The medial pain system, cingulate cortex, and parallel processing of nociceptive information

Can EEG-Neurofeedback Training Enhance Effective Connectivity in People With Chronic Secondary Musculoskeletal Pain? A Secondary Analysis of a Feasibility Randomized Controlled Clinical Trial

INTRODUCTION

Persistent musculoskeletal pain is associated with altered functional and effective connectivity (EC) between cortical regions involved in pain processing. Especially, disruptions in the infraslow fluctuation (ISF) frequency band can contribute to pain persistence. ISF electroencephalography-neurofeedback (EEG-NF) has emerged as a potential non-invasive neuromodulatory intervention targeting cortical brain regions to restore balance and modulate pain-related pathways. However, limited research explores its effect on EC, a measure of directional information flow critical to pain experience and modulation.

METHODS

A secondary analysis was performed using data from a randomized, double-blind, sham-controlled feasibility clinical trial. Participants with chronic painful knee osteoarthritis (OA) were randomized to receive either ISF-NF or sham-NF. Nine neurofeedback sessions targeted the pregenual anterior cingulate cortex (pgACC), dorsal anterior cingulate cortex (dACC), and bilateral primary somatosensory cortex (SSC: S1Lt & S1Rt). EEG data was collected at baseline and post-intervention. Granger causality was used to measure EC changes, and between-group statistical analyses were conducted with adjustments for multiple comparisons.

RESULTS

Twenty-one participants (mean age: 61.7 ± 7.6 years; 62% female) completed the study. ISF-NF training significantly improved EC between pgACC and dACC, pgACC and SSC, and other targeted regions, while reducing EC from S1Rt to dACC. Changes were observed predominantly in the ISF frequency band, indicating enhanced cortical communication and modulation of pain pathways.

CONCLUSION

ISF-NF training enhanced EC in cortical regions implicated in pain processing, supporting its potential as a neuromodulatory intervention for chronic musculoskeletal pain. Further trials are needed to confirm clinical efficacy and optimize protocol designs.

Closed-Loop Infraslow Brain-Computer Interface can Modulate Cortical Activity and Connectivity in Individuals With Chronic Painful Knee Osteoarthritis: A Secondary Analysis of a Randomized Placebo-Controlled Clinical Trial

Introduction. Chronic pain is a percept due to an imbalance in the activity between sensory-discriminative, motivational-affective, and descending pain-inhibitory brain regions. Evidence suggests that electroencephalography (EEG) infraslow fluctuation neurofeedback (ISF-NF) training can improve clinical outcomes. It is unknown whether such training can induce EEG activity and functional connectivity (FC) changes. A secondary data analysis of a feasibility clinical trial was conducted to determine whether EEG ISF-NF training can significantly alter EEG activity and FC between the targeted cortical regions in people with chronic painful knee osteoarthritis (OA). Methods. A parallel, two-arm, double-blind, randomized, sham-controlled clinical trial was conducted. People with chronic knee pain associated with OA were randomized to receive sham NF training or source-localized ratio ISF-NF training protocol to down-train ISF bands at the somatosensory (SSC), dorsal anterior cingulate (dACC), and uptrain pregenual anterior cingulate cortices (pgACC). Resting state EEG was recorded at baseline and immediate post-training. Results. The source localization mapping demonstrated a reduction (P = .04) in the ISF band activity at the left dorsolateral prefrontal cortex (LdlPFC) in the active NF group. Region of interest analysis yielded significant differences for ISF (P = .008), slow (P = .007), beta (P = .043), and gamma (P = .012) band activities at LdlPFC, dACC, and bilateral SSC. The FC between pgACC and left SSC in the delta band was negatively correlated with pain bothersomeness in the ISF-NF group. Conclusion. The EEG ISF-NF training can modulate EEG activity and connectivity in individuals with chronic painful knee osteoarthritis, and the observed EEG changes correlate with clinical pain measures.

Local Field Potential Biomarkers of Non-Motor Symptoms in Parkinson's Disease: Insights From the Subthalamic Nucleus in Deep Brain Stimulation

Non-motor symptoms can severely affect the quality of life of Parkinson's disease-afflicted patients, with the most common ones being pain, sleep impairments, and neuropsychiatric manifestations. In advanced cases, complex fluctuations of motor and non-motor symptoms can occur despite optimal medication. Research on deep brain stimulation of the subthalamic nucleus suggests that it may provide benefits for treating non-motor symptoms in addition to improving motor symptoms. With recent advancements in deep brain stimulation technology, simultaneous recording of local field potentials and delivery of therapeutic stimulation is possible. This opens new possibilities for better understanding the pathophysiology of non-motor symptoms in Parkinson's disease and for identifying potential electrophysiological biomarkers that accurately represent these symptoms. Specifically, this review aims to highlight potential local field potential biomarkers of non-motor symptoms in the subthalamic nucleus. The main findings indicate that activities in the beta frequency band are associated with nociception and sleep impairments such as insomnia and rapid eye movement sleep behavior disorders. Additionally, activities in the theta and alpha frequency bands seem to reflect neurocognitive manifestations, including depression and impulse control disorders. A better understanding of these biomarkers could improve the clinical management of non-motor symptoms in Parkinson's disease. They hold promise for adjusting deep brain stimulation parameters in open-loop settings and might eventually be applied in closed-loop deep brain stimulation systems, though their true impact remains uncertain.

The altered resting-state functional connectivity of thalamic subregions in patients with globus pharyngeus

Globus Pharyngeus (GP) is a somatic symptom that accompanies mood distress. Although the etiology of GP remains unclear, its specific symptom of a false lump sensation in the throat without physical obstruction raises the possibility of alterations in brain networks responsible for somatosensory and emotion processing in patients with GP. To address this possibility, we investigated resting-state functional connectivity (rsFC) in 31 patients with GP and 24 healthy individuals using resting-state functional magnetic resonance imaging. Considering its significance in somatosensory and emotional functions, we focused on rsFC in the subregions of the thalamus. We found significantly decreased rsFC between the right caudal temporal thalamus (rcTtha) and the midcingulate cortex (MCC) as well as significantly decreased rsFC between the right rostral temporal thalamus (rrTtha) and the left cerebellum in the patients with GP. Additionally, within the patient group, the abnormalities in rsFC between the rcTtha and the MCC were correlated with the severity of somatization symptoms but not with depression and anxiety. These findings suggest alterations in the rsFC of thalamic subregions in patients with GP, shedding light on the pathogenesis of GP and potentially leading to improved diagnosis and treatment approaches for the condition.

