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Abstract
Neural oscillations play an important role in the integration and segregation of brain regions that are important for brain functions, including pain. Disturbances in oscillatory activity are associated with several disease states, including chronic pain. Studies of neural oscillations related to pain have identified several functional bands, especially alpha, beta, and gamma bands, implicated in nociceptive processing. In this review, we introduce several properties of neural oscillations that are important to understand the role of brain oscillations in nociceptive processing. We also discuss the role of neural oscillations in the maintenance of efficient communication in the brain. Finally, we discuss the role of neural oscillations in healthy and chronic pain nociceptive processing. These data and concepts illustrate the key role of regional and interregional neural oscillations in nociceptive processing underlying acute and chronic pains.
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Affiliation(s)
- Junseok A. Kim
- Division of Brain, Imaging and Behaviour, Krembil Brain Institute, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Karen D. Davis
- Division of Brain, Imaging and Behaviour, Krembil Brain Institute, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Surgery, University of Toronto, Toronto, Ontario, Canada
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Leone C, Di Lionardo A, Diotallevi G, Mollica C, Di Pietro G, Di Stefano G, La Cesa S, Cruccu G, Truini A. Conduction velocity of the cold spinal pathway in healthy humans. Eur J Pain 2020; 24:1923-1931. [PMID: 32735696 DOI: 10.1002/ejp.1640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 07/19/2020] [Accepted: 07/25/2020] [Indexed: 11/05/2022]
Abstract
OBJECTIVES We aimed to investigate the conduction velocity of the cold spinal pathway in healthy humans. METHODS Using a cold stimulator consisting of micro-Peltier elements that was able to produce steep cooling ramps up to -300°C/s, we recorded cold-evoked potentials after stimulation of the dorsal midline at C5, T2, T6 and T10 vertebral levels and calculated the conduction velocity of the cold spinal pathway. In all participants, we used laser stimulation to deliver painful heat (Aδ-fibres-mediated) and warm (C-fibres-mediated) stimuli to the same sites in order to compare the conduction velocity of the cold spinal pathway with that of the nociceptive and warm spinal pathways. RESULTS Cold stimulation evoked large-amplitude vertex potentials from all stimulation sites. The mean conduction velocity of the cold spinal pathway was 12.0 m/s, which did not differ from that of the nociceptive spinal pathway (10.5 m/s). The mean conduction velocity of the warm spinal pathway was 2.0 m/s. DISCUSSION This study provides previously unreported findings regarding cold spinal pathway conduction velocity in humans that may be useful in the assessment of spinal cord lesions as well as in intraoperative monitoring during spinal surgery. SIGNIFICANCE This neurophysiological study provides previously unreported findings on cold spinal pathway conduction velocity in healthy humans. Cold-evoked potentials may represent an alternative to laser-evoked potential recording, useful to assess spinothalamic tract in patients with spinal cord lesions and monitor patients during spinal surgery.
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Affiliation(s)
- Caterina Leone
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | | | | | - Cristina Mollica
- Department of Methods and Models for Economics, Territory and Finance, Sapienza University, Rome, Italy
| | | | | | - Silvia La Cesa
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | - Giorgio Cruccu
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | - Andrea Truini
- Department of Human Neuroscience, Sapienza University, Rome, Italy
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Castellote JM, Valls-Solé J. Temporal relationship between perceptual and physiological events triggered by nociceptive heat stimuli. Sci Rep 2019; 9:3264. [PMID: 30824733 PMCID: PMC6397156 DOI: 10.1038/s41598-019-39509-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 12/18/2018] [Indexed: 12/20/2022] Open
Abstract
A combined assessment tool for the perceptual-motor aspects of pain processing will be valuable to clinicians. Fifteen healthy subjects were exposed to contact-heat stimulation (Pathway, Medoc, Israel) to assess perception through a simple task (motor response or conscious appraisal of the time the stimulus was felt) or with a dual task (both responses). The outcome measure was the temporal relationship between contact heat evoked potentials (CHEPS), reaction time (RT) and conscious awareness (AW). There were different temporal profiles for CHEPs, RT and AW to changes in stimulus intensity, AW being the least affected. Performing the dual task led to a significantly more pronounced effect on RT than on AW, while CHEPS were not influenced by task performance. Our results support the dissociation between physiological, behavioral and cognitive events elicited by nociceptive stimuli. The time of conscious appraisal of stimulus occurrence is a complementary information to other responses such as evoked potentials or behavioral tasks. The combined assessment of physiological and behavioral aspects of pain processing may provide clinicians with information on the different paths followed by nociceptive afferent inputs in the central nervous system.
