Isoflurane affects brain functional connectivity in rats 1 month after exposure

Isoflurane, the most commonly used preclinical anesthetic, induces brain plasticity and long-term cellular and molecular changes leading to behavioral and/or cognitive consequences. These changes are most likely associated with network-level changes in brain function. To elucidate the mechanisms underlying long-term effects of isoflurane, we investigated the influence of a single isoflurane exposure on functional connectivity, brain electrical activity, and gene expression. Male Wistar rats (n = 22) were exposed to 1.8% isoflurane for 3 h. Control rats (n = 22) spent 3 h in the same room without exposure to anesthesia. After 1 month, functional connectivity was evaluated with resting-state functional magnetic resonance imaging (fMRI; n = 6 + 6) and local field potential measurements (n = 6 + 6) in anesthetized animals. A whole genome expression analysis (n = 10+10) was also conducted with mRNA-sequencing from cortical and hippocampal tissue samples. Isoflurane treatment strengthened thalamo-cortical and hippocampal-cortical functional connectivity. Cortical low-frequency fMRI power was also significantly increased in response to the isoflurane treatment. The local field potential results indicating strengthened hippocampal-cortical alpha and beta coherence were in good agreement with the fMRI findings. Furthermore, altered expression was found in 20 cortical genes, several of which are involved in neuronal signal transmission, but no gene expression changes were noted in the hippocampus. Isoflurane induced prolonged changes in thalamo-cortical and hippocampal-cortical function and expression of genes contributing to signal transmission in the cortex. Further studies are required to investigate whether these changes are associated with the postoperative behavioral and cognitive symptoms commonly observed in patients and animals.

Music Playing and Interhemispheric Communication: Older Professional Musicians Outperform Age-Matched Non-Musicians in Fingertip Cross-Localization Test

OBJECTIVE

Numerous investigations have documented that age-related changes in the integrity of the corpus callosum are associated with age-related decline in the interhemispheric transfer of information. Conversely, there is accumulating evidence for more efficient white matter organization of the corpus callosum in individuals with extensive musical training. However, the relationship between making music and accuracy in interhemispheric transfer remains poorly explored.

METHODS

To test the hypothesis that musicians show enhanced functional connectivity between the two hemispheres, 65 professional musicians (aged 56-90 years) and 65 age- and sex-matched non-musicians performed the fingertip cross-localization test. In this task, subjects must respond to a tactile stimulus presented to one hand using the ipsilateral (intra-hemispheric test) or contralateral (inter-hemispheric test) hand. Because the transfer of information from one hemisphere to another may imply a loss of accuracy, the value of the difference between the intrahemispheric and interhemispheric tests can be utilized as a reliable measure of the effectiveness of hemispheric interactions.

RESULTS

Older professional musicians show significantly greater accuracy in tactile interhemispheric transfer than non-musicians who suffer from age-related decline.

CONCLUSIONS

Musicians have more efficient interhemispheric communication than age-matched non-musicians. This finding is in keeping with studies showing that individuals with extensive musical training have a larger corpus callosum. The results are discussed in relation to relevant data suggesting that music positively influences aging brain plasticity.

A web-based adapted physical activity program (e-APA) versus health education program (e-HE) in patients with schizophrenia and healthy volunteers: study protocol for a randomized controlled trial (PEPSY V@Si)

Patients with schizophrenia (SZ) have a high level of cardiovascular morbidity and some clinical symptoms of illness remain resistant to pharmacological approaches. A large number of studies support the effectiveness of physical activity (PA) in SZ. The aims of this trial is to assess the effects of a remote, web-based adapted PA program (e-APA) compared to a health education program (e-HE) on brain plasticity in SZ and healthy volunteers (HV) and on psychiatric, neurocognitive, circadian and physical variables. The study is an interventional, multicenter, randomized open-label trial. Forty-two SZ will be randomized to either the active group (e-APA, N = 21) or nonactive group (e-HE, N = 21), and 21 HV will be matched to SZ according to age, gender, and level of PA in both e-APA and e-HE groups. Interventions will consist of 32 sessions (2 × 60 min/week, for 16 weeks) via supervised home-based videoconferencing. Cerebral magnetic resonance imaging, psychiatric symptoms, neurocognitive and circadian rhythms assessments as well as physical tests and biological analyses will be assessed at baseline and 16 weeks after the intervention. To our knowledge, this is the first study aiming to evaluate the efficacy of APA delivered by supervised home-based videoconferencing in SZ. Moreover, using multimodal MRI, this study could clarify the pathophysiological mechanisms underlying the efficacy of APA. Finally, this innovative approach might also increase participation in long-term PA since PA-based programs are known to have low adherence and early dropout. Trial registration: ClinicalTrials.gov identifier: NCT03261817. Registered on 16 August 2017.

Stimulation of the Serotonin Receptor 7 Restores Brain Histone H3 Acetylation and MeCP2 Corepressor Protein Levels in a Female Mouse Model of Rett Syndrome

Rett syndrome (RTT) is a rare neurological disorder caused by mutations in the X-linked MECP2 gene, characterized by severe behavioral and physiological impairments for which no cure is available. The stimulation of serotonin receptor 7 (5-HT7R) with its selective agonist LP-211 (0.25 mg/kg/day for 7 days) was proved to rescue neurobehavioral alterations in a mouse model of RTT. In the present study, we aimed at gaining insight into the mechanisms underpinning the efficacy of 5-HT7R pharmacological stimulation by investigating its epigenetic outcomes in the brain of RTT female mice bearing a truncating MeCP2 mutation. Treatment with LP-211 normalized the reduced histone H3 acetylation and HDAC3/NCoR levels, and increased HDAC1/Sin3a expression in RTT mouse cortex. Repeated 5-HT7R stimulation also appeared to strengthen the association between NCoR and MeCP2 in the same brain region. A different profile was found in RTT hippocampus, where LP-211 rescued H3 hyperacetylation and increased HDAC3 levels. Overall, the present data highlight a new scenario on the relationship between histone acetylation and serotoninergic pathways. 5-HT7R is confirmed as a pivotal therapeutic target for the recovery of neuronal function supporting the translational value of this promising pharmacological approach for RTT.

Contemporary clinical neurophysiology applications in dystonia

The complex phenomenological understanding of dystonia has transcended from the clinics to genetics, imaging and neurophysiology. One way in which electrophysiology will impact into the clinics are cases wherein a dystonic clinical presentation may not be typical or a "forme fruste" of the disorder. Indeed, the physiological imprints of dystonia are present regardless of its clinical manifestation. Underpinnings in the understanding of dystonia span from the peripheral, segmental and suprasegmental levels to the cortex, and various electrophysiological tests have been applied in the course of time to elucidate the origin of dystonia pathophysiology. While loss of inhibition remains to be the key finding in this regard, intricacies and variabilities exist, thus leading to a notion that perhaps dystonia should best be gleaned as network disorder. Interestingly, the complex process has now spanned towards the understanding in terms of networks related to the cerebellar circuitry and the neuroplasticity. What is evolving towards a better and cohesive view will be neurophysiology attributes combined with structural dynamic imaging. Such a sound approach will significantly lead to better therapeutic modalities in the future.

Visual motion processing recruits regions selective for auditory motion in early deaf individuals

In early deaf individuals, the auditory deprived temporal brain regions become engaged in visual processing. In our study we tested further the hypothesis that intrinsic functional specialization guides the expression of cross-modal responses in the deprived auditory cortex. We used functional MRI to characterize the brain response to horizontal, radial and stochastic visual motion in early deaf and hearing individuals matched for the use of oral or sign language. Visual motion showed enhanced response in the 'deaf' mid-lateral planum temporale, a region selective to auditory motion as demonstrated by a separate auditory motion localizer in hearing people. Moreover, multivariate pattern analysis revealed that this reorganized temporal region showed enhanced decoding of motion categories in the deaf group, while visual motion-selective region hMT+/V5 showed reduced decoding when compared to hearing people. Dynamic Causal Modelling revealed that the 'deaf' motion-selective temporal region shows a specific increase of its functional interactions with hMT+/V5 and is now part of a large-scale visual motion selective network. In addition, we observed preferential responses to radial, compared to horizontal, visual motion in the 'deaf' right superior temporal cortex region that also show preferential response to approaching/receding sounds in the hearing brain. Overall, our results suggest that the early experience of auditory deprivation interacts with intrinsic constraints and triggers a large-scale reallocation of computational load between auditory and visual brain regions that typically support the multisensory processing of motion information.

