Evidence of a Specific Spinal Pathway for the Sense  of Warmth in Humans

Iannetti, Gian Domenico; Truini, Andrea; Romaniello, A.; Galeotti, F.; Rizzo, Cristiano; Manfredi, M.; Cruccu, G.

doi:10.1152/jn.00393.2002

Cited by 122 publications

(80 citation statements)

References 73 publications

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“…In this respect, evidence for a specific, slowly conducting, spino-thalamic pathway for warmth discrimination in humans, which would be similar to the one observed in cats, and which could rely on afferent information conveyed by warm-sensitive second order unmyelinated C-fibers, has been recently provided for the first time (159). In a recent study, healthy awake humans have been reported to experience conscious warm sensations, upon delivery of CO 2 laser stimuli over the vertebrae column, inducing a brief, laser-dependent increase in skin temperature (up to 39°C).…”

Section: Spinal Integrationmentioning

confidence: 75%

“…Also, conduction velocities of cat and monkey' spino-thalamic cold-sensitive myelinated neurons (~8 and ~5.6 m/s respectively) (65, 88) resemble estimated conduction velocities (~10 m/s) of cold-sensitive myelinated fibers in the human spino-thalamic tract (168,249). Finally, cat' spino-thalamic warm-sensitive unmyelinated C-fibers (conduction velocities: 1.5-3 m/s) (5) resemble estimated conduction velocities of unmyelinated warm-sensitive C-fibers in the human spino-thalamic tract (~2.2 m/s) (159,168,249).…”

Section: Spinal Integrationmentioning

confidence: 86%

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Neurophysiology of Skin Thermal Sensations

Filingeri

2016

Comprehensive Physiology

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Undoubtedly, adjusting our thermoregulatory behavior represents the most effective mechanism to maintain thermal homeostasis and ensure survival in the diverse thermal environments that we face on this planet. Remarkably, our thermal behavior is entirely dependent on the ability to detect variations in our internal (i.e. body) and external environment, via sensing changes in skin temperature and wetness. In the past 30 years, we have seen a significant expansion of our understanding of the molecular, neuroanatomical and neurophysiological mechanisms that allow humans to sense temperature and humidity. The discovery of temperature-activated ion channels which gate the generation of action potentials in thermosensitive neurons, along with the characterization of the spino-thalamo-cortical thermosensory pathway, and the development of neural models for the perception of skin wetness, are only some of the recent advances which have provided incredible insights on how biophysical changes in skin temperature and wetness are transduced into those neural signals which constitute the physiological substrate of skin thermal and wetness sensations. Understanding how afferent thermal inputs are integrated and how these contribute to behavioral and autonomic thermoregulatory responses under normal brain function is critical to determine how these mechanisms are disrupted in those neurological conditions which see the concurrent presence of afferent thermosensory abnormalities and efferent thermoregulatory dysfunctions. Furthermore, advancing the knowledge on skin thermal and wetness sensations is crucial to support the development of neuro-prosthetics. In light of the above, this review will focus on the peripheral and central neurophysiological mechanisms underpinning skin thermal and wetness sensations in humans.

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Section: Spinal Integrationmentioning

confidence: 75%

Section: Spinal Integrationmentioning

confidence: 86%

Neurophysiology of Skin Thermal Sensations

Filingeri

2016

Comprehensive Physiology

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“…Indeed, because the thermal activation threshold of C-fiber afferents is consistently lower than the thermal activation threshold of A␦-fiber afferents (difference, 2.3-3°C) (Plaghki et al, 2010), reducing the energy density of the laser stimulus constitutes one of the previously validated methods to activate C-nociceptors selectively (for review, see Plaghki andMouraux, 2002, 2005;Plaghki, 2007), and this approach has been already used successfully in several previous studies (Treede et al, 1995;Towell et al, 1996;Magerl et al, 1999;Agostino et al, 2000;Tran et al, 2002;Cruccu et al, 2003;Iannetti et al, 2003;Mouraux et al, 2003;Qiu et al, 2006;Mouraux and Plaghki, 2007).…”

