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Pain Reports Apr 2024Homeostatic plasticity (HP) is a negative feedback mechanism that prevents excessive facilitation or depression of cortical excitability (CE). Cortical HP responses in... (Review)
Review
Homeostatic plasticity (HP) is a negative feedback mechanism that prevents excessive facilitation or depression of cortical excitability (CE). Cortical HP responses in humans have been investigated by using 2 blocks of noninvasive brain stimulation with a no-stimulation block in between. A healthy HP response is characterized by reduced CE after 2 excitatory stimulation blocks and increased CE when using inhibitory stimulation. Conversely, impaired HP responses have been demonstrated in experimental and chronic pain conditions. Therefore, this systematic review aimed to provide an overview of the effect of pain on cortical HP in humans. Scopus, Embase, and PubMed were searched from inception until November 20, 2023. The included studies (1) compared experimental or clinical pain conditions with healthy controls, (2) induced HP using 2 blocks of stimulation with a no-stimulation interval, and (3) evaluated CE measures such as motor-evoked potentials. Four studies were included, consisting of 5 experiments and 146 participants, of whom 63 were patients with chronic pain and 48 were subjected to an experimental pain model. This systematic review found support for an HP impairment in pain compared with that in pain-free states, reflected by a lack of CE reduction after excitatory-excitatory HP induction over the primary motor cortex. Inhibitory-inhibitory HP induction did not produce a consistent HP response across studies, independent of pain or pain-free states. Standardization of HP induction protocols and outcome calculations is needed to ensure reproducibility and study comparison. Future HP studies may consider investigating sensory domains including nociception, which would further our understanding of abnormal HP regulation in pain conditions.
PubMed: 38444774
DOI: 10.1097/PR9.0000000000001141 -
Journal of Neuroengineering and... Mar 2024The regulation of gait is critical to many activities of everyday life. When walking, somatosensory information obtained from mechanoreceptors throughout body is... (Review)
Review
BACKGROUND
The regulation of gait is critical to many activities of everyday life. When walking, somatosensory information obtained from mechanoreceptors throughout body is delivered to numerous supraspinal networks and used to execute the appropriate motion to meet ever-changing environmental and task demands. Aging and age-related conditions oftentimes alter the supraspinal sensorimotor control of walking, including the responsiveness of the cortical brain regions to the sensorimotor inputs obtained from the peripheral nervous system, resulting in diminished mobility in the older adult population. It is thus important to explicitly characterize such supraspinal sensorimotor elements of walking, providing knowledge informing novel rehabilitative targets. The past efforts majorly relied upon mental imagery or virtual reality to study the supraspinal control of walking. Recent efforts have been made to develop magnetic resonance imaging (MRI)-compatible devices simulating specific somatosensory and/or motor aspects of walking. However, there exists large variance in the design and functionality of these devices, and as such inconsistent functional MRI (fMRI) observations.
METHODS
We have therefore completed a systematic review to summarize current achievements in the development of these MRI-compatible devices and synthesize available imaging results emanating from studies that have utilized these devices.
RESULTS
The device design, study protocol and neuroimaging observations of 26 studies using 13 types of devices were extracted. Three of these devices can provide somatosensory stimuli, eight motor stimuli, and two both types of stimuli. Our review demonstrated that using these devices, fMRI data of brain activation can be successfully obtained when participants remain motionless and experience sensorimotor stimulation during fMRI acquisition. The activation in multiple cortical (e.g., primary sensorimotor cortex) and subcortical (e.g., cerebellum) regions has been each linked to these types of walking-related sensorimotor stimuli.
CONCLUSION
The observations of these publications suggest the promise of implementing these devices to characterize the supraspinal sensorimotor control of walking. Still, the evidence level of these neuroimaging observations was still low due to small sample size and varied study protocols, which thus needs to be confirmed via studies with more rigorous design.
Topics: Humans; Aged; Walking; Magnetic Resonance Imaging; Gait; Neuroimaging; Aging
PubMed: 38443983
DOI: 10.1186/s12984-024-01323-y -
Translational Neuroscience Jan 2023Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders diagnosed in childhood. Two common features of ADHD are impaired...
Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders diagnosed in childhood. Two common features of ADHD are impaired behavioural inhibition and sustained attention. The Go/No-Go experimental paradigm with concurrent functional magnetic resonance imaging (fMRI) scanning has previously revealed important neurobiological correlates of ADHD such as the supplementary motor area and the prefrontal cortex. The coordinate-based meta-analysis combined with quantitative techniques, such as activation likelihood estimate (ALE) generation, provides an unbiased and objective method of summarising these data to understand the brain network architecture and connectivity in ADHD children. Go/No-Go task-based fMRI studies involving children and adolescent subjects were selected. Coordinates indicating foci of activation were collected to generate ALEs using threshold values (voxel-level: < 0.001; cluster-level: < 0.05). ALEs were matched to one of seven canonical brain networks based on the cortical parcellation scheme derived from the Human Connectome Project. Fourteen studies involving 457 children met the eligibility criteria. No significant convergence of Go/No-Go related brain activation was found for ADHD groups. Three significant ALE clusters were detected for brain activation relating to controls or ADHD < controls. Significant clusters were related to specific areas of the default mode network (DMN). Network-based analysis revealed less extensive DMN, dorsal attention network, and limbic network activation in ADHD children compared to controls. The presence of significant ALE clusters may be due to reduced homogeneity in the selected sample demographic and experimental paradigm. Further investigations regarding hemispheric asymmetry in ADHD subjects would be beneficial.
PubMed: 38410259
DOI: 10.1515/tnsci-2022-0299 -
Neurophysiologie Clinique = Clinical... Feb 2024To update a systematic review of the efficacy and safety of transcranial direct current stimulation (tDCS) for analgesia, for antidepressant effects, and to reduce the... (Meta-Analysis)
Meta-Analysis
OBJECTIVES
To update a systematic review of the efficacy and safety of transcranial direct current stimulation (tDCS) for analgesia, for antidepressant effects, and to reduce the impact of fibromyalgia (FM), looking for optimal areas of stimulation.
METHODS
We searched five databases to identify randomized controlled trials comparing active and sham tDCS for FM. The primary outcome was pain intensity, and secondary outcome measures included FM Impact Questionnaire (FIQ) and depression score. Meta-analysis was conducted using standardized mean difference (SMD). Subgroup analysis was performed to determine the effects of different regional stimulation, over the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), opercular-insular cortex (OIC), and occipital nerve (ON) regions. We analyzed the minimal clinically important difference (MCID) by the value of the mean difference (MD) for an 11-point scale for pain, the Beck Depressive Inventory-II (BDI-II), and the Fibromyalgia Impact Questionnaire (FIQ) score. We described the certainty of the evidence (COE) using the tool GRADE profile.
RESULTS
Twenty studies were included in the analysis. Active tDCS had a positive effect on pain (SMD= -1.04; 95 % CI -1.38 to -0.69), depression (SMD= -0.46; 95 % CI -0.64 to -0.29), FIQ (SMD= -0.73; 95 % CI -1.09 to -0.36), COE is moderate. Only group M1 (SD=-1.57) and DLPFC (SD=-1.44) could achieve MCID for analgesia; For BDI-II, only group DLPFC (SD=-5.36) could achieve an MCID change. Adverse events were mild.
CONCLUSION
tDCS is a safe intervention that relieves pain intensity, reduces depression, and reduces the impact of FM on life. Achieving an MCID is related to the stimulation site and the target symptom.
Topics: Humans; Fibromyalgia; Pain; Pain Management; Transcranial Direct Current Stimulation
PubMed: 38387108
DOI: 10.1016/j.neucli.2024.102944 -
Journal of Psychiatry & Neuroscience :... 2024Transcranial magnetic stimulation (TMS) is a noninvasive neurostimulation modality that has been used to study human synaptic plasticity. Leveraging work in ex vivo...
BACKGROUND
Transcranial magnetic stimulation (TMS) is a noninvasive neurostimulation modality that has been used to study human synaptic plasticity. Leveraging work in ex vivo preparations, mechanistically informed pharmacological adjuncts to TMS have been used to improve our fundamental understanding of TMS-induced synaptic plasticity.
METHODS
We systematically reviewed the literature pairing pharmacological adjuncts with TMS plasticity-induction protocols in humans. We searched MEDLINE, PsycINFO, and Embase from 2013 to Mar. 10, 2023. Studies published before 2013 were extracted from a previous systematic review. We included studies using repetitive TMS, theta-burst stimulation, paired associative stimulation, and quadripulse stimulation paradigms in healthy and clinical populations.
RESULTS
Thirty-six studies met our inclusion criteria (28 in healthy and 8 in clinical populations). Most pharmacological agents have targeted the glutamatergic -methyl-d-aspartate (NMDA; 15 studies) or dopamine receptors (13 studies). The NMDA receptor is necessary for TMS-induced plasticity; however, sufficiency has not been shown across protocols. Dopaminergic modulation of TMS-induced plasticity appears to be dose-dependent. The GABAergic, cholinergic, noradrenergic, and serotonergic neurotransmitter systems have small evidence bases supporting modulation of TMS-induced plasticity, as do voltage-gated calcium and sodium channels. Studies in clinical populations suggest that pharmacological adjuncts to TMS may rescue motor cortex plasticity, with implications for therapeutic applications of TMS and a promising clinical trial in depression.
