An fMRI study of the anterior cingulate cortex and surrounding medial wall activations evoked by noxious cutaneous heat and cold stimuli

Effects of Head-Only Exposure to 900 MHz GSM Electromagnetic Fields in Rats: Changes in Neuronal Activity as Revealed by c-Fos Imaging without Concomitant Cognitive Impairments

Over the last two decades, animal models have been used to evaluate the physiological and cognitive effects of mobile phone exposure. Here, we used a head-only exposure system in rats to determine whether exposure to 900 MHz GSM electromagnetic fields (EMFs) induces regional changes in neuronal activation as revealed by c-Fos imaging. In a first study, rats were exposed for 2 h to brain average specific absorption rates (BASARs) ranging from 0.5 to 6 W/kg. Changes in neuronal activation were found to be dose-dependent, with significant increases in c-Fos expression occurring at BASAR of 1 W/kg in prelimbic, infralimbic, frontal, and cingulate cortices. In a second study, rats were submitted to either a spatial working memory (WM) task in a radial maze or a spatial reference memory (RM) task in an open field arena. Exposures (45 min) were conducted before each daily training session (BASARs of 1 and 3.5 W/kg). Control groups included sham-exposed and control cage animals. In both tasks, behavioral performance evolved similarly in the four groups over testing days. However, c-Fos staining was significantly reduced in cortical areas (prelimbic, infralimbic, frontal, cingulate, and visual cortices) and in the hippocampus of animals engaged in the WM task (BASARs of 1 and 3.5 W/kg). In the RM task, EMF exposure-induced decreases were limited to temporal and visual cortices (BASAR of 1 W/kg). These results demonstrate that both acute and subchronic exposures to 900 MHz EMFs can produce region-specific changes in brain activity patterns, which are, however, insufficient to induce detectable cognitive deficits in the behavioral paradigms used here.

Noninvasive targeted modulation of pain circuits with focused ultrasonic waves

ABSTRACT

Direct interventions into deep brain circuits constitute promising treatment modalities for chronic pain. Cingulotomy and deep brain stimulation targeting the anterior cingulate cortex have shown notable improvements in the unpleasantness of pain, but these interventions require brain surgeries. In this study, we have developed an approach that can modulate this deep brain affective hub entirely noninvasively, using low-intensity transcranial-focused ultrasound. Twenty patients with chronic pain received two 40-minute active or sham stimulation protocols and were monitored for one week in a randomized crossover trial. Sixty percent of subjects experienced a clinically meaningful reduction of pain on day 1 and on day 7 following the active stimulation, while sham stimulation provided such benefits only to 15% and 20% of subjects, respectively. On average, active stimulation reduced pain by 60.0% immediately following the intervention and by 43.0% and 33.0% on days 1 and 7 following the intervention. The corresponding sham levels were 14.4%, 12.3%, and 6.6%. The stimulation was well tolerated, and no adverse events were detected. Side effects were generally mild and resolved within 24 hours. Together, the direct, ultrasonic stimulation of the anterior cingulate cortex offers rapid, clinically meaningful, and durable improvements in pain severity.

Aberrant functional connectivity in anterior cingulate gyrus subregions in migraine without aura patients

Background

The anterior cingulate gyrus (ACG) is an important regulatory region for pain-related information. However, the ACG is composed of subregions with different functions. The mechanisms underlying the brain networks of different subregions of the ACG in patients with migraine without aura (MwoA) are currently unclear.

Methods

In the current study, resting-state functional magnetic resonance imaging (rsfMRI) and functional connectivity (FC) were used to investigate the functional characteristics of ACG subregions in MwoA patients. The study included 17 healthy volunteers and 28 MwoA patients. The FC calculation was based on rsfMRI data from a 3 T MRI scanner. The brain networks of the ACG subregions were compared using a general linear model to see if there were any differences between the two groups. Spearman correlation analysis was used to examine the correlation between FC values in abnormal brain regions and clinical variables.

Results

Compared with healthy subjects, MwoA patients showed decreased FC between left subgenual ACG and left middle cingulate gyrus and right middle temporal gyrus. Meanwhile, MwoA patients also showed increased FC between pregenual ACG and right angular gyrus and increased FC between right pregenual ACG and right superior occipital gyrus. The FC values between pregenual ACG and right superior occipital gyrus were significantly positively correlated with the visual analogue scale.

Conclusion

Disturbances of FC between ACG subregions and default model network and visual cortex may play a key role in neuropathological features, perception and affection of MwoA. The current study provides further insights into the complex scenario of MwoA mechanisms.

Effective brain connectivity related to non-painful thermal stimuli using EEG

Understanding the brain response to thermal stimuli is crucial in the sensory experience. This study focuses on non-painful thermal stimuli, which are sensations induced by temperature changes without causing discomfort. These stimuli are transmitted to the central nervous system through specific nerve fibers and are processed in various regions of the brain, including the insular cortex, the prefrontal cortex, and anterior cingulate cortex. Despite the prevalence of studies on painful stimuli, non-painful thermal stimuli have been less explored. This research aims to bridge this gap by investigating brain functional connectivity during the perception of non-painful warm and cold stimuli using electroencephalography (EEG) and the partial directed coherence technique (PDC). Our results demonstrate a clear contrast in the direction of information flow between warm and cold stimuli, particularly in the theta and alpha frequency bands, mainly in frontal and temporal regions. The use of PDC highlights the complexity of brain connectivity during these stimuli and reinforces the existence of different pathways in the brain to process different types of non-painful warm and cold stimuli.

Cingulotomy: the last man standing in the battle against medically refractory poststroke pain

Introduction

Central poststroke pain (CPSP) places a huge burden on patient lives because patients are often refractory to conventional strategies and have little chance for spontaneous recovery. A subset of patients is even given approval for euthanasia and is without any perspective. Because the anterior cingulate cortex historically seems to be a promising target for patients with both mental and chronic pain disorders, lesioning of this central "hub" with cingulotomy may be a useful strategy for medically refractory CPSP. However, limited research is available on cingulotomy for central pain. Hence, we represent a rare case in which cingulotomy is performed on a patient with CPSP.

Objectives

To describe the potential of cingulotomy in a case with CPSP.

Methods

The case presented in this study concerns a 60-year-old woman who experienced CPSP, caused by a hemorrhagic stroke in the basal ganglia and thalamus. The patient visited several centers and tried multiple off-label treatments; however, she was told nothing else could be done and was even given approval for euthanasia. Hence, anterior cingulotomy was performed.

Results

After surgery, no transient adverse events occurred, except for vocabulary disturbances post stroke, which disappeared after several weeks. After 14 weeks, changes in pain behavior were observed, followed by a decreased pain intensity. At a later follow-up, the pain had completely disappeared.

