Search

Different functional connectivities in the brain, specifically in the frontoparietal and motor cortex-sensorimotor circuits, have been associated with superior performance in athletes. However, previous electroencephalogram (EEG) studies have only focused on the frontoparietal circuit and have not provided a comprehensive understanding of the cognitive-motor processes underlying superior performance. We used EEG coherence analysis to examine the motor cortex-sensorimotor circuit in golfers of different skill levels. Twenty experts, 18 amateurs, and 21 novices performed 60 putts at individual putting distances (40-60% success rate). The imaginary inter-site phase coherence (imISPC) was used to compute 8-13 Hz coherence that can be used to distinguish expert-novice and expert-amateur differences during motor preparation. We assessed the 8-13 Hz imISPC between the Cz and F3, F4, C3, C4, T3, T4, P3, P4, O1, and O2 regions. (1) Amateurs had lower 8-13 Hz imISPC in the central regions (Cz-C3 and C4) than novices and experts, but experts had lower 8-13 Hz imISPC than novices. (2) Skilled golfers (experts and amateurs) had lower 8-13 Hz imISPC in the central-parietal regions (Cz-P3 and P4) than novices. (3) Experts had lower 8-13 Hz imISPC in the central-left temporal regions (Cz-T7) than amateurs and novices. Our study revealed that refinement of the motor cortex-sensorimotor circuit follows a U-shaped coherence pattern based on the stage of learning. The early learning stage (i.e., novice to amateur) is characterized by lower connectivity between the regions associated with motor control and visuospatial processes, whereas the late learning stage (i.e., amateur to expert) is characterized by lower connectivity in the regions associated with verbal-analytic and motor control processes., (© 2022. The Author(s).)

Nitrergic neurons (NNs) are inhibitory neurons capable of releasing nitric oxide (NO) that are labeled with nicotinamide adenine dinucleotide phosphate diaphorase histochemistry. The rat primary somatosensory (S1) and motor (M1) cortices are a favorable model to investigate NN populations by comparing their morphology, since these areas share the border of forepaw representation. The distribution of the Type I NN of the forepaw representation in the S1 and M1 cortices of the rat in different laminar compartments and the morphological parameters related to the cell body and dendritic arborization were measured and compared. We observed that the neuronal density in the S1 (130 NN/mm 3 ) was higher than the neuronal density in the M1 (119 NN/mm 3 ). Most NN neurons were multipolar (S1 with 58%; M1 with 69%), and a minority of the NN neurons were horizontal (S1 with 6%; M1 with 12%). NN found in S1 had a higher verticality index than NN found in M1, and no significant differences were observed for the other morphological parameters. We also demonstrated significant differences in most of the morphological parameters of the NN between different cortical compartments of S1 and M1. Our results indicate that the NN of the forepaw in S1 and M1 corresponds to a neuronal population, where the functionality is independent of the different types of sensory and motor processing. However, the morphological differences found between the cortical compartments of S1 and M1, as well as the higher density of NNs found in S1, indicate that the release of NO varies between the areas., (© 2021 Wiley Periodicals LLC.)

Parkinson's disease (PD) is characterised by the emergence of beta frequency oscillatory synchronisation across the cortico-basal-ganglia circuit. The relationship between the anatomy of this circuit and oscillatory synchronisation within it remains unclear. We address this by combining recordings from human subthalamic nucleus (STN) and internal globus pallidus (GPi) with magnetoencephalography, tractography and computational modelling. Coherence between supplementary motor area and STN within the high (21-30 Hz) but not low (13-21 Hz) beta frequency range correlated with 'hyperdirect pathway' fibre densities between these structures. Furthermore, supplementary motor area activity drove STN activity selectively at high beta frequencies suggesting that high beta frequencies propagate from the cortex to the basal ganglia via the hyperdirect pathway. Computational modelling revealed that exaggerated high beta hyperdirect pathway activity can provoke the generation of widespread pathological synchrony at lower beta frequencies. These findings suggest a spectral signature and a pathophysiological role for the hyperdirect pathway in PD., (© 2021. The Author(s).)

Functional circuits consist of neurons with diverse axonal projections and gene expression. Understanding the molecular signature of projections requires high-throughput interrogation of both gene expression and projections to multiple targets in the same cells at cellular resolution, which is difficult to achieve using current technology. Here, we introduce BARseq2, a technique that simultaneously maps projections and detects multiplexed gene expression by in situ sequencing. We determined the expression of cadherins and cell-type markers in 29,933 cells and the projections of 3,164 cells in both the mouse motor cortex and auditory cortex. Associating gene expression and projections in 1,349 neurons revealed shared cadherin signatures of homologous projections across the two cortical areas. These cadherins were enriched across multiple branches of the transcriptomic taxonomy. By correlating multigene expression and projections to many targets in single neurons with high throughput, BARseq2 provides a potential path to uncovering the molecular logic underlying neuronal circuits.

Decision-making via monitoring others' actions is a cornerstone of interpersonal exchanges. Although the ventral premotor cortex (PMv) and the medial prefrontal cortex (MPFC) are cortical nodes in social brain networks, the two areas are rarely concurrently active in neuroimaging, inviting the hypothesis that they are functionally independent. Here we show in macaques that the ability of the MPFC to monitor others' actions depends on input from the PMv. We found that delta-band coherence between the two areas emerged during action execution and action observation. Information flow especially in the delta band increased from the PMv to the MPFC as the biological nature of observed actions increased. Furthermore, selective blockade of the PMv-to-MPFC pathway using a double viral vector infection technique impaired the processing of observed, but not executed, actions. These findings demonstrate that coordinated activity in the PMv-to-MPFC pathway has a causal role in social action monitoring.

A challenge for neuroscience is to understand the conscious and unconscious processes underlying construction of willed actions. We investigated the neural substrate of human motor awareness during awake brain surgery. In a first experiment, awake patients performed a voluntary hand motor task and verbally monitored their real-time performance, while different brain areas were transiently impaired by direct electrical stimulation (DES). In a second experiment, awake patients retrospectively reported their motor performance after DES. Based on anatomo-clinical evidence from motor awareness disorders following brain damage, the premotor cortex (PMC) was selected as a target area and the primary somatosensory cortex (S1) as a control area. In both experiments, DES on both PMC and S1 interrupted movement execution, but only DES on PMC dramatically altered the patients' motor awareness, making them unconscious of the motor arrest. These findings endorse PMC as a crucial hub in the anatomo-functional network of human motor awareness.

Myelination increases the conduction velocity in long-range axons and is prerequisite for many brain functions. Impaired myelin regulation or impairment of myelin itself is frequently associated with deficits in learning and cognition in neurological and psychiatric disorders. However, it has not been revealed what perturbation of neural activity induced by myelin impairment causes learning deficits. Here, we measured neural activity in the motor cortex during motor learning in transgenic mice with a subtle impairment of their myelin. This deficit in myelin impaired motor learning, and was accompanied by a decrease in the amplitude of movement-related activity and an increase in the frequency of spontaneous activity. Thalamocortical axons showed variability in axonal conduction with a large spread in the timing of postsynaptic cortical responses. Repetitive pairing of forelimb movements with optogenetic stimulation of thalamocortical axon terminals restored motor learning. Thus, myelin regulation helps to maintain the synchrony of cortical spike-time arrivals through long-range axons, facilitating the propagation of the information required for learning. Our results revealed the pathological neuronal circuit activity with impaired myelin and suggest the possibility that pairing of noninvasive brain stimulation with relevant behaviors may ameliorate cognitive and behavioral abnormalities in diseases with impaired myelination., (© 2019 The Authors. Glia published by Wiley Periodicals, Inc.)

