Postcentral gyrus resection of opercular gliomas is a risk factor for motor deficits caused by damaging the radiologically invisible arteries supplying the descending motor pathway.

BACKGROUND: Postoperative motor deficits are among the worst morbidities of glioma surgery. We aim to investigate factors associated with postoperative motor deficits in patients with frontoparietal opercular gliomas. METHODS: Thirty-four patients with frontoparietal opercular gliomas were retrospectively investigated. We examined the postoperative ischemic changes and locations obtained from MRI. RESULTS: Twenty-one patients (62%) presented postoperative ischemic changes. Postoperative MRI was featured with ischemic changes, all located at the subcortical area of the resection cavity. Six patients had postoperative motor deficits, whereas 28 patients did not. Compared to those without motor deficits, those with motor deficits were associated with old age, pre- and postcentral gyri resection, and postcentral gyrus resection (P = 0.023, 0,024, and 0.0060, respectively). A merged image of the resected cavity and T1-weighted brain atlas of the Montreal Neurological Institute showed that a critical area for postoperative motor deficits is the origin of the long insular arteries (LIAs) and the postcentral gyrus. Detail anatomical architecture created by the Human Connectome Project database and T2-weighted images showed that the subcortical area of the operculum of the postcentral gyrus is where the medullary arteries supply, and the motor pathways originated from the precentral gyrus run. CONCLUSIONS: We verified that the origin of the LIAs could damage the descending motor pathways during the resection of frontoparietal opercular gliomas. Also, we identified that motor pathways run the subcortical area of the operculum of the postcentral gyrus, indicating that the postcentral gyrus is an unrecognized area of damaging the descending motor pathways.

Dynamic brain fluctuations outperform connectivity measures and mirror pathophysiological profiles across dementia subtypes: A multicenter study.

From molecular mechanisms to global brain networks, atypical fluctuations are the hallmark of neurodegeneration. Yet, traditional fMRI research on resting-state networks (RSNs) has favored static and average connectivity methods, which by overlooking the fluctuation dynamics triggered by neurodegeneration, have yielded inconsistent results. The present multicenter study introduces a data-driven machine learning pipeline based on dynamic connectivity fluctuation analysis (DCFA) on RS-fMRI data from 300 participants belonging to three groups: behavioral variant frontotemporal dementia (bvFTD) patients, Alzheimer's disease (AD) patients, and healthy controls. We considered non-linear oscillatory patterns across combined and individual resting-state networks (RSNs), namely: the salience network (SN), mostly affected in bvFTD; the default mode network (DMN), mostly affected in AD; the executive network (EN), partially compromised in both conditions; the motor network (MN); and the visual network (VN). These RSNs were entered as features for dementia classification using a recent robust machine learning approach (a Bayesian hyperparameter tuned Gradient Boosting Machines (GBM) algorithm), across four independent datasets with different MR scanners and recording parameters. The machine learning classification accuracy analysis revealed a systematic and unique tailored architecture of RSN disruption. The classification accuracy ranking showed that the most affected networks for bvFTD were the SN + EN network pair (mean accuracy = 86.43%, AUC = 0.91, sensitivity = 86.45%, specificity = 87.54%); for AD, the DMN + EN network pair (mean accuracy = 86.63%, AUC = 0.89, sensitivity = 88.37%, specificity = 84.62%); and for the bvFTD vs. AD classification, the DMN + SN network pair (mean accuracy = 82.67%, AUC = 0.86, sensitivity = 81.27%, specificity = 83.01%). Moreover, the DFCA classification systematically outperformed canonical connectivity approaches (including both static and linear dynamic connectivity). Our findings suggest that non-linear dynamical fluctuations surpass two traditional seed-based functional connectivity approaches and provide a pathophysiological characterization of global brain networks in neurodegenerative conditions (AD and bvFTD) across multicenter data.

Structural correlates of atypical visual and motor cortical oscillations in pediatric-onset multiple sclerosis.