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Affiliation(s)
- J M Castellote
- National School of Occupational Medicine, Carlos III Institute of Health and CIBERNED, Madrid, Spain. .,Department of Physical Medicine and Rehabilitation, School of Medicine, Complutense University of Madrid, Madrid, Spain.
| | - J Valls-Solé
- EMG and Motor Control Section, Neurology Department, Hospital Clinic, University of Barcelona, Barcelona, Spain
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Bocci T, Santarcangelo E, Vannini B, Torzini A, Carli G, Ferrucci R, Priori A, Valeriani M, Sartucci F. Cerebellar direct current stimulation modulates pain perception in humans. Restor Neurol Neurosci 2016; 33:597-609. [PMID: 25777683 DOI: 10.3233/rnn-140453] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PURPOSE The cerebellum is involved in a wide number of integrative functions, but its role in pain experience and in the nociceptive information processing is poorly understood. In healthy volunteers we evaluated the effects of transcranial cerebellar direct current stimulation (tcDCS) by studying the changes in the perceptive threshold, pain intensity at given stimulation intensities (VAS:0-10) and laser evoked potentials (LEPs) variables (N1 and N2/P2 amplitudes and latencies). METHODS Fifteen subjects were studied before and after anodal, cathodal and sham tcDCS. LEPs were obtained using a neodymium:yttrium-aluminium-perovskite (Nd:YAP) laser and recorded from the dorsum of the left hand. VAS was evaluated by delivering laser pulses at two different intensities, respectively two and three times the perceptive threshold. RESULTS Cathodal polarization dampened significantly the perceptive threshold and increased the VAS score, while the anodal one had opposite effects. Cathodal tcDCS increased significantly the N1 and N2/P2 amplitudes and decreased their latencies, whereas anodal tcDCS elicited opposite effects. Motor thresholds assessed through transcranial magnetic stimulation were not affected by cerebellar stimulation. CONCLUSIONS tcDCS modulates pain perception and its cortical correlates. Since it is effective on both N1 and N2/P2 components, we speculate that the cerebellum engagement in pain processing modulates the activity of both somatosensory and cingulate cortices. Present findings prompt investigation of the cerebellar direct current polarization as a possible novel and safe therapeutic tool in chronic pain patients.
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Affiliation(s)
- Tommaso Bocci
- Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Pisa, Italy.,Department of Medical and Surgical Sciences and Neuroscience, University of Siena, Siena, Italy
| | - Enrica Santarcangelo
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - Beatrice Vannini
- Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Pisa, Italy
| | - Antonio Torzini
- Department of Medical and Surgical Sciences and Neuroscience, University of Siena, Siena, Italy.,Department of Clinical and Experimental Medicine, Cisanello Neurology Unit, Pisa University Medical School, Pisa, Italy
| | - Giancarlo Carli
- Department of Medical and Surgical Sciences and Neuroscience, University of Siena, Siena, Italy
| | - Roberta Ferrucci
- Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy
| | - Alberto Priori
- Department of Neurological Sciences, University of Milan, Fondazione IRCCS Ospedale Maggiore Policlinico, Milan, Italy
| | - Massimiliano Valeriani
- Division of Neurology, Ospedale Bambino Gesù, IRCCS, Rome, Italy.,Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark
| | - Ferdinando Sartucci
- Department of Clinical and Experimental Medicine, Unit of Neurology, Pisa University Medical School, Pisa, Italy.,Department of Clinical and Experimental Medicine, Cisanello Neurology Unit, Pisa University Medical School, Pisa, Italy
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Xia XL, Peng WW, Iannetti GD, Hu L. Laser-evoked cortical responses in freely-moving rats reflect the activation of C-fibre afferent pathways. Neuroimage 2016; 128:209-217. [PMID: 26747747 PMCID: PMC4767222 DOI: 10.1016/j.neuroimage.2015.12.042] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/16/2015] [Accepted: 12/23/2015] [Indexed: 12/29/2022] Open
Abstract
The limited success of translating basic animal findings into effective clinical treatments of pain can be partly ascribed to the use of sub-optimal models. Murine models of pain often consist in recording (1) threshold responses (like the tail-flick reflex) elicited by (2) non-nociceptive specific inputs in (3) anaesthetized animals. The direct cortical recording of laser-evoked potentials (LEPs) elicited by stimuli of graded energies in freely-moving rodents avoids these three important pitfalls, and has thus the potential of improving such translation. Murine LEPs are classically reported to consist of two distinct components, reflecting the activity of Aδ- and C-fibre afferent pathways. However, we have recently demonstrated that the so-called "Aδ-LEPs" in fact reflect the activation of the auditory system by laser-generated ultrasounds. Here we used ongoing white noise to avoid the confound represented by the early auditory response, and thereby comprehensively characterized the physiological properties of C-fibre LEPs recorded directly from the exposed surface of the rat brain. Stimulus-response functions indicated that response amplitude is positively related to the stimulus energy, as well as to nocifensive behavioral score. When displayed using average reference, murine LEPs consist of three distinct deflections, whose polarity, order, and topography are surprisingly similar to human LEPs. The scalp topography of the early N1 wave is somatotopically-organized, likely reflecting the activity of the primary somatosensory cortex, while topographies of the later N2 and P2 waves are more centrally distributed. These results indicate that recording LEPs in freely-moving rats is a valid model to improve the translation of animal results to human physiology and pathophysiology.