Cortical hyperexcitability has been found in early Amyotrophic Lateral Sclerosis (ALS) and is hypothesized to be a key factor in pathogenesis. The current pilot study aimed to investigate cortical inhibitory/excitatory balance in ALS using short-echo Magnetic Resonance Spectroscopy (MRS). Patients suffering from ALS were scanned on a 3 T Trio Siemens MR scanner using Spin Echo Full Intensity Acquired Localized (SPECIAL) Magnetic Resonance Spectroscopy in primary motor cortex and the occipital lobe. Data was compared to a group of healthy subjects. Nine patients completed the scan. MRS data was of an excellent quality allowing for quantification of a range of metabolites of interest in ALS. In motor cortex, patients had Glutamate/GABA and GABA/Cr- ratios comparable to healthy subjects. However, Glutamate/Cr (p = 0.002) and the neuronal marker N-acetyl-aspartate (NAA/Cr) (p = 0.034) were low, possibly due to grey-matter atrophy, whereas Glutathione/Cr (p = 0.04) was elevated. In patients, NAA levels correlated significantly with both hand strength (p = 0.027) and disease severity (p = 0.016). In summary SPECIAL MRS at 3 T allows of reliable quantification of a range of metabolites of interest in ALS, including both excitatory and inhibitory neurotransmitters. The method is a promising new technique as a biomarker for future studies on ALS pathophysiology and monitoring of disease progression.

Reorganization of residual descending motor circuits underlies poststroke recovery. We previously clarified a causal relationship between the cortico-rubral tract and intensive limb use-induced functional recovery after internal capsule hemorrhage (ICH). However, other descending tracts, such as the cortico-reticular tract, might also be involved in rehabilitation-induced compensation. To investigate whether rehabilitation-induced recovery after ICH involves a shift in the compensatory circuit from the cortico-rubral tract to the cortico-reticular tract, we established loss of function of the cortico-rubral tract or/and cortico-reticular tract using two sets of viral vectors comprising the Tet-on system and designer receptors exclusively activated by the designer drug system. We used an ICH model that destroyed almost 60% of the corticofugal fibers. Anterograde tracing in rehabilitated rats revealed abundant sprouting of axons from the motor cortex in the red nucleus but not in the medullary reticular formation during the early phase of recovery. This primary contribution of the cortico-rubral tract was demonstrated by its selective blockade, whereas selective cortico-reticular tract silencing had little effect. Interestingly, cortico-rubral tract blockade from the start of rehabilitation induced an obvious increase of axon sprouting in the reticular formation with substantial functional recovery. Additional cortico-reticular tract silencing under the cortico-rubral tract blockade significantly worsened the recovered forelimb function. Furthermore, the alternative recruitment of the cortico-reticular tract was gradually induced by intensive limb use under cortico-rubral tract blockade, in which cortico-reticular tract silencing caused an apparent motor deficit. These findings indicate that individual cortico-brainstem pathways have dynamic compensatory potency to support rehabilitative functional recovery after ICH. SIGNIFICANCE STATEMENT This study aimed to clarify the interaction between the cortico-rubral and the cortico-reticular tract during intensive rehabilitation and functional recovery after capsular stroke. Pathway-selective disturbance by two sets of viral vectors revealed that the cortico-rubral tract was involved in rehabilitation-induced recovery of forelimb function from an early phase after internal capsule hemorrhage, but that the cortico-reticular tract was not. The sequential disturbance of both tracts revealed that the cortico-reticular tract was recruited and involved in rehabilitation-induced recovery when the cortico-rubral tract failed to function. Our data demonstrate a dynamic compensatory action of individual cortico-brainstem pathways for recovery through poststroke rehabilitation., (Copyright © 2019 the authors.)

In vivo 1 H magnetic resonance spectroscopy ( 1 H-MRS) investigations of amyotrophic lateral sclerosis (ALS) mouse brain may provide neurochemical profiles and alterations in association with ALS disease progression. We aimed to longitudinally follow neurochemical evolutions of striatum, brainstem and motor cortex of mice transgenic for G93A mutant human superoxide dismutase type-1 (G93A-SOD1), an ALS model. Region-specific neurochemical alterations were detected in asymptomatic G93A-SOD1 mice, particularly in lactate (-19%) and glutamate (+8%) of brainstem, along with γ-amino-butyric acid (-30%), N-acetyl-aspartate (-5%) and ascorbate (+51%) of motor cortex. With disease progression towards the end-stage, increased numbers of metabolic changes of G93A-SOD1 mice were observed (e.g. glutamine levels increased in the brainstem (>+66%) and motor cortex (>+54%)). Through ALS disease progression, an overall increase of glutamine/glutamate in G93A-SOD1 mice was observed in the striatum ( p  < 0.01) and even more so in two motor neuron enriched regions, the brainstem and motor cortex ( p  < 0.0001). These 1 H-MRS data underscore a pattern of neurochemical alterations that are specific to brain regions and to disease stages of the G93A-SOD1 mouse model. These neurochemical changes may contribute to early diagnosis and disease monitoring in ALS patients.

Mouse lemurs are the smallest of the living primates, and are members of the understudied radiation of strepsirrhine lemurs of Madagascar. They are thought to closely resemble the ancestral primates that gave rise to present day primates. Here we have used multiple histological and immunochemical methods to identify and characterize sensory areas of neocortex in four brains of adult lemurs obtained from a licensed breeding colony. We describe the laminar features for the primary visual area (V1), the secondary visual area (V2), the middle temporal visual area (MT) and area prostriata, somatosensory areas S1(3b), 3a, and area 1, the primary motor cortex (M1), and the primary auditory cortex (A1). V1 has "blobs" with "nonblob" surrounds, providing further evidence that this type of modular organization might have evolved early in the primate lineage to be retained in all extant primates. The laminar organization of V1 further supports the view that sublayers of layer 3 of primates have been commonly misidentified as sublayers of layer 4. S1 (area 3b) is proportionately wider than the elongated area observed in anthropoid primates, and has disruptions that may distinguish representations of the hand, face, teeth, and tongue. Primary auditory cortex is located in the upper temporal cortex and may include a rostral area, R, in addition to A1. The resulting architectonic maps of cortical areas in mouse lemurs can usefully guide future studies of cortical connectivity and function., (© 2018 Wiley Periodicals, Inc.)

