Special Issue "Functional Neuroimaging of Pain"

A special issue of Brain Sciences (ISSN 2076-3425).

Deadline for manuscript submissions: closed (29 February 2016) | Viewed by 21896

Special Issue Editor

Prof. Dr. Patrick W. Stroman
E-Mail Website
Guest Editor
1. Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
2. Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
3. Department of Physics, Queen's University, Kingston, ON K7L 3N6, Canada
Interests: functional MRI; neuroimaging; methods; analysis; spinal cord; brainstem; pain; spinal cord injury; connectivity

Special Issue Information

Dear Colleagues,

Pain is an unpleasant sensory and emotional experience, and research into understanding pain, and aberrant pain conditions, presents many challenges. These challenges arise in part from the need to carry out human studies, so as to investigate the integrated system that results in pain, including the cognitive/emotional component. In addition, pain depends on an extensive network spanning from the spinal cord, with ascending pathways signaling sensory qualities, and descending pathways providing modulation of pain from cortical and upper brainstem regions. These regions are inaccessible in human research participants, except by means of non-invasive neuroimaging methods. Pain results from a balance of inhibitory and facilitory neuronal signalings, which regulate pain sensitivity, and adjust it, depending on the situation. This balance results in pain being highly variable across individuals. It is expected that many chronic pain conditions result from an imbalance of these inhibitory and facilitory mechanisms. A number of currently used methods, such as quantitative sensory testing, provide methods of probing human pain responses and of characterizing changes with chronic pain conditions, but do not reveal the underlying neuronal processes.

In the past few decades, functional neuroimaging has significantly advanced our understanding of pain processes. Prior to non-invasive neuroimaging methods, our understanding of the role of the brain in pain processing was limited, and was based largely on animal electrophysiological studies and quantitative sensory testing. Functional neuroimaging, such as fMRI and PET, has revolutionized our understanding of human pain processing by making the cortex accessible. Functional MRI has also been extended to the spinal cord and brainstem, so as to make the entire human CNS accessible. With the advances in our understanding of pain processing in recent decades, and advances in methods of non-invasively detecting the underlying neural processes in different pain conditions or chronic pain states, we have a wealth of tools available for research into understanding debilitating pain conditions and developing new capabilities for diagnosis and treatment.

Prof. Dr. Patrick W. Stroman
Guest Editor

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Keywords

  • pain
  • human
  • fMRI
  • PET
  • brain
  • brainstem
  • spinal cord

Published Papers (6 papers)