Conclusion

Anterior cingulotomy seems to be a suitable "last-resort" option for patients with CPSP. Future research, including homogenous groups, to define the best location for lesioning is required to allow the revival of this "old" technique in the current era.

fMRI, LFP, and anatomical evidence for hierarchical nociceptive routing pathway between somatosensory and insular cortices

The directional organization of multiple nociceptive regions, particularly within obscure operculoinsular areas, underlying multidimensional pain processing remains elusive. This study aims to establish the fundamental organization between somatosensory and insular cortices in routing nociceptive information. By employing an integrated multimodal approach of high-field fMRI, intracranial electrophysiology, and transsynaptic viral tracing in rats, we observed a hierarchically organized connection of S1/S2 → posterior insula → anterior insula in routing nociceptive information. The directional nociceptive pathway determined by early fMRI responses was consistent with that examined by early evoked LFP, intrinsic effective connectivity, and anatomical projection, suggesting fMRI could provide a valuable facility to discern directional neural circuits in animals and humans non-invasively. Moreover, our knowledge of the nociceptive hierarchical organization of somatosensory and insular cortices and the interface role of the posterior insula may have implications for the development of targeted pain therapies.

[Involvement of the trigeminal nerve system in the sense of smell]

A systematic review of literature on the issue of involvement in the sense of smell, as well as the interaction between the trigeminal and olfactory nerves, was carried out. The article discusses the features of the chemical perception systems, as well as the treatment of olfactory disorders using transcranial electrical stimulation of the trigeminal nerve.

The Role of the Skin in Interoception: A Neglected Organ?

In the past 2 decades, interoception has received increasing attention in the fields of psychology and cognitive science, as well as neuroscience and physiology. A plethora of studies adopted the perception of cardiac signals as a proxy for interoception. However, recent findings have cast doubt on the methodological and intrinsic validity of the tasks used thus far. Therefore, there is an ongoing effort to improve the existing cardiac interoceptive tasks and to identify novel channels to target the perception of the physiological state of the body. Amid such scientific abundancy, one could question whether the field has been partially neglecting one of our widest organs in terms of dimensions and functions: the skin. According to some views grounded on anatomical and physiological evidence, skin-mediated signals such as affective touch, pain, and temperature have been redefined as interoceptive. However, there is no agreement in this regard. Here, we discuss some of the anatomical, physiological, and experimental arguments supporting the scientific study of interoception by means of skin-mediated signals. We argue that more attention should be paid to the skin as a sensory organ that monitors the bodily physiological state and further propose thermosensation as a particularly attractive model of skin-mediated interoception.

Nomogram for Early Prediction of Outcome in Coma Patients with Severe Traumatic Brain Injury Receiving Right Median Nerve Electrical Stimulation Treatment

BACKGROUND

Accurate outcome prediction can serve to approach, quantify and categorize severe traumatic brain injury (TBI) coma patients for right median electrical stimulation (RMNS) treatment, which can support rehabilitation plans. As a proof of concept for individual risk prediction, we created a novel nomogram model combining amplitude-integrated electroencephalography (AEEG) and clinically relevant parameters.

METHODS

This study retrospective collected and analyzed a total of 228 coma patients after severe TBI in two medical centers. According to the extended Glasgow Outcome Scale (GOSE), patients were divided into a good outcome (GOSE 3-8) or a poor outcome (GOSE 1-2) group. Their clinical and biochemical indicators, together with EEG features, were explored retrospectively. The risk factors connected to the outcome of coma patients receiving RMNS treatment were identified using Cox proportional hazards regression. The discriminative capability and calibration of the model to forecast outcome were assessed by C statistics, calibration plots, and Kaplan-Meier curves on a personalized nomogram forecasting model.

RESULTS

The study included 228 patients who received RMNS treatment for long-term coma after a severe TBI. The median age was 40 years, and 57.8% (132 of 228) of the patients were male. 67.0% (77 of 115) of coma patients in the high-risk group experienced a poor outcome after one year and the comparative data merely was 30.1% (34 of 113) in low-risk group patients. The following variables were integrated into the forecasting of outcome using the backward stepwise selection of Akaike information criterion: age, Glasgow Coma Scale (GCS) at admission, EEG reactivity (normal, absence, or the stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs)), and AEEG background pattern (A mode, B mode, or C mode). The C statistics revealed that the nomograms' discriminative potential and calibration demonstrated good predictive ability (0.71).

CONCLUSION

Our findings show that the nomogram model using AEEG parameters has the potential to predict outcomes in severe TBI coma patients receiving RMNS treatment. The model could classify patients into prognostic groups and worked well in internal validation.

Effects of intravascular photobiomodulation on motor deficits and brain perfusion images in intractable myasthenia gravis: A case report

BACKGROUND

Myasthenia gravis (MG) is an autoimmune disorder caused by neuromuscular junction failure characterized by muscle weakness and fatigability. We herein report a case of MG that received intravascular laser irradiation of blood (ILIB) interventions and regained muscle power and better quality of life. To our knowledge, no previous study has investigated the benefits of ILIB treatment on patients with MG. We also evaluated the changes in brain perfusion scan and the MG activities of daily living (MG-ADL) and quantitative MG (QMG) scales.

CASE SUMMARY

A 59-year-old man presented to our outpatient hospital experiencing ptosis, diplopia, fibromyalgia, muscle fatigue, and fluctuating weakness in his limbs for 1 year. Based on his history, physical examination, and laboratory investigations, the final diagnosis was a flare-up of MG with poor endurance and muscle fatigue. The patient agreed to receive ILIB. Brain single-photon emission computed tomography (SPECT) was performed both before and after ILIB therapy. After receiving three courses of ILIB, the brain SPECT images showed greatly increased perfusion of the frontal lobe and anterior cingulate gyri. The patient’s MG-ADL scale score decreased markedly from 17/24 to 3/24. The QMG scale score also decreased remarkably from 32/39 to 9/39. The symptoms of MG became barely detectable and the patient was able to perform his activities of daily living and regain muscle power.

CONCLUSION

ILIB might have beneficial effects on MG, and brain SPECT images provided direct evidence of a positive correlation between ILIB and clinical performance.

Electroencephalographic Measurement on Post-stroke Sensory Deficiency in Response to Non-painful Cold Stimulation

Background

Reduced elementary somatosensation is common after stroke. However, the measurement of elementary sensation is frequently overlooked in traditional clinical assessments, and has not been evaluated objectively at the cortical level. This study designed a new configuration for the measurement of post-stroke elementary thermal sensation by non-painful cold stimulation (NPCS). The post-stroke cortical responses were then investigated during elementary NPCS on sensory deficiency via electroencephalography (EEG) when compared with unimpaired persons.

Method

Twelve individuals with chronic stroke and fifteen unimpaired controls were recruited. A 64-channel EEG system was used to investigate the post-stroke cortical responses objectively during the NPCS. A subjective questionnaire of cold sensory intensity was also administered via a numeric visual analog scale (VAS). Three water samples with different temperatures (i.e., 25, 10, and 0°C) were applied to the skin surface of the ventral forearm for 3 s via glass beaker, with a randomized sequence on either the left or right forearm of a participant. EEG relative spectral power (RSP) and topography were used to evaluate the neural responses toward NPCS with respect to the independent factors of stimulation side and temperature.

Results

For unimpaired controls, NPCS initiated significant RSP variations, mainly located in the theta band with the highest discriminative resolution on the different temperatures (P < 0.001). For stroke participants, the distribution of significant RSP spread across all EEG frequency bands and the temperature discrimination was lower than that observed in unimpaired participants (P < 0.05). EEG topography showed that the NPCS could activate extensive and bilateral sensory cortical areas after stroke. Significant group differences on RSP intensities were obtained in each EEG band (P < 0.05). Meanwhile, significant asymmetry cortical responses in RSP toward different upper limbs were observed during the NPCS in both unimpaired controls and participants with stroke (P < 0.05). No difference was found between the groups in the VAS ratings of the different temperatures (P > 0.05).