The cerebral cortex requires cerebellar input for optimizing sensorimotor processing. However, how the sensorimotor cortex uses cerebellar information is far from understood. One critical and unanswered question is how cerebellar functional entities (zones or modules) are connected to distinct parts of the sensorimotor cortices. Here, we utilized retrograde transneuronal infection of rabies virus (RABV) to study the organization of connections from the cerebellar cortex to M1, M2, and S1 of the rat cerebral cortex. RABV was co-injected with cholera toxin β-subunit (CTb) into each of these cortical regions and a survival time of 66-70 h allowed for third-order retrograde RABV infection of Purkinje cells. CTb served to identify the injection site. RABV+ Purkinje cells throughout cerebellar zones were identified by reference to the cerebellar zebrin pattern. All injections, including those into S1, resulted in multiple, zonally arranged, strips of RABV+ Purkinje cells. M1 injections were characterized by input from Purkinje cells in the vermal X-zone, medial paravermis (C1- and Cx-zones), and lateral hemisphere (D2-zone); M2 receives input from D2- and C3-zones; connections to S1 originate from X-, Cx-, C3-, and D2-zones. We hypothesize that individual domains of the sensorimotor cortex require information from a specific combination of cerebellar modules.

The axonal composition of cortical projections originating in premotor, supplementary motor (SMA), primary motor (a4), somatosensory and parietal areas and descending towards the brain stem and spinal cord was characterized in the monkey with histological tract tracing, electron microscopy (EM) and diffusion MRI (dMRI). These 3 approaches provided complementary information. Histology provided accurate assessment of axonal diameters and size of synaptic boutons. dMRI revealed the topography of the projections (tractography), notably in the internal capsule. From measurements of axon diameters axonal conduction velocities were computed. Each area communicates with different diameter axons and this generates a hierarchy of conduction delays in this order: a4 (the shortest), SMA, premotor (F7), parietal, somatosensory, premotor F4 (the longest). We provide new interpretations for i) the well-known different anatomical and electrophysiological estimates of conduction velocity; ii) why conduction delays are probably an essential component of the cortical motor command; and iii) how histological and dMRI tractography can be integrated.

Motor cortex (M1) lesions result in motor impairments, yet how M1 contributes to the control of movement remains controversial. To investigate the role of M1 in sensory guided motor coordination, we trained mice to navigate a virtual corridor using a spherical treadmill. This task required directional adjustments through spontaneous turning, while unexpected visual offset perturbations prompted induced turning. We found that M1 is essential for execution and learning of this visually guided task. Turn-selective layer 2/3 and layer 5 pyramidal tract (PT) neuron activation was shaped differentially with learning but scaled linearly with turn acceleration during spontaneous turns. During induced turns, however, layer 2/3 neurons were activated independent of behavioral response, while PT neurons still encoded behavioral response magnitude. Our results are consistent with a role of M1 in the detection of sensory perturbations that result in deviations from intended motor state and the initiation of an appropriate corrective response., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Learning a novel motor skill is dependent both on regional changes within the primary motor cortex (M1) contralateral to the active hand and also on modulation between and within anatomically distant but functionally connected brain regions. Interregional changes are particularly important in functional recovery after stroke, when critical plastic changes underpinning behavioral improvements are observed in both ipsilesional and contralesional M1s. It is increasingly understood that reduction in GABA in the contralateral M1 is necessary to allow learning of a motor task. However, the physiological mechanisms underpinning plasticity within other brain regions, most importantly the ipsilateral M1, are not well understood. Here, we used concurrent two-voxel magnetic resonance spectroscopy to simultaneously quantify changes in neurochemicals within left and right M1s in healthy humans of both sexes in response to transcranial direct current stimulation (tDCS) applied to left M1. We demonstrated a decrease in GABA in both the stimulated (left) and nonstimulated (right) M1 after anodal tDCS, whereas a decrease in GABA was only observed in nonstimulated M1 after cathodal stimulation. This GABA decrease in the nonstimulated M1 during cathodal tDCS was negatively correlated with microstructure of M1:M1 callosal fibers, as quantified by diffusion MRI, suggesting that structural features of these fibers may mediate GABA decrease in the unstimulated region. We found no significant changes in glutamate. Together, these findings shed light on the interactions between the two major network nodes underpinning motor plasticity, offering a potential framework from which to optimize future interventions to improve motor function after stroke. SIGNIFICANCE STATEMENT Learning of new motor skills depends on modulation both within and between brain regions. Here, we use a novel two-voxel magnetic resonance spectroscopy approach to quantify GABA and glutamate changes concurrently within the left and right primary motor cortex (M1) during three commonly used transcranial direct current stimulation montages: anodal, cathodal, and bilateral. We also examined how the neurochemical changes in the unstimulated hemisphere were related to white matter microstructure between the two M1s. Our results provide insights into the neurochemical changes underlying motor plasticity and may therefore assist in the development of further adjunct therapies., (Copyright © 2018 Bachtiar, Johnstone et al.)

Changes in cortical and striatal function underlie the transition from novel actions to refined motor skills. How discrete, anatomically defined corticostriatal projections function in vivo to encode skill learning remains unclear. Using novel fiber photometry approaches to assess real-time activity of associative inputs from medial prefrontal cortex to dorsomedial striatum and sensorimotor inputs from motor cortex to dorsolateral striatum, we show that associative and sensorimotor inputs co-engage early in action learning and disengage in a dissociable manner as actions are refined. Disengagement of associative, but not sensorimotor, inputs predicts individual differences in subsequent skill learning. Divergent somatic and presynaptic engagement in both projections during early action learning suggests potential learning-related in vivo modulation of presynaptic corticostriatal function. These findings reveal parallel processing within associative and sensorimotor circuits that challenges and refines existing views of corticostriatal function and expose neuronal projection- and compartment-specific activity dynamics that encode and predict action learning., (Published by Elsevier Inc.)

The α 4 β 2 nicotinic acetylcholine receptor (nAChR) is important in central nervous system physiology and in mediating several of the pharmacological effects of nicotine on cognition, attention, and affective states. It is also the likely receptor that mediates nicotine addiction. This receptor assembles in two distinct stoichiometries: ( α 4) 2 ( β 2) 3 and ( α 4) 3 ( β 2) 2 , which are referred to as high-sensitivity (HS) and low-sensitivity (LS) nAChRs, respectively, based on a difference in the potency of acetylcholine to activate them. The physiologic and pharmacological differences between these two receptor subtypes have been described in heterologous expression systems. However, the presence of each stoichiometry in native tissue currently remains unknown. In this study, different ratios of rat α 4 and β 2 subunit cDNA were transfected into human embryonic kidney 293 cells to create a novel model system of HS and LS α 4 β 2 nAChRs expressed in a mammalian cell line. The HS and LS nAChRs were characterized through pharmacological and biochemical methods. Isolation of surface proteins revealed higher amounts of α 4 or β 2 subunits in the LS or HS nAChR populations, respectively. In addition, sazetidine-A displayed different efficacies in activating these two receptor stoichiometries. Using this model system, a neurophysiological "two-concentration" acetylcholine or carbachol paradigm was developed and validated to determine α 4/ β 2 subunit stoichiometry. This paradigm was then used in layers I-IV of slices of the rat motor cortex to determine the percent contribution of HS and LS α 4 β 2 receptors in this brain region. We report that the majority of α 4 β 2 nAChRs in this brain region possess a stoichiometry of the ( α 4) 3 ( β 2) 2 LS subtype., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)

The architecture of the neocortex classically consists of six layers, based on cytological criteria and on the layout of intra/interlaminar connections. Yet, the comparison of cortical cytoarchitectonic features across different species proves overwhelmingly difficult, due to the lack of a reliable model to analyze the connection patterns of neuronal ensembles forming the different layers. We first defined a set of suitable morphometric cell features, obtained in digitized Nissl-stained sections of the motor cortex of the horse, chimpanzee, and crab-eating macaque. We then modeled them using a quite general non-parametric data representation model, showing that the assessment of neuronal cell complexity (i.e., how a given cell differs from its neighbors) can be performed using a suitable measure of statistical dispersion such as the mean absolute deviation-mean absolute deviation (MAD). Along with the non-parametric combination and permutation methodology, application of MAD allowed not only to estimate, but also to compare and rank the motor cortical complexity across different species. As to the instances presented in this paper, we show that the pyramidal layers of the motor cortex of the horse are far more irregular than those of primates. This feature could be related to the different organizations of the motor system in monodactylous mammals.