Transcranial direct current stimulation modulates brain functional connectivity in autism

Autism spectrum disorder (ASD) is characterized by deficits in social interactions, impairments in language and communication, and highly restricted behavioral interests. Transcranial direct current stimulation (tDCS) is a widely used form of noninvasive stimulation and may have therapeutic potential for ASD. So far, despite the widespread use of this technique in the neuroscience field, its effects on network-level neural activity and the underlying mechanisms of any effects are still unclear. In the present study, we used electroencephalography (EEG) to investigate tDCS induced brain network changes in children with ASD before and after active and sham stimulation. We recorded 5 min of resting state EEG before and after a single session of tDCS (of approximately 20 min) over dorsolateral prefrontal cortex (DLPFC). Two network-based methods were applied to investigate tDCS modulation on brain networks: 1) temporal network dynamics were analyzed by comparing "flexibility" changes before vs after stimulation, and 2) frequency specific network changes were identified using non-negative matrix factorization (NMF). We found 1) an increase in network flexibility following tDCS (rapid network configuration of dynamic network communities), 2) specific increase in interhemispheric connectivity within the alpha frequency band following tDCS. Together, these results demonstrate that tDCS could help modify both local and global brain network dynamics, and highlight stimulation-induced differences in the manifestation of network reconfiguration. Meanwhile, frequency-specific subnetworks, as a way to index local and global information processing, highlight the core modulatory effects of tDCS on the modular architecture of the functional connectivity patterns within higher frequency bands.

Visual field restoration after Simpson grade I resection of symptomatic occipital lobe meningioma: illustrative case and review of the literature

Intracranial meningiomas mostly affect patients in their fifth decade and beyond, raising pertinent questions regarding the risk of surgery, particularly in the elderly. Here, we describe the case of a septuagenarian patient with occipital meningioma causing severe visual field cuts that experienced full recovery of the visual function after a Simpson I resection of the lesion. This case illustrates the potential of recovery of the brain, even in the case of severely impaired function in elderly patients. To complete the picture, we review the literature on occipital meningiomas, advocating for systematic reports and increase data collection on post-operative neurological recovery in the elderly.

Sustained and transient gray matter volume changes after n-back training: A VBM study

Working memory training causes functional adaptations in the brain, which include changes in activation and functional connectivity that remain stable over time. Few studies have investigated gray matter (GM) changes after working memory training, and they have produced heterogeneous results without clarifying the stable effects of training. The present study was designed to test for sustained and transient anatomic changes after only 200 min of working memory training. The voxel-based morphometry technique was used in order to investigate the GM changes produced by a brief single n-back training, immediately and 5 weeks after finishing it. The sample was composed by 59 human participants who underwent MRI scanning and were assigned to either a training group or a passive control group. Results showed sustained GM volume enlargement in the right superior parietal cortex and a transient GM decrease in the right putamen. The brain adaptation in the right superior parietal cortex was stronger in individuals who showed greater improvements in performance. The results provide further evidence that a brief working memory training is able to produce brain plasticity in structures related to the trained task.

Brain plasticity dynamics during tactile Braille learning in sighted subjects: Multi-contrast MRI approach

A growing body of empirical evidence supports the notion of diverse neurobiological processes underlying learning-induced plasticity changes in the human brain. There are still open questions about how brain plasticity depends on cognitive task complexity, how it supports interactions between brain systems and with what temporal and spatial trajectory. We investigated brain and behavioural changes in sighted adults during 8-months training of tactile Braille reading whilst monitoring brain structure and function at 5 different time points. We adopted a novel multivariate approach that includes behavioural data and specific MRI protocols sensitive to tissue properties to assess local functional and structural and myelin changes over time. Our results show that while the reading network, located in the ventral occipitotemporal cortex, rapidly adapts to tactile input, sensory areas show changes in grey matter volume and intra-cortical myelin at different times. This approach has allowed us to examine and describe neuroplastic mechanisms underlying complex cognitive systems and their (sensory) inputs and (motor) outputs differentially, at a mesoscopic level.

NPY-Y1 receptor signaling controls spatial learning and perineuronal net expression

Perineuronal nets (PNNs) are extracellular matrix structures that form around some types of neurons at the end of critical periods, limiting neuronal plasticity. In the adult brain, PNNs play a crucial role in the regulation of learning and cognitive processes. Neuropeptide Y (NPY) is involved in the regulation of many physiological functions, including learning and memory abilities, via activation of Y1 receptors (Y1Rs). Here we demonstrated that the conditional depletion of the gene encoding the Y1R for NPY in adult forebrain excitatory neurons (Npy1r^rfb mutant mice), induces a significant slowdown in spatial learning, which is associated with a robust intensification of PNN expression and an increase in the number of c-Fos expressing cells in the cornus ammonis 1 (CA1) of the dorsal hippocampus. Importantly, the enzymatic digestion of PNNs in CA1 normalizes c-Fos activity and completely rescues learning abilities of Npy1r^rfb mice. These data highlight a previously unknown functional link between NPY-Y1R transmission and PNNs, which may play a role in the control of dorsal hippocampal excitability and related cognitive functions.

How visual is the « number sense »? Insights from the blind

Is vision a necessary building block for the foundations of mathematical cognition? A straightforward model to test the causal role visual experience plays in the development of numerical abilities is to study people born without sight. In this review we will demonstrate that congenitally blind people can develop numerical abilities that equal or even surpass those of sighted individuals, despite representing numbers using a qualitatively different representational format. We will also show that numerical thinking in blind people maps onto regions typically involved in visuo-spatial processing in the sighted, highlighting how intrinsic computational biases may constrain the reorganization of numerical networks in case of early visual deprivation. More generally, we will illustrate how the study of arithmetic abilities in congenitally blind people represents a compelling model to understand how sensory experience scaffolds the development of higher-level cognitive representations.

[Electroacupuncture-induced plasticity between hand and face representations in the motor cortex in healthy subjects]

OBJECTIVE

To observe the plasticity between hand and face representations of the motor cortex of healthy volunteers after electroacupuncture(EA) at Hegu(LI4), so as to provide a scientific basis for the theory of "Hegu is indicated for orofacial problems".

METHODS

Using a cross-over design (self-controlled study), 10 healthy volunteers were randomly assigned to an acupuncture group and a sham acupuncture group (two-weeks wash-out period between the two groups). Subjects in the acupuncture group received EA stimulation (2 Hz, 0.5 to 1 mA, 30 min) at LI4 on their left hands. Adhesive pads sticked on the left hands of subject in the sham acupuncture group, thus, the placebo needle provided participants with a similar appearance to that in the acupuncture group but no skin penetration, and the placebo needles were connected to an EA device with a broken wire inside. Using transcranial magnetic stimulation technology, the motor evoked potentials (MEPs) of the first dorsal interosseous muscle and the orbicularis oculi muscle in hand and face representations in the contralateral motor cortex were recorded before and after EA and sham EA, and the total amplitude, effective stimulation area and center of gravity of MEPs were calculated.

RESULTS

Compared with that before intervention, for acupuncture group, the total amplitude of MEPs in hand representation in the contrala-teral motor cortex was significantly increased(P<0.05),while the total amplitude of MEPs in face representation was significantly decreased (P<0.05). The effective stimulation area in hand representation was significantly increased(P<0.01), and there was no difference in face representation(P>0.05). The difference in the center of gravity of the X-axis in hand representation was statistically significant (P<0.05)，with the center of gravity moved an average of 0.6 cm to the outside, and there was no difference in face representation (P>0.05). There was no difference in the center of gravity of the Y-axis in hand and face representations(P>0.05). For sham acupuncture group, there were no differences in total amplitude of MEPs, effective stimulation area and the center of gravity in hand and face representations (P>0.05).