We have previously demonstrated that pediatric-onset multiple sclerosis (POMS) negatively impacts the visual pathway as well as motor processing speed. Relationships between MS-related diffuse structural damage of gray and white matter (WM) tissue and cortical responses to visual and motor stimuli remain poorly understood. We used magnetoencephalography in 14 POMS patients and 15 age- and sex-matched healthy controls to assess visual gamma (30-80 Hz), motor gamma (60-90 Hz), and motor beta (15-30 Hz) cortical oscillatory responses to a visual-motor task. Then, 3T MRI was used to: (a) calculate fractional anisotropy (FA) of the posterior visual and corticospinal motor WM pathways and (b) quantify volume and thickness of the cuneus and primary motor cortex. Visual gamma band power was reduced in POMS and was associated with reduced FA of the optic radiations but not with loss of cuneus volume or thickness. Activity in the primary motor cortex, as measured by postmovement beta rebound amplitude associated with peak latency, was decreased in POMS, although this reduction was not predicted by structural metrics. Our findings implicate loss of WM integrity as a contributor to reduced electrical responses in the visual cortex in POMS. Future work in larger cohorts will inform on the cognitive implications of this finding in terms of visual processing function and will determine whether the progressive loss of brain volume known to occur in POMS ultimately contributes to both progressive dysfunction in such tasks as well as progressive reduction in cortical electrical responses in the visual cortex.

Simultaneous cortical and subcortical recordings in humans with movement disorders: Acute and chronic paradigms.

Invasive basal ganglia recordings in humans have significantly advanced our understanding of the neurophysiology of movement disorders. A recent technical advance has been the addition of electrocorticography to basal ganglia recording, for evaluating distributed motor networks. Here we review the rationale, results, and ethics of this multisite recording technique in movement disorders, as well as its application in chronic recording paradigms utilizing implantable neural interfaces that include a sensing function.

Effects of injuries to descending motor pathways on restoration of gait in patients with pontine hemorrhage.

BACKGROUND AND PURPOSE: Gait disturbance due to injuries of the descending motor pathway, including corticospinal tract (CST), corticoreticular pathway (CRP), and medial and lateral vestibulospinal tracts (VSTs), are commonly encountered disabling sequelae of pontine hemorrhage. We investigated relations between changes in the CST, CRP, and medial and lateral VST and corresponding changes in gait function in patients with pontine hemorrhage. METHOD: Nine consecutive stroke patients with pontine hemorrhage, and 6 age-matched normal subjects were recruited. Four patients were allocated to group A (can't walk independently) and 5 to group B (can walk independently). Diffusion tensor imaging (DTI) data were acquired twice at acute to subacute stage and chronic stage after stroke onset. Diffusion tensor tractography (DTT) was used to reconstruct CST, CRP, medial and lateral VST. RESULT: The CRP shows a significantly different between groups A and B in both initial and follow up DTT (p > 0.05). In contrast, CST, medial VST and lateral VST did not show a significant difference (p > 0.05). Regarding DTI parameters of CRPs in group A, percentages of patients with fractional anisotropy (FA) and mean diffusivity (MD) values more than two standard deviation from normal were higher by follow up DTI than by initial DTI, however, the CRPs in group B only showed increased abnormal range of MD. CONCLUSIONS: The CST does not play an essential role in recovery of independent walking and vestibulospinal tracts may not crucially affect recovery of independent walking in patients with pontine hemorrhage. In contrast, and intact CRP or changes of the CRP integrity appear to be related to the recovery of gait function.

Motor tract integrity predicts walking recovery: A diffusion MRI study in subacute stroke.

OBJECTIVE: To identify candidate biomarkers of walking recovery with motor tract integrity measurements using fractional anisotropy (FA) from the corticospinal tract (CST) and alternative motor pathways in patients with moderate to severe subacute stroke. METHODS: Walking recovery was first assessed with generalized linear mixed model (GLMM) with repeated measures of walking scores (WS) over 2 years of follow-up in a longitudinal study of 29 patients with subacute ischemic stroke. Baseline FA measures from the ipsilesional and contralesional CST (i-CST and c-CST), cortico-reticulospinal pathway (i-CRP and c-CRP), and cerebellar peduncles were derived from a 60-direction diffusion MRI sequence on a 3T scanner. We performed correlation tests between WS and FA measures. Third, we investigated using GLMM whether motor tract integrity contributes to predict walking recovery. RESULTS: We observed significant improvements of WS over time with a plateau reached at ≈6 months after stroke. WS significantly correlated with FA measures from i-CST, c-CST, i-CRP, and bilateral cerebellar peduncles. Walking recovery was predicted by FA measures from 3 tracts: i-CST, i-CRP, and contralesional superior cerebellar peduncle (c-SCP). Diffusion tensor imaging (DTI) predictors captured 80.5% of the unexplained variance of the model without DTI. CONCLUSIONS: We identified i-CST and alternative motor-related tracts (namely i-CRP and c-SCP) as candidate biomarkers of walking recovery. The role of the SCP in walk recovery may rely on cerebellar nuclei projections to the thalamus, red nucleus, and reticular formation. Our findings suggest that a set of white matter tracts, part of subcortical motor networks, contribute to walking recovery in patients with moderate to severe stroke.