The mechanisms underlying the emergence of learned motor skill representation in primary motor cortex (M1) are not well understood. Specifically, how motor representation in the deep output layer 5b (L5b) is shaped by motor learning remains virtually unknown. In rats undergoing motor skill training, we detect a subpopulation of task-recruited L5b neurons that not only become more movement-encoding, but their activities are also more structured and temporally aligned to motor execution with a timescale of refinement in tens-of-milliseconds. Field potentials evoked at L5b in vivo exhibit persistent long-term potentiation (LTP) that parallels motor performance. Intracortical dopamine denervation impairs motor learning, and disrupts the LTP profile as well as the emergent neurodynamical properties of task-recruited L5b neurons. Thus, dopamine-dependent recruitment of L5b neuronal ensembles via synaptic reorganization may allow the motor cortex to generate more temporally structured, movement-encoding output signal from M1 to downstream circuitry that drives increased uniformity and precision of movement during motor learning.

The present study investigated whether changes in oxyhemoglobin (O 2 Hb) concentration over time differed across brain regions according to differences in gross movement intensity. Thirteen healthy adults (21.2 ± 1.0 years, 8 women) participated in this study. After 180 s of rest, the participants performed 600 s of exercise on a cycle ergometer. Exercise intensity was set at 30%VO 2 peak and 50%VO 2 peak. The prefrontal cortex (PFC) and primary motor cortex (M1) were chosen as regions of interest. In addition, mean arterial pressure (MAP) and scalp blood flow (SBF) were measured simultaneously. O 2 Hb concentration in PFC and M1 was significantly decreased in initial phase of the exercise, while it was significantly increased from the mid to final phase for both intensities compared with resting state values (p < 0.01). The O 2 Hb concentrations in the PFC and M1 were significantly decreased in the initial exercise phase. However, the MAP and SBF values did not exhibit a similar pattern. The main findings of our study were the follows: (1) During cycle ergometer exercise at the 30% and 50% O 2 Hb peak, the after O 2 Hb concentrations were transiently decreased in the initial exercise phase, and the concentrations then steadily increased in both the PFC and M1; and (2) the duration of the transient decreases in the O 2 Hb concentrations varied according to the brain region and exercise intensity.

Our previous studies have shown that water immersion (WI) changes sensorimotor processing and cortical excitability in the sensorimotor regions of the brain. The present study examined the site specificity of the brain activation during WI using functional near infrared spectroscopy (fNIRS). Cortical oxyhaemoglobin (O 2 Hb) levels in the anterior and posterior parts of the supplementary motor area (pre-SMA and SMA), primary motor cortex (M1), primary somatosensory cortex (S1), and posterior parietal cortex (PPC) were recorded using fNIRS (OMM-3000; Shimadzu Co.) before, during, and after WI in nine healthy participants. The cortical O 2 Hb levels in SMA, M1, S1, and PPC significantly increased during the WI and increased gradually along with the filling of the WI tank. These changes were not seen in the pre-SMA. The results show that WI-induced increases in cortical O 2 Hb levels are at least somewhat site specific: there was little brain activation in response to somatosensory input in the pre-SMA, but robust activation in other areas.

The possibility that a metabolomic approach can inform about the pathophysiology of a given form of epilepsy was addressed. Using chemometric analyses of HRMAS NMR data, we compared several brain structures in three rat strains with different susceptibilities to absence epilepsy: Genetic Absence Epilepsy Rats from Strasbourg (GAERS), Non Epileptic Control rats (NEC), and Wistar rats. Two ages were investigated: 14 days postnatal (P14) before the onset of seizures and 5 month old adults with fully developed seizures (Adults). The relative concentrations of 19 metabolites were assessed using (1)H HRMAS NMR experiments. Univariate and multivariate analyses including multiblock models were used to identify the most discriminant metabolites. A strain-dependent evolution of glutamate, glutamine, scyllo-inositol, alanine, and glutathione was highlighted during cerebral maturation. In Adults, data from somatosensory and motor cortices allowed discrimination between GAERS and NEC rats with higher levels of scyllo-inositol, taurine, and phosphoethanolamine in NEC. This epileptic metabolic phenotype was in accordance with current pathophysiological hypothesis of absence epilepsy (i.e., seizure-generating and control networks) and putative resistance of NEC rats and was observed before seizure onset. This methodology could be very efficient in a clinical context.

Background and Objective: γ-Aminobutyric acid (GABA) is the dominant inhibitory neurotransmitter in the brain and is important in motor learning. We aimed to measure GABA content in primary motor cortex poststroke (using GABA-edited magnetic resonance spectroscopy [MRS]) and in relation to motor recovery during 2 weeks of constraint-induced movement therapy (CIMT)., Methods: Twenty-one patients (3-12 months poststroke) and 20 healthy subjects were recruited. Magnetic resonance imaging structural T1 and GABA-edited MRS were performed at baseline and after CIMT, and once in healthy subjects. GABA:creatine (GABA:Cr) ratio was measured by GABA-edited MRS. Motor function was measured using Wolf Motor Function Test (WMFT)., Results: Baseline comparison between stroke patients (n = 19) and healthy subjects showed a significantly lower GABA:Cr ratio in stroke patients (P < .001) even after correcting for gray matter content in the voxel (P < .01) and when expressing GABA relative to N-acetylaspartic acid (NAA; P = .03). After 2 weeks of CIMT patients improved significantly on WMFT, but no consistent change across the group was observed for the GABA:Cr ratio (n = 17). However, the extent of improvement on WMFT correlated significantly with the magnitude of GABA:Cr changes (P < .01), with decreases in GABA:Cr ratio being associated with better improvements in motor function., Conclusions: In patients 3 to 12 months poststroke, GABA levels are lower in the primary motor cortex than in healthy subjects. The observed association between GABA and recovery warrants further studies on the potential use of GABA MRS as a biomarker in poststroke recovery., (© The Author(s) 2014.)