CONCLUSION

EA at LI4 can induce plasticity between the hand and face representations of the motor cortex in healthy volunteers (exciting the hand representation of the motor cortex, while inhibiting the motor cortex representation), which provides a scientific basis for treating facial and mouth diseases by acupuncture at LI4 and the theory of selecting acupoints of the corresponding meridian distal to the disease location.

Intensity dependent effect of cognitive training on motor cortical plasticity and cognitive performance in humans

Intervention-induced neuroplastic changes within the motor or cognitive system have been shown in the human brain. While cognitive and motor brain areas are densely interconnected, it is unclear whether this interconnectivity allows for a shared susceptibility to neuroplastic changes. Using the preparation for a theoretical exam as training intervention that primarily engages the cognitive system, we tested the hypothesis whether neuroplasticity acts across interconnected brain areas by investigating the effect on excitability and synaptic plasticity in the motor cortex. 39 healthy students (23 female) underwent 4 weeks of cognitive training while revision time, physical activity, concentration, fatigue, sleep quality and stress were monitored. Before and after cognitive training, cognitive performance was evaluated, as well as motor excitability using transcranial magnetic stimulation and long-term-potentiation-like (LTP-like) plasticity using paired-associative-stimulation (PAS). Cognitive training ranged individually from 1 to 7 h/day and enhanced attention and verbal working memory. While motor excitability did not change, LTP-like plasticity increased in an intensity-depending manner: the longer the daily revision time, the smaller the increase of neuroplasticity, and vice versa. This effect was not influenced by physical activity, concentration, fatigue, sleep quality or stress. Motor cortical plasticity is strengthened by a behavioural intervention that primarily engages cognitive brain areas. We suggest that this effect is due to an enhanced susceptibility to LTP-like plasticity, probably induced by heterosynaptic activity that modulates postsynaptic excitability in motorcortical neurones. The smaller increase of PAS efficiency with higher cognitive training intensity suggests a mechanism that balances and stabilises the susceptibility for synaptic potentiation.

Sigma-1 (σ1) receptor activity is necessary for physiological brain plasticity in mice

The sigma-1 receptor (S1R) is a membrane-associated protein expressed in neurons and glia at mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs). S1R interacts with different partners to regulate cellular responses, including ER stress, mitochondrial physiology and Ca2+ fluxes. S1R shapes cellular plasticity by directly modulating signaling pathways involved in inflammatory responses, cell survival and death. We here analyzed its impact on brain plasticity in vivo, in mice trained in a complex maze, the Hamlet test. The device, providing strong enriched environment (EE) conditions, mimics a small village. It has a central agora and streets expanding from it, leading to functionalized houses where animals can Drink, Eat, Hide, Run, or Interact. Animals were trained in groups, 4 h/day for two weeks, and their maze exploration and topographic memory could be analyzed. Several groups of mice were considered: non-trained vs. trained; repeatedly administered with saline vs. NE-100, a selective S1R antagonist; and wildtype vs. S1R KO mice. S1R inactivation altered maze exploration and prevented topographic learning. EE induced a strong plasticity measured through resilience to behavioral despair or to the amnesic effects of scopolamine, and increases in S1R expression and bdnf mRNA levels in the hippocampus; increases in neurogenesis (proliferation and maturation); and increases of histone acetylation in the hippocampus and cortex. S1R inactivation altered all these parameters significantly, showing that S1R activity plays a major role in physiological brain plasticity. As S1R is a major resident protein in MAMs, modulating ER responses and mitochondrial homeostasy, MAM physiology appeared impacted by enriched environment.

Regional brain gray matter volume in world-class artistic gymnasts

The relationship between long-term intensive training and brain plasticity in gymnasts has recently been reported. However, the relationship between abilities in different gymnastic events and brain structural changes has not been explored. This study aimed to evaluate the correlation between world-class gymnasts (WCGs)' specific abilities in different gymnastics events and their gray matter (GM) volume. Ten right-handed Japanese male WCGs and 10 right-handed gender- and age-matched controls with no history of gymnastic training participated in this study. Whole brain three-dimensional T1-weighted images (magnetization-prepared rapid gradient-echo sequence) with 0.90 mm3 voxels were obtained using a 3 T-MRI scanner from each subject. Volume-based morphometry (VolBM) was used to compare GM volume differences between WCGs and controls. We then explored the correlation between specific gymnastic abilities using different gymnastic apparatuses, and GM volume. Significantly higher GM volumes (false discovery rate-corrected p < 0.05) in the inferior parietal lobule, middle temporal gyrus, precentral gyrus, rostral middle frontal gyrus, and superior frontal gyrus were demonstrated in WCGs, compared with controls using VolBM. Moreover, significant positive correlations were observed between brain regions and the difficulty scores for each gymnastic event, for example, rings and inferior parietal lobule and parallel bars and rostral middle frontal gyrus. These results may reflect the neural basis of an outstanding gymnastic ability resulting from brain plasticity in areas associated with spatial perception, vision, working memory, and motor control.

Virtual reality-based treatment for regaining upper extremity function induces cortex grey matter changes in persons with acquired brain injury

Background

Individuals with acquired brain injuries (ABI) are in need of neurorehabilitation and neurorepair. Virtual anatomical interactivity (VAI) presents a digital game-like format in which ABI survivors with upper limb paresis use an unaffected limb to control a standard input device and a commonplace computer mouse to control virtual limb movements and tasks in a virtual world.

Methods

In a prospective cohort study, 35 ambulatory survivors of ABI (25/71% stroke, 10/29% traumatic brain injury) were enrolled. The subjects were divided into three groups: group A received VAI therapy only, group B received VAI and physical/occupational therapy (P/OT), and group C received P/OT only. Motor skills were evaluated by muscle strength (hand key pinch strength, grasp, and three-jaw chuck pinch) and active range of motion (AROM) of the shoulder, elbow, and wrist. Changes were analyzed by ANOVA, ANCOVA, and one-tailed Pearson correlation analysis. MRI data was acquired for group A, and volumetric changes in grey matter were analyzed using voxel-based morphometry (VBM) and correlated with quantified motor skills.

Results

AROM of the shoulder, elbow, and wrist improved in all three groups. VBM revealed grey matter increases in five brain areas: the tail of the hippocampus, the left caudate, the rostral cingulate zone, the depth of the central sulcus, and the visual cortex. A positive correlation between the grey matter volumes in three cortical regions (motor and premotor and supplementary motor areas) and motor test results (power and AROM) was detected.

Conclusions

Our findings suggest that the VAI rehabilitation program significantly improved motor function and skills in the affected upper extremities of subjects with acquired brain injuries. Significant increases in grey matter volume in the motor and premotor regions of affected hemisphere and correlations of motor skills and volume in nonaffected brain regions were present, suggesting marked changes in structural brain plasticity.

Trial registration

The trial “Limitations of motor brain activity – use of virtual reality for simulation of therapeutic interventions” has been registered under reference number ISRCTN11757651.

Clinical Application of Brain Plasticity in Neurosurgery

Brain plasticity is an ongoing process of reorganization not only on the macroscopic level but also from underlying changes at the cellular and molecular levels of neurons. This evolution has not yet been fully understood. The objective of this paper is to review and understand neuroplasticity through the review of literature, imaging, and intraoperative evidence.

Novel FMRI-Compatible wrist robotic device for brain activation assessment during rehabilitation exercise

Magnetic Resonance Imaging (MRI) can be applied to study the effects of rehabilitation strategies for neuroscience research. An MRI-wrist robot is designed and used as a clinical tool to examine the process of the brain plasticity changes. In this robot, the patient actuation is accomplished with two standard air cylinders, located inside the MRI chamber with two degrees of freedom (flexion-extension and ulna-radial deviation) with pneumatic air transmission, consisting of simple mechanism converting rotary motion to linear independently. A pilot study of brain image aiming at revealing more effective therapeutic strategies carried out to confirm the technical aspects of the development and validation. In a healthy subject, both wrist movement of robot and subject demonstrated brain activity in the contralateral primary somatosensory cortex. Because the robot does not move during the patient's body, a stand was designed to allow the wrist robot and patient to fit comfortably within the MRI machine. While all the parts of the robot were carefully selected with strict MRI compatibility requirements, the robot was tested by presenting some pilot imaging data with null effects on the image quality, as well. Finally, the possible further development of the robot has been introduced for a rehabilitation assessment.

