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Frontiers in Neuroscience 2022Neuroplasticity following deafness has been widely demonstrated in both humans and animals, but the anatomical substrate of these changes is not yet clear in human...
Neuroplasticity following deafness has been widely demonstrated in both humans and animals, but the anatomical substrate of these changes is not yet clear in human brain. However, it is of high importance since hearing loss is a growing problem due to aging population. Moreover, knowing these brain changes could help to understand some disappointing results with cochlear implant, and therefore could improve hearing rehabilitation. A systematic review and a coordinate-based meta-analysis were realized about the morphological brain changes highlighted by MRI in severe to profound hearing loss, congenital and acquired before or after language onset. 25 papers were included in our review, concerning more than 400 deaf subjects, most of them presenting prelingual deafness. The most consistent finding is a volumetric decrease in gray matter around bilateral auditory cortex. This change was confirmed by the coordinate-based meta-analysis which shows three converging clusters in this region. The visual areas of deaf children is also significantly impacted, with a decrease of the volume of both gray and white matters. Finally, deafness is responsible of a gray matter increase within the cerebellum, especially at the right side. These results are largely discussed and compared with those from deaf animal models and blind humans, which demonstrate for example a much more consistent gray matter decrease along their respective primary sensory pathway. In human deafness, a lot of other factors than deafness could interact on the brain plasticity. One of the most important is the use of sign language and its age of acquisition, which induce among others changes within the hand motor region and the visual cortex. But other confounding factors exist which have been too little considered in the current literature, such as the etiology of the hearing impairment, the speech-reading ability, the hearing aid use, the frequent associated vestibular dysfunction or neurocognitive impairment. Another important weakness highlighted by this review concern the lack of papers about postlingual deafness, whereas it represents most of the deaf population. Further studies are needed to better understand these issues, and finally try to improve deafness rehabilitation.
PubMed: 35418829
DOI: 10.3389/fnins.2022.850245 -
Brain Sciences Mar 2022Although Alcohol Use Disorder (AUD) is highly prevalent worldwide, treating this condition remains challenging. Further, potential treatments for AUD do not fully... (Review)
Review
BACKGROUND
Although Alcohol Use Disorder (AUD) is highly prevalent worldwide, treating this condition remains challenging. Further, potential treatments for AUD do not fully address alcohol-induced neuroadaptive changes. Understanding the effects of pharmacotherapies for AUD on the human brain may lead to tailored, more effective treatments, and improved individual clinical outcomes.
OBJECTIVES
We systematically reviewed the literature for studies investigating pharmacotherapies for AUD that included neuroimaging-based treatment outcomes. We searched the PubMed, Scielo, and PsycINFO databases up to January 2021.
STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS
Eligible studies included those investigating pharmacotherapies for AUD and employing functional magnetic resonance imaging (fMRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and/or proton magnetic resonance spectroscopy (H-MRS).
STUDY APPRAISAL AND SYNTHESIS METHODS
Two independent reviewers screened studies' titles and abstracts for inclusion. Data extraction forms were shared among all the authors to standardize data collection. We gathered information on the following variables: sample size; mean age; sociodemographic and clinical characteristics; alcohol use status; study design and methodology; main neuroimaging findings and brain-regions of interest (i.e., brain areas activated by alcohol use and possible pharmacological interactions); and limitations of each study.
RESULTS
Out of 177 studies selected, 20 studies provided relevant data for the research topic. Findings indicate that: (1) Acamprosate and gabapentin may selectively modulate limbic regions and the anterior cingulate cortex; (2) Naltrexone and disulfiram effects may involve prefrontal, premotor, and cerebellar regions; (3) Pharmacotherapies acting on glutamate and GABA neurotransmission involve primarily areas underpinning reward and negative affective states, and; (4) Pharmacotherapies acting on opioid and dopamine systems may affect areas responsible for the cognitive and motor factors of AUD.
LIMITATIONS
Most of the studies were focused on naltrexone. A small number of studies investigated the action of disulfiram and gabapentin, and no neuroimaging studies investigated topiramate. In addition, the time between medication and neuroimaging scans varied widely across studies.