Objective: To compare the results of magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in amyotrophic lateral sclerosis (ALS) patients., Methods: Nineteen ALS patients and thirteen age-matched healthy controls underwent MRS and DTI between October 2013 and July 2014. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) were collected as the quantitative results of the imaging study. The ALS functional rating scale-revised (ALSFRS-R) and disease progression rate were evaluated to assess patients' disability. The imaging study results were compared between ALS patients and healthy controls. The relationship between disability assessment and imaging study results was analyzed., Results: NAA/Cr in the motor cortex and FA in the corticospinal tract (CST) of both sides were significantly lower in patients than controls. There was no significant difference between the two groups in Cho/Cr, tract length, tract volume, ADC or NAA. No relationship was found between ALSFRS-R and FA (r=0.243, p=0.316) in the right CST; NAA (r=0.095, p=0.699) or NAA/Cr (r=0.172, p=0.481) in the left motor cortex; or NAA (r=0.320, p=0.182) or NAA/Cr (r=0.193, p=0.492) in the right motor cortex. There was no relationship between the disease progression rate and FA, NAA, or NAA/Cr on either side., Conclusion: NAA/Cr and FA can help diagnose ALS. Regional brain NAA/Cr and FA values could not assess the ALSFRS-R or disease progression rate., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Rationale: Chorioamnionitis has been associated with increased risk for fetal brain damage. Although, it is now accepted that synaptic dysfunction might be responsible for functional deficits, synaptic densities/numbers after a fetal inflammatory challenge have not been studied in different regions yet. Therefore, we tested in this study the hypothesis that LPS-induced chorioamnionitis caused profound changes in synaptic densities in different regions of the fetal sheep brain., Material and Methods: Chorioamnionitis was induced by a 10 mg intra-amniotic LPS injection at two different exposure intervals. The fetal brain was studied at 125 days of gestation (term = 150 days) either 2 (LPS2D group) or 14 days (LPS14D group) after LPS or saline injection (control group). Synaptophysin immunohistochemistry was used to quantify the presynaptic density in layers 2-3 and 5-6 of the motor cortex, somatosensory cortex, entorhinal cortex, and piriforme cortex, in the nucleus caudatus and putamen and in CA1/2, CA3, and dentate gyrus of the hippocampus., Results: There was a significant reduction in presynaptic bouton densities in layers 2-3 and 5-6 of the motor cortex and in layers 2-3 of the entorhinal and the somatosensory cortex, in the nucleus caudate and putamen and the CA1/2 and CA3 of the hippocampus in the LPS2D compared to control animals. Only in the motor cortex and putamen, the presynaptic density was significantly decreased in the LPS14 D compared to the control group. No changes were found in the dentate gyrus of the hippocampus and the piriforme cortex., Conclusion: We demonstrated that LPS-induced chorioamnionitis caused a decreased density in presynaptic boutons in different areas in the fetal brain. These synaptic changes seemed to be region-specific, with some regions being more affected than others, and seemed to be transient in some regions.

While Parkinson's disease is the result of dopaminergic dysfunction of the nigrostriatal system, the clinical manifestations of Parkinson's disease are brought about by alterations in multiple neural components, including cortical areas. We examined how 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration affected extracellular cortical glutamate levels by comparing glutamate levels in normal and MPTP-lesioned nonhuman primates (Macaca mulatta). Extracellular glutamate levels were measured using glutamate microelectrode biosensors. Unilateral MPTP-administration rendered the animals with hemiparkinsonian symptoms, including dopaminergic deficiencies in the substantia nigra and the premotor and motor cortices, and with statistically significant decreases in basal glutamate levels in the primary motor cortex on the side ipsilateral to the MPTP-lesion. These results suggest that the functional changes of the glutamatergic system, especially in the motor cortex, in models of Parkinson's disease could provide important insights into the mechanisms of this disease., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In traumatic brain injury mechanical forces applied to the cranium and brain cause irreversible primary neuronal and astroglial damage associated with terminal dendritic beading and spine loss representing acute damage to synaptic circuitry. Oedema develops quickly after trauma, raising intracranial pressure that results in a decrease of blood flow and consequently in cerebral ischaemia, which can cause secondary injury in the peri-contusional cortex. Spreading depolarizations have also been shown to occur after traumatic brain injury in humans and in animal models and are thought to accelerate and exacerbate secondary tissue injury in at-risk cortical territory. Yet, the mechanisms of acute secondary injury to fine synaptic circuitry within the peri-contusional cortex after mild traumatic brain injury remain unknown. A mild focal cortical contusion model in adult mouse sensory-motor cortex was implemented by the controlled cortical impact injury device. In vivo two-photon microscopy in the peri-contusional cortex was used to monitor via optical window yellow fluorescent protein expressing neurons, enhanced green fluorescent protein expressing astrocytes and capillary blood flow. Dendritic beading in the peri-contusional cortex developed slowly and the loss of capillary blood flow preceded terminal dendritic injury. Astrocytes were swollen indicating oedema and remained swollen during the next 24 h throughout the imaging session. There were no recurrent spontaneous spreading depolarizations in this mild traumatic brain injury model; however, when spreading depolarizations were repeatedly induced outside the peri-contusional cortex by pressure-injecting KCl, dendrites undergo rapid beading and recovery coinciding with passage of spreading depolarizations, as was confirmed with electrophysiological recordings in the vicinity of imaged dendrites. Yet, accumulating metabolic stress resulting from as few as four rounds of spreading depolarization significantly added to the fraction of beaded dendrites that were incapable to recover during repolarization, thus facilitating terminal injury. In contrast, similarly induced four rounds of spreading depolarization in another set of control healthy mice caused no accumulating dendritic injury as dendrites fully recovered from beading during repolarization. Taken together, our data suggest that in the mild traumatic brain injury the acute dendritic injury in the peri-contusional cortex is gated by the decline in the local blood flow, most probably as a result of developing oedema. Furthermore, spreading depolarization is a specific mechanism that could accelerate injury to synaptic circuitry in the metabolically compromised peri-contusional cortex, worsening secondary damage following traumatic brain injury.

Transcranial magnetic stimulation (TMS) can provide an index of intracortical excitability/inhibition balance. However, the neurochemical substrate of these measures remains unclear. Pharmacological studies suggest the involvement of GABAA and GABAB receptors in TMS protocols aimed at measuring intracortical inhibition, but this link remains inferential. Proton magnetic resonance spectroscopy ((1)H-MRS) permits measurement of GABA and glutamate + glutamine (Glx) concentrations in the human brain and might help in the direct empirical assessment of the relationship between TMS inhibitory measures and neurotransmitter concentrations. In the present study, MRS-derived relative concentrations of GABA and Glx measured in the left M1 of healthy participants were correlated with TMS measures of intracortical inhibition. Glx levels were found to correlate positively with TMS-induced silent period duration, whereas no correlation was found between GABA concentration and TMS measures. The present data demonstrate that specific TMS measures of intracortical inhibition are linked to shifts in cortical Glx, rather than GABA neurotransmitter levels. Glutamate might specifically interact with GABAB receptors, where higher MRS-derived Glx concentrations seem to be linked to higher levels of receptor activity.

