"Warmth-insensitive fields": evidence of sparse and irregular innervation of human skin by the warmth sense

Green, Barry; Cruz, Alberto

doi:10.1080/08990229870682

Cited by 57 publications

(43 citation statements)

References 33 publications

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“…Green and Cruz (1998) found that small patches of healthy skin in which warmth sensitivity was absent had significantly higher heat pain thresholds than adjacent skin with normal warmth sensitivity. Similarly, Defrin et al (2001;2002) reported that in spinal cord injury patients, regions of the body where warmth sensitivity had been lost had abnormally high heat pain thresholds.…”

Section: Discussionmentioning

confidence: 97%

Nociceptive sensations evoked from ‘spots’ in the skin by mild cooling and heating

Green

Roman

Schoen

et al. 2008

Pain

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It was recently found that nociceptive sensations (stinging, pricking, or burning) can be evoked by cooling or heating the skin to innocuous temperatures (e.g., 29°, 37°C). Here we show that this lowthreshold thermal nociception (LTN) can be traced to sensitive 'spots' in the skin equivalent to classically defined warm spots and cold spots. Because earlier work had shown that LTN is inhibited by simply touching a thermode to the skin, a spatial search procedure was devised that minimized tactile stimulation by sliding small thermodes (16 mm 2 and 1 mm 2 ) set to 28° or 36°C slowly across the lubricated skin of the forearm. The procedure uncovered three types of temperature-sensitive sites (thermal, bimodal and nociceptive) that contained one or more thermal, nociceptive or (rarely) bimodal spots. Repeated testing indicated that bimodal and nociceptive sites were less stable over time than thermal sites, and that mechanical contact differentially inhibited nociceptive sensations. Intensity ratings collected over a range of temperatures showed that LTN increased monotonically on heat-sensitive sites but not on cold-sensitive sites. These results provide psychophysical evidence that stimulation from primary afferent fibers with thresholds in the range of warm fibers and cold fibers is relayed to the pain pathway. However, the labile nature of LTN implies that these lowthreshold nociceptive inputs are subject to inhibitory controls. The implications of these findings for the roles of putative temperature receptors and nociceptors in innocuous thermoreception and thermal pain are discussed.

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Section: Discussionmentioning

confidence: 97%

Nociceptive sensations evoked from ‘spots’ in the skin by mild cooling and heating

Green

Roman

Schoen

et al. 2008

Pain

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“…Ten subjects were dismissed after session 1 because they did not develop mechanical hyperalgesia after a 5 min, 46°C heating (see below, Induction and quantification of hyperalgesia). Four subjects were dismissed after session 1 because of too large areas on the volar forearm that were insensitive to warmth (tested by touching different spots on the forearm for 3 s with the thermode heated to 40°C) (Green and Cruz, 1998). Twenty-one subjects were dismissed after session 2 because of large dayto-day variability (Ͼ25% increase or decrease in pinprick hyperalgesic area).…”

Section: Methodsmentioning

confidence: 99%

Placebo-Induced Changes in Spinal Cord Pain Processing

Matre¹,

Casey²,

Knardahl³

2006

J. Neurosci.

120

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Pain is an essential sensory modality, signaling injury or threat of injury. Pain perception depends on both biological and psychological factors. However, it is not known whether psychological factors modify spinal mechanisms or if its effect is limited to cortical processing. Here, we use a placebo analgesic model to show that psychological factors affect human spinal nociceptive processes. Mechanical hyperalgesia (hypersensitivity) after an injury is attributable to sensitized sensory neurons in the spinal cord. After a 5 min, 46°C heating of the skin, subjects developed areas of mechanical hyperalgesia. This area was smaller in a placebo condition compared with a baseline condition. This result suggests that placebo analgesia affects the spinal cord as well as supra-spinal pain mechanisms in humans and provides strong supporting evidence that placebo analgesia is not simply altered reporting behavior. Central sensitization is thought to mediate the exaggerated pain after innocuous sensory stimulation in several clinical pain conditions that follow trauma and nervoussystem injury. These new data indicate that expectation about pain and analgesia is an important component of the cognitive control of central sensitization.

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“…During pretesting, a 41°C search stimulus was applied to the dorsum of the subject's foot to identify areas sensitive to innocuous heat. Six probe-sized (2.6 cm 2 ) warmth-sensitive areas were identified and used as guides for placement of the thermal stimuli to avoid warmth-insensitive regions during the experiment (10).…”

Section: Methodsmentioning

confidence: 99%

Sex differences in the cerebral BOLD signal response to painful heat stimuli

Moulton¹,

Keaser²,

Gullapalli³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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There are limited data addressing the question of sex differences in pain-related cerebral processing. This study examined whether pain-related blood oxygenation level-dependent (BOLD) signal change measured with functional magnetic resonance imaging (fMRI) demonstrated sex differences, under conditions of equivalent pain perception. Twenty-eight healthy volunteers (17 women, 11 men) were subject to a fMRI scan while noxious heat stimuli were applied to the dorsum of the left foot. Significant BOLD signal modulation was observed in several nociceptive processing regions of interest (ROIs) in all subjects. There were no sex differences in the spatial extent of BOLD signal change for any ROI, but the signal amplitude was lower for women in most ROIs and significantly so for the primary somatosensory cortex (S1), the midanterior cingulate cortex, and the dorsolateral prefrontal cortex (DLPFC). The BOLD signal response could be positive or negative, and frequently, both polarities were observed within a single ROI. In most ROIs, women show proportionately more voxels with negative signal change than men, and this difference was statistically significant for the S1 and the DLPFC. The time course of the negative signal change was very similar to that of the positive signal change, suggesting that the latter was not "driving" the former. The location of negative and positive clusters formed distinct patterns in several of the ROIs, and these patterns suggest something other than a local "steal" phenomenon as an explanation for the negative signal changes. Sex differences in baseline cerebral blood flow may contribute to the BOLD signal differences observed in this study. nociception; fMRI; somatosensory cortex; neuroimaging; prefrontal cortex; negative blood oxygenation level-dependent signal A NUMBER OF STUDIES HAVE FOUND that women are more sensitive to experimental painful stimulation than men. Yet, this is neither a universal nor large effect, given that no differences are found in approximately one-third of the published studies, and statistically significant differences are often in the smallto-moderate range (9, 27). Nonetheless, enough of a difference is found with enough regularity to suggest that women and men may perceive painful stimuli differently. Related to this are observations from both animal and human studies that nociceptive processing may be different between men and women, thereby providing a basis for sex differences in perception and behavior (7,19).Only a few neuroimaging studies have reported sex differences in cerebral responses to noxious stimuli. A 15 O-positron emission tomography (PET) study reported significantly greater activation in women vs. men in several regions of interest (ROIs) in response to noxious heat (24). In that report, sex differences in the PET results may have been related to sex differences in perceived pain intensity. In contrast, a subsequent PET study reported significantly greater activation in men vs. women in some of the same ROIs in response to painful laser sti...

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"Warmth-insensitive fields": evidence of sparse and irregular innervation of human skin by the warmth sense

Cited by 57 publications

References 33 publications

Nociceptive sensations evoked from ‘spots’ in the skin by mild cooling and heating

Nociceptive sensations evoked from ‘spots’ in the skin by mild cooling and heating

Placebo-Induced Changes in Spinal Cord Pain Processing

Sex differences in the cerebral BOLD signal response to painful heat stimuli

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