Conclusion

The post-stroke cortical responses during NPCS on sensory deficiency were characterized by the wide distribution of representative RSP bands, lowered resolution toward different temperatures, and extensive activated sensory cortical areas.

Supraspinal Mechanisms Underlying Ocular Pain

Supraspinal mechanisms of pain are increasingly understood to underlie neuropathic ocular conditions previously thought to be exclusively peripheral in nature. Isolating individual causes of centralized chronic conditions and differentiating them is critical to understanding the mechanisms underlying neuropathic eye pain and ultimately its treatment. Though few functional imaging studies have focused on the eye as an end-organ for the transduction of noxious stimuli, the brain networks related to pain processing have been extensively studied with functional neuroimaging over the past 20 years. This article will review the supraspinal mechanisms that underlie pain as they relate to the eye.

Distinct spatio-temporal and spectral brain patterns for different thermal stimuli perception

Understanding the human brain's perception of different thermal sensations has sparked the interest of many neuroscientists. The identification of distinct brain patterns when processing thermal stimuli has several clinical applications, such as phantom-limb pain prediction, as well as increasing the sense of embodiment when interacting with neurorehabilitation devices. Notwithstanding the remarkable number of studies that have touched upon this research topic, understanding how the human brain processes different thermal stimuli has remained elusive. More importantly, very intense thermal stimuli perception dynamics, their related cortical activations, as well as their decoding using effective features are still not fully understood. In this study, using electroencephalography (EEG) recorded from three healthy human subjects, we identified spatial, temporal, and spectral patterns of brain responses to different thermal stimulations ranging from extremely cold and hot stimuli (very intense), moderately cold and hot stimuli (intense), to a warm stimulus (innocuous). Our results show that very intense thermal stimuli elicit a decrease in alpha power compared to intense and innocuous stimulations. Spatio-temporal analysis reveals that in the first 400 ms post-stimulus, brain activity increases in the prefrontal and central brain areas for very intense stimulations, whereas for intense stimulation, high activity of the parietal area was observed post-500 ms. Based on these identified EEG patterns, we successfully classified the different thermal stimulations with an average test accuracy of 84% across all subjects. En route to understanding the underlying cortical activity, we source localized the EEG signal for each of the five thermal stimuli conditions. Our findings reveal that very intense stimuli were anticipated and induced early activation (before 400 ms) of the anterior cingulate cortex (ACC). Moreover, activation of the pre-frontal cortex, somatosensory, central, and parietal areas, was observed in the first 400 ms post-stimulation for very intense conditions and starting 500 ms post-stimuli for intense conditions. Overall, despite the small sample size, this work presents novel findings and a first comprehensive approach to explore, analyze, and classify EEG-brain activity changes evoked by five different thermal stimuli, which could lead to a better understanding of thermal stimuli processing in the brain and could, therefore, pave the way for developing a real-time withdrawal reaction system when interacting with prosthetic limbs. We underpin this last point by benchmarking our EEG results with a demonstration of a real-time withdrawal reaction of a robotic prosthesis using a human-like artificial skin.

The role of endogenous opioid neuropeptides in neurostimulation-driven analgesia

Due to the prevalence of chronic pain worldwide, there is an urgent need to improve pain management strategies. While opioid drugs have long been used to treat chronic pain, their use is severely limited by adverse effects and abuse liability. Neurostimulation techniques have emerged as a promising option for chronic pain that is refractory to other treatments. While different neurostimulation strategies have been applied to many neural structures implicated in pain processing, there is variability in efficacy between patients, underscoring the need to optimize neurostimulation techniques for use in pain management. This optimization requires a deeper understanding of the mechanisms underlying neurostimulation-induced pain relief. Here, we discuss the most commonly used neurostimulation techniques for treating chronic pain. We present evidence that neurostimulation-induced analgesia is in part driven by the release of endogenous opioids and that this endogenous opioid release is a common endpoint between different methods of neurostimulation. Finally, we introduce technological and clinical innovations that are being explored to optimize neurostimulation techniques for the treatment of pain, including multidisciplinary efforts between neuroscience research and clinical treatment that may refine the efficacy of neurostimulation based on its underlying mechanisms.

A lateralized model of the pain-depression dyad

Chronic pain and depression are two frequently co-occurring and debilitating conditions. Even though the former is treated as a physical affliction, and the latter as a mental illness, both disorders closely share neural substrates. Here, we review the association of pain with depression, especially when symptoms are lateralized on either side of the body. We also explore the overlapping regions in the forebrain implicated in these conditions. Finally, we synthesize these findings into a model, which addresses gaps in our understanding of comorbid pain and depression. Our lateralized pain-depression dyad model suggests that individuals diagnosed with depression should be closely monitored for pain symptoms in the left hemibody. Conversely, for patients in pain, with the exception of acute pain with a known source, referrals in today's pain centers for psychological evaluation should be part of standard practice, within the framework of an interdisciplinary approach to pain treatment.

Role of the Anterior Cingulate Cortex in Translational Pain Research

As the most common symptomatic reason to seek medical consultation, pain is a complex experience that has been classified into different categories and stages. In pain processing, noxious stimuli may activate the anterior cingulate cortex (ACC). But the function of ACC in the different pain conditions is not well discussed. In this review, we elaborate the commonalities and differences from accumulated evidence by a variety of pain assays for physiological pain and pathological pain including inflammatory pain, neuropathic pain, and cancer pain in the ACC, and discuss the cellular receptors and signaling molecules from animal studies. We further summarize the ACC as a new central neuromodulation target for invasive and non-invasive stimulation techniques in clinical pain management. The comprehensive understanding of pain processing in the ACC may lead to bridging the gap in translational research between basic and clinical studies and to develop new therapies.

Virtual Reality for Neurorehabilitation and Cognitive Enhancement

Our access to computer-generated worlds changes the way we feel, how we think, and how we solve problems. In this review, we explore the utility of different types of virtual reality, immersive or non-immersive, for providing controllable, safe environments that enable individual training, neurorehabilitation, or even replacement of lost functions. The neurobiological effects of virtual reality on neuronal plasticity have been shown to result in increased cortical gray matter volumes, higher concentration of electroencephalographic beta-waves, and enhanced cognitive performance. Clinical application of virtual reality is aided by innovative brain–computer interfaces, which allow direct tapping into the electric activity generated by different brain cortical areas for precise voluntary control of connected robotic devices. Virtual reality is also valuable to healthy individuals as a narrative medium for redesigning their individual stories in an integrative process of self-improvement and personal development. Future upgrades of virtual reality-based technologies promise to help humans transcend the limitations of their biological bodies and augment their capacity to mold physical reality to better meet the needs of a globalized world.