CONCLUSIONS
We identified key-brain regions modulated by treatments available for AUD. Some of the regions modulated by naltrexone are not specific to the brain reward system, such as the parahippocampal gyrus (temporal lobe), parietal and occipital lobes. Other treatments also modulate not specific regions of the reward system, but play a role in the addictive behaviors, including the insula and dorsolateral prefrontal cortex. The role of these brain regions in mediating the AUD pharmacotherapy response warrants investigation in future research studies.
PubMed: 35326342
DOI: 10.3390/brainsci12030386 -
Effects of Cardiorespiratory Fitness on Cerebral Oxygenation in Healthy Adults: A Systematic Review.Frontiers in Physiology 2022Exercise is known to improve cognitive functioning and the cardiorespiratory hypothesis suggests that this is due to the relationship between cardiorespiratory fitness... (Review)
Review
INTRODUCTION
Exercise is known to improve cognitive functioning and the cardiorespiratory hypothesis suggests that this is due to the relationship between cardiorespiratory fitness (CRF) level and cerebral oxygenation. The purpose of this systematic review is to consolidate findings from functional near-infrared spectroscopy (fNIRS) studies that examined the effect of CRF level on cerebral oxygenation during exercise and cognitive tasks.
METHODS
Medline, Embase, SPORTDiscus, and Web of Science were systematically searched. Studies categorizing CRF level using direct or estimated measures of V̇O and studies measuring cerebral oxygenation using oxyhemoglobin ([HbO]) and deoxyhemoglobin ([HHb]) were included. Healthy young, middle-aged, and older adults were included whereas patient populations and people with neurological disorders were excluded.
RESULTS
Following PRISMA guidelines, 14 studies were retained following abstract and full-text screening. Cycle ergometer or treadmill tests were used as direct measures of CRF, and one study provided an estimated value using a questionnaire. Seven studies examined the effects of CRF on cerebral oxygenation during exercise and the remaining seven evaluated it during cognitive tasks. Increased [HbO] in the prefrontal cortex (PFC) was observed during cognitive tasks in higher compared to lower fit individuals. Only one study demonstrated increased [HHb] in the higher fit group. Exercise at submaximal intensities revealed increased [HbO] in the PFC in higher compared to lower fit groups. Greater PFC [HHb] was also observed in long- vs. short-term trained males but not in females. Primary motor cortex (M1) activation did not differ between groups during a static handgrip test but [HHb] increased beyond maximal intensity in a lower compared to higher fit group.
CONCLUSION
Consistent with the cardiorespiratory hypothesis, higher fit young, middle-aged, and older adults demonstrated increased cerebral oxygenation compared to lower fit groups. Future research should implement randomized controlled trials to evaluate the effectiveness of interventions that improve CRF and cerebral oxygenation longitudinally.
PubMed: 35309063
DOI: 10.3389/fphys.2022.838450 -
Brain Imaging and Behavior Oct 2022Motor training is a widely used therapy in many pain conditions. The brain's capacity to undergo functional and structural changes i.e., neuroplasticity is fundamental... (Review)
Review
Motor training is a widely used therapy in many pain conditions. The brain's capacity to undergo functional and structural changes i.e., neuroplasticity is fundamental to training-induced motor improvement and can be assessed by transcranial magnetic stimulation (TMS). The aim was to investigate the impact of pain on training-induced motor performance and neuroplasticity assessed by TMS. The review was carried out in accordance with the PRISMA-guidelines and a Prospero protocol (CRD42020168487). An electronic search in PubMed, Web of Science and Cochrane until December 13, 2019, identified studies focused on training-induced neuroplasticity in the presence of experimentally-induced pain, 'acute pain' or in a chronic pain condition, 'chronic pain'. Included studies were assessed by two authors for methodological quality using the TMS Quality checklist, and for risk of bias using the Newcastle-Ottawa Scale. The literature search identified 231 studies. After removal of 71 duplicates, 160 abstracts were screened, and 24 articles were reviewed in full text. Of these, 17 studies on acute pain (n = 7) or chronic pain (n = 10), including a total of 258 patients with different pain conditions and 248 healthy participants met the inclusion criteria. The most common types of motor training were different finger tasks (n = 6). Motor training was associated with motor cortex functional neuroplasticity and six of seven acute pain studies and five of ten chronic pain studies showed that, compared to controls, pain can impede such trainings-induced neuroplasticity. These findings may have implications for motor learning and performance and with putative impact on rehabilitative procedures such as physiotherapy.
