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Lars Arendtnielsen - One of the best experts on this subject based on the ideXlab platform.
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assessment of pressure pain thresholds and central sensitization of pain in lateral epicondylalgia
Pain Medicine, 2013Co-Authors: Anders Jespersen, Thomas Gravennielsen, Lars Arendtnielsen, Else Marie Bartels, Kirstine Amris, Soren Torppedersen, Henning Bliddal, Bente DanneskioldsamsoeAbstract:OBJECTIVE.: To assess pain sensitivity and spreading hyperalgesia in lateral epicondylalgia (LE). SUBJECTS.: Twenty-two women with LE, and 38 controls were included. OUTCOME MEASURES.: Computerized cuff pressure algometry was used for assessment of pressure-pain threshold and tolerance. The stimulus was applied using a single (stimulation-area: 241 cm(2) ) or double-chambered (stimulation-area: 482 cm(2) ) tourniquet on the arm and leg. Spatial Summation was expressed as the ratio between pressure-pain thresholds to single and double cuff-chamber stimulation. During 10-minute constant pressure stimulation at intensity relative to the individual pain threshold, the pain intensity was continuously recorded using an electronic visual analogue scale (VAS), and from this the degree of temporal Summation was estimated. For LE, a Doppler ultrasound examination of the elbow was made to identify inflammation. RESULTS.: In LE compared with controls the pressure-pain threshold and tolerance were on average reduced by respectively 31% (nonsignificant) and 18% (nonsignificant) on the lower arm and by 32% (P < 0.05) and 22% (P < 0.05) on the lower leg (spreading sensitization). Within the LE group, pressure-pain thresholds were on average reduced by 20% (P < 0.05) and pain tolerance by 10% (nonsignificant) on the painful compared with the asymptomatic side. Spatial Summation (P < 0.01) and temporal Summation (P < 0.05) was facilitated in LE compared with controls. In LE patients without signs of peripheral inflammation assessed by Doppler ultrasound, temporal Summation was significantly stronger than in patients with ongoing inflammation (P < 0.01). CONCLUSION.: Patients with LE may be subgrouped based on pain hypersensitivity and Doppler ultrasound into clinically meaningful subgroups with varying duration of symptoms and different degrees of central sensitization. These groups may require different pain management strategies.
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normalization of widespread hyperesthesia and facilitated Spatial Summation of deep tissue pain in knee osteoarthritis patients after knee replacement
Arthritis & Rheumatism, 2012Co-Authors: Thomas Gravennielsen, Lars Arendtnielsen, Theresa Wodehouse, R M Langford, B L KiddAbstract:Objective The modest association between radiographic joint damage and pain in osteoarthritis (OA) has led to the suggestion of facilitated central pain processing. This study evaluated the importance of ongoing tissue pathology in the maintenance of enhanced central pain processing. Methods Pain assessment was performed on 48 patients with symptomatic knee OA and 21 sex- and age-matched pain-free healthy control subjects. Twenty of the OA patients subsequently underwent total knee replacement surgery and were reassessed. Pressure–pain thresholds (PPTs) were recorded using a pressure algometer (both over and distant from the knee) and a double-chamber inflatable cuff mounted around the calf. Spatial Summation was assessed by relating PPTs using the dual- and single-chamber cuff. Conditioned pain modulation (CPM) was assessed by recording the increase in PPT in response to experimental arm pain. Results PPTs at the knee and at sites away from the knee were reduced in OA patients as compared with healthy pain-free control subjects (P < 0.0001). Cuff PPTs were decreased in OA patients as compared with the healthy controls (P < 0.05), who also exhibited a greater degree of Spatial Summation (P < 0.05). Whereas an elevation of PPTs was noted in the healthy controls in response to experimental arm pain (P < 0.0001), no such CPM was observed in the OA patients. Following joint replacement in the OA patients, there was a reduction in the widespread mechanical hyperesthesia, along with normalization of Spatial Summation ratios and restoration of CPM. Conclusion The widespread hyperesthesia and enhanced Spatial Summation observed in OA patients imply sensitized central pain mechanisms together with the loss of CPM. Normalization of the results following joint replacement implies that these central pain processes are maintained by peripheral input.