Using near-infrared spectroscopy (NIRS) and multichannel probes, we studied hemoglobin (Hb) concentration changes when single-pulse transcranial magnetic stimulation (TMS) was applied over the left hemisphere primary motor cortex (M1). Seventeen measurement probes were centered over left M1. Subjects were studied in both active and relaxed conditions, with TMS intensity set at 100%, 120%, and 140% of the active motor threshold. The magnetic coils were placed so as to induce anteromedially directed currents in the brain. Hb concentration changes were more prominent at channels over M1 and posterior to it. Importantly, Hb concentration changes at M1 after TMS differed depending on whether the target muscle was in an active or relaxed condition. In the relaxed condition, Hb concentration increased up to 3-6 s after TMS, peaking at ∼6 s, and returned to the baseline. In the active condition, a smaller increase in Hb concentrations continued up to 3-6 s after TMS (early activation), followed by a decrease in Hb concentration from 9 to 12 s after TMS (delayed deactivation). Hb concentration changes in the active condition at higher stimulus intensities were more pronounced at locations posterior to M1 than at M1. We conclude that early activation occurs when M1 is activated transsynaptically. The relatively late deactivation may result from the prolonged inhibition of the cerebral cortex after activation. The posterior-dominant activation at higher intensities in the active condition may result from an additional activation of the sensory cortex due to afferent inputs from muscle contraction evoked by the TMS.

Secretin and its receptors show wide distribution in the central nervous system. It was demonstrated previously that intravenous (i.v.) and intracerebroventricular (i.c.v.) application of secretin influenced the behavior of rat, mouse, and human. In our previous experiment, we used a special animal model, Japanese waltzing mice (JWM). These animals run around without stopping (the ambulation distance is very limited) and they do not bother with their environment. The i.c.v. secretin attenuated this hyperactive repetitive movement. In the present work, the effect of i.c.v. and intranasal (i.n.) application of secretin was compared. We have also looked for the presence of secretin receptors in the brain structures related to motor functions. Two micrograms of i.c.v. secretin improved the horizontal movement of JWM, enhancing the ambulation distance. It was nearly threefold higher in treated than in control animals. The i.n. application of secretin to the left nostril once or twice a day or once for 3 days more effectively enhanced the ambulation distance than i.c.v. administration. When secretin was given twice a day for 3 days it had no effect. Secretin did not improve the explorative behavior (the rearing), of JWM. With the use of in situ hybridization, we have found very dense secretin receptor labeling in the cerebellum. In the primary motor cortex and in the striatum, only a few labeled cells were seen. It was supposed that secretin exerted its effect through specific receptors, mainly present in the cerebellum.

Long-term potentiation (LTP) of synaptic efficacy is considered a fundamental mechanism of learning and memory. At the cellular level a large body of evidence demonstrated that the major neuromodulatory neurotransmitters dopamine (DA), norepinephrine (NE), and acetylcholine (ACh) influence LTP magnitude. Noninvasive brain stimulation protocols provide the opportunity to study LTP-like plasticity at the systems level of human cortex. Here we applied paired associative stimulation (PAS) to induce LTP-like plasticity in the primary motor cortex of eight healthy subjects. In a double-blind, randomized, placebo-controlled, crossover design, the acute effects of a single oral dose of the neuromodulatory drugs cabergoline (DA agonist), haloperidol (DA antagonist), methylphenidate (indirect NE agonist), prazosine (NE antagonist), tacrine (ACh agonist), and biperiden (ACh antagonist) on PAS-induced LTP-like plasticity were examined. The antagonists haloperidol, prazosine, and biperiden depressed significantly the PAS-induced LTP-like plasticity observed under placebo, whereas the agonists cabergoline, methylphenidate, and tacrine had no effect. Findings demonstrate that antagonists in major neuromodulatory neurotransmitter systems suppress LTP-like plasticity at the systems level of human cortex, in accord with evidence of their modulating action of LTP at the cellular level. This provides further supportive evidence for the known detrimental effects of these drugs on LTP-dependent mechanisms such as learning and memory.

In our monkey model, cortical ARC and BDNF expressions were strongly correlated with spontaneous physical activity. The expressions of ARC and BDNF were inversely correlated with serum CRP levels, suggesting that CRP could be a putative peripheral marker of brain resiliency.

Continuous theta burst stimulation (cTBS) is a novel transcranial stimulation technique that causes significant inhibition of synaptic transmission for

We developed a method that uses Channelrhodopsin-2 (ChR2) for transcranial optogenetic stimulation. This method is based on scanning a light beam over the brain, thereby photostimulating ChR2-expressing neurons in intact mice. As a proof of principle, we applied this technique to the motor cortex of transgenic mice expressing ChR2 in cortical pyramidal cells. Photostimulation induced limb movements that were time-locked with millisecond precision and could be induced at frequencies up to 20 Hz. By scanning this light beam, we could map the distribution of neurons associated with limb movement. With this approach we could simultaneously define motor maps controlling two limbs and could reproducibly generate such cortical motor maps over periods of weeks. This method allows non-invasive mapping of brain circuitry in living animals and could help define the connection between behavior and brain circuitry.

Three ascending pathways of information processing have been identified so far in the vibrissal system of rodents. In the ventral posterior medial nucleus of the thalamus, two of these pathways convey information through the core and tail of barrel-associated structures, called barreloids. The other pathway transits through the posterior group nucleus. The present study provides anatomical and electrophysiological evidence for the existence of an additional pathway that passes through the head of the barreloids. This pathway arises from multiwhisker-responsive cells in the principal trigeminal nucleus and differs from the classic lemniscal pathway, in that constituent thalamic cells have multiwhisker receptive field and receive corticothalamic input from lamina 6 of the vibrissa motor cortex. It is suggested that this pathway might be involved in relaying signals encoding phase of whisker motion during free whisking.

Objective: To investigate the value of objective biomarkers for upper (UMN) and lower (LMN) motor neuron involvement in ALS., Methods: We prospectively studied 64 patients with ALS and its subsets using clinical measures, proton MR spectroscopic imaging ((1)H MRSI), diffusion tensor imaging, transcranial magnetic stimulation, and the motor unit number estimation (MUNE) at baseline and every 3 months for 15 months and compared them with control subjects., Results: (1)H MRSI measures of the primary motor cortex N-acetyl-aspartate (NAA) concentration were markedly reduced in ALS (p = 0.009) and all UMN syndromes combined (ALS, familial ALS [fALS], and primary lateral sclerosis; p = 0.03) vs control values. Central motor conduction time to the tibialis anterior was prolonged in ALS (p < 0.0005) and combined UMN syndromes (p = 0.001). MUNE was lower in ALS (p < 0.0005) and all LMN syndromes combined (ALS, fALS, and progressive muscular atrophy; p = 0.001) vs controls. All objective markers correlated well with the ALS Functional Rating Scale-Revised, finger and foot tapping, and strength testing, suggesting these markers related to disease activity. Regarding changes over time, MUNE changed rapidly, whereas neuroimaging markers changed more slowly and did not significantly differ from baseline., Conclusions: (1)H MR spectroscopic imaging measures of the primary motor cortex N-acetyl-aspartate (NAA) concentration and ratio of NAA to creatine, central motor conduction time to the tibialis anterior, and motor unit number estimation significantly differed between ALS, its subsets, and control subjects, suggesting they have potential to provide insight into the pathobiology of these disorders.