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Research

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Article
Exercise Strengthens Central Nervous System Modulation of Pain in Fibromyalgia
Brain Sci. 2016, 6(1), 8; https://doi.org/10.3390/brainsci6010008 - 26 Feb 2016
Cited by 43 | Viewed by 5701
Abstract
To begin to elucidate the mechanisms underlying the benefits of exercise for chronic pain, we assessed the influence of exercise on brain responses to pain in fibromyalgia (FM). Complete data were collected for nine female FM patients and nine pain-free controls (CO) who [...] Read more.
To begin to elucidate the mechanisms underlying the benefits of exercise for chronic pain, we assessed the influence of exercise on brain responses to pain in fibromyalgia (FM). Complete data were collected for nine female FM patients and nine pain-free controls (CO) who underwent two functional neuroimaging scans, following exercise (EX) and following quiet rest (QR). Brain responses and pain ratings to noxious heat stimuli were compared within and between groups. For pain ratings, there was a significant (p < 0.05) Condition by Run interaction characterized by moderately lower pain ratings post EX compared to QR (d = 0.39–0.41) for FM but similar to ratings in CO (d = 0.10–0.26), thereby demonstrating that exercise decreased pain sensitivity in FM patients to a level that was analogous to pain-free controls. Brain responses demonstrated a significant within-group difference in FM patients, characterized by less brain activity bilaterally in the anterior insula following QR as compared to EX. There was also a significant Group by Condition interaction with FM patients showing less activity in the left dorsolateral prefrontal cortex following QR as compared to post-EX and CO following both conditions. These results suggest that exercise appeared to stimulate brain regions involved in descending pain inhibition in FM patients, decreasing their sensitivity to pain. Thus, exercise may benefit patients with FM via improving the functional capacity of the pain modulatory system. Full article
(This article belongs to the Special Issue Functional Neuroimaging of Pain)
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Article
Hemodynamic and Light-Scattering Changes of Rat Spinal Cord and Primary Somatosensory Cortex in Response to Innocuous and Noxious Stimuli
Brain Sci. 2015, 5(4), 400-418; https://doi.org/10.3390/brainsci5040400 - 29 Sep 2015
Cited by 7 | Viewed by 3136
Abstract
Neuroimaging technologies with an exceptional spatial resolution and noninvasiveness have become a powerful tool for assessing neural activity in both animals and humans. However, the effectiveness of neuroimaging for pain remains unclear partly because the neurovascular coupling during pain processing is not completely [...] Read more.
Neuroimaging technologies with an exceptional spatial resolution and noninvasiveness have become a powerful tool for assessing neural activity in both animals and humans. However, the effectiveness of neuroimaging for pain remains unclear partly because the neurovascular coupling during pain processing is not completely characterized. Our current work aims to unravel patterns of neurovascular parameters in pain processing. A novel fiber-optic method was used to acquire absolute values of regional oxy- (HbO) and deoxy-hemoglobin concentrations, oxygen saturation rates (SO2), and the light-scattering coefficients from the spinal cord and primary somatosensory cortex (SI) in 10 rats. Brief mechanical and electrical stimuli (ranging from innocuous to noxious intensities) as well as a long-lasting noxious stimulus (formalin injection) were applied to the hindlimb under pentobarbital anesthesia. Interhemispheric comparisons in the spinal cord and SI were used to confirm functional activation during sensory processing. We found that all neurovascular parameters showed stimulation-induced changes; however, patterns of changes varied with regions and stimuli. Particularly, transient increases in HbO and SO2 were more reliably attributed to brief stimuli, whereas a sustained decrease in SO2 was more reliably attributed to formalin. Only the ipsilateral SI showed delayed responses to brief stimuli. In conclusion, innocuous and noxious stimuli induced significant neurovascular responses at critical centers (e.g., the spinal cord and SI) along the somatosensory pathway; however, there was no single response pattern (as measured by amplitude, duration, lateralization, decrease or increase) that was able to consistently differentiate noxious stimuli. Our results strongly suggested that the neurovascular response patterns differ between brief and long-lasting noxious stimuli, and can also differ between the spinal cord and SI. Therefore, a use of multiple-parameter strategy tailored by stimulus modality (brief or long-lasting) as well as region-dependent characteristics may be more effective in detecting pain using neuroimaging technologies. Full article
(This article belongs to the Special Issue Functional Neuroimaging of Pain)
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Article
The Scalp Confounds Near-Infrared Signal from Rat Brain Following Innocuous and Noxious Stimulation
Brain Sci. 2015, 5(4), 387-399; https://doi.org/10.3390/brainsci5040387 - 29 Sep 2015
Viewed by 2837
Abstract
Functional near-infrared imaging (fNIRI) is a non-invasive, low-cost and highly portable technique for assessing brain activity and functions. Both clinical and experimental evidence suggest that fNIRI is able to assess brain activity at associated regions during pain processing, indicating a strong possibility of [...] Read more.
Functional near-infrared imaging (fNIRI) is a non-invasive, low-cost and highly portable technique for assessing brain activity and functions. Both clinical and experimental evidence suggest that fNIRI is able to assess brain activity at associated regions during pain processing, indicating a strong possibility of using fNIRI-derived brain activity pattern as a biomarker for pain. However, it remains unclear how, especially in small animals, the scalp influences fNIRI signal in pain processing. Previously, we have shown that the use of a multi-channel system improves the spatial resolution of fNIRI in rats (without the scalp) during pain processing. Our current work is to investigate a scalp effect by comparing with new data from rats with the scalp during innocuous or noxious stimulation (n = 6). Results showed remarkable stimulus-dependent differences between the no-scalp and intact-scalp groups. In conclusion, the scalp confounded the fNIRI signal in pain processing likely via an autonomic mechanism; the scalp effect should be a critical factor in image reconstruction and data interpretation. Full article
(This article belongs to the Special Issue Functional Neuroimaging of Pain)
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Review