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widespread pain hypersensitivity and facilitated temporal Summation of deep tissue pain in whiplash associated disorder an explorative study of women
Journal of Rehabilitation Medicine, 2012Co-Authors: Dag Lemming, Thomas Gravennielsen, Lars Arendtnielsen, Jan Sorensen, Bjorn GerdleAbstract:Objective: Widespread deep tissue pain hyperalgesia was evaluated in women with chronic whiplash associated disorder (n=25) and controls (n=10) using computerized cuff pressure algometry and hypertonic saline infusion. Methods: A pneumatic double-chamber cuff was placed around: (i) the arm and (ii) the leg. Cuff inflation rate was constant and the pain intensity was registered continuously on a visual analogue scale (VAS); thresholds of detection and tolerance were extracted. For assessment of Spatial Summation the protocol was repeated with a single-chamber cuff inflated around the leg. Temporal Summation of pain was assessed from the leg with constant cuff pressure stimulation at 2 different pressure intensities for 10 min. Hypertonic saline was infused in the tibialis anterior muscle. Results: Cuff pressure pain thresholds were lower in subjects with whiplash associated disorder compared with controls (pless than0.05). Tonic pressure stimulation evoked higher maximal VAS and larger areas under the VAS curve in subjects with whiplash associated disorder compared with controls (pless than0.05). The pain threshold and tolerance were higher during single cuff than double cuff stimulation. The area under the VAS curve after intramuscular saline infusion was larger in whiplash associated disorder (pless than0.05). Conclusion: The results indicated widespread hyperalgesia in chronic whiplash associated disorder and facilitated temporal Summation outside the primary pain area, suggesting involvement of central sensitization.
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Spatial and temporal Summation of pain evoked by mechanical pressure stimulation
European Journal of Pain, 2009Co-Authors: Hongling Nie, Thomas Gravennielsen, Lars ArendtnielsenAbstract:Chronic pain patients often suffer from widespread and long lasting pain. The integrative effect of combined Spatial and temporal Summation on pain intensity has not been quantitatively tested. The present study was designed to investigate: (1) if the size of the stimulation area would facilitate the temporal Summation of pain to repetitive pressure stimulation, and (2) if temporal Summation is effective when stimulating separated sites, repetitively. Twenty healthy male subjects participated in this study. The test sites were located on the bilateral upper trapezius and tibialis anterior muscles. The ten stimuli (each with a duration of 1s) were applied to a single site at three inter-stimulus intervals (ISI: 1, 5, 30s) using five different probe sizes (0.5, 1, 2, 4 and 8cm(2)). The stimulation intensity was equal to the pressure pain threshold (PPT) determined for each probe size. Similar repetitive stimulations at two inter-stimulus intervals (5s and 30s) using two sizes of probes (0.5cm(2) and 2cm(2)) were applied to ten separate sites. The PPT at the trapezius muscle decreased significantly with the increase in stimulus area from 0.5cm(2) to 8cm(2) (P<0.001) due to Spatial Summation. Temporal Summation of pain was evoked by repetitive pressure stimuli on the same site for all ISI and was more pronounced at 5s and 30s ISI with larger probe areas (2, 4, and 8cm(2)) compared to smaller probe areas. There was no temporal Summation of pain to stimuli with ISI 5 and 30s when stimulating the separated sites. The current study indicated that Spatial Summation facilitated the temporal Summation of pain for stimuli given at 5s and 30s ISI. The combination of temporal and Spatial integration of nociceptive input facilitates the pain intensity, suggesting that temporal Summation is clinically relevant in conditions with widespread pain.
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age effects on pain thresholds temporal Summation and Spatial Summation of heat and pressure pain
Pain, 2005Co-Authors: Stefan Lautenbacher, Miriam Kunz, Peter Strate, Jesper Ellerbaek Nielsen, Lars ArendtnielsenAbstract:Experimental data on age-related changes in pain perception have so far been contradictory. It has appeared that the type of pain induction method is critical in this context, with sensitivity to heat pain being decreased whereas sensitivity to pressure pain may be even enhanced in the elderly. Furthermore, it has been shown that temporal Summation of heat pain is more pronounced in the elderly but it has remained unclear whether age differences in temporal Summation are also evident when using other pain induction methods. No studies on age-related changes in Spatial Summation of pain have so far been conducted. The aim of the present study was to provide a comprehensive survey on age-related changes in pain perception, i.e. in somatosensory thresholds (warmth, cold, vibration), pain thresholds (heat, pressure) and Spatial and temporal Summation of heat and pressure pain. We investigated 20 young (mean age 27.1 years) and 20 elderly (mean age 71.6 years) subjects. Our results confirmed and extended previous findings by showing that somatosensory thresholds for non-noxious stimuli increase with age whereas pressure pain thresholds decrease and heat pain thresholds show no age-related changes. Apart from an enhanced temporal Summation of heat pain, pain Summation was not found to be critically affected by age. The results of the present study provide evidence for stimulus-specific changes in pain perception in the elderly, with deep tissue (muscle) nociception being affected differently by age than superficial tissue (skin) nociception. Summation mechanisms contribute only moderately to age changes in pain perception.