Enhanced long-term potentiation in the anterior cingulate cortex of tree shrew

Synaptic plasticity is a key cellular model for learning, memory and chronic pain. Most previous studies were carried out in rats and mice, and less is known about synaptic plasticity in non-human primates. In the present study, we used integrative experimental approaches to study long-term potentiation (LTP) in the anterior cingulate cortex (ACC) of adult tree shrews. We found that glutamate is the major excitatory transmitter and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionicacid (AMPA) receptors mediate postsynaptic responses. LTP in tree shrews was greater than that in adult mice and lasted for at least 5 h. N-methyl-d-aspartic acid (NMDA) receptors, Ca2+ influx and adenylyl cyclase 1 (AC1) contributed to tree shrew LTP. Our results suggest that LTP is a major form of synaptic plasticity in the ACC of primate-like animals. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

EEG-Based Cortical Alterations in Individuals With Chronic Knee Pain Secondary to Osteoarthritis: A Cross-sectional Investigation

Chronic painful knee osteoarthritis (OA) is a disabling physical health condition. Alterations in brain responses to arthritic changes in the knee may explain persistent pain. This study investigated source localized, resting-state electroencephalography activity and functional connectivity in people with knee OA, compared to healthy controls. Adults aged 44 to 85 years with knee OA (n = 37) and healthy control (n = 39) were recruited. Resting-state electroencephalography was collected for 10 minutes and decomposed into infraslow frequency (ISF) to gamma frequency bands. Standard low-resolution electromagnetic brain tomography statistical nonparametric maps were conducted, current densities of regions of interest were compared between groups and correlation analyses were performed between electroencephalography (EEG) measures and clinical pain and functional outcomes in the knee OA group. Standard low-resolution electromagnetic brain tomography nonparametric maps revealed higher (P = .006) gamma band activity over the right insula (RIns) in the knee OA group. A significant (P < .0001) reduction in ISF band activity at the pregenual anterior cingulate cortex, whereas higher theta, alpha, beta, and gamma band activity at the dorsal anterior cingulate cortex, pregenual anterior cingulate cortex, the somatosensory cortex, and RIns in the knee OA group were identified. ISF activity of the dorsal anterior cingulate cortex was positively correlated with pain measures and psychological distress scores. Theta and alpha activity of RIns were negatively correlated with pain interference. In conclusion, aberrations in infraslow and faster frequency EEG oscillations at sensory discriminative, motivational-affective, and descending inhibitory cortical regions were demonstrated in people with chronic painful knee OA. Moreover, EEG oscillations were correlated with pain and functional outcome measures. PERSPECTIVE: This study confirms alterations in the rsEEG oscillations and its relationship with pain experience in people with knee OA. The study provides potential cortical targets and the EEG frequency bands for neuromodulatory interventions for managing chronic pain experience in knee OA.

Transcranial magnetic stimulation therapy for central post-stroke pain: systematic review and meta-analysis

Introduction

Although rare, central post-stroke pain remains one of the most refractory forms of neuropathic pain. It has been reported that repetitive transcranial magnetic stimulation (rTMS) may be effective in these cases of pain.

Aim

The aim of this study was to investigate the efficacy of rTMS in patients with central post-stroke pain (CPSP).

Methods

We included randomized controlled trials or Controlled Trials published until October 3rd, 2022, which studied the effect of rTMS compared to placebo in CPSP. We included studies of adult patients (>18 years) with a clinical diagnosis of stroke, in which the intervention consisted of the application of rTMS to treat CSP.

Results

Nine studies were included in the qualitative analysis; 6 studies (4 RCT and 2 non-RCT), with 180 participants, were included in the quantitative analysis. A significant reduction in CPSP was found in favor of rTMS compared with sham, with a large effect size (SMD: -1.45; 95% CI: -1.87; -1.03; p < 0.001; I2: 58%).

Conclusion

The findings of the present systematic review with meta-analysis suggest that there is low quality evidence for the effectiveness of rTMS in reducing CPSP.

Systematic review registration

Identifier (CRD42022365655).

Perspectives on pain in Down syndrome

Down syndrome (DS) or trisomy 21 is a genetic condition often accompanied by chronic pain caused by congenital abnormalities and/or conditions, such as osteoarthritis, recurrent infections, and leukemia. Although DS patients are more susceptible to chronic pain as compared to the general population, the pain experience in these individuals may vary, attributed to the heterogenous structural and functional differences in the central nervous system, which might result in abnormal pain sensory information transduction, transmission, modulation, and perception. We tried to elaborate on some key questions and possible explanations in this review. Further clarification of the mechanisms underlying such abnormal conditions induced by the structural and functional differences is needed to help pain management in DS patients.

Network targets for therapeutic brain stimulation: towards personalized therapy for pain

Precision neuromodulation of central brain circuits is a promising emerging therapeutic modality for a variety of neuropsychiatric disorders. Reliably identifying in whom, where, and in what context to provide brain stimulation for optimal pain relief are fundamental challenges limiting the widespread implementation of central neuromodulation treatments for chronic pain. Current approaches to brain stimulation target empirically derived regions of interest to the disorder or targets with strong connections to these regions. However, complex, multidimensional experiences like chronic pain are more closely linked to patterns of coordinated activity across distributed large-scale functional networks. Recent advances in precision network neuroscience indicate that these networks are highly variable in their neuroanatomical organization across individuals. Here we review accumulating evidence that variable central representations of pain will likely pose a major barrier to implementation of population-derived analgesic brain stimulation targets. We propose network-level estimates as a more valid, robust, and reliable way to stratify personalized candidate regions. Finally, we review key background, methods, and implications for developing network topology-informed brain stimulation targets for chronic pain.

Emotion, motivation, decision-making, the orbitofrontal cortex, anterior cingulate cortex, and the amygdala

The orbitofrontal cortex and amygdala are involved in emotion and in motivation, but the relationship between these functions performed by these brain structures is not clear. To address this, a unified theory of emotion and motivation is described in which motivational states are states in which instrumental goal-directed actions are performed to obtain rewards or avoid punishers, and emotional states are states that are elicited when the reward or punisher is or is not received. This greatly simplifies our understanding of emotion and motivation, for the same set of genes and associated brain systems can define the primary or unlearned rewards and punishers such as sweet taste or pain. Recent evidence on the connectivity of human brain systems involved in emotion and motivation indicates that the orbitofrontal cortex is involved in reward value and experienced emotion with outputs to cortical regions including those involved in language, and is a key brain region involved in depression and the associated changes in motivation. The amygdala has weak effective connectivity back to the cortex in humans, and is implicated in brainstem-mediated responses to stimuli such as freezing and autonomic activity, rather than in declarative emotion. The anterior cingulate cortex is involved in learning actions to obtain rewards, and with the orbitofrontal cortex and ventromedial prefrontal cortex in providing the goals for navigation and in reward-related effects on memory consolidation mediated partly via the cholinergic system.

Interhemispheric neural characteristics of noxious mechano-nociceptive stimulation in the anterior cingulate cortex

Background

Pain is an unpleasant sensory and emotional experience. One of the most critical regions of the brain for pain processing is the anterior cingulate cortex (ACC). Several studies have examined the role of this region in thermal nociceptive pain. However, studies on mechanical nociceptive pain have been very limited to date. Although several studies have investigated pain, the interactions between the two hemispheres are still not clear. This study aimed to investigate nociceptive mechanical pain in the ACC bilaterally.

Methods

Local field potential (LFP) signals were recorded from seven male Wistar rats' ACC regions of both hemispheres. Mechanical stimulations with two intensities, high-intensity noxious (HN) and non-noxious (NN) were applied to the left hind paw. At the same time, the LFP signals were recorded bilaterally from awake and freely moving rats. The recorded signals were analyzed from different perspectives, including spectral analysis, intensity classification, evoked potential (EP) analysis, and synchrony and similarity of two hemispheres.

Results

By using spectro-temporal features and support vector machine (SVM) classifier, HN vs. no-stimulation (NS), NN vs. NS, and HN vs. NN were classified with accuracies of 89.6, 71.1, and 84.7%, respectively. Analyses of the signals from the two hemispheres showed that the EPs in the two hemispheres were very similar and occurred simultaneously; however, the correlation and phase locking value (PLV) between the two hemispheres changed significantly after HN stimulation. These variations persisted for up to 4 s after the stimulation. In contrast, variations in the PLV and correlation for NN stimulation were not significant.