Topics: Humans; Magnetic Resonance Imaging; Neuronal Plasticity; Transcranial Magnetic Stimulation; Motor Cortex; Chronic Pain; Chronic Disease
PubMed: 35301674
DOI: 10.1007/s11682-021-00621-6 -
Frontiers in Aging Neuroscience 2022Arterial spin labeling (ASL) studies have revealed inconsistent regional cerebral blood flow (CBF) alterations in patients with type 2 diabetes mellitus (T2DM). The aim...
OBJECTIVE
Arterial spin labeling (ASL) studies have revealed inconsistent regional cerebral blood flow (CBF) alterations in patients with type 2 diabetes mellitus (T2DM). The aim of this systematic review and meta-analysis was to identify concordant regional CBF alterations in T2DM.
METHODS
A systematic review was conducted to the published literatures comparing cerebral perfusion between patients with T2DM and healthy controls using ASL. The seed-based mapping (SDM) was further used to perform quantitative meta-analysis on voxel-based literatures and to estimate the regional CBF alterations in patients with T2DM. Metaregression was performed to explore the associations between clinical characteristics and cerebral perfusion alterations.
RESULTS
A total of 13 studies with 14 reports were included in the systematic review and 7 studies with 7 reports were included in the quantitative meta-analysis. The qualitative review found widespread CBF reduction in cerebral lobes in T2DM. The meta-analysis found increased regional CBF in right supplementary motor area and decreased regional CBF in bilateral middle occipital gyrus, left caudate nucleus, right superior parietal gyrus, and left calcarine fissure/surrounding cortex in T2DM.
CONCLUSION
The patterns of cerebral perfusion alterations, characterized by the decreased CBF in occipital and parietal lobes, might be the neuropathology of visual impairment and cognitive aging in T2DM.
PubMed: 35250549
DOI: 10.3389/fnagi.2022.847218 -
Intensive Care Medicine Apr 2022To assess the ability of clinical examination, blood biomarkers, electrophysiology or neuroimaging assessed within 7 days from return of spontaneous circulation (ROSC)...
PURPOSE
To assess the ability of clinical examination, blood biomarkers, electrophysiology or neuroimaging assessed within 7 days from return of spontaneous circulation (ROSC) to predict good neurological outcome, defined as no, mild, or moderate disability (CPC 1-2 or mRS 0-3) at discharge from intensive care unit or later, in comatose adult survivors from cardiac arrest (CA).
METHODS
PubMed, EMBASE, Web of Science and the Cochrane Database of Systematic Reviews were searched. Sensitivity and specificity for good outcome were calculated for each predictor. The risk of bias was assessed using the QUIPS tool.
RESULTS
A total of 37 studies were included. Due to heterogeneities in recording times, predictor thresholds, and definition of some predictors, meta-analysis was not performed. A withdrawal or localisation motor response to pain immediately or at 72-96 h after ROSC, normal blood values of neuron-specific enolase (NSE) at 24 h-72 h after ROSC, a short-latency somatosensory evoked potentials (SSEPs) N20 wave amplitude > 4 µV or a continuous background without discharges on electroencephalogram (EEG) within 72 h from ROSC, and absent diffusion restriction in the cortex or deep grey matter on MRI on days 2-7 after ROSC predicted good neurological outcome with more than 80% specificity and a sensitivity above 40% in most studies. Most studies had moderate or high risk of bias.