Hillel Adesnik - One of the best experts on this subject based on the ideXlab platform.
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Spatial integration during active tactile sensation drives orientation perception
Neuron, 2021Co-Authors: Jennifer Brown, Hillel Adesnik, Ian A Oldenburg, Gregory Telian, Sandon Griffin, Mieke Voges, Vedant JainAbstract:Active haptic sensation is critical for object identification, but its neural circuit basis is poorly understood. We combined optogenetics, two-photon imaging, and high-speed behavioral tracking in mice solving a whisker-based object orientation discrimination task. We found that orientation discrimination required animals to summate input from multiple whiskers specifically along the whisker arc. Animals discriminated the orientation of the stimulus per se as their performance was invariant to the location of the presented stimulus. Populations of barrel cortex neurons summated across whiskers to encode each orientation. Finally, acute optogenetic inactivation of the barrel cortex and cell-type-specific optogenetic suppression of layer 4 excitatory neurons degraded performance, implying that infragranular layers alone are not sufficient to solve the task. These data suggest that Spatial Summation over an active haptic array generates representations of an object's orientation, which may facilitate encoding of complex three-dimensional objects during active exploration.
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Spatial integration during active tactile sensation drives elementary shape perception
bioRxiv, 2020Co-Authors: Hillel Adesnik, Jennifer Brown, Ian A Oldenburg, Gregory Telian, Sandon Griffin, Mieke Voges, Vedant JainAbstract:Active haptic sensation is critical for object identification and manipulation, such as for tool use in humans, or prey capture in rodents. The neural circuit basis for recognizing objects through active touch alone is poorly understood. To address this gap, we combined optogenetics, two photon imaging, and high-speed behavioral tracking in mice solving a novel surface orientation discrimination task with their whiskers. We found that orientation discrimination required animals to summate input from multiple whiskers specifically along the whisker arc. Many animals discriminated the orientation of the stimulus per se, as their performance was invariant to the specific location of the presented stimulus. Two photon imaging showed that populations of neurons in the barrel cortex encoded each of the discriminated orientations, and this coding depended on integration over the whisker array. Finally, acute optogenetic inactivation of the barrel cortex strongly impaired surface orientation discrimination, and even cell-type specific optogenetic suppression of layer 4 excitatory neurons degraded performance, implying a role for superficial layers in this computation. These data suggest a model in which Spatial Summation over an active haptic array generates representations of an objects surface orientations. These computations may facilitate the encoding of complex three-dimensional objects during active exploration.
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a neural circuit for Spatial Summation in visual cortex
Nature, 2012Co-Authors: William Bruns, Hiroki Taniguchi, Hillel Adesnik, Josh Z Huang, Massimo ScanzianiAbstract:The response of cortical neurons to a sensory stimulus is modulated by the context. In the visual cortex, for example, stimulation of a pyramidal cell's receptive-field surround can attenuate the cell’s response to a stimulus in the centre of its receptive field, a phenomenon called surround suppression. Whether cortical circuits contribute to surround suppression or whether the phenomenon is entirely relayed from earlier stages of visual processing is debated. Here we show that, in contrast to pyramidal cells, the response of somatostatin-expressing inhibitory neurons (SOMs) in the superficial layers of the mouse visual cortex increases with stimulation of the receptive-field surround. This difference results from the preferential excitation of SOMs by horizontal cortical axons. By perturbing the activity of SOMs, we show that these neurons contribute to pyramidal cells' surround suppression. These results establish a cortical circuit for surround suppression and attribute a particular function to a genetically defined type of inhibitory neuron. The activity of somatostatin-expressing inhibitory neurons (SOMs) in the superficial layers of the mouse visual cortex increases with stimulation of the receptive-field surround, thereby contributing to the surround suppression of pyramidal cells. The neurons of the primary visual cortex respond preferentially to stimuli of particular Spatial size and are suppressed when stimuli are larger than their receptive fields. This form of modulation of neural response by contextual information is thought to underlie many perceptual phenomena, but the source of the suppression is not well understood. These authors report the identification of a circuit in the mouse visual cortex that contributes to surround suppression through a mechanism involving somatostatin-expressing interneurons.