Conclusions

This study showed that the ACC area was able to distinguish the intensity of mechanical stimulation based on the power activities of neural responses. In addition, our results suggest that the ACC region is activated bilaterally due to nociceptive mechanical pain. Additionally, stimulations above the pain threshold (HN) significantly affect the synchronicity and correlation between the two hemispheres compared to non-noxious stimuli.

Temporal pain processing in the primary somatosensory cortex and anterior cingulate cortex

Pain is known to have sensory and affective components. The sensory pain component is encoded by neurons in the primary somatosensory cortex (S1), whereas the emotional or affective pain experience is in large part processed by neural activities in the anterior cingulate cortex (ACC). The timing of how a mechanical or thermal noxious stimulus triggers activation of peripheral pain fibers is well-known. However, the temporal processing of nociceptive inputs in the cortex remains little studied. Here, we took two approaches to examine how nociceptive inputs are processed by the S1 and ACC. We simultaneously recorded local field potentials in both regions, during the application of a brain-computer interface (BCI). First, we compared event related potentials in the S1 and ACC. Next, we used an algorithmic pain decoder enabled by machine-learning to detect the onset of pain which was used during the implementation of the BCI to automatically treat pain. We found that whereas mechanical pain triggered neural activity changes first in the S1, the S1 and ACC processed thermal pain with a reasonably similar time course. These results indicate that the temporal processing of nociceptive information in different regions of the cortex is likely important for the overall pain experience.

Source localized infraslow neurofeedback training in people with chronic painful knee osteoarthritis: A randomized, double-blind, sham-controlled feasibility clinical trial

Persistent pain is a key symptom in people living with knee osteoarthritis (KOA). Infra-slow Neurofeedback (ISF-NF) training is a recent development focusing on modulating cortical slow-wave activity to improve pain outcomes. A parallel, two-armed double-blinded, randomized sham-controlled, feasibility clinical trial aimed to determine the feasibility and safety of a novel electroencephalography-based infraslow fluctuation neurofeedback (EEG ISF-NF) training in people with KOA and determine the variability of clinical outcomes and EEG changes following NF training. Eligible participants attended nine 30-min ISF-NF training sessions involving three cortical regions linked to pain. Feasibility measures were monitored during the trial period. Pain and functional outcomes were measured at baseline, post-intervention, and follow-up after 2 weeks. Resting-state EEG was recorded at baseline and immediate post-intervention. Participants were middle-aged (61.7 ± 7.6 years), New Zealand European (90.5%), and mostly females (62%) with an average knee pain duration of 4 ± 3.4 years. The study achieved a retention rate of 91%, with 20/22 participants completing all the sessions. Participants rated high levels of acceptance and “moderate to high levels of perceived effectiveness of the training.” No serious adverse events were reported during the trial. Mean difference (95% CI) for clinical pain and function measures are as follows for pain severity [active: 0.89 ± 1.7 (−0.27 to 2.0); sham: 0.98 ± 1.1 (0.22–1.7)], pain interference [active: 0.75 ± 2.3 (−0.82 to 2.3); Sham: 0.89 ± 2.1 (−0.60 to 2.4)], pain unpleasantness [active: 2.6 ± 3.7 (0.17–5.1); sham: 2.8 ± 3 (0.62–5.0)] and physical function [active: 6.2 ± 13 (−2.6 to 15); sham: 1.6 ± 12 (−6.8 to 10)]. EEG sources demonstrated frequency-specific neuronal activity, functional connectivity, and ISF ratio changes following NF training. The findings of the study indicated that the ISF-NF training is a feasible, safe, and acceptable intervention for pain management in people with KOA, with high levels of perceived effectiveness. The study also reports the variability in clinical, brain activity, and connectivity changes following training.

Pain modalities in the body and brain: Current knowledge and future perspectives

Development and validation of pain biomarkers has become a major issue in pain research. Recent advances in multimodal data acquisition have allowed researchers to gather multivariate and multilevel whole-body measurements in patients with pain conditions, and data analysis techniques such as machine learning have led to novel findings in neural biomarkers for pain. Most studies have focused on the development of a biomarker to predict the severity of pain with high precision and high specificity, however, a similar approach to discriminate different modalities of pain is lacking. Identification of more accurate and specific pain biomarkers will require an in-depth understanding of the modality specificity of pain. In this review, we summarize early and recent findings on the modality specificity of pain in the brain, with a focus on distinct neural activity patterns between chronic clinical and acute experimental pain, direct, social, and vicarious pain, and somatic and visceral pain. We also suggest future directions to improve our current strategy of pain management using our knowledge of modality-specific aspects of pain.

Pain-induced Impact on Movement: Motor Coordination Variability and Accuracy-based Skill

INTRODUCTION

Studies on pain are generally conducted for two purposes: first, to study patients with pain who have physical changes due to nerve and muscle lesions, and second, to regain the appropriate kinematic post-pain pattern. The present study aimed to investigate the effect of pain on the coordination variability pattern and throwing accuracy.

METHODS

The study participants included 30 people aged 18-25 years who volunteered to participate in the study. Participants practiced and acquired skills in 10 blocks of 15 trials. In the test phase associated with pain, Individuals were randomly divided into three groups: local pain, remote pain, and control. In their respective groups, participants were tested in a 15-block trial, 24 hours, and 1 week after acquisition.

RESULTS

The results revealed that pain did not affect the throwing accuracy (P=0.456). Besides, in the phase of acceleration in throwing, movement variability in the pain-related groups in the shoulder and elbow joints (P=0.518), elbow and wrist (P=0.399), and the deceleration and dart drop phase movement variability in the pain-related groups in the shoulder and elbow joints (P=0.622), elbow and wrist (P=0.534).

CONCLUSION

Based on the results, the accuracy and coordination variability in pain-related groups were similar. However, to confirm these results, more research is needed on performing motor functions in the presence of pain.

HIGHLIGHTS

Pain are generally conducted for two purposes.pain which has physical changes due to nerve and muscle lesions and pain to regain the appropriate kinematic post-pain pattern.People who experience pain show poor motor results.Pain restriction is ordinary in joints and the body compensates by increasing movement.

PLAIN LANGUAGE SUMMARY

One of the constant concerns of sports science experts is to find ways to improve performance or to know the factors that strengthen or weaken motor learning. After injury, pain has been described as one of the passive symptoms, and the mechanism of how overexertion of joints and muscles increases injury and pain is unknown. Following any injury, pain is one of the most important causes of disability and one of the most important problems in people's general health. Many treated individuals present with pain and impaired movement, and typically changes in movement control are a result of the pain. Research evidence suggests that pain induces changes in cortical excitability and the neuroplasticity model that accompanies practice of a new motor task interferes with the performance improvement that must occur simultaneously. According to the new approaches of motor and biomechanical learning and control, movement variability, especially in movement coordination, is considered as an important and influential factor of a person with different conditions. Novice athletes show high non-functional variability in order to reduce the degrees of freedom and then simplify their motor task, in contrast to skilled people, they display functional variability that allows them to perform a motor task better. in variable conditions. Scientists and researchers have concluded that in the presence of pain, there are changes in the pattern requirements and muscle coordination. Clearly, variability is a main feature of most neurological and musculoskeletal pains, and it is necessary for therapists to diagnose and classify incomplete movements and to effectively manage symptoms by controlling incomplete movements, so conducting such research in this field in order to show muscle and movement changes It is necessary under the influence of pain.