Anterior Cingulate Cortex and the Control of Dynamic Behavior in Primates

The brain mechanism for controlling continuous behavior in dynamic contexts must mediate action selection and learning across many timescales, responding differentially to the level of environmental uncertainty and volatility. In this review, we argue that a part of the frontal cortex known as the anterior cingulate cortex (ACC) is particularly well suited for this function. First, the ACC is interconnected with prefrontal, parietal, and subcortical regions involved in valuation and action selection. Second, the ACC integrates diverse, behaviorally relevant information across multiple timescales, producing output signals that temporally encapsulate decision and learning processes and encode high-dimensional information about the value and uncertainty of future outcomes and subsequent behaviors. Third, the ACC signals behaviorally relevant information flexibly, displaying the capacity to represent information about current and future states in a valence-, context-, task- and action-specific manner. Fourth, the ACC dynamically controls instrumental- and non-instrumental information seeking behaviors to resolve uncertainty about future outcomes. We review electrophysiological and circuit disruption studies in primates to develop this point, discuss its relationship to novel therapeutics for neuropsychiatric disorders in humans, and conclude by relating ongoing research in primates to studies of medial frontal cortical regions in rodents.

Emotional affection on a sustained attention task: The importance the aging process and depression

Chronic pain is a complex experience that has now become a major public health issue. This has prompted many researchers to study attention, understanding it to be a crucial factor that allows altering the experience of pain, while attributing considerable importance to sustained attention. Accordingly, the main studies in this field stress the importance of emotion regulation processes and emotions on the perception of painful stimuli and attentional processes themselves. Nevertheless, only a handful of studies have been found that directly study the relationship between these variables. Within this context, this article sets out to analyse emotional regulation processes, emotional variables (depression and anxiety), the experience of pain, and age on the ability to maintain the vigilance response in a sample of patients with chronic pain. This involved selecting a sample of 49 patients with rheumatoid arthritis and examining their performance in an ad-hoc sustained attention test. With a view to complying with the study's main purpose, the participants were also assessed through the use of the following self-report measures: the Beck Depression Inventory (BDI-I); the Hospital Anxiety and Depression Scale (HADS); the McGill Pain Questionnaire, and the Difficulties in Emotion Regulation Scale (DERS). Linear regression analyses revealed a significant impact of the aging process on the performance times in the attention task. Likewise, age and depression recorded a significant correlation with the mistakes made during the task. These results suggest that higher depression levels and an older age might be related to a worse adaptation to pain management techniques based on attention processes, such as mindfulness.

The human cingulum: From the limbic tract to the connectionist paradigm

The cingulum is a core component of the limbic lobe and part of the circuit that was described by Papez where environmental experiences become endowed with emotional awareness. Recent techniques for the study of cerebral connectivity have updated this fasciculus' morphology and led to the acknowledgment that its involvement in superior functions goes far beyond emotion processing. Long and robust, the cingulum is a long association fasciculus with terminations in all cerebral lobes. These observations plead for a pivotal rethinking of its role in the human brain and lead to the conclusion that to merely consider it as the main fasciculus of the limbic system was actually a reductionism. This paper summarizes the key facts regarding why the cingulum is now perceived as a primary interconnecting apparatus in the medial aspect of the cerebral hemisphere.

Decoding of Pain Perception using EEG Signals for a Real-Time Reflex System in Prostheses: A Case Study

In recent times, we have witnessed a push towards restoring sensory perception to upper-limb amputees, which includes the whole spectrum from gentle touch to noxious stimuli. These are essential components for body protection as well as for restoring the sense of embodiment. Notwithstanding the considerable advances that have been made in designing suitable sensors and restoring tactile perceptions, pain perception dynamics and its decoding using effective bio-markers, are still not fully understood. Here, using electroencephalography (EEG) recordings, we identified and validated a spatio-temporal signature of brain activity during innocuous, moderately more intense, and noxious stimulation of an amputee's phantom limb using transcutaneous nerve stimulation (TENS). Based on the spatio-temporal EEG features, we developed a system for detecting pain perception and reaction in the brain, which successfully classified three different stimulation conditions with a test accuracy of 94.66%, and we investigated the cortical activity in response to sensory stimuli in these conditions. Our findings suggest that the noxious stimulation activates the pre-motor cortex with the highest activation shown in the central cortex (Cz electrode) between 450 ms and 750 ms post-stimulation, whereas the highest activation for the moderately intense stimulation was found in the parietal lobe (P2, P4, and P6 electrodes). Further, we localized the cortical sources and observed early strong activation of the anterior cingulate cortex (ACC) corresponding to the noxious stimulus condition. Moreover, activation of the posterior cingulate cortex (PCC) was observed during the noxious sensation. Overall, although this is a single case study, this work presents a novel approach and a first attempt to analyze and classify neural activity when restoring sensory perception to amputees, which could chart a route ahead for designing a real-time pain reaction system in upper-limb prostheses.

Immediate effects of noxious and innocuous thermal stimulation on brain activation in patients with stroke

Case-control studies have shown that noxious thermal stimulation (TS) can improve arm function in patients with stroke. However, the neural mechanisms underlying this improvement are largely unknown. We explored functional neural activation due to noxious and innocuous TS intervention applied to the paretic arm of patients with stroke. Sixteen participants with unilateral cortical infarctions were allocated to one of two groups: noxious TS (8 patients; temperature combination: hot pain 46°C to 47°C, cold pain 7°C-8°C) or innocuous TS (n = 8; temperature combination: hot 40°C-41°C, cold 20°C-21°C). All subjects underwent fMRI scanning before and after 30 min TS intervention and performed a finger tapping task with the affected hand. Immediate brain activation effects were assessed according to thermal type (noxious vs. innocuous TS) and time (pre-TS vs post-TS). Regions activated by noxious TS relative to innocuous TS (P < .05, adjusted for multiple comparisons) were related to motor performance and sensory function in the bilateral primary somatosensory cortices, anterior cingulate cortex, insula, thalamus, hippocampus and unilateral primary motor cortex, secondary somatosensory cortex at the contralateral side of lesion, and unilateral supplementary motor area at the ipsilateral side of lesion. Greater activation responses were observed in the side contralateral to the lesion, suggesting a significant intervention effect. Our preliminary findings suggest that noxious TS may induce neuroplastic changes unconstrained to the local area.Trial registration: NCT01418404.

Influence of Alternate Hot and Cold Thermal Stimulation in Cortical Excitability in Healthy Adults: An fMRI Study

Stroke rehabilitation using alternate hot and cold thermal stimulation (altTS) has been reported to improve motor function in hemiplegia; however, the influence of brain excitability induced by altTS remains unclear. This study examined cortical activation induced by altTS in healthy adults, focusing on motor-related areas. This involved a repeated crossover experimental design with two temperature settings (innocuous altTS with alternate heat-pain and cold-pain thermal and noxious altTS with alternate heat and cold thermal) testing both arms (left side and right side). Thirty-one healthy, right-handed participants received four episodes of altTS on four separate days. Functional magnetic resonance imaging scans were performed both before and after each intervention to determine whether altTS intervention affects cortical excitability, while participants performed a finger-tapping task during scanning. The findings revealed greater response intensity of cortical excitability in participants who received noxious altTS in the primary motor cortex, supplementary motor cortex, and somatosensory cortex than in those who received innocuous altTS. Moreover, there was more motor-related excitability in the contra-lateral brain when heat was applied to the dominant arm, and more sensory-associated excitability in the contra-lateral brain when heat was applied to the nondominant arm. The findings highlight the effect of heat on cortical excitability and provide insights into the application of altTS in stroke rehabilitation.