LIMITATIONS
This review is limited by the predominance in the literature of studies with small sample sizes and crossover designs.
CONCLUSION
Pharmacologically enhanced TMS largely parallels findings from ex vivo preparations. As this area expands and novel targets are tested, adequately powered samples in healthy and clinical populations will inform the mechanisms of TMS-induced plasticity in health and disease.
Topics: Humans; Transcranial Magnetic Stimulation; Neuronal Plasticity; Motor Cortex; Dopamine; Calcium; Evoked Potentials, Motor
PubMed: 38359933
DOI: 10.1503/jpn.230090 -
Epilepsy & Behavior : E&B Mar 2024The term 'functional/dissociative seizures (FDS)' refers to a paroxysmal, transient clinical manifestation that may include motor, sensory, vegetative, psychological and... (Review)
Review
INTRODUCTION
The term 'functional/dissociative seizures (FDS)' refers to a paroxysmal, transient clinical manifestation that may include motor, sensory, vegetative, psychological and cognitive signs, similar to the manifestations observed in epileptic seizures. In recent years, there has been an increase of literature in the field of brain imaging research on functional neurological disorders and, more specifically, on FDS. However, most of the studies have been carried out on limited samples. We propose an update of this review work by performing a systematic review of studies performed since 2017 in the field of neuroimaging in patients with FDS.
METHODS
We conducted a systematic review of the literature using the PRISMA methodology and reproduced most of the methodological elements of the latest systematic literature review.
RESULTS
Our work over the last five years has identified 14 articles. It is still difficult to isolate a distinct structure or network specifically involved in the mechanism of FDS. However, certain structures are recurrently involved in imaging studies, notably the amygdala, the orbitofrontal cortex, and the anterior cingulate cortex.
CONCLUSION
The contribution of neuroimaging may allow a more precise explanation of the disorder for patients, avoiding the stigma frequently associated with this diagnosis. as with other 'conversion' phenomena which have traditionally been considered only as 'medically unexplained'. In the longer term and beyond a better understanding of the physiopathology of the disorder, the challenge of this neuroimaging work would be to identify specific imaging biomarkers for a diagnosis of FDS.
Topics: Humans; Psychogenic Nonepileptic Seizures; Conversion Disorder; Dissociative Disorders; Seizures; Epilepsy
PubMed: 38281393
DOI: 10.1016/j.yebeh.2024.109654 -
Brain Sciences Dec 2023Negative symptoms in schizophrenia impose a significant burden with limited effective pharmacological treatment options. Recent trials have shown preliminary evidence... (Review)
Review
Negative symptoms in schizophrenia impose a significant burden with limited effective pharmacological treatment options. Recent trials have shown preliminary evidence for the efficacy of using intermittent theta burst stimulation (iTBS) in treating negative symptoms in schizophrenia. We aim to systematically review the current evidence of iTBS in the treatment of the negative symptoms of schizophrenia as an augmentation therapy. The study protocol was developed and registered on Prospero (registration ID: 323381). MEDLINE, EMBASE, Web of Science (Scopus), PsycINFO and Wan Fang databases were searched for sham-controlled, randomized trials of iTBS among patients with schizophrenia. The mean difference in major outcome assessments for negative symptoms was calculated. The quality of evidence was assessed using the Cochrane Risk of Bias Tool (version 1) and the GRADE system. Moreover, 12 studies including a total of 637 participants were included. Compared to sham treatment, the pooled analysis was in favor of iTBS treatment for negative symptoms (mean weight effect size: 0.59, = 0.03) but not for positive symptoms (mean weight effect size: 0.01, = 0.91) and depressive symptoms (mean weight effect size: 0.35, = 0.16). A significant treatment effect was also observed on the iTBS target site left dorsal prefrontal cortex (mean weight effect size: 0.86, = 0.007) and for stimulation with 80% motor threshold (mean weight effect size: 0.86, = 0.02). Thus, our synthesized data support iTBS as a potential treatment for negative symptoms among patients with schizophrenia. However, the long-term efficacy and safety issues of iTBS in a larger population have yet to be examined.
PubMed: 38248233
DOI: 10.3390/brainsci14010018 -
Neuroscience and Biobehavioral Reviews Feb 2024Reactive response inhibition cancels impending actions to enable adaptive behavior in ever-changing environments and has wide neuropsychiatric implications. A canonical... (Review)
Review
Reactive response inhibition cancels impending actions to enable adaptive behavior in ever-changing environments and has wide neuropsychiatric implications. A canonical paradigm to measure the covert inhibition latency is the stop-signal task (SST). To probe the cortico-subcortical network underlying motor inhibition, transcranial magnetic stimulation (TMS) has been applied over central nodes to modulate SST performance, especially to the right inferior frontal cortex and the presupplementary motor area. Since the vast parameter spaces of SST and TMS enabled diverse implementations, the insights delivered by emerging TMS-SST studies remain inconclusive. Therefore, a systematic review was conducted to account for variability and synthesize converging evidence. Results indicate certain protocol specificity through the consistent perturbations induced by online TMS, whereas offline protocols show paradoxical effects on different target regions besides numerous null effects. Ancillary neuroimaging findings have verified and dissociated the underpinning network dynamics. Sources of heterogeneity in designs and risk of bias are highlighted. Finally, we outline best-practice recommendations to bridge methodological gaps and subserve the validity as well as replicability of future work.