Empathy at birth: Mother's cortex synchronizes with that of her newborn in pain

Early neonatal relation with the caregiver is vital for newborn survival and for the promotion of an appropriate neural development. The aim of this study was to assess if the empathic cortical response of a mother to her baby's pain is synchronized with the neonatal cortical response to the painful stimulation. We used hyperscanning, a functional neuroimaging approach that allows studying functional synchronization between two brains. Sixteen mother-newborn dyads were recruited. Maternal and neonatal cortical activities were simultaneously monitored, by near-infrared spectroscopy, during a heel prick performed on the baby and observed by the mother. Multiple paired t test was used to identify cortical activation, and wavelet transform coherence method was used to explore possible synchronization between the maternal and neonatal cortical areas. Activations were observed in mother's parietal cortex, bilaterally, and in newborn's superior motor/somatosensory cortex. The main functional synchronization analysis showed that mother's left parietal cortex activity cross-correlated with that of her newborn's superior motor/somatosensory cortex. Such synchronization dynamically changed throughout assessment, becoming positively cross-correlated only after the leading role in synchronizing cortical activities was taken up by the newborn. Thus, maternal empathic cortical response to baby pain was guided by and synchronized to the newborn's cortical response to pain. We conclude that, in case of potential danger for the infant, brain areas involved in mother-newborn relationship appear to be already co-regulated at birth.

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.

A Narrative Review of Neuroimaging Studies in Acupuncture for Migraine

Acupuncture has been widely used as an alternative and complementary therapy for migraine. With the development of neuroimaging techniques, the central mechanism of acupuncture for migraine has gained increasing attention. This review aimed to analyze the study design and main findings of neuroimaging studies of acupuncture for migraine to provide the reference for future research. The original studies were collected and screened in three English databases (PubMed, Embase, and Cochrane Library) and four Chinese databases (Chinese National Knowledge Infrastructure, Chinese Biomedical Literature database, the Chongqing VIP database, and Wanfang database). As a result, a total of 28 articles were included. Functional magnetic resonance imaging was the most used neuroimaging technique to explore the cerebral activities of acupuncture for migraine. This review manifested that acupuncture could elicit cerebral responses on patients with migraine, different from sham acupuncture. The results indicated that the pain systems, including the medial pain pathway, lateral pain pathway, and descending pain modulatory system, participated in the modulation of the cerebral activities of migraine by acupuncture.

Methamphetamine and Modulation Functionality of the Prelimbic Cortex for Developing a Possible Treatment of Alzheimer's Disease in an Animal Model

Alzheimer’s disease (AD) is a progressive neurodegenerative condition that causes cognitive impairment and other neuropsychiatric symptoms. Previously, little research has thus far investigated whether methamphetamine (MAMPH) can enhance cognitive function or ameliorate AD symptoms. This study examined whether a low dose of MAMPH can induce conditioned taste aversion (CTA) learning, or can increase plasma corticosterone levels, neural activity, and neural plasticity in the medial prefrontal cortex (mPFC) (responsible for cognitive function), the nucleus accumbens (NAc) and the amygdala (related to rewarding and aversive emotion), and the hippocampus (responsible for spatial learning). Furthermore, the excitations or lesions of the prelimbic cortex (PrL) can affect MAMPH-induced CTA learning, plasma corticosterone levels, and neural activity or plasticity in the mPFC [i.e., PrL, infralimbic cortex (IL), cingulate cortex 1 (Cg1)], the NAc, the amygdala [i.e., basolateral amygdala (BLA) and central amygdala (CeA)], and the hippocampus [i.e., CA1, CA2, CA3, and dentate gyrus (DG)]. In the experimental procedure, the rats were administered either saline or NMDA solutions, which were injected into the PrL to excite or destroy PrL neurons. Additionally, rats received 0.1% saccharin solution for 15 min, followed by intraperitoneal injections of either normal saline or 1 mg/kg MAMPH to induce CTA. A one-way ANOVA was performed to analyze the effects of saccharin intake on CTA, plasma corticosterone levels, and the expression of c-Fos and p-ERK. The results showed that the MAMPH induced CTA learning and increased plasma corticosterone levels. The mPFC, and particularly the PrL and IL and the DG of the hippocampus, appeared to show increased neural activity in c-Fos expression or neural plasticity in p-ERK expression. The excitation of the PrL neurons upregulated neural activity in c-Fos expression and neural plasticity in p-ERK expression in the PrL and IL. In summary, MAMPH may be able to improve cognitive and executive function in the brain and reduce AD symptoms. Moreover, the excitatory modulation of the PrL with MAMPH administration can facilitate MAMPH-induced neural activity and plasticity in the PrL and IL of the mPFC. The present data provide clinical implications for developing a possible treatment for AD in an animal model.

Optogenetic Stimulation of the Anterior Cingulate Cortex Modulates the Pain Processing in Neuropathic Pain: A Review

Neuropathic pain is characterized by hypersensitivity, hyperalgesia, and allodynia, which is caused by damage to the somatosensory nervous system. It substantially impairs the quality of life. The management of neuropathic pain is challenging and should comprise alternative therapies. Researchers working on neural modulation methods in the field of optogenetics have recently referred to novel techniques that involve the activation or inhibition of signaling proteins by specific wavelengths of light. The use of optogenetics in neuropathic pain facilitates the investigation of pain pathways involved in chronic pain and has the potential for therapeutic use. Neuropathic pain is often accompanied by negative stimuli involving a broad network of brain regions. In particular, the anterior cingulate cortex (ACC) is a part of the limbic system that has highly interconnected structures involved in processing components of pain. The ACC is a key region for acute pain perception as well as the development of neuropathic pain, characterized by long-term potentiation induced in pain pathways. The exact mechanism for neuropathic pain in the ACC is unclear. Current evidence supports the potential of optogenetics methods to modulate the neuronal activity in the ACC for neuropathic pain. We anticipate the neuronal modulation in the ACC will be used widely to manage neuropathic pain.

Neonatal anoxia increases nociceptive response in rats: Sex differences and lumbar spinal cord and insula alterations

Neonatal anoxia is a well-known world health problem that results in neurodevelopmental deficits, such as sensory alterations that are observed in patients with cerebral palsy and autism disorder, for which oxygen deprivation is a risk factor. Nociceptive response, as part of the sensory system, has been reported as altered in these patients. To determine whether neonatal oxygen deprivation alters nociceptive sensitivity and promotes medium- and long-term inflammatory feedback in the central nervous system, Wistar rats of around 30 h old were submitted to anoxia (100% nitrogen flux for 25 min) and evaluated on PND23 (postpartum day) and PND90. The nociceptive response was assessed by mechanical, thermal, and tactile tests in the early postnatal and adulthood periods. The lumbar spinal cord (SC, L4-L6) motor neurons (MNs) and the posterior insular cortex neurons were counted and compared with their respective controls after anoxia. In addition, we evaluated the possible effect of anoxia on the expression of astrocytes in the SC at adulthood. The results showed increased nociceptive responses in both males and females submitted to anoxia, although these responses were different according to the nociceptive stimulus. A decrease in MNs in adult anoxiated females and an upregulation of GFAP expression in the SC were observed. In the insular cortex, a decrease in the number of cells of anoxiated males was observed in the neonatal period. Our findings suggest that oxygen-deprived nervous systems in rats may affect their response at the sensorimotor pathways and respective controlling centers with sex differences, which were related to the used stimulus.