Pain-Evoked Reorganization in Functional Brain Networks

Recent studies indicate that a significant reorganization of cerebral networks may occur in patients with chronic pain, but how immediate pain experience influences the organization of large-scale functional networks is not yet well characterized. To investigate this question, we used functional magnetic resonance imaging in 106 participants experiencing both noxious and innocuous heat. Painful stimulation caused network-level reorganization of cerebral connectivity that differed substantially from organization during innocuous stimulation and standard resting-state networks. Noxious stimuli increased somatosensory network connectivity with (a) frontoparietal networks involved in context representation, (b) "ventral attention network" regions involved in motivated action selection, and (c) basal ganglia and brainstem regions. This resulted in reduced "small-worldness," modularity (fewer networks), and global network efficiency and in the emergence of an integrated "pain supersystem" (PS) whose activity predicted individual differences in pain sensitivity across 5 participant cohorts. Network hubs were reorganized ("hub disruption") so that more hubs were localized in PS, and there was a shift from "connector" hubs linking disparate networks to "provincial" hubs connecting regions within PS. Our findings suggest that pain reorganizes the network structure of large-scale brain systems. These changes may prioritize responses to painful events and provide nociceptive systems privileged access to central control of cognition and action during pain.

Peripheral and Central Mechanisms of Itch

Itch is a unique sensory experience that is encoded by genetically distinguishable neurons both in the peripheral nervous system (PNS) and central nervous system (CNS) to elicit a characteristic behavioral response (scratching). Itch interacts with the other sensory modalities at multiple locations, from its initiation in a particular dermatome to its transmission to the brain where it is finally perceived. In this review, we summarize the current understanding of the molecular and neural mechanisms of itch by starting in the periphery, where itch is initiated, and discussing the circuits involved in itch processing in the CNS.

Functional brain activity during motor control and pain processing in chronic jaw pain

Changes in brain function in chronic pain have been studied using paradigms that deliver acute pain-eliciting stimuli or assess the brain at rest. Although motor disability accompanies many chronic pain conditions, few studies have directly assessed brain activity during motor function in individuals with chronic pain. Using chronic jaw pain as a model, we assessed brain activity during a precisely controlled grip force task and during a precisely controlled pain-eliciting stimulus on the forearm. We used multivariate analyses to identify regions across the brain whose activity together best separated the groups. We report 2 novel findings. First, although the parameters of grip force production were similar between the groups, the functional activity in regions including the prefrontal cortex, insula, and thalamus best separated the groups. Second, although stimulus intensity and pain perception were similar between the groups, functional activity in brain regions including the dorsal lateral prefrontal cortex, rostral ventral premotor cortex, and inferior parietal lobule best separated the groups. Our observations suggest that chronic jaw pain is associated with changes in how the brain processes motor and pain-related information even when the effector producing the force or experiencing the pain-eliciting stimulus is distant from the jaw. We also demonstrate that motor tasks and multivariate analyses offer alternative approaches for studying brain function in chronic jaw pain.

Top-Down Cortical Control of Acute and Chronic Pain

Acute pain has an evolutionary role in the detection of physical harm and the response to it. In some cases, however, acute pain can impair function and lead to other morbidities. Chronic pain, meanwhile, can present as a psychopathological condition that significantly interferes with daily living. Most basic and translational pain research has focused on the molecular and cellular mechanisms in the spinal and peripheral nervous systems. In contrast, the brain plays a key role in the affective manifestation and cognitive control of pain. In particular, several cortical regions, such as the somatosensory cortex, prefrontal cortex, insular, and anterior cingulate cortex, are well known to be activated by acute pain signals, and neurons in these regions have been demonstrated to undergo changes in response to chronic pain. Furthermore, these cortical regions can project to a number of forebrain and limbic structures to exert powerful top-down control of not only sensory pain transmission but also affective pain expression, and such cortical regulatory mechanisms are particularly relevant in chronic pain states. Newer techniques have emerged that allow for detailed studies of central pain circuits in animal models, as well as how such circuits are modified by the presence of chronic pain and other predisposing psychosomatic factors. These mechanistic approaches can complement imaging in human studies. At the therapeutic level, a number of pharmacological and nonpharmacological interventions have recently been shown to engage these top-down control systems to provide analgesia. In this review, we will discuss how pain signals reach important cortical regions and how these regions in turn project to subcortical areas of the brain to exert profound modulation of the pain experience. In addition, we will discuss the clinical relevance of such top-down pain regulation mechanisms.

Discordant Relationship Between Evaluation of Facial Expression and Subjective Pain Rating Due to the Low Pain Magnitude

Introduction

Facial expression to pain is an important pain indicator; however, facial movements look unresponsive when perceiving mild pain. The present study investigates whether pain magnitude modulates the relationship between subjective pain rating and an observer's evaluation of facial expression.

Methods

Twelve healthy volunteers were recruited to obtain 108 samples for pain rating with Visual Analogue Scale (VAS). Subjects underwent three different mechanical painful stimuli (monofilament forces of 100 g, 300 g, and 600 g) over three sessions and their facial expressions were videotaped throughout all sessions. Three observers independently evaluated facial expression of the subjects with a four-point categorical scale (no pain, mild pain, moderate pain, and severe pain). The correlations between subjective pain ratings and the evaluation of facial expression were analyzed in dichotomous group which was low pain ratings (VAS<30), or high pain rating (VAS≥30).

Results

Subjective pain ratings was significantly correlated with the evaluation of facial expression in high pain ratings, however no correlation was found between them in mild pain ratings. In mild pain ratings, most of the subjects (78%) were rated as no pain by observers, despite the fact that subjects reported pain.

Conclusion

The results suggest that the evaluation of facial expression of pain was difficult for the observer to detect pain severity when the subjects feel mild pain.

N-palmitoylethanolamide in the anterior cingulate cortex attenuates inflammatory pain behaviour indirectly via a CB1 receptor-mediated mechanism

The neural substrates and mechanisms mediating the antinociceptive effects of the endogenous bioactive lipid, N-palmitoylethanolamide (PEA), require further investigation. We investigated the effects of exogenous PEA administration into the anterior cingulate cortex (ACC), an important brain region linked with cognitive and affective modulation of pain, on formalin-evoked nociceptive behaviour in rats. Potential involvement of peroxisome proliferator-activated receptor isoforms (PPAR) α and γ or endocannabinoid-mediated entourage effects at cannabinoid1 (CB1) receptors or transient receptor potential subfamily V member 1 (TRPV1) in mediating the effects of PEA was also investigated. Intra-ACC administration of PEA significantly attenuated the first and early second phases of formalin-evoked nociceptive behaviour. This effect was attenuated by the CB1 receptor antagonist AM251, but not by the PPARα antagonist GW6471, the PPARγ antagonist GW9662, or the TRPV1 antagonist 5'-iodo resiniferatoxin. All antagonists, administered alone, significantly reduced formalin-evoked nociceptive behaviour, suggesting facilitatory/permissive roles for these receptors in the ACC in inflammatory pain. Post-mortem tissue analysis revealed a strong trend for increased levels of the endocannabinoid anandamide in the ACC of rats that received intra-ACC PEA. Expression of c-Fos, a marker of neuronal activity, was significantly reduced in the basolateral nucleus of the amygdala, but not in the central nucleus of the amygdala, the rostral ventromedial medulla or the dorsal horn of the spinal cord. In conclusion, these data indicate that PEA in the ACC can reduce inflammatory pain-related behaviour, possibly via AEA-induced activation of CB1 receptors and associated modulation of neuronal activity in the basolateral amygdala.