Cortical plasticity after hand prostheses use: Is the hypothesis of deafferented cortex "invasion" always true?

OBJECTIVE

To study motor cortex plasticity after a period of training with a new prototype of bidirectional hand prosthesis in three left trans-radial amputees, correlating these changes with the modification of Phantom Limb Pain (PLP) in the same period.

METHODS

Each subject underwent a brain motor mapping with Transcranial Magnetic Stimulation (TMS) and PLP evaluation with questionnaires during a six-month training with a prototype of bidirectional hand prosthesis.

RESULTS

The baseline motor maps showed in all three amputees a smaller area of muscles representation of the amputated side compared to the intact limb. After training, there was a partial reversal of the baseline asymmetry. The two subjects affected by PLP experienced a statistically significant reduction of pain.

CONCLUSIONS

Two apparently opposite findings, the invasion of the "deafferented" cortex by neighbouring areas and the "persistence" of neural structures after amputation, could vary according to different target used for measurement. Our results do not support a correlation between PLP and motor cortical changes.

SIGNIFICANCE

The selection of the target and of the task is essential for studies investigating motor brain plasticity. This study boosts against a direct and unique role of motor cortical changes on PLP genesis.

Sex hormones and proteins involved in brain plasticity

It is well known that peripheral sex steroid hormones cross the blood-brain barrier and control a broad spectrum of reproductive behaviors. However, their role in other essential brain functions was investigated since the 1980s, when the accumulation of pregnenolone and dehydroepiandrosterone in the brain of mammalian species was determined. Since then, numerous studies have demonstrated the participation of sex hormones in brain plasticity processes. Sex hormones through both genomic and non-genomic mechanisms of action are capable of inducing gene transcription or activating signaling cascades that result in the promotion of different physiological and pathological events of brain plasticity, such as remodeling or formation of dendritic spines, neurogenesis, synaptogenesis or myelination. In this chapter, we will present the effects of sex hormones and proteins involved in brain plasticity.

Increased amygdala and decreased hippocampus volume after schedule-induced polydipsia in high drinker compulsive rats

Fronto-limbic structures and serotonin 2A receptors (5-HT_2A) have been implicated in the pathophysiology and treatment of compulsive spectrum disorders. Schedule-Induced Polydipsia (SIP), characterized by the development of excessive drinking under intermittent food reinforcement schedules, is a valid preclinical model for studying the compulsive phenotype. In the present study, we explored the individual differences and effect of SIP in brain volume and 5-HT_2A receptor binding in fronto-limbic structures in rats selected according to their compulsive drinking behavior. Rats were divided into high (HD) and low drinkers (LD) by SIP (20 sessions); later, we analyzed the brains of HD and LD selected rats, in two different conditions: non-re-exposure (NRE) or re-exposure to SIP (RE), with four groups: LD-NRE, LD-RE, HD-NRE and HD-RE. Histological analyses were carried out for volumetric (stereology) and receptor binding (autoradiography) in the prelimbic and infralimbic cortex, dorsal hippocampus and basolateral amygdala. After SIP re-exposure, HD-RE showed an increased basolateral amygdala and a reduced hippocampus volume compared to HD-NRE rats, and also compared to LD-RE rats. No differences were found between HD and LD in NRE condition. Moreover, HD rats exhibit a lower 5-HT_2A receptor binding in the basolateral amygdala, independently of SIP re-exposure, compared to LD rats. However, LD-RE showed a decreased 5-HT_2A receptor binding in basolateral amygdala compared to LD-NRE. No differences were found in the remaining structures. These findings suggest that SIP might be differentially impacting HD and LD brains, pointing towards a possible explanation of how the latent vulnerability to compulsivity is triggered.

The posterior parietal cortex mediates early offline-rather than online-motor sequence learning

Learning of new motor skills occurs particularly during training on a task (i.e. online) but has been observed between training-blocks lasting up to days after the end of the training (i.e. offline). Offline-learning occurs as further improvement in task performance indicated by increased accuracy and/or faster responses as well as less interference with respect to a distracting condition. Successful motor learning requires the functional interplay between cortical as well as subcortical brain areas. While the involvement of the primary motor cortex in online-as well as early offline-learning is well established, the functional significance of the posterior parietal cortex (PPC) is less clear. Since the PPC may act as sensory-motor interface, a causal involvement in motor learning is conceivable. In order to characterize the functional significance of the left PPC for motor sequence learning, transcranial direct current stimulation (tDCS) was applied either immediately prior to, during or immediately after training on a serial reaction time task (SRTT) in a total of 54 healthy volunteers. While the analysis did not provide evidence for a significant modulation of reaction times during SRTT training (i.e. online-learning), cathodal tDCS decelerated reaction times of the learned sequences as compared to anodal and sham stimulation 30 min after the end of training. The findings suggest that cathodal tDCS over the left parietal cortex interferes with the reproduction of learned sequences.

The Promotoer, a brain-computer interface-assisted intervention to promote upper limb functional motor recovery after stroke: a study protocol for a randomized controlled trial to test early and long-term efficacy and to identify determinants of response

BACKGROUND

Stroke is a leading cause of long-term disability. Cost-effective post-stroke rehabilitation programs for upper limb are critically needed. Brain-Computer Interfaces (BCIs) which enable the modulation of Electroencephalography (EEG) sensorimotor rhythms are promising tools to promote post-stroke recovery of upper limb motor function. The "Promotoer" study intends to boost the application of the EEG-based BCIs in clinical practice providing evidence for a short/long-term efficacy in enhancing post-stroke hand functional motor recovery and quantifiable indices of the participants response to a BCI-based intervention. To these aims, a longitudinal study will be performed in which subacute stroke participants will undergo a hand motor imagery (MI) training assisted by the Promotoer system, an EEG-based BCI system fully compliant with rehabilitation requirements.

METHODS

This longitudinal 2-arm randomized controlled superiority trial will include 48 first ever, unilateral, subacute stroke participants, randomly assigned to 2 intervention groups: the BCI-assisted hand MI training and a hand MI training not supported by BCI. Both interventions are delivered (3 weekly session; 6 weeks) as add-on regimen to standard intensive rehabilitation. A multidimensional assessment will be performed at: randomization/pre-intervention, 48 h post-intervention, and at 1, 3 and 6 month/s after end of intervention. Primary outcome measure is the Fugl-Meyer Assessment (FMA, upper extremity) at 48 h post-intervention. Secondary outcome measures include: the upper extremity FMA at follow-up, the Modified Ashworth Scale, the Numeric Rating Scale for pain, the Action Research Arm Test, the National Institute of Health Stroke Scale, the Manual Muscle Test, all collected at the different timepoints as well as neurophysiological and neuroimaging measures.

DISCUSSION

We expect the BCI-based rewarding of hand MI practice to promote long-lasting retention of the early induced improvement in hand motor outcome and also, this clinical improvement to be sustained by a long-lasting neuroplasticity changes harnessed by the BCI-based intervention. Furthermore, the longitudinal multidimensional assessment will address the selection of those stroke participants who best benefit of a BCI-assisted therapy, consistently advancing the transfer of BCIs to a best clinical practice.

TRIAL REGISTRATION

Name of registry: BCI-assisted MI Intervention in Subacute Stroke (Promotoer).

