are central to well-being. A subgroup of afferent nerve fibers, C-tactile (CT) afferents, are primed to respond to affective, socially relevant touch and may mitigate the effects of stress. The endocannabinoid ligand anandamide (AEA) modulates both social reward and stress.
View Article and Find Full Text PDFJ Physiol
January 2025
School of Life Sciences, The University of Nottingham, Queen's Medical Centre, Nottingham, UK.
C-low threshold mechanoreceptors (C-LTMRs) in animals (termed C-tactile (CT) fibres in humans) are a subgroup of C-fibre primary afferents, which innervate hairy skin and respond to low-threshold punctate indentations and brush stimuli. These afferents respond to gentle touch stimuli and are implicated in mediating pleasant/affective touch. These afferents have traditionally been studied using low-throughput, technically challenging approaches, including microneurography in humans and teased fibre electrophysiology in other mammals.
View Article and Find Full Text PDFNeuroscience
January 2025
Department of Orofacial Pain and Jaw Function, Malmö University, Malmö, Sweden; Scandinavian Center for Orofacial Neurosciences (SCON).
Occlusal tactile acuity (OTA) and bite force are essential components of the sensorimotor control of oral behaviors. While these variables have been studied independently, it has not yet been revealed whether compressive force impacts the occlusal perception mediated by the mechanoreceptive afferents in the periodontal ligament. The present study examined the effect of repetition and maximum bite force on OTA by testing nine aluminum foils of different thicknesses together with a sham test with no foil, three times each, in randomized order in 36 healthy individuals.
View Article and Find Full Text PDFJ Integr Neurosci
December 2024
IRCCS Centro Neurolesi Bonino-Pulejo, 98124 Messina, Italy.
The evidence on how touch-based therapy acts on the brain activity opens novel cues for the treatment of chronic pain conditions for which no definitive treatment exists. Touch-based therapies, particularly those involving C-tactile (CT)-optimal touch, have gained increasing attention for their potential in modulating pain perception and improving psychological well-being. While previous studies have focused on the biomechanical effects of manual therapy, recent research has shifted towards understanding the neurophysiological mechanisms underlying these interventions.
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