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Affiliation(s)
- X L Xia
- Institute of Psychology, Chinese Academy of Sciences, Beijing, China; Key Laboratory of Cognition and Personality (Ministry of Education), Faculty of Psychology, Southwest University, Chongqing, China
| | - W W Peng
- Institute of Psychology, Chinese Academy of Sciences, Beijing, China; Key Laboratory of Cognition and Personality (Ministry of Education), Faculty of Psychology, Southwest University, Chongqing, China
| | - G D Iannetti
- Department of Neuroscience, Physiology and Pharmacology, University College London, UK
| | - L Hu
- Institute of Psychology, Chinese Academy of Sciences, Beijing, China; Department of Neuroscience, Physiology and Pharmacology, University College London, UK; Key Laboratory of Cognition and Personality (Ministry of Education), Faculty of Psychology, Southwest University, Chongqing, China.
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Cortical Responsiveness to Nociceptive Stimuli in Patients with Chronic Disorders of Consciousness: Do C-Fiber Laser Evoked Potentials Have a Role? PLoS One 2015; 10:e0144713. [PMID: 26674634 PMCID: PMC4684218 DOI: 10.1371/journal.pone.0144713] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 11/23/2015] [Indexed: 01/18/2023] Open
Abstract
It has been shown that the presence of Aδ-fiber laser evoked potentials (Aδ-LEP) in patients suffering from chronic disorders of consciousness (DOC), such as vegetative state (VS) and minimally conscious state (MCS), may be the expression of a residual cortical pain arousal. Interestingly, the study of C-fiber LEP (C-LEP) could be useful in the assessment of cortical pain arousal in the DOC individuals who lack of Aδ-LEP. To this end, we enrolled 38 DOC patients following post-anoxic or post-traumatic brain injury, who met the international criteria for VS and MCS diagnosis. Each subject was clinically evaluated, through the coma recovery scale-revised (CRS-R) and the nociceptive coma scale-revised (NCS-R), and electrophysiologically tested by means of a solid-state laser for Aδ-LEP and C-LEP. VS individuals showed increased latencies and reduced amplitudes of both the Aδ-LEP and C-LEP components in comparison to MCS patients. Although nearly all of the patients had both the LEP components, some VS individuals showed only the C-LEP ones. Notably, such patients had a similar NCS-R score to those having both the LEP components. Hence, we could hypothesize that C-LEP generators may be rearranged or partially spared in order to still guarantee cortical pain arousal when Aδ-LEP generators are damaged. Therefore, the residual presence of C-LEP should be assessed when Aδ-LEP are missing, since a potential pain experience should be still present in some patients, so to properly initiate, or adapt, the most appropriate pain treatment.
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Steady-state evoked potentials to tag specific components of nociceptive cortical processing. Neuroimage 2012; 60:571-81. [DOI: 10.1016/j.neuroimage.2011.12.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 12/02/2011] [Accepted: 12/04/2011] [Indexed: 11/20/2022] Open
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Wang AL, Mouraux A, Liang M, Iannetti GD. Stimulus Novelty, and Not Neural Refractoriness, Explains the Repetition Suppression of Laser-Evoked Potentials. J Neurophysiol 2010; 104:2116-24. [DOI: 10.1152/jn.01088.2009] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Brief radiant laser pulses selectively activate skin nociceptors and elicit transient brain responses (laser-evoked potentials [LEPs]). When LEPs are elicited by pairs of stimuli (S1–S2) delivered at different interstimulus intervals (ISIs), the S2-LEP is strongly reduced at short ISIs (250 ms) and progressively recovers at longer ISIs (2,000 ms). This finding has been interpreted in terms of order of arrival of nociceptive volleys and refractoriness of neural generators of LEPs. However, an alternative explanation is the modulation of another experimental factor: the novelty of the eliciting stimulus. To test this alternative hypothesis, we recorded LEPs elicited by pairs of nociceptive stimuli delivered at four ISIs (250, 500, 1,000, 2,000 ms), using two different conditions. In the constant condition, the ISI was identical across the trials of each block, whereas in the variable condition, the ISI was varied randomly across trials and single-stimulus trials were intermixed with paired trials. Therefore the time of occurrence of S2 was both less novel and more predictable in the constant than in the variable condition. In the constant condition, we observed a significant ISI-dependent suppression of the biphasic negative–positive wave (N2–P2) complex of the S2-LEP. In contrast, in the variable condition, the S2-LEP was completely unaffected by stimulus repetition. The pain ratings elicited by S2 were not different in the two conditions. These results indicate that the repetition-suppression of the S2-LEP is not due to refractoriness in nociceptive afferent pathways, but to a modulation of novelty and/or temporal predictability of the eliciting stimulus. This provides further support to the notion that stimulus saliency constitutes a crucial determinant of LEP magnitude and that a significant fraction of the brain activity time-locked to a brief and transient sensory stimulus is not directly related to the quality and the intensity of the corresponding sensation, but to bottom-up attentional processes.