Topics: Humans; Transcranial Magnetic Stimulation; Motor Cortex; Inhibition, Psychological; Neuroimaging; Task Performance and Analysis
PubMed: 38194868
DOI: 10.1016/j.neubiorev.2023.105532 -
Journal of Integrative Neuroscience Nov 2023Gambling Disorder (GD) is a behavioral addiction listed within the diagnostic category of substance-related and addictive disorders. Recently, transcranial magnetic...
BACKGROUND
Gambling Disorder (GD) is a behavioral addiction listed within the diagnostic category of substance-related and addictive disorders. Recently, transcranial magnetic stimulation (TMS), which non-invasively stimulates the brain and has neuromodulatory properties, has emerged as an innovative treatment tool for GD, thus offering a new option for the management of this complex disorder. The present review explored the efficacy of TMS as a possible non-pharmacological treatment for GD.
METHODS
An exhaustive search was performed across the MEDLINE, Web of Science, and EMBASE databases using a specific search string related to GD and TMS. A total of 20 papers were selected for full-text examination, out of which eight fulfilled the inclusion criteria and were therefore systematically analyzed in the present review.
RESULTS
This review included eight studies: three randomized-controlled trials (RCTs), three non-controlled studies, one case series, and one case report. Two cross-over RCTs described a decrease in craving after high-frequency (excitatory), repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (DLPFC) and the medial prefrontal cortex (PFC), respectively; another study applying low-frequency (inhibitory) rTMS on the right DLPFC did not find any positive effect on craving. Among uncontrolled studies, one demonstrated the beneficial effect of high-frequency rTMS over the left DLPFC, while another showed the efficacy of a continuous theta burst stimulation protocol directed over the pre-supplementary motor area, bilaterally.
CONCLUSION
The included studies showed the promising effect of excitatory stimulation over the left PFC. However, further investigation is needed, particularly in terms of standardizing stimulation protocols and psychometric assessments.
Topics: Humans; Transcranial Magnetic Stimulation; Gambling; Craving; Prefrontal Cortex; Dorsolateral Prefrontal Cortex; Treatment Outcome
PubMed: 38176943
DOI: 10.31083/j.jin2206164 -
Journal of Integrative Neuroscience Nov 2023Premonitory urge (PU) is an aversive bodily sensation that signals the onset of tic disorder.To our knowledge, PU typically precedes the appearance of tic symptoms, and... (Meta-Analysis)
Meta-Analysis
INTRODUCTION
Premonitory urge (PU) is an aversive bodily sensation that signals the onset of tic disorder.To our knowledge, PU typically precedes the appearance of tic symptoms, and both age and tic severity are correlated with PU. However, inconsistent findings have also been reported. Hence, we conducted a meta-analysis to examine the relationship among premonitory symptoms, patient age and the severity of tic symptoms, as well as to summarize the research on the neural underpinnings of PU in Tourette syndrome (TS).
METHODS
We conducted a literature search of relevant studies published between December 2005 and April 2022 using databases such as PubMed, Elsevier, PsycINFO, and Web of Science. Our analysis was carried out using R software with the assistance of the "meta" and "metafor" packages.
RESULTS
Our meta-analysis included 22 studies with a total of 1236 tic disorder patients. The mean Premonitory Urge for Tics Scale (PUTS) score was 20.17, with a 95% confidence interval of [18.14, 21.68]. Through meta-regression, we found that age and tic severity play important moderating roles in PU severity ( < 0.0001). Neuroimaging studies suggest that PU is related to the insula, prefrontal cortex (PFC), anterior cingulate cortex (ACC), and supplementary motor area (SMA), regardless of the structural or functional level.
CONCLUSIONS
Our meta-analysis confirmed the positive relationship between the severity of tics and PU and identified age as a significant factor influencing PU. The neural mechanisms underlying PU remain largely unknown, but evidence suggests that the insula, PFC, ACC, and SMA are related regions.
Topics: Humans; Gyrus Cinguli; Neuroimaging; Tic Disorders; Tics; Tourette Syndrome
PubMed: 38176915
DOI: 10.31083/j.jin2206159