Thomas Gravennielsen - One of the best experts on this subject based on the ideXlab platform.
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assessment of pressure pain thresholds and central sensitization of pain in lateral epicondylalgia
Pain Medicine, 2013Co-Authors: Anders Jespersen, Thomas Gravennielsen, Lars Arendtnielsen, Else Marie Bartels, Kirstine Amris, Soren Torppedersen, Henning Bliddal, Bente DanneskioldsamsoeAbstract:OBJECTIVE.: To assess pain sensitivity and spreading hyperalgesia in lateral epicondylalgia (LE). SUBJECTS.: Twenty-two women with LE, and 38 controls were included. OUTCOME MEASURES.: Computerized cuff pressure algometry was used for assessment of pressure-pain threshold and tolerance. The stimulus was applied using a single (stimulation-area: 241 cm(2) ) or double-chambered (stimulation-area: 482 cm(2) ) tourniquet on the arm and leg. Spatial Summation was expressed as the ratio between pressure-pain thresholds to single and double cuff-chamber stimulation. During 10-minute constant pressure stimulation at intensity relative to the individual pain threshold, the pain intensity was continuously recorded using an electronic visual analogue scale (VAS), and from this the degree of temporal Summation was estimated. For LE, a Doppler ultrasound examination of the elbow was made to identify inflammation. RESULTS.: In LE compared with controls the pressure-pain threshold and tolerance were on average reduced by respectively 31% (nonsignificant) and 18% (nonsignificant) on the lower arm and by 32% (P < 0.05) and 22% (P < 0.05) on the lower leg (spreading sensitization). Within the LE group, pressure-pain thresholds were on average reduced by 20% (P < 0.05) and pain tolerance by 10% (nonsignificant) on the painful compared with the asymptomatic side. Spatial Summation (P < 0.01) and temporal Summation (P < 0.05) was facilitated in LE compared with controls. In LE patients without signs of peripheral inflammation assessed by Doppler ultrasound, temporal Summation was significantly stronger than in patients with ongoing inflammation (P < 0.01). CONCLUSION.: Patients with LE may be subgrouped based on pain hypersensitivity and Doppler ultrasound into clinically meaningful subgroups with varying duration of symptoms and different degrees of central sensitization. These groups may require different pain management strategies.
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normalization of widespread hyperesthesia and facilitated Spatial Summation of deep tissue pain in knee osteoarthritis patients after knee replacement
Arthritis & Rheumatism, 2012Co-Authors: Thomas Gravennielsen, Lars Arendtnielsen, Theresa Wodehouse, R M Langford, B L KiddAbstract:Objective The modest association between radiographic joint damage and pain in osteoarthritis (OA) has led to the suggestion of facilitated central pain processing. This study evaluated the importance of ongoing tissue pathology in the maintenance of enhanced central pain processing. Methods Pain assessment was performed on 48 patients with symptomatic knee OA and 21 sex- and age-matched pain-free healthy control subjects. Twenty of the OA patients subsequently underwent total knee replacement surgery and were reassessed. Pressure–pain thresholds (PPTs) were recorded using a pressure algometer (both over and distant from the knee) and a double-chamber inflatable cuff mounted around the calf. Spatial Summation was assessed by relating PPTs using the dual- and single-chamber cuff. Conditioned pain modulation (CPM) was assessed by recording the increase in PPT in response to experimental arm pain. Results PPTs at the knee and at sites away from the knee were reduced in OA patients as compared with healthy pain-free control subjects (P < 0.0001). Cuff PPTs were decreased in OA patients as compared with the healthy controls (P < 0.05), who also exhibited a greater degree of Spatial Summation (P < 0.05). Whereas an elevation of PPTs was noted in the healthy controls in response to experimental arm pain (P < 0.0001), no such CPM was observed in the OA patients. Following joint replacement in the OA patients, there was a reduction in the widespread mechanical hyperesthesia, along with normalization of Spatial Summation ratios and restoration of CPM. Conclusion The widespread hyperesthesia and enhanced Spatial Summation observed in OA patients imply sensitized central pain mechanisms together with the loss of CPM. Normalization of the results following joint replacement implies that these central pain processes are maintained by peripheral input.