TRIAL REGISTRATION NUMBER

NCT04353297 ; registration date on the ClinicalTrial.gov platform: April, 15/2020.

iTRAQ-based proteomic analysis after mesenchymal stem cell line transplantation for ischemic stroke

Transplantation with mesenchymal stem cells (MSCs) has been reported to promote functional recovery in animal models of ischemic stroke. However, the molecular mechanisms underlying the therapeutic effects of MSC transplantation have been only partially elucidated. The purpose of this study was to comprehensively identify changes in brain proteins in rats treated with MSCs for ischemic stroke, and to explore the multi-target mechanisms of MSCs using a proteomics-based strategy. Twenty-eight proteins were found to be differentially expressed following B10 MSC transplantation in adult male Wistar rats, as assessed using isobaric tagging for relative and absolute protein quantification (iTRAQ). Subsequent bioinformatic analysis revealed that these proteins were mainly associated with energy metabolism, glutamate excitotoxicity, oxidative stress, and brain structural and functional plasticity. Immunohistochemical staining revealed decreased expression of EAAT1 in the phosphate-buffered saline group as opposed to normal levels in the B10 transplantation group. Furthermore, ATP levels were also significantly higher in the B10 transplantation group, thus supporting the iTRAQ results. Our results suggest that the therapeutic effects of B10 transplantation might arise from the modulation of the acute ischemic cascade via multiple molecular pathways. Thus, our findings provide valuable clues to elucidate the mechanisms underlying the therapeutic effects of MSC transplantation in ischemic stroke.

Long-distance aberrant heterotopic connectivity in a mouse strain with a high incidence of callosal anomalies

Corpus callosum dysgenesis (CCD) is a developmental brain condition in which some white matter fibers fail to find their natural course across the midplane, reorganizing instead to form new aberrant pathways. This type of white matter reorganization is known as long-distance plasticity (LDP). The present work aimed to characterize the Balb/c mouse strain as a model of CCD. We employed high-resolution anatomical MRI in 81 Balb/c and 27 C57bl6 mice to show that the Balb/c mouse strain presents a variance in the size of the CC that is 3.9 times higher than the variance of normotypical C57bl6. We also performed high-resolution diffusion-weighted imaging (DWI) in 8 Balb/c and found that the Balb/c strain shows aberrant white matter bundles, such as the Probst (5/8 animals) and the Sigmoid bundles (7/8 animals), which are similar to those found in humans with CCD. Using a histological tracer technique, we confirmed the existence of these aberrant bundles in the Balb/c strain. Interestingly, we also identified sigmoid-like fibers in the C57bl6 strain, thought to a lesser degree. Next, we used a connectome approach and found widespread brain connectivity differences between Balb/c and C57bl6 strains. The Balb/c strain also exhibited increased variability of global connectivity. These findings suggest that the Balb/c strain presents local and global changes in brain structural connectivity. This strain often presents with callosal abnormalities, along with the Probst and the Sigmoid bundles, making it is an attractive animal model for CCD and LDP in general. Our results also show that even the C57bl6 strain, which typically serves as a normotypical control animal in a myriad of studies, presents sigmoid-fashion pattern fibers laid out in the brain. These results suggest that these aberrant fiber pathways may not necessarily be a pathological hallmark, but instead an alternative roadmap for misguided axons. Such findings offer new insights for interpreting the significance of CCD-associated LDP in humans.

Vagus nerve stimulation and Neurotrophins: a biological psychiatric perspective

Since 2004, vagus nerve stimulation (VNS) has been used in treatment-resistant or treatment-intolerant depressive episodes. Today, VNS is suggested as possible therapy for a larger spectrum of psychiatric disorders, including schizophrenia, obsessive compulsive disorders, and panic disorders. Despite a large body of literature supports the application of VNS in patients' treatment, the exact mechanism of action of VNS remains not fully understood. In the present study, the major knowledges on the brain areas and neuronal pathways regulating neuroimmune and autonomic response subserving VNS effects are reviewed. Furthermore, the involvement of the neurotrophins (NTs) Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF) in vagus nerve (VN) physiology and stimulation is revised. The data on brain NGF/BDNF synthesis and in turn on the activity-dependent plasticity, connectivity rearrangement and neurogenesis, are presented and discussed as potential biomarkers for optimizing stimulatory parameters for VNS. A vagus nerve-neurotrophin interaction model in the brain is finally proposed as a working hypothesis for future studies addressed to understand pathophysiology of psychiatric disturbance.

Video games as rich environments to foster brain plasticity

This chapter highlights the key role of two main factors, attentional control and reward processing, in unlocking brain plasticity. We first review the evidence for the role that each of these mechanisms plays in neuroplasticity, and then make the case that tools and technologies that combine these two are likely to result in maximal and broad, generalized benefits. In this context, we review the evidence concerning the impact of video game play on brain plasticity, with an eye toward plasticity-driving methods such as the seamless integration of neurofeedback into the video game platforms.

Intraspecific variation in testosterone-induced neuroplasticity in two canary strains

Temperate zone songbird species, such as the canary (Serinus canaria), can serve as model systems to investigate adult seasonal plasticity in brain and behavior. An increase in day length, experienced by canaries in the early spring stimulates gonadal recrudescence and an associated increase in circulating testosterone concentrations. This increase in plasma testosterone results in marked morphological changes in well-defined neural circuitry regulating reproductive behaviors including birdsong as well as behavioral changes such as increases in song length and complexity. An obvious measure of plasticity in neural morphology can be assessed via changes in brain nuclei volume and testosterone actions on a number of cellular features including the integration and incorporation of new neurons in the adult canary brain. Previous work in our lab suggests that there may be systematic intraspecific variability within canaries in testosterone-induced adult neuroplasticity. For example, the song nucleus HVC increases in size in response to testosterone in male canaries but we found that males of the American Singer strain exhibited minimal and variable responses as compared to other canary strains such as the Border canary strain, which is thought to be closer to wild type canaries. In this study, we systematically compared the effects of testosterone on the volume of song nuclei and the number of new neurons as assessed with the neurogenesis marker doublecortin in American Singer and Border canaries. We found more pronounced testosterone-induced neuroplasticity in the Border strain than the American Singer. These data suggest that the process of selection for certain strain phenotypes is also associated with significant changes in hormone-regulated brain plasticity.

Comparing perineuronal nets and parvalbumin development between blackbird species with differences in early developmental song exposure

Brood parasitic songbirds are a natural system in which developing birds are isolated from species-typical song and therefore present a unique opportunity to compare neural plasticity in song learners raised with and without conspecific tutors. We compared perineuronal nets (PNN) and parvalbumin (PV) in song control nuclei in juveniles and adults of two closely related icterid species (i.e. blackbirds): brown-headed cowbirds (Molothrus ater; brood parasite) and red-winged blackbirds (Agelaius phoeniceus; non-parasite). The number of PV cells per nucleus was significantly higher in adults compared with juveniles in the nucleus HVC and the robust nucleus of the arcopallium (RA), whereas no significant species difference appeared in any region of interest. The number of PNN per nuclei was significantly higher in adults compared with juveniles in HVC, RA and Area X, but only RA exhibited a significant difference between species. PV cells surrounded by PNN (PV+PNN) also exhibited age-related differences in HVC, RA and Area X, but RA was the only region in which PV+PNN exhibited significant species differences. Furthermore, a significant interaction existed in RA between age and species with respect to PNN and PV+PNN, revealing RA as a region displaying differing plasticity patterns across age and species. Additional comparisons of PNN and PV between adult male and female cowbirds revealed that males have greater numbers of all three measures in RA compared with females. Species-, sex- and age-related differences in RA suggest that species differences in neural plasticity are related to differences in song production rather than sensitivity to song learning, despite a stark contrast in early exposure to conspecific male tutors.

Stroke and potential benefits of brain-computer interface

To treat stroke and, in particular, to alleviate the personal and social burden of stroke survivors is a main challenge for neuroscience research. Advancements in the knowledge of neurobiologic mechanisms subserving stroke-related damage and recovery provide key data to guide clinicians to tailor interventions to specific patient's needs. How does the brain-computer interface (BCI) fit into this scenario? A technique created to allow completely paralyzed individuals to control the environment recently introduced a new line of development: to provide a means to possibly control formation and changes in the brain network organization. In a sort of revolution, similar to the change from geocentric to heliocentric planet organization envisioned by Copernicus, we are facing a critical change in BCI research, moving from a brain to computer direction to a computer to brain one. This direction change will profoundly open up new avenues for BCI research and clinical applications. In this chapter, we address this change and discuss present and future applications of this new line idea of BCI use in stroke.