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Affiliation(s)
- A. L. Wang
- Department of Neuroscience, Physiology and Pharmacology, University College London, London
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom; and
| | - A. Mouraux
- Institute of Neurosciences, Université Catholique de Louvain, Louvan, Belgium
| | - M. Liang
- Department of Neuroscience, Physiology and Pharmacology, University College London, London
| | - G. D. Iannetti
- Department of Neuroscience, Physiology and Pharmacology, University College London, London
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom; and
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Mouraux A, Iannetti GD. Nociceptive laser-evoked brain potentials do not reflect nociceptive-specific neural activity. J Neurophysiol 2009; 101:3258-69. [PMID: 19339457 DOI: 10.1152/jn.91181.2008] [Citation(s) in RCA: 271] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Brief radiant laser pulses can be used to activate cutaneous Adelta and C nociceptors selectively and elicit a number of transient brain responses [laser-evoked potentials (LEPs)] in the ongoing EEG. LEPs have been used extensively in the past 30 years to gain knowledge about the cortical mechanisms underlying nociception and pain in humans, by assuming that they reflect at least neural activities uniquely or preferentially involved in processing nociceptive input. Here, by applying a novel blind source separation algorithm (probabilistic independent component analysis) to 124-channel event-related potentials elicited by a random sequence of nociceptive and non-nociceptive somatosensory, auditory, and visual stimuli, we provide compelling evidence that this assumption is incorrect: LEPs do not reflect nociceptive-specific neural activity. Indeed, our results indicate that LEPs can be entirely explained by a combination of multimodal neural activities (i.e., activities also elicited by stimuli of other sensory modalities) and somatosensory-specific, but not nociceptive-specific, neural activities (i.e., activities elicited by both nociceptive and non-nociceptive somatosensory stimuli). Regardless of the sensory modality of the eliciting stimulus, the magnitude of multimodal activities correlated with the subjective rating of saliency, suggesting that these multimodal activities are involved in stimulus-triggered mechanisms of arousal or attentional reorientation.
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Affiliation(s)
- A Mouraux
- Department of Clinical Neurology, University of Oxford, OX1 3QX Oxford, United Kingdom
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Iannetti GD, Hughes NP, Lee MC, Mouraux A. Determinants of laser-evoked EEG responses: pain perception or stimulus saliency? J Neurophysiol 2008; 100:815-28. [PMID: 18525021 PMCID: PMC2525705 DOI: 10.1152/jn.00097.2008] [Citation(s) in RCA: 288] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Accepted: 05/31/2008] [Indexed: 11/22/2022] Open
Abstract
Although laser-evoked electroencephalographic (EEG) responses are increasingly used to investigate nociceptive pathways, their functional significance remains unclear. The reproducible observation of a robust correlation between the intensity of pain perception and the magnitude of the laser-evoked N1, N2, and P2 responses has led some investigators to consider these responses a direct correlate of the neural activity responsible for pain intensity coding in the human cortex. Here, we provide compelling evidence to the contrary. By delivering trains of three identical laser pulses at four different energies, we explored the modulation exerted by the temporal expectancy of the stimulus on the relationship between intensity of pain perception and magnitude of the following laser-evoked brain responses: the phase-locked N1, N2, and P2 waves, and the non-phase-locked laser-induced synchronization (ERS) and desynchronization (ERD). We showed that increasing the temporal expectancy of the stimulus through stimulus repetition at a constant interstimulus interval 1) significantly reduces the magnitudes of the laser-evoked N1, N2, P2, and ERS; and 2) disrupts the relationship between the intensity of pain perception and the magnitude of these responses. Taken together, our results indicate that laser-evoked EEG responses are not determined by the perception of pain per se, but are mainly determined by the saliency of the eliciting nociceptive stimulus (i.e., its ability to capture attention). Therefore laser-evoked EEG responses represent an indirect readout of the function of the nociceptive system.
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Affiliation(s)
- G D Iannetti
- Department of Physiology, Anatomy, and Genetics, University of Oxford, South Parks Road, OX1 3QX, Oxford, UK.
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