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widespread pain hypersensitivity and facilitated temporal Summation of deep tissue pain in whiplash associated disorder an explorative study of women
Journal of Rehabilitation Medicine, 2012Co-Authors: Dag Lemming, Thomas Gravennielsen, Lars Arendtnielsen, Jan Sorensen, Bjorn GerdleAbstract:Objective: Widespread deep tissue pain hyperalgesia was evaluated in women with chronic whiplash associated disorder (n=25) and controls (n=10) using computerized cuff pressure algometry and hypertonic saline infusion. Methods: A pneumatic double-chamber cuff was placed around: (i) the arm and (ii) the leg. Cuff inflation rate was constant and the pain intensity was registered continuously on a visual analogue scale (VAS); thresholds of detection and tolerance were extracted. For assessment of Spatial Summation the protocol was repeated with a single-chamber cuff inflated around the leg. Temporal Summation of pain was assessed from the leg with constant cuff pressure stimulation at 2 different pressure intensities for 10 min. Hypertonic saline was infused in the tibialis anterior muscle. Results: Cuff pressure pain thresholds were lower in subjects with whiplash associated disorder compared with controls (pless than0.05). Tonic pressure stimulation evoked higher maximal VAS and larger areas under the VAS curve in subjects with whiplash associated disorder compared with controls (pless than0.05). The pain threshold and tolerance were higher during single cuff than double cuff stimulation. The area under the VAS curve after intramuscular saline infusion was larger in whiplash associated disorder (pless than0.05). Conclusion: The results indicated widespread hyperalgesia in chronic whiplash associated disorder and facilitated temporal Summation outside the primary pain area, suggesting involvement of central sensitization.
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Spatial and temporal Summation of pain evoked by mechanical pressure stimulation
European Journal of Pain, 2009Co-Authors: Hongling Nie, Thomas Gravennielsen, Lars ArendtnielsenAbstract:Chronic pain patients often suffer from widespread and long lasting pain. The integrative effect of combined Spatial and temporal Summation on pain intensity has not been quantitatively tested. The present study was designed to investigate: (1) if the size of the stimulation area would facilitate the temporal Summation of pain to repetitive pressure stimulation, and (2) if temporal Summation is effective when stimulating separated sites, repetitively. Twenty healthy male subjects participated in this study. The test sites were located on the bilateral upper trapezius and tibialis anterior muscles. The ten stimuli (each with a duration of 1s) were applied to a single site at three inter-stimulus intervals (ISI: 1, 5, 30s) using five different probe sizes (0.5, 1, 2, 4 and 8cm(2)). The stimulation intensity was equal to the pressure pain threshold (PPT) determined for each probe size. Similar repetitive stimulations at two inter-stimulus intervals (5s and 30s) using two sizes of probes (0.5cm(2) and 2cm(2)) were applied to ten separate sites. The PPT at the trapezius muscle decreased significantly with the increase in stimulus area from 0.5cm(2) to 8cm(2) (P<0.001) due to Spatial Summation. Temporal Summation of pain was evoked by repetitive pressure stimuli on the same site for all ISI and was more pronounced at 5s and 30s ISI with larger probe areas (2, 4, and 8cm(2)) compared to smaller probe areas. There was no temporal Summation of pain to stimuli with ISI 5 and 30s when stimulating the separated sites. The current study indicated that Spatial Summation facilitated the temporal Summation of pain for stimuli given at 5s and 30s ISI. The combination of temporal and Spatial integration of nociceptive input facilitates the pain intensity, suggesting that temporal Summation is clinically relevant in conditions with widespread pain.
Ruth Defrin - One of the best experts on this subject based on the ideXlab platform.