Patients' views on early sensory relearning following nerve repair-a Q-methodology study

STUDY DESIGN

Descriptive study.

INTRODUCTION

Early sensory relearning where the dynamic capacity of the brain is used has been shown to improve sensory outcome after nerve repair. However, no previous studies have examined how patients experience early sensory relearning.

PURPOSE OF THE STUDY

To describe patient's views on early sensory relearning.

METHODS

Statements' scores were analyzed by factor analysis.

RESULTS

Thirty-seven consecutive adult patients with median and/or ulnar nerve repair who completed early sensory relearning were included. Three factors were identified, explaining 45% of the variance: (1) "Believe sensory relearning is meaningful, manage to get an illusion of touch and complete the sensory relearning"; (2) "Do not get an illusion of touch easily and need support in their sensory relearning" (3) "Are not motivated, manage to get an illusion of touch but do not complete sensory relearning".

DISCUSSION

Many patients succeed in implementing their sensory relearning. However, a substantial part of the patient population need more support, have difficulties to create illusion of touch, and lack motivation to complete the sensory relearning. To enhance motivation and meaningfulness by relating the training clearly to everyday occupations and to the patient's life situation is a suggested way to proceed.

CONCLUSION

The three unique factors indicate motivation and sense of meaningfulness as key components which should be taken into consideration in developing programs for person-centered early sensory relearning.

LEVEL OF EVIDENCE

3.

New concepts in the study of the sexual differentiation and activation of reproductive behavior, a personal view

Since the beginning of this century, research methods in neuroendocrinology enjoyed extensive refinements and innovation. These advances allowed collection of huge amounts of new data and the development of new ideas but have not led to this point, with a few exceptions, to the development of new conceptual advances. Conceptual advances that took place largely resulted from the ingenious insights of several investigators. I summarize here some of these new ideas as they relate to the sexual differentiation and activation by sex steroids of reproductive behaviors and I discuss how our research contributed to the general picture. This selective review clearly demonstrates the importance of conceptual changes that have taken place in this field since beginning of the 21st century. The recent technological advances suggest that our understanding of hormones, brain and behavior relationships will continue to improve in a very fundamental manner over the coming years.

Molecular mechanisms and cellular events involved in the neuroprotective actions of estradiol. Analysis of sex differences

Estradiol, either from peripheral or central origin, activates multiple molecular neuroprotective and neuroreparative responses that, being mediated by estrogen receptors or by estrogen receptor independent mechanisms, are initiated at the membrane, the cytoplasm or the cell nucleus of neural cells. Estrogen-dependent signaling regulates a variety of cellular events, such as intracellular Ca²⁺ levels, mitochondrial respiratory capacity, ATP production, mitochondrial membrane potential, autophagy and apoptosis. In turn, these molecular and cellular actions of estradiol are integrated by neurons and non-neuronal cells to generate different tissue protective responses, decreasing blood-brain barrier permeability, oxidative stress, neuroinflammation and excitotoxicity and promoting synaptic plasticity, axonal growth, neurogenesis, remyelination and neuroregeneration. Recent findings indicate that the neuroprotective and neuroreparative actions of estradiol are different in males and females and further research is necessary to fully elucidate the causes for this sex difference.

Trajectories of brain remodeling in temporal lobe epilepsy

Temporal lobe epilepsy has been usually associated with progressive brain atrophy due to neuronal cell loss. However, recent animal models demonstrated a dual effect of epileptic seizures with initial enhancement of hippocampal neurogenesis followed by abnormal astrocyte proliferation and neurogenesis depletion in the chronic stage. Our aim was to test for the hypothesized bidirectional pattern of epilepsy-associated brain remodeling in the context of the presence and absence of mesial temporal lobe sclerosis. We acquired MRIs from a large cohort of mesial temporal lobe epilepsy patients with or without hippocampus sclerosis on radiological examination. The statistical analysis tested explicitly for common and differential brain patterns between the two patients' cohorts and healthy controls within the computational anatomy framework of voxel-based morphometry. The main effect of disease was associated with continuous hippocampus volume loss ipsilateral to the seizure onset zone in both temporal lobe epilepsy cohorts. The post hoc simple effects tests demonstrated bilateral hippocampus volume increase in the early epilepsy stages in patients without hippocampus sclerosis. Early age of onset and longer disease duration correlated with volume decrease in the ipsilateral hippocampus. Our findings of seizure-induced hippocampal remodeling are associated with specific patterns of mesial temporal lobe atrophy that are modulated by individual clinical phenotype features. Directionality of hippocampus volume changes strongly depends on the chronicity of disease. Specific anatomy differences represent a snapshot within a progressive continuum of seizure-induced structural remodeling.

Platelets: The missing link between the blood and brain?

It is becoming increasingly clear that interactions between the peripheral immune system and the central nervous system are important in maintaining healthy brain function. Platelets are small blood cells traditionally known for their role in wound healing. However, platelets have recently been shown to exhibit many alternative functions. In this perspective, we summarize the repertoire of platelet functions, focusing on how these cells contribute to the maintenance of brain homeostasis and propose the mechanisms via which they could communicate with brain cells, including exosome and microparticle release and receptor interactions at local sites. In particular, we highlight the potential role that platelets play in maintaining brain plasticity via the modulation of new neuron generation from neural precursor cells, an interaction which could have important implications in the development of therapeutic interventions to promote cognitive function in aging and disease.

Diffusional plasticity induced by electroacupuncture intervention in rat model of peripheral nerve injury

Electroacupuncture (EA) is an adjuvant therapy for peripheral nerve injury (PNI). Both peripheral and central alterations contribute to the rehabilitation process. We employed diffusion tensor imaging (DTI) to investigate the diffusion plasticity of afferent and efferent pathways caused by EA in model of peripheral nerve injury and reparation. Twenty-four rats were divided into three groups: normal group, model group and intervention group. Rats of the model group and the intervention group underwent sciatic nerve transection and anastomosis. EA intervention was performed on the intervention group at ST-36 and GB-30 for three months. Gait assessment and DTI were conducted at days post-operative (DPO) 30, 60 and 90. We selected corticospinal tract, spinothalamic tract and internal capsule as regions of interest and analyzed diffusion metrics including fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD). FA values and RD values displayed significant differences or obvious tendency while AD values maintained a stable level. RD values displayed better indicative performance than FA in internal capsule. The intervention group presented significant correlation between RD values and Regularity Index (RI) during the intervention period. The effect of EA on peripheral nerve injury repairing rats appeared to be accelerated recovery process of sensory and motor neural pathway. We proposed that RD was a potential in vivo indicator for structural plasticity caused by EA and PNI.

Structural and functional reorganization following unilateral internal capsule infarction contribute to neurological function recovery

PURPOSE

To investigate proliferative reorganization in the bilateral corticospinal tract (CST) and functional reorganization in the sensorimotor network (SMN) after internal capsule stroke, and to examine the significance of this reorganization.

METHODS

We recruited 17 patients with first-onset acute stroke (16 male, 1 female, mean age 52 ± 10 years) and 17 age- and sex-matched healthy controls. We excluded patients aged < 18 or > 65 years and those with lesions outside the unilateral internal capsule. All subjects underwent diffusion tensor imaging and resting-state functional MRI on days 7, 30, and 90 from symptom onset. We measured fractional anisotropy (FA) in the CST, interhemispheric functional connectivity (FC) within the SMN, and pre-MRI clinical scores, including the National Institutes of Health Stroke Scale (NIHSS), Barthel Index (BI), and Fugl-Meyer (FM). Correlations among the changes in FA, FC, and clinical scores were analyzed.

RESULTS

From day 7 to 90 after stroke, FA in the bilateral CST increased (ipsilesional side, Pinternal capsule = 0.009, Pcentrum semiovale = 0.001; contralesional side, Pinternal capsule = 0.006, Pcentrum semiovale = 0.017), as did FC (P < 0.05); NIHSS scores decreased (P < 0.05), while FM and BI progressively increased (P < 0.05). Increased FA in bilateral CST was negatively correlated with decreased NIHSS scores. Increased FA in only the ipsilesional side was positively correlated with increased FM. Increased FC was positively correlated only with increased BI.