Visceral pain, mechanisms, and implications in musculoskeletal clinical practice

The global impact of visceral pain is extremely high, representing a significant portion of all forms of chronic pain. In musculoskeletal practice, at least one-third of people with persistent noncancerous pain report recurrent abdominal, pelvic, or chest pain symptoms. Visceral pain can be felt in several different areas of the body and can migrate throughout a region, even though the site of origin does not appear to change. Traditionally, clinicians have examined musculoskeletal pain through a reductionist lens that ignores the influence of the visceral system on musculoskeletal pain. The hypothesis presented is that visceral pain has an important influence on developing and maintaining different types of musculoskeletal pain through processes within the peripheral or central nervous systems, as a result of a visceral nociceptive stimulus generated by pathoanatomical or functional alterations. The hypothesis predicts that a consideration of the function of the visceral system in musculoskeletal pain conditions will improve clinical outcomes, moving beyond a linear model and adopting a more holistic approach, especially in the more complex groups of patients.

Neural basis of affective touch and pain: A novel model suggests possible targets for pain amelioration

Pain is one of the most common health problems and has a severe impact on quality of life. Yet, a suitable and efficient treatment is still not available for all patient populations suffering from pain. Interestingly, recent research shows that low threshold mechanosensory C‐tactile (CT) fibres have a modulatory influence on pain. CT‐fibres are activated by slow gentle stroking of the hairy skin, providing a pleasant sensation. Consequently, slow gentle stroking is known as affective touch. Currently, a clear overview of the way affective touch modulates pain, at a neural level, is missing. This review aims to present such an overview. To explain the interaction between affective touch and pain, first the neural basis of the affective touch system and the neural processing of pain will be described. To clarify these systems, a schematic illustration will be provided in every section. Hereafter, a novel model of interactions between affective touch and pain systems will be introduced. Finally, since affective touch might be suitable as a new treatment for chronic pain, possible clinical implications will be discussed.

Resting-state fMRI analysis in apathetic Alzheimer's disease

PURPOSE

Diagnosis of comorbid psychiatric conditions are a significant determinant for the prognosis of neurodegenerative diseases. Apathy, which is a behavioral executive dysfunction, frequently accompanies Alzheimer's disease (AD) and leads to higher daily functional loss. We assume that frontal lobe hypofunction in apathetic AD patients are more apparent than the AD patients without apathy. This study aims to address the neuroanatomical correlates of apathy in the early stage of AD using task-free functional magnetic resonance imaging (MRI).

METHODS

Patients (n=20) were recruited from the Neurology and Psychiatry Departments of İstanbul University, İstanbul School of Medicine whose first referrals were 6- to 12-month history of progressive cognitive decline. Patients with clinical dementia rating 0.5 and 1 were included in the study. The patient group was divided into two subgroups as apathetic and non-apathetic AD according to their psychiatric examination and assessment scores. A healthy control group was also included (n=10). All subjects underwent structural and functional MRI. The resting-state condition was recorded eyes open for 5 minutes.

RESULTS

The difference between the three groups came up in the pregenual anterior cingulate cortex (pgACC) at the trend level (P = 0.056). Apathetic AD group showed the most constricted activation area at pgACC.

CONCLUSION

The region in and around anterior default mode network (pgACC) seems to mediate motivation to initiate behavior, and this function appears to weaken as the apathy becomes more severe in AD.

Assessment of motor skill accuracy and coordination variability after application of local and remote experimental pain

Motor learning is a relatively permanent change in motor performance. Also, one of the factors that can affect movement acquisition and movement patterns is pain and injury. The present study aims to investigate the effect of the induced local and remote pain during dart-throwing skill acquisition by examining motor skill accuracy and coordination variability. Three groups of 30 participants with a mean age of 18-25 were randomly assigned to local and remote pain or control groups. Capsaicin gel was applied to the pain groups for measuring the severity of pain using the Visual Analogue Scale (VAS). The results revealed that pain had no impact on dart-throwing skill acquisition, and there was no significant difference (p = 0.732) among the three groups at three stages of retention test. The results also showed that there was a significant difference among the three groups in terms of variability in shoulder-elbow (p = 0.025) and elbow-wrist joints (p = 0.000) in the deceleration and dart-throwing phases. The Central Nervous System seems to make adjustments when the task is associated with pain during the acquisition phase. Also, the groups with or without pain have notably various strategies, so differently, to perceive motor skills.

Role of mu-opioid receptor in nociceptive modulation in anterior cingulate cortex of rats

Lots of studies have demonstrated that anterior cingulate cortex plays important roles in the pain perception and pain modulation. The present study explored the role of mu-opioid receptor in nociceptive modulation in anterior cingulate cortex of rats with neuropathic pain. Neuropathic pain model was set up by chronic constriction injury of the left sciatic nerve of rats. The hindpaw withdrawal latency to thermal and mechanical stimulation, by hot plate and Randall Selitto Test respectively, was used to evaluate the rat’s responses to noxious stimulation. Results showed that intra-anterior cingulate cortex injection of morphine could induce the antinociception dose-dependently. By intra-anterior cingulate cortex injection of opioid receptor antagonist, the morphine-induced antinociception could be attenuated by naloxone, as well as much significantly by the selective mu-opioid receptor antagonist β-funaltrexamine, indicating that mu-opioid receptor is involved in the morphine-induced antinociception in anterior cingulate cortex of rats with neuropathic pain. The morphine-induced antinociception was much more decreased in rats with neuropathic pain than that in normal rats, and there was a significant decrease in mu-opioid receptor messenger RNA levels in anterior cingulate cortex of rats with neuropathic pain, indicating that there may be a down-regulation in mu-opioid receptor expression in anterior cingulate cortex of rats with neuropathic pain. To further confirm the role of mu-opioid receptor in morphine-induced antinociception in anterior cingulate cortex, normal rats were received intra-anterior cingulate cortex administration of small interfering RNA targeting mu-opioid receptor and it was found that there was a down-regulation in mu-opioid receptor messenger RNA levels, as well as a down-regulation in mu-opioid receptor expression in anterior cingulate cortex tested by real-time polymerase chain reaction and western blotting. Furthermore, the morphine-induced antinociceptive effect decreased significantly in rats with small interfering RNA targeting mu-opioid receptor, which indicated that knockdown mu-opioid receptor in anterior cingulate cortex could also attenuate morphine-induced antinociceptive effect. These results strongly suggest that mu-opioid receptor plays a significant role in nociceptive modulation in anterior cingulate cortex of rats.