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Spatial resolution of the pain system a proximal to distal gradient of sensitivity revealed with psychophysical testing
Experimental Brain Research, 2012Co-Authors: Irit Weissmanfogel, Nurit Brayerzwi, Ruth DefrinAbstract:The Spatial resolution of the pain system has not been studied in depth, and results are contradictory regarding the gradient of Spatial resolution. Microneurographic recordings have revealed smaller receptive fields and higher density of nociceptors in more distal than proximal leg regions, whereas histological studies report higher density of C-fibers in more proximal than distal body regions. Due to this controversy, we conducted various psychophysical tests in order to examine the nociceptive Spatial resolution and its gradient. Heat-pain threshold (HPT), perceived pain intensity, Spatial Summation (SS) of pain, two-point discrimination (2PD) of pain, and pain localization were measured in four body regions: upper back, thigh, lower leg, and foot. The highest HPT was demonstrated in the lower leg as compared with more proximal regions (P < 0.0001). SS was observed in all the regions and was found to be smallest in the foot (P < 0.05). The smallest 2PD and localization distances were found in the foot (P < 0.01) as compared with the lower leg and upper back. It appears that the nociceptive Spatial resolution has a proximal-to-distal pattern of performance, namely that the Spatial resolution of pain is finer in more distal than proximal body regions, similar to that of the touch system.
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Spatial Summation of thermal sensations depends on skin type and skin sensitivity
Experimental Brain Research, 2009Co-Authors: Ruth Defrin, Laura Petrini, Lars Arendt-nielsenAbstract:The objective of the present study was to examine the extent to which Spatial Summation (SS) of thermal senses is affected by skin type and skin thermal sensitivity. A total of 19 healthy subjects underwent measurements of warm- and cold-sensation threshold (WST and CST) with a large (9 cm^2) and small (2.25 cm^2) stimulation area, within the glabrous (palm) and hairy skin (dorsal surface) of the hand. SS of WST was also measured in warm-sensitive and warm-insensitive hairy skin sites. WST and CST significantly increased as stimulation area decreased (at a similar amount), in both hairy and glabrous skin. SS of CST in the glabrous skin was larger than that of hairy skin. A significant SS of WS existed in both warm-sensitive and warm-insensitive sites but the amount of SS was larger in warm-insensitive sites. Sex did not affect any of the factors tested. The similar amount of SS for WST and CST suggest that despite possible differences in receptor density, these two sub-systems share common features. Based on the stimulation areas used herein and on receptive-field (RF) sizes, SS of WST and CST appears to occur within RF of a single neuron. The larger magnitude of SS in the glabrous than hairy skin might suggest a larger integration of sensory information from the former, possibly due to a greater functional role of the palm.
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interactions between Spatial Summation 2 point discrimination and habituation of heat pain
European Journal of Pain, 2008Co-Authors: Ruth Defrin, Geoff Pope, Karen D DavisAbstract:Recently, Spatial Summation (SS) of two discrete noxious stimuli was found to occur at separation distances less than 10cm in the forearm. Interestingly though, with larger separation distances there is 2-point discrimination (2PD) but not SS. However, previous studies have not examined the interactions between these Spatial phenomena and temporal aspects of pain. Therefore, our aims were to (1) examine the inverse relationship between SS and 2PD in the leg, and (2) assess whether SS and 2PD of pain are affected by repetitive noxious stimulation. Twenty-four subjects received multiple series of 16 repeated noxious heat stimuli (22s inter-stimulus interval) at various intensities delivered with one or two thermal probes separated by either 0.4cm or 15cm. For each configuration, subjects rated the amount of perceived pain on a Visual Analogue Scale (VAS) (to evaluate SS) and stated the number of pain spots (to evaluate 2PD) following each stimulus. A significant SS of pain occurred only with the probe separation of 0.4cm (in which perceived pain significantly increased compared with a single probe, p<0.001) whereas 2PD occurred only at the probe separation of 15cm (p<0.001). When the stimulation temperature was fixed (but evoked different initial pain scores for different stimulation configurations), habituation occurred only with a single probe and two probes separated by 15cm. However, when the initial pain score was fixed (but the stimulus temperature varied) habituation occurred with all stimulation configurations but significantly less for two probes separated by 0.4cm. Sex was not a factor in SS and 2PD of pain, however there was greater habituation in females than males. In conclusion, SS of pain counteracts 2PD of pain and to a lesser extent, pain habituation.