CONCLUSION

Proliferative reorganization in the CST and functional reorganization in the SMN support and promote neurological functional recovery after internal capsule infarction.

Motor and Sensory Cortical Changes after Contralateral Cervical Seventh Nerve Root (CC7) Transfer in Patients with Brachial Plexus Injuries

BACKGROUND

Previous animal studies demonstrated that the sensory and motor functions in ipsilesional upper limbs that had been reconstructed by CC7 transfer eventually associated with the contralesional brain cortices that had originally mediated the functions of the ipsilesional upper limbs before brachial plexus injury (BPI). Our hypothesis was that the same findings would be seen in humans.

METHODS

Four patients with total BPI treated with CC7 transfer were included. Changes in the locations of the activated areas in the primary motor (M1) and somatosensory (S1) cortices corresponding to the motor outputs to and sensory inputs from the ipsilesional limbs were investigated using functional near-infrared spectroscopy (fNIRS) 2-3 years and 6-7 years after surgery.

RESULTS

One patient was excluded from the evaluation of motor function after CC7 transfer. The motor and sensory functions of the ipsilesional upper limb in all patients were still controlled by the ipsilesional brain hemisphere 2-3 years after CC7 transfer. The reconstructed motions of the ipsilesional upper limbs correlated with the contralesional M1 in one patient and the bilateral M1s in another patient (both of whom demonstrated good motor recovery in the ipsilesional upper limbs) and with the ipsilesional M1 in a third patient with poor motor recovery in the ipsilesional upper limb. Sensory stimulation of the ipsilesional hands 6-7 years after CC7 transfer activated the contralesional S1 in two patients who achieved good sensory recovery in the ipsilesional hands but activated the ipsilesional S1 in the other two patients with poor sensory recovery of the ipsilesional hands.

CONCLUSIONS

Transhemispheric transposition of the activated brain cortices associated with the recovery of motor and sensory functions of the ipsilesional upper limbs was seen in patients with CC7 transfer as has been reported for animal models of CC7 transfer.

Time course of sensorimotor cortex reorganization during upper extremity task accompanying motor recovery early after stroke: An fNIRS study

BACKGROUND

The acute phase of stroke is accompanied by functional changes and interplay of both hemispheres. However, our understanding of how the time course of upper limb functional motor recovery is related to the progression of brain reorganization in the sensorimotor areas remains limited. This study aimed to assess the time course of hemodynamic patterns of cortical sensorimotor areas using functional near infrared spectroscopy (fNIRS) and motor recovery within three months after a stroke.

METHOD

Eight right-handed first ischemic/hemorrhagic stroke patients (60±8 years, 3 women) with mild to severe hemiparesis were examined with repetitive fNIRS measurements and motor recovery tests (Fugl-Meyer score) during two months. Hemodynamic changes over the ipsilesional and contralesional sensorimotor areas were collected from a multi-channel fNIRS system during intermittent isometric muscle contractions at self-selected submaximal force levels for each arm. Lateralization index was computed to evaluate the changes in the interhemispheric balance between the cortical sensorimotor areas.

RESULTS

Lateralization index values during non-paretic arm movements showed no significant changes over time in patients and were comparable to those observed in eight healthy controls. Paretic-arm movements were associated early with a bilateral cortical activity before shifting to ipsilesional patterns (p < 0.01). Progressive lateralization observed over the two months (p < 0.05) evolved concomitantly with an increase in the Fugl-Meyer score (p < 0.001).

CONCLUSIONS

Cortical reorganization monitoring using fNIRS during the first weeks after stroke may be applied for assessing progressive brain plasticity in addition to clinical measures of performance.

Plastic changes in brain morphology in relation to learning and environmental enrichment in the guppy (Poecilia reticulata)

Despite the common assumption that the brain is malleable to surrounding conditions mainly during ontogeny, plastic neural changes can occur also in adulthood. One of the driving forces responsible for alterations in brain morphology is increasing environmental complexity that may demand enhanced cognitive abilities (e.g. attention, memory and learning). However, studies looking at the relationship between brain morphology and learning are scarce. Here, we tested the effects of both learning and environmental enrichment on neural plasticity in guppies (Poecilia reticulata), by means of either a reversal-learning test or a spatial-learning test. Given considerable evidence supporting environmentally induced plastic alterations, two separate control groups that were not subjected to any cognitive test were included to account for potential changes induced by the experimental setup alone. We did not find any effect of learning on any of our brain measurements. However, we found strong evidence for an environmental effect, where fish given access to the spatial-learning environment had larger relative brain size and optic tectum size in relation to those exposed to the reversal-learning environment. Our results demonstrate the plasticity of the adult brain to respond adaptively mainly to environmental conditions, providing support for the environmental enhancement theory.

Making sense of gut feelings in the traumatic brain injury pathogenesis

Traumatic brain injury (TBI) is a devastating condition which often initiates a sequel of neurological disorders that can last throughout lifespan. From metabolic perspective, TBI also compromises systemic physiology including the function of body organs with subsequent malfunctions in metabolism. The emerging panorama is that the effects of TBI on the periphery strike back on the brain and exacerbate the overall TBI pathogenesis. An increasing number of clinical reports are alarming to show that metabolic dysfunction is associated with incidence of long-term neurological and psychiatric disorders. The autonomic nervous system, associated hypothalamic-pituitary axis, and the immune system are at the center of the interface between brain and body and are central to the regulation of overall homeostasis and disease. We review the strong association between mechanisms that regulate cell metabolism and inflammation which has important clinical implications for the communication between body and brain. We also discuss the integrative actions of lifestyle interventions such as diet and exercise on promoting brain and body health and cognition after TBI.

The expectant social mind: A systematic review of face processing during pregnancy and the effect of depression and anxiety

Pregnancy carries enormous changes in the psychological and neurophysiological domains. It has been suggested that pregnant women undergo a cognitive reorganization aimed at increasing the salience of social stimuli (i.e., the tendency of social cues to capture observer's attention, so that their processing results prioritized). The goal of the present work was to systematically review the empirical evidence of a change in face processing during pregnancy. Moreover, we explored whether face processing is associated with antenatal depression and anxiety and the extent to which this is part of a potential mechanism to explain detrimental effects of maternal psychopathology on infant outcomes. We identified 19 relevant studies and discussed them based on their methodological qualities. The results of the review suggest that even though it is not possible to draw firm conclusions, pregnancy is likely to be a plasticity window for face processing at the behavioral and neural levels. Evidence confirms the detrimental effect of depression and anxiety on face processing during pregnancy. Clinical implications for parenting interventions are discussed.

Thumbs up: Imagined hand movements counteract the adverse effects of post-surgical hand immobilization. Clinical, behavioral, and fMRI longitudinal observations

Motor imagery (M.I.) training has been widely used to enhance motor behavior. To characterize the neural foundations of its rehabilitative effects in a pathological population we studied twenty-two patients with rhizarthrosis, a chronic degenerative articular disease in which thumb-to-fingers opposition becomes difficult due to increasing pain while the brain is typically intact. Before and after surgery, patients underwent behavioral tests to measure pain and motor performance and fMRI measurements of brain motor activity.

After surgery, the affected hand was immobilized, and patients were enrolled in a M.I. training. The sample was split in those who had a high compliance with the program of scheduled exercises (T+, average compliance: 84%) and those with low compliance (T−, average compliance: 20%; cut-off point: 55%). We found that more intense M.I. training counteracts the adverse effects of immobilization reducing pain and expediting motor recovery. fMRI data from the post-surgery session showed that T+ patients had decreased brain activation in the premotor cortex and the supplementary motor area (SMA); meanwhile, for the same movements, the T− patients exhibited a reversed pattern. Furthermore, in the post-surgery fMRI session, pain intensity was correlated with activity in the ipsilateral precentral gyrus and, notably, in the insular cortex, a node of the pain matrix.