Section: Steady-state Thermal Stimulation Of A␦-and C-nociceptorsmentioning

confidence: 99%

Nociceptive Steady-State Evoked Potentials Elicited by Rapid Periodic Thermal Stimulation of Cutaneous Nociceptors

Mouraux¹,

Iannetti²,

Colon³

et al. 2011

J. Neurosci.

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The periodic presentation of a sensory stimulus induces, at certain frequencies of stimulation, a sustained electroencephalographic response known as steady-state evoked potential (SS-EP). In the somatosensory, visual, and auditory modalities, SS-EPs are considered to constitute an electrophysiological correlate of cortical sensory networks resonating at the frequency of stimulation. In the present study, we describe and characterize, for the first time, SS-EPs elicited by the selective activation of skin nociceptors in humans. The stimulation consisted of 2.3-s-long trains of 16 identical infrared laser pulses (frequency, 7 Hz), applied to the dorsum of the left and right hand and foot. Two different stimulation energies were used. The low energy activated only C-nociceptors, whereas the high energy activated both A␦-and C-nociceptors. Innocuous electrical stimulation of large-diameter A␤-fibers involved in the perception of touch and vibration was used as control. The high-energy nociceptive stimulus elicited a consistent SS-EP, related to the activation of A␦-nociceptors. Regardless of stimulus location, the scalp topography of this response was maximal at the vertex. This was noticeably different from the scalp topography of the SS-EPs elicited by innocuous vibrotactile stimulation, which displayed a clear maximum over the parietal region contralateral to the stimulated side. Therefore, we hypothesize that the SS-EPs elicited by the rapid periodic thermal activation of nociceptors may reflect the activation of a network that is preferentially involved in processing nociceptive input and may thus provide some important insight into the cortical processes generating painful percepts.

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“…Such stimuli elicit a number of electrical brain responses, some of which can be detected in the human EEG (Carmon et al, 1976;Mouraux et al, 2003). Although the laser stimulus coactivates several distinct ascending somatosensory pathways (Iannetti et al, 2003), the detected responses have been shown to be exclusively related to the activation of type-II A␦ mechano-heat nociceptors (Treede et al, 1995) and spinothalamic neurons located in the anterolateral quadrant of the spinal cord (Treede, 2003). Laser-evoked potentials (LEPs) comprise a number of waves that are time locked to the onset of the stimulus.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

Lee¹,

Mouraux²,

Iannetti³

2009

Journal of Neuroscience

133

114

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Nociception begins when A␦-and C-nociceptors are activated. However, the processing of nociceptive input by the cortex is required before pain can be consciously experienced from nociception. To characterize the cortical activity related to the emergence of this experience, we recorded, in humans, laser-evoked potentials elicited by physically identical nociceptive stimuli that were either perceived or unperceived. Infrared laser pulses, which selectively activate skin nociceptors, were delivered to the hand dorsum either as a pair of rapidly succeeding and spatially displaced stimuli (two-thirds of trials) or as a single stimulus (one-third of trials). After each trial, subjects reported whether one or two distinct painful pinprick sensations, associated with A␦-nociceptor activation, had been perceived. The psychophysical feedback after each pair of stimuli was used to adjust the interstimulus interval (ISI) of the subsequent pair: when a single percept was reported, ISI was increased by 40 ms; when two distinct percepts were reported, ISI was decreased by 40 ms. This adaptive algorithm ensured that the probability of perceiving the second stimulus of the pair tended toward 0.5. We found that the magnitude of the early-latency N1 wave was similar between perceived and unperceived stimuli, whereas the magnitudes of the later N2 and P2 waves were reduced when stimuli were unperceived. These findings suggest that the N1 wave represents an early stage of sensory processing related to the ascending nociceptive input, whereas the N2 and P2 waves represent a later stage of processing related, directly or indirectly, to the perceptual outcome of this nociceptive input.

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Evidence of a Specific Spinal Pathway for the Sense of Warmth in Humans

Cited by 122 publications

References 73 publications

Neurophysiology of Skin Thermal Sensations

Neurophysiology of Skin Thermal Sensations

Nociceptive Steady-State Evoked Potentials Elicited by Rapid Periodic Thermal Stimulation of Cutaneous Nociceptors

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

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