Mapping Cortical Integration of Sensory and Affective Pain Pathways

Pain is an integrated sensory and affective experience. Cortical mechanisms of sensory and affective integration, however, remain poorly defined. Here, we investigate the projection from the primary somatosensory cortex (S1), which encodes the sensory pain information, to the anterior cingulate cortex (ACC), a key area for processing pain affect, in freely behaving rats. By using a combination of optogenetics, in vivo electrophysiology, and machine learning analysis, we find that a subset of neurons in the ACC receives S1 inputs, and activation of the S1 axon terminals increases the response to noxious stimuli in ACC neurons. Chronic pain enhances this cortico-cortical connection, as manifested by an increased number of ACC neurons that respond to S1 inputs and the magnified contribution of these neurons to the nociceptive response in the ACC. Furthermore, modulation of this S1→ACC projection regulates aversive responses to pain. Our results thus define a cortical circuit that plays a potentially important role in integrating sensory and affective pain signals.

The cingulate cortex and limbic systems for emotion, action, and memory

Evidence is provided for a new conceptualization of the connectivity and functions of the cingulate cortex in emotion, action, and memory. The anterior cingulate cortex receives information from the orbitofrontal cortex about reward and non-reward outcomes. The posterior cingulate cortex receives spatial and action-related information from parietal cortical areas. It is argued that these inputs allow the cingulate cortex to perform action-outcome learning, with outputs from the midcingulate motor area to premotor areas. In addition, because the anterior cingulate cortex connects rewards to actions, it is involved in emotion; and because the posterior cingulate cortex has outputs to the hippocampal system, it is involved in memory. These apparently multiple different functions of the cingulate cortex are related to the place of this proisocortical limbic region in brain connectivity.

Pain: A Precision Signal for Reinforcement Learning and Control

Since noxious stimulation usually leads to the perception of pain, pain has traditionally been considered sensory nociception. But its variability and sensitivity to a broad array of cognitive and motivational factors have meant it is commonly viewed as inherently imprecise and intangibly subjective. However, the core function of pain is motivational-to direct both short- and long-term behavior away from harm. Here, we illustrate that a reinforcement learning model of pain offers a mechanistic understanding of how the brain supports this, illustrating the underlying computational architecture of the pain system. Importantly, it explains why pain is tuned by multiple factors and necessarily supported by a distributed network of brain regions, recasting pain as a precise and objectifiable control signal.

Supremacy of Auditory Versus Visual Input in Somatic Empathy and Perceived Pain Level

BACKGROUND

Previous studies support the role of both auditory and visual stimuli in the evocation of empathy, but no research to date has explored the relative effectiveness of each on any type of empathy.

AIMS

The present study compared how auditory and visual presentation influence somatic empathic arousal and perceived pain level.

DESIGN

Exposure to auditory and/or visual information about an individual in pain was manipulated between groups of participants.

METHODS

Students (N = 125) in several classes were randomly assigned in groups to one of three conditions-audio-only, video-only, or audio-video-each portraying an elderly man suffering from a painful kidney stone. Participants indicated his perceived pain and level of danger and relevant physical sensations and completed an empathy status scale.

RESULTS

Consistent with the hypothesis, the results indicated that participants who were presented with an auditory stimulus (audio-only and audio-video conditions) estimated higher and more accurate pain and danger level for the patient compared with those in the visual-only group. Participants in the audio groups also reported experiencing physical sensations, whereas the visual-only group had no such report.

CONCLUSIONS

The study found that auditory information is more impactful in eliciting perceptions of pain in others compared with visual information. Experiences of clinical empathy and patient care may be improved by focusing on patients' auditory pain communications.

Modulation of the Negative Affective Dimension of Pain: Focus on Selected Neuropeptidergic System Contributions

It is well known that emotions can interfere with the perception of physical pain, as well as with the development and maintenance of painful conditions. On the other hand, somatic pain can have significant consequences on an individual’s affective behavior. Indeed, pain is defined as a complex and multidimensional experience, which includes both sensory and emotional components, thus exhibiting the features of a highly subjective experience. Over the years, neural pathways involved in the modulation of the different components of pain have been identified, indicating the existence of medial and lateral pain systems, which, respectively, project from medial or lateral thalamic nuclei to reach distinct cortex regions relating to specific functions. However, owing to the limited information concerning how mood state and painful input affect each other, pain treatment is frequently unsatisfactory. Different neuromodulators, including endogenous neuropeptides, appear to be involved in pain-related emotion and in its affective influence on pain perception, thus playing key roles in vulnerability and clinical outcome. Hence, this review article focuses on evidence concerning the modulation of the sensory and affective dimensions of pain, with particular attention given to some selected neuropeptidergic system contributions.

Loss of Prefrontal Cortical Higher Cognition with Uncontrollable Stress: Molecular Mechanisms, Changes with Age, and Relevance to Treatment

The newly evolved prefrontal cortex (PFC) generates goals for "top-down" control of behavior, thought, and emotion. However, these circuits are especially vulnerable to uncontrollable stress, with powerful, intracellular mechanisms that rapidly take the PFC "off-line." High levels of norepinephrine and dopamine released during stress engage α1-AR and D1R, which activate feedforward calcium-cAMP signaling pathways that open nearby potassium channels to weaken connectivity and reduce PFC cell firing. Sustained weakening with chronic stress leads to atrophy of dendrites and spines. Understanding these signaling events helps to explain the increased susceptibility of the PFC to stress pathology during adolescence, when dopamine expression is increased in the PFC, and with advanced age, when the molecular "brakes" on stress signaling are diminished by loss of phosphodiesterases. These mechanisms have also led to pharmacological treatments for stress-related disorders, including guanfacine treatment of childhood trauma, and prazosin treatment of veterans and civilians with post-traumatic stress disorder.

Imbalance Between Excitatory and Inhibitory Synaptic Transmission in the Primary Somatosensory Cortex Caused by Persistent Nociception in Rats

There is substantial evidence supporting the notion that the primary somatosensory (S1) cortex is an important structure involved in the perceptional component of pain. However, investigations have mainly focused on other pain-related formations, and few reports have been provided to investigate the synaptic plasticity in the S1 cortex in response to persistent pain. In the present study, we report that bee venom (BV) injection triggered an imbalance between excitatory and inhibitory synaptic transmission in the S1 cortex in rats. Using a multi-electrode array recording, we found that BV-induced persistent inflammatory pain led to temporal and spatial enhancement of synaptic plasticity. Moreover, slice patch clamp recordings on identified pyramidal neurons demonstrated that BV injection increased presynaptic and postsynaptic transmission in excitatory synapses and decreased postsynaptic transmission in inhibitory synapses in the layer II/III neurons within the S1 cortex. In immunohistochemistry and Western blot sections, the distribution and expression of total AMPA receptor subunits and gamma-amino butyric acid-A (GABA_A) were unaffected, although the membrane fractions of GluR2 and GABA_A were decreased, and their cytosolic fractions were increased in contrast. The change of GluR1 was opposite to that of GluR2, and GluR3 did not change significantly. Our studies, therefore, provide direct evidence for both presynaptic and postsynaptic changes in synapses within the S1 cortex in persistent nociception, which are probably related to the membrane trafficking of GluR1, GluR2, and GABA_A. Perspective: Increased synaptic plasticity was detected in S1 after peripheral nociception, with enhanced excitatory and decreased inhibitory synaptic transmissions. Increased GluR1, and decreased GABA_Aα1 and GluR2 membrane trafficking were detected. Therefore, the disrupted excitatory/inhibitory balance in transmissions is involved in nociception processing, and S1 can be a potential antinociceptive site.