Residual descending motor pathways influence spasticity after spinal cord injury.

OBJECTIVE: Spasticity is one of the most common symptoms manifested in humans with spinal cord injury (SCI). The neural mechanisms contributing to its development are not yet understood. Using neurophysiological and imaging techniques, we examined the influence of residual descending motor pathways on spasticity in humans with SCI. METHODS: We measured spasticity in 33 individuals with motor complete SCI (determined by clinical examination) without preservation of voluntary motor output in the quadriceps femoris muscle. To examine residual descending motor pathways, we used magnetic and electrical stimulation over the leg motor cortex to elicit motor evoked potentials (MEPs) in the quadriceps femoris muscle and structural magnetic resonance imaging to measure spinal cord atrophy. RESULTS: We found that 60% of participants showed symptoms of spasticity, whereas the other 40% showed no spasticity, demonstrating the presence of 2 clear subgroups of humans with motor complete SCI. MEPs were only present in individuals who had spasticity, and MEP size correlated with the severity of spasticity. Spinal cord atrophy was greater in nonspastic compared with spastic subjects. Notably, the degree of spared tissue in the lateral regions of the spinal cord was positively correlated with the severity of spasticity, indicating preservation of white matter related to motor tracts when spasticity was present. INTERPRETATION: These results support the hypothesis that preservation of descending motor pathways influences spasticity in humans with motor complete SCI; this knowledge might help the rehabilitation and assessment of people with SCI. ANN NEUROL 2019.

Functional MRI evidence of the cortico-olivary efferent pathway during active auditory target processing in humans.

Auditory target detection has been explored by a number of studies, but none have demonstrated activity in the auditory subcortical centers evoked by the top-down attentional mechanism related to target detection in humans. We applied functional magnetic resonance imaging (fMRI) with sparse sampling to explore activity in the auditory centers, particularly in the subcortex, during an active auditory target detection task. Fourteen healthy subjects with normal hearing tapped the left index finger in response to target tonal stimuli presented among other (non-target) stimuli during continuous white noise stimulation. General linear model, region-of-interest, and connectivity analyses were performed. In the cortex, bilateral auditory cortices as well as the cingulate gyrus, thalamus, and supramarginal gyrus were activated to target stimuli and functionally connected to each other. In the subcortex, the superior olivary complex (SOC) and locus coeruleus were activated to the target but not to the non-target or background noise stimuli. The SOC was the only auditory subcortical center that displayed connectivity to the auditory cortical areas as well as the cingulate and supramarginal gyri during target presentation but not during other conditions. SOC activation appears to be the first fMRI evidence of direct cortico-olivary projections in the human brain as well as SOC participation in auditory target detection. Our results may be an initial step towards developing a noninvasive methodology to evaluate the functional integrity of the auditory efferent system in humans.

Epidural Spinal Cord Stimulation Facilitates Immediate Restoration of Dormant Motor and Autonomic Supraspinal Pathways after Chronic Neurologically Complete Spinal Cord Injury.

Epidural Spinal Cord Stimulation (eSCS) in combination with extensive rehabilitation has been reported to restore volitional movement in a select group of subjects after motor-complete spinal cord injury (SCI). Numerous questions about the generalizability of these findings to patients with longer term SCI have arisen, especially regarding the possibility of restoring autonomic function. To better understand the effect of eSCS on volitional movement and autonomic function, two female participants five and 10 years after injury at ages 48 and 52, respectively, with minimal spinal cord preservation on magnetic resonance imaging were implanted with an eSCS system at the vertebral T12 level. We demonstrated that eSCS can restore volitional movement immediately in two female participants in their fifth and sixth decade of life with motor and sensory-complete SCI, five and 10 years after sustaining severe radiographic injuries, and without prescribed or significant pre-habilitation. Both patients experienced significant improvements in surface electromyography power during a volitional control task with eSCS on. Cardiovascular function was also restored with eSCS in one participant with cardiovascular dysautonomia using specific eSCS settings during tilt challenge while not affecting function in a participant with normal cardiovascular function. Orgasm was achieved for the first time since injury in one participant with and immediately after eSCS. Bowel-bladder synergy improved in both participants while restoring volitional urination in one with eSCS. While numerous questions remain, the ability to restore some supraspinal control over motor function below the level of injury, cardiovascular function, sexual function, and bowel and bladder function should promote intense efforts to investigate and develop optimization strategies to maximize recovery in all participants with chronic SCI.

Imaging functional motor connectivity in hemiparetic children with perinatal stroke.