These findings indicate that the motor simulations of M.I. have a facilitative effect on recovery by cortical plasticity mechanisms and optimization of motor control, thereby establishing the rationale for incorporating the systematic use of M.I. into standard rehabilitation for the management of post-immobilization syndromes characteristic of hand surgery.

•

Motor imagery training counteracts the effects of post-surgical hand immobilization.

•

It also reduces pain and expedites motor recovery after immobilization.

•

These effects were accompanied by significant fMRI signs of brain plasticity.

•

The clinical-fMRI evidence advocates for the use of motor imagery in rehabilitation.

Improved tactile frequency discrimination in musicians

Music practice is a multisensory training that is of great interest to neuroscientists because of its implications for neural plasticity. Music-related modulation of sensory systems has been observed in neuroimaging data, and has been supported by results in behavioral tasks. Some studies have shown that musicians react faster than non-musicians to visual, tactile and auditory stimuli. Behavioral enhancement in more complex tasks has received considerably less attention in musicians. This study aims to investigate unisensory and multisensory discrimination capabilities in musicians. More specifically, the goal of this study is to examine auditory, tactile and auditory-tactile discrimination in musicians. The literature suggesting better auditory and auditory-tactile discrimination in musicians is scarce, and no study to date has examined pure tactile discrimination capabilities in musicians. A two-alternative forced-choice frequency discrimination task was used in this experiment. The task was inspired by musical production, and participants were asked to identify whether a frequency was the same as or different than a standard stimulus of 160 Hz in three conditions: auditory only, auditory-tactile only and tactile only. Three waveforms were used to replicate the variability of pitch that can be found in music. Stimuli were presented through headphones for auditory stimulation and a glove with haptic audio exciters for tactile stimulation. Results suggest that musicians have lower discrimination thresholds than non-musicians for auditory-only and auditory-tactile conditions for all waveforms. The results also revealed that musicians have lower discrimination thresholds than non-musicians in the tactile condition for sine and square waveforms. Taken together, these results support the hypothesis that musical training can lead to better unisensory tactile discrimination which is in itself a new and major finding.

Structural and functional connectivity changes in response to short-term neurofeedback training with motor imagery

Recent findings have been challenging current understanding of how fast the human brain change its structural and functional connections in response to training. One powerful way to deepen the inner workings of human brain plasticity is using neurofeedback (NFB) by fMRI, a technique that allows self-induced brain plasticity by means of modulating brain activity in real time. In the present randomized, double-blind and sham-controlled study, we use NFB to train healthy individuals to reinforce brain patterns related to motor execution while performing a motor imagery task, with no overt movement. After 1 h of NFB training, participants displayed increased fractional anisotropy (FA) in the sensorimotor segment of corpus callosum and increased functional connectivity of the sensorimotor resting state network. Increased functional connectivity was also observed in the default mode network. These results were not observed in the control group, which was trained with sham feedback. To our knowledge, this is the first demonstration of white matter FA changes following a very short training schedule (<1 h). Our results suggest that NFB by fMRI can be an interesting tool to explore dynamic aspects of brain plasticity and open new venues for investigating brain plasticity in healthy individuals and in neurological conditions.

Superconditioning TMS unmasks latent voluntary innervation in MND - A case report

Motor neuron disease (MND) includes both ALS and Progressive Muscular Atrophy (PMA) as variants. Abnormalities in brain excitability and upper motor neuron (UMN) function are characteristic of ALS, but by definition are absent in PMA. Transcranial magnetic stimulation (TMS) may be useful in demonstrating UMN pathology, but loss of muscle responsiveness with disease progression limits its usefulness in later stages of MND. We have developed a novel form of TMS comprised of 4 stimulating pulses that can enhance MEPs in target muscles already responding to traditional TMS inputs, in some cases even restoring MEPs in target muscles rendered unresponsive by the disease. An example of restored MEPs in response to this superconditioning TMS pattern (TMSsc) in a person with PMA is described, along with an unexpected finding. Despite a prolonged (> 5 year) history of movement paralysis in his right tibialis anterior (TA), immediately after cessation of TMSsc delivery the subject could now easily contract and relax this muscle; the presence of a latent pathway for voluntary innervation of his right TA was revealed. This modulation of central motor functional connectivity in response to TMSsc suggests a further, clinically-significant benefit of this form of noninvasive brain stimulation beyond its ability to enhance MEPs to traditional TMS inputs.

Strong relationship between NREM sleep, epilepsy and plastic functions - A conceptual review on the neurophysiology background

The aim of this review is to summarize and discuss the strong bond between NREM sleep and epilepsy underlain by the shared link and effect on brain plasticity. Beyond the seizure occurrence rate, sleep relatedness may manifest in the enhancement of interictal epileptic discharges (spikes and pathological ripples). The number of the discharges as well as their propagation increase during NREM sleep, unmasking the epileptic network that is hidden during wakefulness. The interictal epileptic discharges associate with different sleep constituents (sleep slow waves, spindling and high frequency oscillations); known to play essential role in memory and learning. We highlight three major groups of epilepsies, in which sleep-related plastic functions suffer an epileptic derailment. In absence epilepsy mainly involving the thalamo-cortical system, sleep spindles transform to generalized spike-wave activity. In mesio-temporal epilepsy affecting the hippocampal declarative memory system, the sharp wave ripples derail to dysfunctional epileptic oscillations (spikes and pathological ripples). Idiopathic childhood epilepsies affecting the perisylvian network may progress to catastrophic status electricus during NREM sleep. In these major epilepsies, NREM sleep has a pivotal role in the development and course of the disorder. Epilepsy is born in-, and exhibits its pathological properties during NREM sleep. Interictal discharges are important causative agents in this process.

Social plasticity in the fish brain: Neuroscientific and ethological aspects

Social plasticity, defined as the ability to adaptively change the expression of social behavior according to previous experience and to social context, is a key ecological performance trait that should be viewed as crucial for Darwinian fitness. The neural mechanisms for social plasticity are poorly understood, in part due to skewed reliance on rodent models. Fish model organisms are relevant in the field of social plasticity for at least two reasons: first, the diversity of social organization among fish species is staggering, increasing the breadth of evolutionary relevant questions that can be asked. Second, that diversity also suggests translational relevance, since it is more likely that "core" mechanisms of social plasticity are discovered by analyzing a wider variety of social arrangements than relying on a single species. We analyze examples of social plasticity across fish species with different social organizations, concluding that a "core" mechanism is the initiation of behavioral shifts through the modulation of a conserved "social decision-making network", along with other relevant brain regions, by monoamines, neuropeptides, and steroid hormones. The consolidation of these shifts may be mediated via neurogenomic adjustments and regulation of the expression of plasticity-related molecules (transcription factors, cell cycle regulators, and plasticity products).

CD4+ T Cells Affect the Thyroid Hormone Transport at the Choroid Plexus in Mice Raised in Enriched Environment

BACKGROUND

Others and we have shown that T cells have an important role in hippocampal synaptic plasticity, including neurogenesis in the dentate gyrus, spinogenesis, and glutamatergic synaptic function in the CA of the hippocampus. Hippocampus plasticity is particularly involved in the brain effects of the enriched environment (EE), and interestingly CD4+ and CD8+ T cells play essential and differential roles in these effects. However, the precise mechanisms by which they act on the brain remain elusive.

OBJECTIVES

We searched for a putative mechanism of action by which CD4+ T cells could influence brain plasticity and hypothesized that they could regulate protein transport at the level of the blood-CSF barrier in the choroid plexus.

METHOD

We compared mice housed in EE and deprived of CD4+ T cells using a depleting antibody with a control group injected with the control isotype. We analyzed in the hippocampus the gene expression profiles using the Agilent system, and the expression of target proteins in plasma, CSF, and the choroid plexus using ELISA.

RESULTS

We show that CD4+ T cells may influence EE-induced hippocampus plasticity via thyroid hormone signaling by regulating in the choroid plexus the expression of transthyretin, the major transporter of thyroxine (T4) to the brain parenchyma.

CONCLUSIONS

Our study highlights the contribution of close interactions between the immune and neuroendocrine systems in brain plasticity and function.