Objective: To determine the relationship of cerebral degeneration with survival in amyotrophic lateral sclerosis (ALS)., Methods: Patients with probable or definite ALS underwent magnetic resonance spectroscopic imaging (MRSI) of the brain between July 1996 and May 2002, and were followed prospectively until March 2004. Creatine (Cr), choline (Cho) and the neuronal marker N-acetylaspartate (NAA) were quantified as ratios in the motor cortex., Results: In 63 patients compared with 18 healthy people, NAA/Cho was reduced by 13% (p<0.001), NAA/Cr was reduced by 5% (p = 0.01) and Cho/Cr was increased by 8% (p = 0.01). NAA/Cho was used for survival analysis, given its larger effect size and superior test accuracy (a sensitivity of 67% and a specificity of 83%). Median survival after MRSI was 24 months. Multivariate analysis showed reduced survival for lower NAA/Cho (hazard ratio (HR) 0.24, 95% confidence interval (CI) 0.08 to 0.72, p = 0.01), older age (HR 1.03, 95% CI 1.00 to 1.06, p = 0.04) and shorter symptom duration (HR 0.96, 95% CI 0.93 to 0.99, p = 0.01). Patients with NAA/Cho <2.11 had a reduced survival of 19.4 v 31.9 months (HR 2.05, 95% CI 1.12 to 4.03, p = 0.02)., Conclusions: Cerebral degeneration is predictive of reduced survival in ALS.

Some studies have found that unilateral cerebral damage produces significant deficits in the ipsilesional, "less-affected", body side. Other studies have found that such damage results in a paradoxical hyperfunctionality of the ipsilesional body side and a facilitation of learning-induced neuroplastic changes in the contralesional motor cortex. The purpose of this study was to determine whether these effects co-exist and/or vary with lesion severity. After small or large unilateral ischemic lesions of the sensorimotor cortex (SMC) or sham operations, adult male rats were trained for 20 days to acquire a motor task, skilled reaching for food, for the first time with the ipsilesional forelimb. Analyses of movement patterns indicated lesion-size-dependent ipsilesional abnormalities in grasping, retrieving and releasing food pellets. Despite these impairments, success rates were significantly increased and aiming errors reduced in lesion groups compared with sham operates. Performance was best in rats with small lesions that had more minor ipsilesional impairments. In the motor cortex contralateral to the lesion and trained limb, there were significant increases in the density of dendrites immunoreactive for microtubule-associated protein-2 (MAP2) and of N-methyl-D-aspartate receptor subunit 1 (NMDAR1) immunoreactivity compared with sham operates. These effects were correlated with reaching performance. Therefore, enhanced motor skill learning in the "less-affected" forelimb and contralesional neuroplastic changes are muted after larger lesions and co-exist with ipsilesional impairments. These effects may be related to a denervation-induced neural restructuring of the contralesional cortex that both disrupts pre-existing motor engrams and facilitates the establishment of new ones.

Background: The lateral premotor cortex plays a crucial role in visually guided limb movements. It is divided into two main regions, the dorsal (PMd) and ventral (PMv) areas, which are in turn subdivided into functionally and anatomically distinct rostral (PMd-r and PMv-r) and caudal (PMd-c and PMv-c) sub-regions. We analyzed the callosal inputs to these premotor subdivisions following 23 injections of retrograde tracers in eight macaque monkeys. In each monkey, 2-4 distinct tracers were injected in different areas allowing direct comparisons of callosal connectivity in the same brain., Results: Based on large injections covering the entire extent of the corresponding PM area, we found that each area is strongly connected with its counterpart in the opposite hemisphere. Callosal connectivity with the other premotor areas, the primary motor cortex, prefrontal cortex and somatosensory cortex varied from one area to another. The most extensive callosal inputs terminate in PMd-r and PMd-c, with PMd-r strongly connected with prefrontal cortex. Callosal inputs to PMv-c are more extensive than those to PMv-r, whose connections are restricted to its counterpart area. Quantitative analysis of labelled cells confirms these general findings, and allows an assessment of the relative strength of callosal inputs., Conclusion: PMd-r and PMv-r receive their strongest callosal inputs from their respective counterpart areas, whereas PMd-c and PMv-c receive strong inputs from heterotopic areas as well (namely from PMd-r and PMv-r, respectively). Finally, PMd-r stands out as the lateral premotor area with the strongest inputs from the prefrontal cortex, and only the PMd-c and PMv-c receive weak callosal inputs from M1.

Dopamine deficiency in Parkinson's disease leads to numerous molecular changes in basal ganglia. However, the consequences of these changes on the motor cortex remain unclear. Here we show that the immunoreactivity of parvalbumin, which is expressed in GABAergic interneurons, increases in the primary motor cortex of parkinsonian rats. This increase can be reversed by a subsequent lesion of the subthalamic nucleus. These results suggest that dopamine deficiency induces reversible changes in GABAergic cortical cells, which might be linked with parkinsonian symptoms.

The organization of multisynaptic projections from the prefrontal cortex to the primary motor cortex (MI) was examined in macaque monkeys by retrograde transneuronal transport of rabies virus. In the first series of experiments, the virus was injected into the MI forelimb region, and the time-dependent distribution patterns of transsynaptic labeling were analyzed in the frontal lobe with various survivals (2-4 d). Two days after the viral injection, neuronal labeling emerged in the caudal aspects of the nonprimary motor-related areas that are known to project to the MI directly. At the same time, the motor thalamus contained labeled neurons. On the third day, cortical labeling extended into the rostral motor-related areas and, also, prearcuate area 8. Moreover, a number of labeled neurons were located in the internal pallidum and the cerebellar nuclei. At the 4 d postinjection period, neuronal labeling occurred widely in prefrontal areas as well as in the putamen and the cerebellar cortex. In the second series of experiments, the viral injection was made into the MI hindlimb region, and the distribution pattern of prefrontal labeling on the fourth day was compared with that in the forelimb-injection case. The labeled neurons in each prefrontal area were much fewer in the hindlimb-injection case than in the forelimb-injection case. Whereas ventral area 46 was most densely labeled from the forelimb region, only sparse labeling from the hindlimb region was observed in this prefrontal area. The present results suggest the importance of ventral area 46 in the cognitive control of forelimb movements.

Dyskinesia represents a debilitating complication of L-3,4-dihydroxyphenylalanine (L-dopa) therapy for Parkinson's disease. Such motor manifestations are attributed to pathological activity in the motor parts of basal ganglia. However, because consistent funneling of information takes place between the sensorimotor, limbic, and associative basal ganglia domains, we hypothesized that nonmotor domains play a role in these manifestations. Here we report the changes in 2-deoxyglucose (2-DG) accumulation in the sensorimotor, limbic, and associative domains of basal ganglia and thalamic nuclei of four groups of nonhuman primates: normal, parkinsonian, parkinsonian chronically treated with L-dopa without exhibiting dyskinesia, and parkinsonian chronically treated with L-dopa and exhibiting overt dyskinesia. Although nondyskinetic animals display a rather normalized metabolic activity, dyskinetic animals are distinguished by significant changes in 2-DG accumulation in limbic- and associative-related structures and not simply in sensorimotor-related ones, suggesting that dyskinesia is linked to a pathological processing of limbic and cognitive information. We propose that these metabolic changes reflect the underlying neural mechanisms of not simply motor dyskinesias but also affective, motivational, and cognitive disorders associated with long-term exposure to L-dopa.