CONCLUSIONS
In comatose cardiac arrest survivors, clinical, biomarker, electrophysiology, and imaging studies identified patients destined to a good neurological outcome with high specificity within the first week after cardiac arrest (CA).
Topics: Adult; Coma; Heart Arrest; Humans; Hypothermia, Induced; Prognosis; Survivors
PubMed: 35244745
DOI: 10.1007/s00134-022-06618-z -
Clinical Neurophysiology : Official... May 2022Mood disorders have been associated with lateralized brain dysfunction, on the left-side for depression and right-side for mania. Consistently, asymmetry of cortical... (Meta-Analysis)
Meta-Analysis
OBJECTIVE
Mood disorders have been associated with lateralized brain dysfunction, on the left-side for depression and right-side for mania. Consistently, asymmetry of cortical excitability, as measured by transcranial magnetic stimulation (TMS) has been reported. Here, we reviewed and summarized work assessing such measures bilaterally in mood disorders.
METHODS
We performed a systematic review and extracted data to perform meta-analyses of interhemispheric asymmetry of motor cortex excitability, assessed with TMS, across different mood disorders and in healthy subjects. Additionally, potential predictors of interhemispheric asymmetry were explored.
RESULTS
Asymmetry of resting motor threshold (MT) among healthy volunteers was significant, favoring lower right relative to left-hemisphere excitability. MT was also significantly asymmetric in major depressive disorder (MDD), but with lower excitability of the left -hemisphere, when compared to the right, no longer observed in recovered patients. Findings on intracortical facilitation were similar. The few trials including bipolar depression revealed similar trends for imbalance, but with lower right hemisphere excitability, relative to the left.
CONCLUSIONS
There is interhemispheric asymmetry of motor cortical excitability in MDD, with lower excitability on left when compared to right-side. Interhemispheric asymmetry, with lower right relative to left-sided excitability, was found for bipolar depression and was also suggested for healthy volunteers, in a pattern that is clearly distinct from MDD.
SIGNIFICANCE
Mood disorders display asymmetric motor cortical excitability that is distinct from that found in healthy volunteers, supporting the presence of lateralized brain dysfunction in these disorders.
Topics: Cortical Excitability; Depressive Disorder, Major; Evoked Potentials, Motor; Functional Laterality; Humans; Mood Disorders; Motor Cortex; Transcranial Magnetic Stimulation
PubMed: 35240425
DOI: 10.1016/j.clinph.2022.01.137 -
Journal of Neurophysiology Apr 2022Control of limb movements may be impaired after stroke due to the loss of connectivity between the cerebral cortex and spinal cord. A notion to improve motor function in... (Meta-Analysis)
Meta-Analysis Review
Control of limb movements may be impaired after stroke due to the loss of connectivity between the cerebral cortex and spinal cord. A notion to improve motor function in stroke survivors is to use alternate motor fibers, such as the reticulospinal tract (RST), which originate from the brainstem and terminate at different levels of spinal cord. One way of targeting the RST is to use a "StartReact" protocol to foster premature release of a preplanned movement in response to a startling stimulus. Our aim was to find support for the preservation of such StartReact effect in stroke survivors. We conducted a systematic review with meta-analysis of literature published in English up to September 2020, to explore differences in motor responses to startling stimuli in StartReact effects. Protocol of the study was registered (PROSPERO Registration No. CRD42020191581). PubMed, Google Scholar, Web of Science, PsycINFO, and Science Direct were searched for relevant literature. The meta-analysis contained six studies involving a total of 151 stroke and healthy participants. Muscle onset latency data were extracted from the qualifying studies and compared using RevMan. StartReact effect was present in both stroke and healthy groups, represented by shortened muscle onset latency when startling stimulus was present. There was considerable heterogeneity of the outcome measures, which was attributed to the range of motor impairments among stroke survivors and methodologies used. Our findings support the notion of preservation of preprogramming ability and suitability of RST and StartReact effect for motor rehabilitation following stroke.