Altered Spontaneous Brain Activity in Patients with Classical Trigeminal Neuralgia Using Regional Homogeneity: A Resting-State Functional MRI Study

OBJECTIVE

Neuroimaging studies have shown that patients with pain-related conditions have altered neuronal activity and structural functions. The purpose of this study was to investigate whether patients with classical trigeminal neuralgia (CTN) exhibit changes in corresponding neuronal activity via analysis of neuronal activity regional homogeneity (ReHo).

METHODS

A total of 28 patients presenting with sore eyes (12 men and 16 women) were matched with 28 healthy controls (12 men and 16 women). All participants underwent functional magnetic resonance imaging (fMRI). This ReHo method was used to assess the consistency of changes in neural activity in various brain regions. The receiver operating characteristic (ROC) curve was applied to differentiate ReHo values of patients with CTN from ReHo values of healthy controls. Pearson's correlation analysis was applied to evaluate the correlation between ReHo values of different brain regions of patients with CTN and clinical manifestations.

RESULTS

Compared with healthy controls, patients with CTN were found to have increased ReHo values in the inferior cerebellum bilaterally, right inferior temporal gyrus, right middle occipital gyrus, right fusiform gyrus, right superior frontal gyrus, and right precentral gyrus. ROC curve analysis of each brain region revealed near-perfect accuracy regarding the area under the curve. However, no correlation between ReHo values and clinical manifestations in patients with CTN was found.

CONCLUSIONS

CTN is associated with altered neuronal networks in different areas of the brain. ReHo values all possess different degrees of change, implying that CTN has a certain impact on cerebral function.

The cingulate cortex and limbic systems for action, emotion, and memory

Different limbic structures including the hippocampal memory system and the amygdala/orbitofrontal emotion system have very different connectivity and functions, and it has been suggested that we should no longer think of a single limbic system. A framework is provided for understanding the connectivity and functions of different parts of the cingulate cortex in action, emotion, and memory, in the context of connections of different parts of the cingulate cortex with other limbic and neocortical structures. First, the anterior cingulate cortex receives information from the orbitofrontal cortex about reward and nonreward outcomes. The posterior cingulate cortex receives action-related and spatial information from parietal cortical areas. It is argued that these are inputs that allow the cingulate cortex to perform action-outcome learning, with outputs from the midcingulate motor area to premotor areas. Damage to the anterior cingulate cortex impairs action-outcome learning and emotion because of its reward-related representations. Second, the posterior cingulate cortex provides "action" and "spatial" information from the parietal cortex into the hippocampal memory system via the parahippocampal gyrus, and the anterior cingulate cortex (receiving from the orbitofrontal cortex) provides reward-related input into the hippocampal memory system via the posterior cingulate and parahippocampal gyrus. Thus posterior cingulate damage can impair hippocampal episodic memory and retrieval, especially the spatial component. These functions are related to the place of this proisocortical limbic region in brain connectivity.

Hypnosis for cingulate-mediated analgesia and disease treatment

Hypnosis is a technique that induces changes in perceptual experience through response to specific suggestions. By means of functional neuroimaging, a large body of clinical and experimental studies has shown that hypnotic processes modify internal (self-awareness) as well as external (environmental awareness) brain networks. Objective quantifications of this kind permit the characterization of cerebral changes after hypnotic induction and its uses in the clinical setting. Hypnosedation is one such application, as it combines hypnosis with local anesthesia in patients undergoing surgery. The power of this technique lies in the avoidance of general anesthesia and its potential complications that emerge during and after surgery. Hypnosedation is associated with improved intraoperative comfort and reduced perioperative anxiety and pain. It ensures a faster recovery of the patient and diminishes the intraoperative requirements for sedative or analgesic drugs. Mechanisms underlying the modulation of pain perception under hypnotic conditions involve cortical and subcortical areas, mainly the anterior cingulate and prefrontal cortices as well as the basal ganglia and thalami. In that respect, hypnosis-induced analgesia is an effective and highly cost-effective alternative to sedation during surgery and symptom management.

Meditation-based clinical study to determine the correlation of quantitative electroencephalogram (qEEG) and 24-hour EEG activity

BACKGROUND

The heart continuously transmits information to the cerebrum during each pulse, and influences information processing such as perception, cognition, and emotion, which are processed in the cerebrum. This is the basis for the theory of oriental medicine widely used in psychiatric medicine and clinical practice, so-called Simjushinji (heart and brain) theory, that the heart controls the mind. The present study aims to analyze the correlation between heart and brain function by 24-hour active electrocardiogram and quantitative electroencephalogram (EEG) measurement under meditation.

METHODS

This randomized, controlled, assessor-blinded, 2-armed, parallel, multicenter clinical trial will analyze a total of 50 subjects, including 25 each for the test group and the active control group. Subjects will be randomly allocated to the test group (performing resource mindfulness) and the control group (performing stress mindfulness) in a 1:1 ratio. The clinical trial consists of 3 stages. The first and third stages are stable states. The second stage is divided into the test and active comparator groups. Quantitative EEG (qEEG) measurements at stages 1 and 3 will be recorded for 10 minutes; measurements at stage 2 will be recorded for 20 minutes with the eyes closed. The 24-hour Holter Monitoring and heart rate variability will be evaluated at each stage. Before the beginning of stage 3, subjects will complete the questionnaires. The primary outcome will be analyzed by independent t tests of both groups.

DISCUSSION

Scientific studies based on clinical epistemology are expected to serve as a basis for sustainable medical services in the field of psychiatric medicine in Korea. HRV, blood pressure index, and biometric index in qEEG, as determined by 24-hour Holter monitoring, will complement quantitative biomarkers and be useful in various fields.

Can they Feel? The Capacity for Pain and Pleasure in Patients with Cognitive Motor Dissociation

Unresponsive wakefulness syndrome is a disorder of consciousness wherein a patient is awake, but completely non-responsive at the bedside. However, research has shown that a minority of these patients remain aware, and can demonstrate their awareness via functional neuroimaging; these patients are referred to as having ‘cognitive motor dissociation’ (CMD). Unfortunately, we have little insight into the subjective experiences of these patients, making it difficult to determine how best to promote their well-being. In this paper, I argue that the capacity to experience pain or pleasure (sentience) is a key component of well-being for these patients. While patients with unresponsive wakefulness syndrome are believed to be incapable of experiencing pain or pleasure, I argue that there is evidence to support the notion that CMD patients likely can experience pain and pleasure. I analyze current neuroscientific research into the mechanisms of pain experience in patients with disorders of consciousness, and provide an explanation for why CMD patients likely can experience physical pain. I then do the same for physical pleasure. I conclude that providing these patients with pleasurable experiences, and avoiding subjecting them to pain, are viable means of promoting their well-being.

Neuropathic Pain Causes Pyramidal Neuronal Hyperactivity in the Anterior Cingulate Cortex

The anterior cingulate cortex (ACC) is thought to be important for acute pain perception as well as the development of chronic pain after peripheral nerve injury. Nevertheless, how ACC neurons respond to sensory stimulation under chronic pain states is not well understood. Here, we used an in vivo two-photon imaging technique to monitor the activity of individual neurons in the ACC of awake, head restrained mice. Calcium imaging in the dorsal ACC revealed robust somatic activity in layer 5 (L5) pyramidal neurons in response to peripheral noxious stimuli, and the degree of evoked activity was correlated with the intensity of noxious stimulation. Furthermore, the activation of ACC neurons occurred bilaterally upon noxious stimulation to either contralateral or ipsilateral hind paws. Notably, with nerve injury-induced neuropathic pain in one limb, L5 pyramidal neurons in both sides of the ACC showed enhanced activity in the absence or presence of pain stimuli. These results reveal hyperactivity of L5 pyramidal neurons in the bilateral ACC during the development of neuropathic pain.

