Spinal signalling of C-fiber mediated pleasant touch in humans

Marshall, Andrew; Sharma, Manohar; Marley, Kate; Olausson, Håkan; McGlone, Francis

doi:10.7554/elife.51642

“…Although we cannot be sure about the underlying mechanism behind warmth eliciting additional MSNA during hand grip, we provide new insights into the regulation of MSNA during muscle fatigue with other types of somatosensory stimuli. It is known that different somatosensory stimuli have specific afferent pathways, where touch and nociception are largely separate (McGlone et al 2014;Marshall et al 2019), although it is thought that the insula is a target for C-fibre afferents providing input about physiological body conditions (Craig 2002(Craig , 2003. Presently, we found no additional increases or decreases of MSNA with tactile stimulation during hand grip.…”

Section: Discussioncontrasting

confidence: 62%

Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task

Ackerley

¹

,

Sverrisdóttir

²

,

Birklein

³

et al. 2020

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In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and Aβ fibre stimulation, or vibration as Aβ fibre stimulation, to the participant's forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.

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“…Although we cannot be sure about the underlying mechanism behind warmth eliciting additional MSNA during hand-grip, we provide new insights into the regulation of MSNA during muscle fatigue with other types of somatosensory stimuli. It is known that different somatosensory stimuli have specific afferent pathways, where touch and nociception are largely separate (McGlone et al 2014;Marshall et al 2019), although it is thought that the insula is a target for Cfibre afferents providing input about physiological body conditions (Craig 2002;Craig 2003). Presently, we found no additional increases or decreases of MSNA with tactile stimulation during hand-grip.…”

Section: Discussionmentioning

confidence: 99%

Individual Variability of Pleasantness Ratings to Stroking Touch Over Different Velocities

Croy

¹

,

Bierling

²

,

Sailer

³

et al. 2021

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In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and Aβ fibre stimulation, or vibration as Aβ fibre stimulation, to the participant's forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.

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“…More intense stimuli with harmful potential for tissues also use these receptors to inform nociception to the upper centers. However, light stimuli, with low activation potential or with non-harmful potential also activate the same receptors, however, changing the information of these neurons in the posterior horn of the spinal cord [33][34]. These physiological characteristics could also be related to the inhibitory reflex triggered by the evaluator's touch in a dysfunctional zone, as this stimulus could alter responses evoked by the FNEs, from a constant harmful/aggressive information over the tissue to an interpretation of "pleasant" non-harmful sensation [35].…”

Section: The Inhibitory Reflex Evoked By the Touchmentioning

confidence: 99%

“…The stimulation of these fibers can activate cortical areas such as the left insular, anterior cingulate and left prefrontal cortex, and also promote an inhibition in the amygdala [36]. In addition to other functions, these areas also contribute to the interpretation of interoceptions, emotions, and pain, with the possibility of modifying the initial conditions of the neuromatrix, favoring a different interpretation of pain and central desensitization [33,[36][37]. Therefore, these fibers apparently have a great modulatory capacity of interoceptive information enabling adaptations of the autonomic nervous system, altering the levels of immune cells and cytokines present there [38][39].…”

Section: The Inhibitory Reflex Evoked By the Touchmentioning

confidence: 99%

Inhibitory Tests as Assessment Tools for Somatic Dysfunctions: Mechanisms and Practical Applications

Bicalho¹,

Vieira²,

Makita³

et al. 2020

Cureus

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The capital element in the field of osteopathy and several other manual therapy methods, is the somatic dysfunction (SD), a functional imbalance that can involve different tissues and mechanisms in its genesis and maintenance. The main challenges found in the clinical scope are to understand the interaction, hierarchy, and relevance of the SD. Several manual tests are available to functionally evaluate the SD, each one with its applicability to analyze the different parameters of the SD. The so-called inhibitory tests are a category of functional manual tests that can be added to the diagnostic context of the SD. It is a particular type of test in which the evaluator applies manual mechanical stimuli to dysfunctional tissues and assesses the biological responses that occur simultaneously with the application of the stimulus. Its use can consider biomechanical and neurological principles in such a way that different conditions can be analyzed. The objective of this article is to review well-established knowledge and recent scientific discoveries about the SD and its local and global repercussions, in an attempt to offer ideas that can be applied to better understand the mechanisms that imply the use of inhibitory tests as complementary clinical diagnostic tools. It will be discussed some of the possible mechanisms involved in the physiology of the inhibitory tests, their practical applications in some distinct conditions, as well as new proposals of utilization based on the sensitization of metameric related structures under a dysfunctional state.

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Spinal signalling of C-fiber mediated pleasant touch in humans

Cited by 61 publications

References 45 publications

Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task

Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task

Individual Variability of Pleasantness Ratings to Stroking Touch Over Different Velocities

Inhibitory Tests as Assessment Tools for Somatic Dysfunctions: Mechanisms and Practical Applications

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