Anterior cingulate is a source of valence-specific information about value and uncertainty

Anterior cingulate cortex (ACC) is thought to control a wide range of reward, punishment, and uncertainty-related behaviors. However, how it does so is unclear. Here, in a Pavlovian procedure in which monkeys displayed a diverse repertoire of reward-related, punishment-related, and uncertainty-related behaviors, we show that many ACC-neurons represent expected value and uncertainty in a valence-specific manner, signaling value or uncertainty predictions about either rewards or punishments. Other ACC-neurons signal prediction information about rewards and punishments by displaying excitation to both (rather than excitation to one and inhibition to the other). This diversity in valence representations may support the role of ACC in many behavioral states that are either enhanced by reward and punishment (e.g., vigilance) or specific to either reward or punishment (e.g., approach and avoidance). Also, this first demonstration of punishment-uncertainty signals in the brain suggests that ACC could be a target for the treatment of uncertainty-related disorders of mood.

Rewards or punishments elicit diverse behavioral responses; however, the neural circuits underlying such flexibility are unclear. Here Monosov shows that this diversity could be supported by neurons in the anterior cingulate that represent expected value and uncertainty in a valence-specific manner.

The Difference of Neural Networks between Bimanual Antiphase and In-Phase Upper Limb Movements: A Preliminary Functional Magnetic Resonance Imaging Study

Most daily movements require some degree of collaboration between the upper limbs. The neural mechanisms are bimanual-condition specific and therefore should be different between different activities. In this study, we aimed to explore intraregional activation and interregional connectivity during bimanual movement by functional magnetic resonance imaging (fMRI). Ten right-handed, normal subjects were recruited. The neural correlates of unimanual (right side) and bimanual (in-phase and antiphase) upper limb movements were investigated. Connectivity analyses were carried out using the psychophysiological interaction (PPI) model. The cerebellum was strongly activated in both unimanual and bimanual movements, and the cingulate motor area (CMA) was the most activated brain area in antiphase bimanual movement. Moreover, compared with unimanual movement, CMA activation was also observed in antiphase bimanual movement, but not in in-phase bimanual movement. In addition, we carried out the PPI model to study the differences of effective connectivity and found that the cerebellum was more connected with the CMA during antiphase bimanual movement than in-phase bimanual movement. Our findings elucidate the differences of the cerebellar-cerebral functional connectivity between antiphase and in-phase bimanual movements, which could be used to facilitate the development of a neuroscience perspective on bimanual movement control in patients with motor impairments.

Right median nerve electrical stimulation for acute traumatic coma (the Asia Coma Electrical Stimulation trial): study protocol for a randomised controlled trial

Background

Traumatic brain injury (TBI) has become the most common cause of death and disability in persons between 15 and 30 years of age, and about 10–15% of patients affected by TBI will end up in a coma. Coma caused by TBI presents a significant challenge to neuroscientists. Right median nerve electrical stimulation has been reported as a simple, inexpensive, non-invasive technique to speed recovery and improve outcomes for traumatic comatose patients.

Methods/design

This multicentre, prospective, randomised (1:1) controlled trial aims to demonstrate the efficacy and safety of electrical right median nerve stimulation (RMNS) in both accelerating emergence from coma and promoting long-term outcomes. This trial aims to enrol 380 TBI comatose patients to partake in either an electrical stimulation group or a non-stimulation group. Patients assigned to the stimulation group will receive RMNS in addition to standard treatment at an amplitude of 15–20 mA with a pulse width of 300 μs at 40 Hz ON for 20 s and OFF for 40 s. The electrical treatment will last for 8 h per day for 2 weeks. The primary endpoint will be the percentage of patients regaining consciousness 6 months after injury. The secondary endpoints will be Extended Glasgow Outcome Scale, Coma Recovery Scale-Revised and Disability Rating Scale scores at 28 days, 3 months and 6 months after injury; Glasgow Coma Scale, Glasgow Coma Scale Motor Part and Full Outline of Unresponsiveness scale scores on day 1 and day 7 after enrolment and 28 days, 3 months and 6 months after injury; duration of unconsciousness and mechanical ventilation; length of intensive care unit and hospital stays; and incidence of adverse events.

Discussion

Right median nerve electrical stimulation has been used as a safe, inexpensive, non-invasive therapy for neuroresuscitation of coma patients for more than two decades, yet no trial has robustly proven the efficacy and safety of this treatment. The Asia Coma Electrical Stimulation (ACES) trial has the following novel features compared with other major RMNS trials: (1) the ACES trial is an Asian multicentre randomised controlled trial; (2) RMNS therapy starts at an early stage 7–14 days after the injury; and (3) various assessment scales are used to evaluate the condition of patients. We hope the ACES trial will lead to optimal use of right median nerve electrical treatment.

Trial registration

ClinicalTrials.gov, NCT02645578. Registered on 23 December 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2045-x) contains supplementary material, which is available to authorized users.

No Difference Between Noxious and Innocuous Thermal Stimulation on Motor Recovery of Upper Extremity in Patients With Acute Stroke: A Randomized Controlled Trial With 6-Month Follow-up

BACKGROUND

Thermal stimulation (TS) has been developed and incorporated into stroke rehabilitation. However, whether noxious and innocuous TS induce the same effects on motor function recovery after stroke is still unknown. A comparative study of different temperature combination regimens is needed.

OBJECTIVE

To compare the short- and long-term effectiveness between noxious and innocuous TS on motor recovery of upper extremity in patients with acute stroke.

DESIGN

Randomized, controlled trial with concealed allocation, intention-to-treat analysis and blinded outcome assessors.

SETTING

A university hospital rehabilitation department in Taiwan.

PARTICIPANTS

A total of 79 patients with acute ischemic stroke were recruited. The majority had moderate to severe motor impairment of the upper extremity (UE).

INTERVENTION

In addition to traditional rehabilitation, the experimental group (n = 39) underwent noxious TS (heat pain 46-47°C/cold pain 7-8°C), and the control group (n = 40) received innocuous TS (heat 40-41°C/cold 20-21°C). TS intervention was applied for 30 minutes once per day and for a total of 20-24 times during hospital stay. A custom-made TS instrument, comprising 2 thermal stimulators and their respective thermal pads constructed in a closed-loop system, was used.

OUTCOMES

The Fugl-Meyer upper extremity score (the primary outcome), Action Research Arm Test, Motricity Index, Barthel Index, and modified Ashworth scale (the secondary outcomes) were administered by a blinded assessor at baseline, post-12th TS, post-intervention, 1-month, and 6-month follow-ups.

RESULTS

No significant differences between groups were found on the primary outcome at postintervention and follow-up assessments. At 1-month follow-up, the innocuous group showed a small effect (partial η² = 0.02) that was greater than that of the noxious group, but that effect was eliminated at 6 months. Both groups presented significant within-group improvements over time (both P < .001).

CONCLUSIONS

Combining noxious TS with traditional rehabilitation did not yield better short-term or long-term results than combining innocuous TS with traditional rehabilitation on UE functional recovery for individuals with acute stroke.