Topics: Acoustic Stimulation; Electromyography; Humans; Reflex, Startle; Stroke; Stroke Rehabilitation; Survivors
PubMed: 35235444
DOI: 10.1152/jn.00392.2021 -
Frontiers in Integrative Neuroscience 2022To evaluate the evidence for altered cortical and spinal cord functions in individuals with patellofemoral pain (PFP).
OBJECTIVE
To evaluate the evidence for altered cortical and spinal cord functions in individuals with patellofemoral pain (PFP).
METHODS
We conducted a comprehensive search of databases to appraise and analyze the studies published prior to December 10, 2021 that examined spinal reflex excitability measured using Hoffmann reflex (H-reflex) amplitudes, corticospinal excitability measured using transcranial magnetic stimulation (TMS)-elicited motor evoked potential (MEP) amplitudes, motor threshold (MT), or stimulus-response (SR) curves, cortical reorganization assessed using TMS cortical mapping or structural magnetic resonance imaging (MRI), or functional changes of the brain assessed using functional MRI (fMRI) in individuals with PFP.
RESULTS
Eight studies were eligible for analyses. While an earlier study showed that pain had no effect on the H-reflex amplitude of the quadriceps muscle, more recent evidence reported a decrease in vastus medialis (VM) H-reflex amplitude in participants with PFP. VM H-reflex amplitude was correlated with pain, chronicity, physical function, and isometric knee extensor torque production in participants with PFP. Altered corticospinal excitability was reported in participants with PFP, observed as increased MT in the VM and vastus lateralis (VL) muscles. In addition, cortical reorganization has been observed, where decreased number of cortical peaks, shifts and reduced volumes, and increased overlap of motor cortex representations for the VM, VL, and rectus femoris (RF) muscles were reported in participants with PFP.
CONCLUSION
There is emerging evidence on altered cortical and spinal cord functions in individuals with PFP, however, solid conclusions cannot be drawn due to limited literature available. Further research is needed to better understand the adaptations of the brain and spinal cord in this population.
SYSTEMATIC REVIEW REGISTRATION
https://www.crd.york.ac.uk/prospero/, identifier: CRD42020212128.
PubMed: 35197832
DOI: 10.3389/fnint.2022.791719 -
Journal of Neuroengineering and... Feb 2022Transcranial magnetic stimulation (TMS) has attracted plenty of attention as it has been proved to be effective in facilitating motor recovery in patients with stroke.... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Transcranial magnetic stimulation (TMS) has attracted plenty of attention as it has been proved to be effective in facilitating motor recovery in patients with stroke. The aim of this study was to systematically review the effects of repetitive TMS (rTMS) and theta burst stimulation (TBS) protocols in modulating cortical excitability after stroke.
METHODS
A literature search was carried out using PubMed, Medline, EMBASE, CINAHL, and PEDro, to identify studies that investigated the effects of four rTMS protocols-low and high frequency rTMS, intermittent and continuous TBS, on TMS measures of cortical excitability in stroke. A random-effects model was used for all meta-analyses.
RESULTS
Sixty-one studies were included in the current review. Low frequency rTMS was effective in decreasing individuals' resting motor threshold and increasing the motor-evoked potential of the non-stimulated M1 (affected M1), while opposite effects occurred in the stimulated M1 (unaffected M1). High frequency rTMS enhanced the cortical excitability of the affected M1 alone. Intermittent TBS also showed superior effects in rebalancing bilateral excitability through increasing and decreasing excitability within the affected and unaffected M1, respectively. Due to the limited number of studies found, the effects of continuous TBS remained inconclusive. Motor impairment was significantly correlated with various forms of TMS measures.
CONCLUSIONS
Except for continuous TBS, it is evident that these protocols are effective in modulating cortical excitability in stroke. Current evidence does support the effects of inhibitory stimulation in enhancing the cortical excitability of the affected M1.
Topics: Cortical Excitability; Evoked Potentials, Motor; Humans; Motor Cortex; Stroke; Transcranial Magnetic Stimulation
PubMed: 35193624
DOI: 10.1186/s12984-022-00999-4