Despite its pharmacological relevance, the mechanism of the development of tolerance to the action of benzodiazepines is essentially unknown. The acute sedative action of diazepam is mediated via alpha1-GABA(A) receptors. Therefore, we tested whether chronic activation of these receptors by diazepam is sufficient to induce tolerance to its sedative action. Knock-in mice, in which thealpha1-,alpha2-,alpha3-, oralpha(5)-GABA(A) receptors had been rendered insensitive to diazepam by histidine-arginine point mutation, were chronically treated with diazepam (8 d; 15 mg x kg(-1) x d(-1)) and tested for motor activity. Wild-type, alpha2(H101R), and alpha3(H126R) mice showed a robust diminution of the motor-depressant drug action. In contrast, alpha5(H105R) mice failed to display any sedative tolerance. alpha1(H101R) mice showed no alteration of motor activity with chronic diazepam treatment. Autoradiography with [3H]flumazenil revealed no change in benzodiazepine binding sites. However, a decrease in alpha5-subunit radioligand binding was detected selectively in the dentate gyrus with specific ligands. This alteration was observed only in diazepam-tolerant animals, indicating that the manifestation of tolerance to the sedative action of diazepam is associated with a downregulation of alpha5-GABA(A) receptors in the dentate gyrus. Thus, the chronic activation of alpha(5)-GABA(A) receptors is crucial for the normal development of sedative tolerance to diazepam, which manifests itself in conjunction with alpha1-GABA(A) receptors.

Gamma-aminobutyric acid (GABA)ergic neurons in the central nervous system regulate the activity of other neurons and play a crucial role in information processing. To assist an advance in the research of GABAergic neurons, here we produced two lines of glutamic acid decarboxylase-green fluorescence protein (GAD67-GFP) knock-in mouse. The distribution pattern of GFP-positive somata was the same as that of the GAD67 in situ hybridization signal in the central nervous system. We encountered neither any apparent ectopic GFP expression in GAD67-negative cells nor any apparent lack of GFP expression in GAD67-positive neurons in the two GAD67-GFP knock-in mouse lines. The timing of GFP expression also paralleled that of GAD67 expression. Hence, we constructed a map of GFP distribution in the knock-in mouse brain. Moreover, we used the knock-in mice to investigate the colocalization of GFP with NeuN, calretinin (CR), parvalbumin (PV), and somatostatin (SS) in the frontal motor cortex. The proportion of GFP-positive cells among NeuN-positive cells (neocortical neurons) was approximately 19.5%. All the CR-, PV-, and SS-positive cells appeared positive for GFP. The CR-, PV, and SS-positive cells emitted GFP fluorescence at various intensities characteristics to them. The proportions of CR-, PV-, and SS-positive cells among GFP-positive cells were 13.9%, 40.1%, and 23.4%, respectively. Thus, the three subtypes of GABAergic neurons accounted for 77.4% of the GFP-positive cells. They accounted for 6.5% in layer I. In accord with unidentified GFP-positive cells, many medium-sized spherical somata emitting intense GFP fluorescence were observed in layer I., (Copyright 2003 Wiley-Liss, Inc.)

In vivo longitudinal relaxation times of N-acetyl compounds (NA), choline-containing substances (Cho), creatine (Cr), myo-inositol (mI), and tissue water were measured at 1.5 and 3 T using a point-resolved spectroscopy (PRESS) sequence with short echo time (TE). T(1) values were determined in six different brain regions: the occipital gray matter (GM), occipital white matter (WM), motor cortex, frontoparietal WM, thalamus, and cerebellum. The T(1) relaxation times of water protons were 26-38% longer at 3 T than at 1.5 T. Significantly longer metabolite T(1) values at 3 T (11-36%) were found for NA, Cho, and Cr in the motor cortex, frontoparietal WM, and thalamus. The amounts of GM, WM, and cerebrospinal fluid (CSF) within the voxel were determined by segmentation of a 3D image data set. No influence of tissue composition on metabolite T(1) values was found, while the longitudinal relaxation times of water protons were strongly correlated with the relative GM content., (Copyright 2003 Wiley-Liss, Inc.)

The Wobbler mouse is recognized as an animal model for motoneuron disease that exhibits motoneuron pathology. We have recently demonstrated the occurrence of mitochondrial dysfunction in the Wobbler mouse brain. The aim of the present study was to evaluate whether mitochondrial dysfunction occurred at an early age at the time where disease symptoms appear, and whether it was more pronounced in the motor cortex or in the spinal cord. We report here a significant decrease in mitochondrial state 3 and 4 respiration rates at an early age in the Wobbler spinal cord. In addition, there was a pronounced decrease in oxidative phosphorylation in mitochondria isolated from both spinal cord and motor cortex in both age groups. This mitochondrial dysfunction was accompanied by impairment of complex I activity in mitochondria isolated from spinal cord at an early age. Decreases in complex III and IV activities were observed only in mitochondria isolated from the motor cortex at an early age, but impairment of complex III activity prevailed until later in the disease. We conclude that mitochondrial dysfunction ensues at an early stage of the disease and is more pronounced in the spinal cord, which correlates with previous studies that reported degeneration of spinal cord motorneurons.

Objective: To determine identifiable subgroups of patients with primary lateral sclerosis (PLS) with distinct clinical features as a first step in identifying patients likely to have the same disorder., Methods: Twenty-five patients meeting previously proposed diagnostic criteria for PLS were seen for examination, measurement of gait and finger tapping speed, and physiologic tests to assess motor pathways. Motor cortex excitability and central motor conduction time were assessed with transcranial magnetic stimulation. Brainstem motor pathways were assessed by the acoustic startle reflex. MRS was performed in a subgroup of patients to assess metabolites in the motor cortex., Results: Fifty-six percent of the patients with PLS had a similar pattern of symptom progression, which the authors termed ascending. In these patients spasticity began in the legs and progressed slowly and steadily. Spasticity in the arms developed 3.6 years after the legs, on average, and speech impairment followed 1.5 years later. Motor evoked potentials were absent. MRS showed a mean reduction of N-acetylaspartate/creatinine in the motor cortex. The remaining patients with PLS had heterogeneous patterns of symptom progression and physiology., Conclusions: Patients with PLS with an ascending progression of symptoms form a distinct clinical subgroup that may be amenable to investigations of etiology and treatment.

During the multicenter, phase III trial of intrathecal BDNF in ALS, we evaluated the neuronal marker N-acetylaspartate (NAA) as a surrogate marker of therapeutic efficacy using proton magnetic resonance spectroscopic imaging (MRSI) in a prospective and blinded manner. Selected subjects tolerated the study well without pump malfunction. The NAA to creatine (Cr) intensity ratio (NAA/Cr) was measured in the precentral and postcentral gyri, the superior parietal lobule, the supplementary motor area, and the premotor cortex. After 4.5+/-0.6 weeks treatment, NAA/Cr did not change significantly in any of the regions in the BDNF-treated group (n=5) compared to the placebo group (n=6). The lack of change in NAA correlated with the lack of clinical efficacy and supports the validity of NAA/Cr as a surrogate in this setting. MRSI is a feasible and safe method to evaluate intrathecal therapies in ALS.