Heightened brain response to pain anticipation in high-functioning adults with autism spectrum disorder

Autism spectrum disorder (ASD) is marked by both socio-communicative difficulties and abnormalities in sensory processing. Much of the work on sensory deficits in ASD has focused on tactile sensations and the perceptual aspects of somatosensation, such as encoding of stimulus intensity and location. Although aberrant pain processing has often been noted in clinical observations of patients with ASD, it remains largely uninvestigated. Importantly, the neural mechanism underlying higher order cognitive aspects of pain processing such as pain anticipation also remains unknown. Here we examined both pain perception and anticipation in high-functioning adults with ASD and matched healthy controls (HC) using an anticipatory pain paradigm in combination with functional magnetic resonance imaging (fMRI) and concurrent skin conductance response (SCR) recording. Participants were asked to choose a level of electrical stimulation that would feel moderately painful to them. Compared to HC group, ASD group chose a lower level of stimulation prior to fMRI. However, ASD participants showed greater activation in both rostral and dorsal anterior cingulate cortex during the anticipation of stimulation, but not during stimulation delivery. There was no significant group difference in insular activation during either pain anticipation or perception. However, activity in the left anterior insula correlated with SCR during pain anticipation. Taken together, these results suggest that ASD is marked with aberrantly higher level of sensitivity to upcoming aversive stimuli, which may reflect abnormal attentional orientation to nociceptive signals and a failure in interoceptive inference.

Chronic pain induces generalized enhancement of aversion

A hallmark feature of chronic pain is its ability to impact other sensory and affective experiences. It is notably associated with hypersensitivity at the site of tissue injury. It is less clear, however, if chronic pain can also induce a generalized site-nonspecific enhancement in the aversive response to nociceptive inputs. Here, we showed that chronic pain in one limb in rats increased the aversive response to acute pain stimuli in the opposite limb, as assessed by conditioned place aversion. Interestingly, neural activities in the anterior cingulate cortex (ACC) correlated with noxious intensities, and optogenetic modulation of ACC neurons showed bidirectional control of the aversive response to acute pain. Chronic pain, however, altered acute pain intensity representation in the ACC to increase the aversive response to noxious stimuli at anatomically unrelated sites. Thus, chronic pain can disrupt cortical circuitry to enhance the aversive experience in a generalized anatomically nonspecific manner.

Transcranial direct current stimulation over the primary motor vs prefrontal cortex in refractory chronic migraine: A pilot randomized controlled trial

Although transcranial direct current stimulation (tDCS) represents a therapeutic option for the prophylaxis of chronic migraine, the target area for application of the electrical current to the cortex has not yet been well established. Here we sought to determine whether a treatment protocol involving 12 sessions of 2mA, 20min anodal stimulation of the left primary motor (M1) or dorsolateral prefrontal cortex (DLPFC) could offer clinical benefits in the management of pain from migraine. Thirteen participants were assessed before and after treatment, using the Headache Impact Test-6, Visual Analogue Scale and Medical Outcomes Study 36 - Item Short - Form Health Survey. After treatment, group DLPFC exhibited a better performance compared with groups M1 and sham. On intragroup comparison, groups DLPFC and M1 exhibited a greater reduction in headache impact and pain intensity and a higher quality of life after treatment. No significant change was found in group sham. The participants in group M1 exhibited more adverse effects, especially headache, heartburn, and sleepiness, than did those in the other two groups. Transcranial direct current stimulation is a safe and efficacious technique for treating chronic migraine. However, it should be kept in mind that the site of cortical stimulation might modulate the patient's response to treatment.

Heightened Temporal Summation of Pain in Patients with Functional Gastrointestinal Disorders and History of Trauma

BACKGROUND

Individuals with functional gastrointestinal disorders (FGIDs) report experiencing trauma more often than healthy controls, but little is known regarding psychophysical correlates.

PURPOSE

The purpose of this study was to test the hypothesis that adolescents and young adults with FGIDs since childhood and a trauma history (n = 38) would exhibit heightened temporal summation to thermal pain stimuli, an index of central sensitization, and greater clinical symptoms compared to patients with FGIDs and no trauma history (n = 95) and healthy controls (n = 135).

METHODS

Participants completed self-report measures, an experimental pain protocol, and psychiatric diagnostic interview as part of a larger longitudinal study.

RESULTS

FGID + Trauma patients exhibited greater temporal summation than FGID + No Trauma patients and healthy controls. Additionally, FGID + Trauma patients exhibited greater gastrointestinal and non-gastrointestinal symptom severity, number of chronic pain sites, and disability.

CONCLUSIONS

Assessing for trauma history in patients with FGIDs could identify a subset at risk for greater central sensitization and pain-related symptoms.

Plasticity and Cortical Reorganization Associated With Pain

Abstract. This review focuses on plasticity and reorganization associated with pain. It is well established that noxious stimulation activates a large network of neural structures in the human brain, which is often denominated as the neuromatrix of pain. Repeated stimulation is able to induce plasticity in nearly all structures of this neuromatrix. While the plasticity to short-term stimulation is usually transient, long-term stimulation might induce persistent changes within the neuromatrix network and reorganize its functions and structures. Interestingly, a large longitudinal study on patients with subacute back pain found predictors for the persistence of pain versus remission in mesolimbic structures not usually included in the neuromatrix of pain. From these results, new concepts of nociception, pain, and transition from acute to chronic pain emerged. Overall, this review outlines a number of plastic changes in response to pain. However, the role of plasticity for chronic pain has still to be established.

Ameliorating treatment-refractory depression with intranasal ketamine: potential NMDA receptor actions in the pain circuitry representing mental anguish

This article reviews the antidepressant actions of ketamine, an N-methyl-D-aspartame glutamate receptor (NMDAR) antagonist, and offers a potential neural mechanism for intranasal ketamine's ultra-rapid actions based on the key role of NMDAR in the nonhuman primate prefrontal cortex (PFC). Although intravenous ketamine infusions can lift mood within hours, the current review describes how intranasal ketamine administration can have ultra-rapid antidepressant effects, beginning within minutes (5-40 minutes) and lasting hours, but with repeated treatments needed for sustained antidepressant actions. Research in rodents suggests that increased synaptogenesis in PFC may contribute to the prolonged benefit of ketamine administration, beginning hours after administration. However, these data cannot explain the relief that occurs within minutes of intranasal ketamine delivery. We hypothesize that the ultra-rapid effects of intranasal administration in humans may be due to ketamine blocking the NMDAR circuits that generate the emotional representations of pain (eg, Brodmann Areas 24 and 25, insular cortex), cortical areas that can be overactive in depression and which sit above the nasal epithelium. In contrast, NMDAR blockade in the dorsolateral PFC following systemic administration of ketamine may contribute to cognitive deficits. This novel view may help to explain how intravenous ketamine can treat the symptoms of depression yet worsen the symptoms of schizophrenia.

Cortical Responsiveness to Nociceptive Stimuli in Patients with Chronic Disorders of Consciousness: Do C-Fiber Laser Evoked Potentials Have a Role?

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.