LEVEL OF EVIDENCE

II.

High-resolution functional MRI identified distinct global intrinsic functional networks of nociceptive posterior insula and S2 regions in squirrel monkey brain

Numerous functional imaging and electrophysiological studies in humans and animals indicate that the two contiguous areas of secondary somatosensory cortex (S2) and posterior insula (pIns) are core regions in nociceptive processing and pain perception. In this study, we tested the hypothesis that the S2-pIns connection serves as a hub for connecting distinct sensory and affective nociceptive processing networks in the squirrel monkey brain. At 9.4T, we first mapped the brain regions that respond to nociceptive heat stimuli with high-resolution fMRI, and then used seed-based resting-state fMRI (rsfMRI) analysis to delineate and refine the global intrinsic functional connectivity circuits of the proximal S2 and pIns regions. In each subject, nociceptive (47.5°C) heat-evoked fMRI activations were detected in many brain regions, including primary somatosensory (S1), S2, pIns, area 7b, anterior cingulate cortex (ACC), primary motor cortex, prefrontal cortex, supplementary motor area, thalamus, and caudate. Using the heat-evoked fMRI activation foci in S2 and pIns as the seeds, voxel-wise whole-brain resting-state functional connectivity (rsFC) analysis revealed strong functional connections between contralateral S2 and pIns, as well as their corresponding regions in the ipsilateral hemisphere. Spatial similarity and overlap analysis identified each region as part of two distinct intrinsic functional networks with 7% overlap: sensory S2-S1-area 7b and affective pIns-ACC-PCC networks. Moreover, a high degree of overlap was observed between the combined rsFC maps of nociceptive S2 and pIns regions and the nociceptive heat-evoked activation map. In summary, our study provides evidence for the existence of two distinct intrinsic functional networks for S2 and pIns nociceptive regions, and these two networks are joined via the S2-pIns connection. Brain regions that are involved in processing nociceptive inputs are also highly interconnected at rest. The presence of robust and distinct S1-S2-area 7b and pIns-ACC-PCC rsFC networks under anesthesia underscores their fundamental roles in processing nociceptive information.

Pain and motor processing in the human cerebellum

Pain-related adaptations in movement require a network architecture that allows for integration across pain and motor circuits. Previous studies addressing this issue have focused on cortical areas such as the midcingulate cortex. Here, we focus on pain and motor processing in the human cerebellum. The goal of this study was to identify areas of activation in the cerebellum, which are common to pain and motor processing, and to determine whether the activation is limited to the superior and inferior cerebellar motor maps or extends into multimodal areas of the posterior cerebellum. Our observations identified overlapping activity in left and right lobules VI and VIIb during pain and motor processing. Activation in these multimodal regions persisted when pain and motor processes were combined within the same trial, and activation in contralateral left lobule VIIb persisted when stimulation was controlled for. Functional connectivity analyses revealed significant correlations in the BOLD time series between multimodal cerebellar regions and sensorimotor regions in the cerebrum including anterior midcingulate cortex, supplementary motor area, and thalamus. The current findings are the first to show multimodal processing in lobules VI and VIIb for motor control and pain processing and suggest that the posterior cerebellum may be important in understanding pain-related adaptations in motor control.

IMAGING OF BRAIN FUNCTION BASED ON THE ANALYSIS OF FUNCTIONAL CONNECTIVITY - IMAGING ANALYSIS OF BRAIN FUNCTION BY FMRI AFTER ACUPUNCTURE AT LR3 IN HEALTHY INDIVIDUALS

Objective:

This Study observed the relevant brain areas activated by acupuncture at the Taichong acupoint (LR3) and analyzed the functional connectivity among brain areas using resting state functional magnetic resonance imaging (fMRI) to explore the acupoint specificity of the Taichong acupoint.

Methods:

A total of 45 healthy subjects were randomly divided into the Taichong (LR3) group, sham acupuncture group and sham acupoint group. Subjects received resting state fMRI before acupuncture, after true (sham) acupuncture in each group. Analysis of changes in connectivity among the brain areas was performed using the brain functional connectivity method.

Results:

The right cerebrum temporal lobe was selected as the seed point to analyze the functional connectivity. It had a functional connectivity with right cerebrum superior frontal gyrus, limbic lobe cingulate gyrus and left cerebrum inferior temporal gyrus (BA 37), inferior parietal lobule compared by before vs. after acupuncture at LR3, and right cerebrum sub-lobar insula and left cerebrum middle frontal gyrus, medial frontal gyrus compared by true vs. sham acupuncture at LR3, and right cerebrum occipital lobe cuneus, occipital lobe sub-gyral, parietal lobe precuneus and left cerebellum anterior lobe culmen by acupuncture at LR3 vs. sham acupoint.

Conclusion:

Acupuncture at LR3 mainly specifically activated the brain functional network that participates in visual function, associative function, and emotion cognition, which are similar to the features on LR3 in tradition Chinese medicine. These brain areas constituted a neural network structure with specific functions that had specific reference values for the interpretation of the acupoint specificity of the Taichong acupoint.

Acupuncture Decreases Blood Pressure Related to Hypothalamus Functional Connectivity with Frontal Lobe, Cerebellum, and Insula: A Study of Instantaneous and Short-Term Acupuncture Treatment in Essential Hypertension

The therapeutic effects of acupuncture in decreasing blood pressure are ambiguous and underlying acupuncture in hypertension treatment has not been investigated. Our objective was to observe the change of quality of life and compare the differences in brain functional connectivity by investigating instantaneous and short-term acupuncture treatment in essential hypertension patients. A total of 30 patients were randomly divided into the LR3 group and sham acupoint group. Subjects received resting-state fMRI among preacupuncture, postinstantaneous, and short-term acupuncture treatment in two groups. Hypothalamus was selected as the seed point to analyze the changes in connectivity. We found three kinds of results: (1) There was statistical difference in systolic blood pressure in LR3 group after the short-term treatment and before acupuncture. (2) Compared with sham acupoint, acupuncture at LR3 instantaneous effects in the functional connectivity with seed points was more concentrated in the frontal lobe. (3) Compared with instantaneous effects, acupuncture LR3 short-term effects in the functional connectivity with seed points had more regions in frontal lobe, cerebellum, and insula. These brain areas constituted a neural network structure with specific functions that could explain the mechanism of therapy in hypertension patients by LR3 acupoint.

In vivo correlates of thermoregulatory defense in humans: Temporal course of sub-cortical and cortical responses assessed with fMRI

Extensive studies in rodents have established the role of neural pathways that are activated during thermoregulation. However, few studies have been conducted in humans to assess the complex, hierarchically organized thermoregulatory network in the CNS that maintains thermal homeostasis, especially as it pertains to cold exposure. To study the human thermoregulatory network during whole body cold exposure, we have used functional MRI to characterize changes in the BOLD signal within the constituents of the thermoregulatory network in 20 young adult controls during non-noxious cooling and rewarming of the skin by a water-perfused body suit. Our results indicate significant decreases of BOLD signal during innocuous whole body cooling stimuli in the midbrain, the right anterior insula, the right anterior cingulate, and the right inferior parietal lobe. Whereas brain activation in these areas decreased during cold exposure, brain activation increased significantly in the bilateral orbitofrontal cortex during this period. The BOLD signal time series derived from significant activation sites in the orbitofrontal cortex showed opposed phase to those observed in the other brain regions, suggesting complementary processing mechanisms during mild hypothermia. The significance of our findings lies in the recognition that whole body cooling evokes a response in a hierarchically organized thermoregulatory network that distinguishes between cold and warm stimuli. This network seems to generate a highly resolved interoceptive representation of the body's condition that provides input to the orbitofrontal cortex, where higher-order integration takes place and invests internal states with emotional significance that motivate behavior. Hum Brain Mapp 37:3188-3202, 2016. © 2016 Wiley Periodicals, Inc.