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Review
Disorders of Consciousness: Painless or Painful Conditions?—Evidence from Neuroimaging Studies
Brain Sci. 2016, 6(4), 47; https://doi.org/10.3390/brainsci6040047 - 08 Oct 2016
Cited by 15 | Viewed by 3727
Abstract
The experience of pain in disorders of consciousness is still debated. Neuroimaging studies, using functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET), multichannel electroencephalography (EEG) and laser-evoked potentials, suggest that the perception of pain increases with the level of consciousness. Brain activation [...] Read more.
The experience of pain in disorders of consciousness is still debated. Neuroimaging studies, using functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET), multichannel electroencephalography (EEG) and laser-evoked potentials, suggest that the perception of pain increases with the level of consciousness. Brain activation in response to noxious stimuli has been observed in patients with unresponsive wakefulness syndrome (UWS), which is also referred to as a vegetative state (VS), as well as those in a minimally conscious state (MCS). However, all of these techniques suggest that pain-related brain activation patterns of patients in MCS more closely resemble those of healthy subjects. This is further supported by fMRI findings showing a much greater functional connectivity within the structures of the so-called pain matrix in MCS as compared to UWS/VS patients. Nonetheless, when interpreting the results, a distinction is necessary between autonomic responses to potentially harmful stimuli and conscious experience of the unpleasantness of pain. Even more so if we consider that the degree of residual functioning and cortical connectivity necessary for the somatosensory, affective and cognitive-evaluative components of pain processing are not yet clear. Although procedurally challenging, the particular value of the aforementioned techniques in the assessment of pain in disorders of consciousness has been clearly demonstrated. The study of pain-related brain activation and functioning can contribute to a better understanding of the networks underlying pain perception while addressing clinical and ethical questions concerning patient care. Further development of technology and methods should aim to increase the availability of neuroimaging, objective assessment of functional connectivity and analysis at the level of individual cases as well as group comparisons. This will enable neuroimaging to truly become a clinical tool to reliably investigate pain in severely brain-injured patients as well as an asset for research. Full article
(This article belongs to the Special Issue Functional Neuroimaging of Pain)
Review
Altered Neural Activity Associated with Mindfulness during Nociception: A Systematic Review of Functional MRI
Brain Sci. 2016, 6(2), 14; https://doi.org/10.3390/brainsci6020014 - 19 Apr 2016
Cited by 13 | Viewed by 3510
Abstract
Objective: To assess the neural activity associated with mindfulness-based alterations of pain perception. Methods: The Cochrane Central, EMBASE, Ovid Medline, PsycINFO, Scopus, and Web of Science databases were searched on 2 February 2016. Titles, abstracts, and full-text articles were independently screened by two [...] Read more.
Objective: To assess the neural activity associated with mindfulness-based alterations of pain perception. Methods: The Cochrane Central, EMBASE, Ovid Medline, PsycINFO, Scopus, and Web of Science databases were searched on 2 February 2016. Titles, abstracts, and full-text articles were independently screened by two reviewers. Data were independently extracted from records that included topics of functional neuroimaging, pain, and mindfulness interventions. Results: The literature search produced 946 total records, of which five met the inclusion criteria. Records reported pain in terms of anticipation (n = 2), unpleasantness (n = 5), and intensity (n = 5), and how mindfulness conditions altered the neural activity during noxious stimulation accordingly. Conclusions: Although the studies were inconsistent in relating pain components to neural activity, in general, mindfulness was able to reduce pain anticipation and unpleasantness ratings, as well as alter the corresponding neural activity. The major neural underpinnings of mindfulness-based pain reduction consisted of altered activity in the anterior cingulate cortex, insula, and dorsolateral prefrontal cortex. Full article
(This article belongs to the Special Issue Functional Neuroimaging of Pain)
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Review
Objectifying “Pain” in the Modern Neurosciences: A Historical Account of the Visualization Technologies Used in the Development of an “Algesiogenic Pathology”, 1850 to 2000
Brain Sci. 2015, 5(4), 521-545; https://doi.org/10.3390/brainsci5040521 - 17 Nov 2015
Cited by 2 | Viewed by 2657
Abstract
Particularly with the fundamental works of the Leipzig school of experimental psychophysiology (between the 1850s and 1880s), the modern neurosciences witnessed an increasing interest in attempts to objectify “pain” as a bodily signal and physiological value. This development has led to refined psychological [...] Read more.
Particularly with the fundamental works of the Leipzig school of experimental psychophysiology (between the 1850s and 1880s), the modern neurosciences witnessed an increasing interest in attempts to objectify “pain” as a bodily signal and physiological value. This development has led to refined psychological test repertoires and new clinical measurement techniques, which became progressively paired with imaging approaches and sophisticated theories about neuropathological pain etiology. With the advent of electroencephalography since the middle of the 20th century, and through the use of brain stimulation technologies and modern neuroimaging, the chosen scientific route towards an ever more refined “objectification” of pain phenomena took firm root in Western medicine. This article provides a broad overview of landmark events and key imaging technologies, which represent the long developmental path of a field that could be called “algesiogenic pathology.” Full article
(This article belongs to the Special Issue Functional Neuroimaging of Pain)
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