Sieu K. Khuu - One of the best experts on this subject based on the ideXlab platform.
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a comparison of goldmann iii v and Spatially equated test stimuli in visual field testing the importance of complete and partial Spatial Summation
Ophthalmic and Physiological Optics, 2017Co-Authors: Sieu K. Khuu, Barbara Zangerl, Michael KalloniatisAbstract:Purpose Goldmann size V (GV) test stimuli are less variable with a greater dynamic range and have been proposed for measuring contrast sensitivity instead of size III (GIII). Since GIII and GV operate within partial Summation, we hypothesise that actual GV (aGV) thresholds could predict GIII (pGIII) thresholds, facilitating comparisons between actual GIII (aGIII) thresholds with pGIII thresholds derived from smaller GV variances. We test the suitability of GV for detecting visual field (VF) loss in patients with early glaucoma, and examine eccentricity-dependent effects of number and depth of defects. We also hypothesise that stimuli operating within complete Spatial Summation ('Spatially equated stimuli') would detect more and deeper defects. Methods Sixty normal subjects and 20 glaucoma patients underwent VF testing on the Humphrey Field Analyzer using GI-V sized stimuli on the 30-2 test grid in full threshold mode. Point-wise partial Summation slope values were generated from GI-V thresholds, and we subsequently derived pGIII thresholds using aGV. Difference plots between actual GIII (aGIII) and pGIII thresholds were used to compare the amount of discordance. In glaucoma patients, the number of 'events' (points below the 95% lower limit of normal), defect depth and global indices were compared between stimuli. Results 90.5% of pGIII and aGIII points were within ±3 dB of each other in normal subjects. In the glaucoma cohort, there was less concordance (63.2% within ±3 dB), decreasing with increasing eccentricity. GIII found more defects compared to GV-derived thresholds, but only at outermost test locations. Greater defect depth was found using aGIII compared to aGV and pGIII, which increased with eccentricity. Global indices revealed more severe loss when using GIII compared to GV. Spatially equated stimuli detected the greatest number of 'events' and largest defect depth. Conclusions Whilst GV may be used to reliably predict GIII values in normal subjects, there was less concordance in glaucoma patients. Similarities in 'event' detection and defect depth in the central VF were consistent with the fact that GIII and GV operate within partial Summation in this region. Eccentricity-dependent effects in 'events' and defect depth were congruent with changes in Spatial Summation across the VF and the increase in critical area with disease. The Spatially equated test stimuli showed the greatest number of defective locations and larger sensitivity loss.
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Equating Spatial Summation in visual field testing reveals greater loss in optic nerve disease
Ophthalmic and Physiological Optics, 2016Co-Authors: Michael Kalloniatis, Sieu K. KhuuAbstract:Purpose To test the hypothesis that visual field assessment in ocular disease measured with target stimuli within or close to complete Spatial Summation results in larger threshold elevation compared to when measured with the standard Goldmann III target size. The hypothesis predicts a greater loss will be identified in ocular disease. Additionally, we sought to develop a theoretical framework that would allow comparisons of thresholds with disease progression when using different Goldmann targets. Methods The Humphrey Field Analyser (HFA) 30-2 grid was used in 13 patients with early/established optic nerve disease using the current Goldmann III target size or a combination of the three smallest stimuli (target size I, II and III). We used data from control subjects at each of the visual field locations for the different target sizes to establish the number of failed points (events) for the patients with optic nerve disease, as well as global indices for mean deviation (MD) and pattern standard deviation (PSD). Results The 30-2 visual field testing using alternate target size stimuli showed that all 13 patients displayed more defects (events) compared to the standard Goldmann III target size. The median increase for events was seven additional failed points: (range 1–26). The global indices also increased when the new testing approach was used (MD −3.47 to −6.25 dB and PSD 4.32 to 6.63 dB). Spatial Summation mapping showed an increase in critical area (Ac) in disease and overall increase in thresholds when smaller target stimuli were used. Conclusions When compared to the current Goldmann III paradigm, the use of alternate sized targets within the 30-2 testing protocol revealed a greater loss in patients with optic nerve disease for both event analysis and global indices (MD and PSD). We therefore provide evidence in a clinical setting that target size is important in visual field testing.