Higher pain rating results in lower variability of somatosensory cortex activation by painful mechanical stimuli: An fMRI study

OBJECTIVE

The aim of this study was to find pain-related brain activity which corresponds to self-report pain ratings based on degree of response and repeatability.

METHODS

Three painful mechanical stimuli were applied to the right hands of 25 healthy volunteers using monofilaments (forces of 0.98N, 2.94N, and 5.88N). Simultaneously, brain activities were evaluated using functional MRI for a constant stimulus conducted three times in a session. In first assessment, the average percent signal change (PSC) of neuronal response was measured for each region of interest (ROI), secondary repeatability of PSC conducted three times over the session was evaluated for each ROI.

RESULTS

Although the average PSCs for trice stimuli conducted in one session increased in accordance with pain ratings in the somatosensory cortex (S1) and anterior cingulate cortex (ACC), there was a different response between S1 and ACC when subjects rated intense pain; a stable response in S1 against a variable response in ACC.

CONCLUSIONS

These results imply that there are different cognitive responses between sensory discrimination and affective component to constant painful stimulus each time.

SIGNIFICANCE

Consistency of brain activity based on PSC may be an important biomarker which, along with its neuronal activity, gauges self-report pain ratings.

Music reduces pain and increases resting state fMRI BOLD signal amplitude in the left angular gyrus in fibromyalgia patients

Music reduces pain in fibromyalgia (FM), a chronic pain disease, but the functional neural correlates of music-induced analgesia (MIA) are still largely unknown. We recruited FM patients (n = 22) who listened to their preferred relaxing music and an auditory control (pink noise) for 5 min without external noise from fMRI image acquisition. Resting state fMRI was then acquired before and after the music and control conditions. A significant increase in the amplitude of low frequency fluctuations of the BOLD signal was evident in the left angular gyrus (lAnG) after listening to music, which in turn, correlated to the analgesia reports. The post-hoc seed-based functional connectivity analysis of the lAnG showed found higher connectivity after listening to music with right dorsolateral prefrontal cortex (rdlPFC), the left caudate (lCau), and decreased connectivity with right anterior cingulate cortex (rACC), right supplementary motor area (rSMA), precuneus and right precentral gyrus (rPreG). Pain intensity (PI) analgesia was correlated (r = 0.61) to the connectivity of the lAnG with the rPreG. Our results show that MIA in FM is related to top-down regulation of the pain modulatory network by the default mode network (DMN).

Brain Network Response to Acupuncture Stimuli in Experimental Acute Low Back Pain: An fMRI Study

Most neuroimaging studies have demonstrated that acupuncture can significantly modulate brain activation patterns in healthy subjects, while only a few studies have examined clinical pain. In the current study, we combined an experimental acute low back pain (ALBP) model and functional magnetic resonance imaging (fMRI) to explore the neural mechanisms of acupuncture analgesia. All ALBP subjects first underwent two resting state fMRI scans at baseline and during a painful episode and then underwent two additional fMRI scans, once during acupuncture stimulation (ACUP) and once during tactile stimulation (SHAM) pseudorandomly, at the BL40 acupoint. Our results showed that, compared with the baseline, the pain state had higher regional homogeneity (ReHo) values in the pain matrix, limbic system, and default mode network (DMN) and lower ReHo values in frontal gyrus and temporal gyrus; compared with the OFF status, ACUP yielded broad deactivation in subjects, including nearly all of the limbic system, pain status, and DMN, and also evoked numerous activations in the attentional and somatosensory systems; compared with SHAM, we found that ACUP induced more deactivations and fewer activations in the subjects. Multiple brain networks play crucial roles in acupuncture analgesia, suggesting that ACUP exceeds a somatosensory-guided mind-body therapy for ALBP.

Polymorphism in the µ-opioid receptor gene (OPRM1) modulates neural processing of physical pain, social rejection and error processing

Variations of the µ-opioid receptor gene OPRM1 have been shown to modulate pain perception with some evidence pointing towards a modulation of not only physical but also "psychological pain". In line with suggestions of a common neural network involved in the processing of physical pain and negative and distressing stimuli, like social rejection as a psychologically harmful event, we examined the influence of the A118G polymorphism on the neural processing of physical and non-physical pain. Using fMRI, we investigated a sample of 23 females with the more frequent AA genotype, and eight females with the relatively rare but more pain-sensitive AG genotype during electrical stimulation to the dorsum of the non-dominant hand. Non-physical pain was investigated using Cyberball, a virtual ball-tossing game, to induce experiences of non-self-dependent social rejection. A Go/NoGo task with an increased risk of self-dependent erroneous performance was used as a control task to investigate the effects of negative feedback as a more cognitive form of distress. Relative to A118G homozygous A-allele carriers, G-allele carriers showed significantly increased activation of the supplementary motor area/superior frontal gyrus and the precentral gyrus during electrical stimulation. Increased activation of the secondary sensorimotor cortex (SII) was found during social exclusion and during negative feedback. We demonstrate that brain regions particularly related to the somatosensory component of pain processing are modulated by variations in OPRM1. Influences were evident for both physical and psychological pain processing supporting the assumption of shared neural pathways.

Right Median Nerve Electrical Stimulation for Acute Traumatic Coma Patients

The right median nerve as a peripheral portal to the central nervous system can be electrically stimulated to help coma arousal after traumatic brain injury (TBI). The present study set out to examine the efficacy and safety of right median nerve electrical stimulation (RMNS) in a cohort of 437 comatose patients after severe TBI from August 2005 to December 2011. The patients were enrolled 2 weeks after their injury and assigned to the RMNS group (n=221) receiving electrical stimulation for 2 weeks or the control group (n = 216) treated by standard management according to the date of birth in the month. The baseline data were similar. After the 2-week treatment, the RMNS-treated patients demonstrated a more rapid increase of the mean Glasgow Coma Score, although statistical significance was not reached (8.43 ± 4.98 vs. 7.47 ± 5.37, p = 0.0532). The follow-up data at 6-month post-injury showed a significantly higher proportion of patients who regained consciousness (59.8% vs. 46.2%, p = 0.0073). There was a lower proportion of vegetative persons in the RMNS group than in the control group (17.6% vs. 22.0%, p = 0.0012). For persons regaining consciousness, the functional independence measurement (FIM) score was higher among the RMNS group patients (91.45 ± 8.65 vs. 76.23 ± 11.02, p < 0.001). There were no unique complications associated with the RMNS treatment. The current study, although with some limitations, showed that RMNS may serve as an easy, effective, and noninvasive technique to promote the recovery of traumatic coma in the early phase.