Perinatal stroke causes lifelong disability, particularly hemiparetic cerebral palsy. Arterial ischemic strokes (AIS) are large, cortical, and subcortical injuries acquired near birth due to acute occlusion of the middle cerebral artery. Periventricular venous infarctions (PVI) are smaller, subcortical strokes acquired prior to 34 weeks gestation involving injury to the periventricular white matter. Both stroke types can damage motor pathways, thus, we investigated resulting alterations in functional motor networks and probed function. We measured blood oxygen level dependent (BOLD) fluctuations at rest in 38 participants [10 arterial patients (age = 14.7 ± 4.1 years), 10 venous patients (age = 13.5 ± 3.7 years), and 18 typically developing controls (TDCs) (age = 15.3 ± 5.1 years)] and explored strength and laterality of functional connectivity in the motor network. Inclusion criteria included MRI-confirmed, unilateral perinatal stroke, symptomatic hemiparetic cerebral palsy, and 6-19 years old at time of imaging. Seed-based functional connectivity analyses measured temporal correlations in BOLD response over the whole brain using primary motor cortices as seeds. Laterality indices based on mean z-scores in lesioned and nonlesioned hemispheres explored laterality. In AIS patients, significant differences in both strength and laterality of motor network connections were observed compared with TDCs. In PVI patients, motor networks largely resembled those of healthy controls, albeit slightly weaker and asymmetric, despite subcortical damage and hemiparesis. Functional connectivity strengths were not related to motor outcome scores for either stroke group. This study serves as a foundation to better understand how resting-state fMRI can assess motor functional connectivity and potentially be applied to explore mechanisms of interventional therapies after perinatal stroke.

Cerebral blood flow features in chronic subcortical stroke: Lesion location-dependent study.

We investigated the influence of lesion location on cerebral blood flow (CBF) in chronic subcortical stroke patients. Three-dimensional pseudocontinuous arterial spin labeling was employed to obtain CBF images in normal controls (NC) and patients with left hemisphere subcortical infarctions involving motor pathways. Stroke patients were divided into two subgroups based on the infarction location (basal ganglia (BS) or pontine (PS). We mapped CBF alterations in a voxel-wise manner and compared them to detect differences among groups with height-level false discovery rate correction. Regions with significant group differences were extracted to perform post hoc analyses among the BS, PS and NC groups using a general linear model with age, gender, years of education, and interval after stroke as covariates. The BS group displayed significantly increased CBF in the contralesional putamen relative to NC and significantly decreased CBF in the ipsilesional sensorimotor cortex, ipsilesional thalamus and contralesional cerebellum. The PS group displayed significantly increased CBF in the contralesional inferior frontal gyrus relative to both the NC and BS groups. Nevertheless, the PS group showed significantly decreased CBF mainly in the cerebellum. Our results suggest different alteration patterns of CBF in chronic stroke patients with different infarct locations within subcortical motor pathways, potentially providing important information for the initiation of individualized rehabilitation strategies for subcortical stroke patients involving different infarct types.

Laterality of cerebellar afferent and efferent pathways in a healthy right-handed population: A diffusion tensor imaging study.

The cerebellum communicates with the cerebral cortex through the cortico-ponto-cerebellar tract (CPCT, cerebellar afferent) and the dentato-rubro-thalamo-cortical tract (DRTCT, cerebellar efferent). This study explored the laterality of CPCT and DRTCT in a right-handed population. Forty healthy right-handed subjects (18 males and 22 females with age range of 26-79 years old) who underwent diffusion tensor imaging (DTI) were retrospectively enrolled. Bilateral CPCT, DRTCT, and the corticospinal tract (CST) were reconstructed using probabilistic diffusion tensor tractography (DTT). Tract volume (TV) and fractional anisotropy (FA) were compared between dominant and non-dominant tracts. Subjects were divided into age groups (20-40, 41-60, and 61-80 years), and the DTI-derived parameters of the groups were compared to determine age-related differences. TV and FA of non-dominant CPCT were higher than those of dominant CPCT, and the dominant CST was higher than the non-dominant CST. The TV and FA of DRTCT showed no side-to-side difference. The 61-80 years age group had the highest TV of the dominant and non-dominant DRTCT among the three groups and the highest FA of the non-dominant CPCT and DRTCT. The results revealed the structural characteristics of CPCT and DRTCT using probabilistic DTT. Normal asymmetric patterns and age-related changes in cerebellar white matter tracts may be important to researchers investigating cerebro-cerebellar structural connectivity.

Efferent thermoregulatory pathways regulating cutaneous blood flow and sweating.

Cutaneous vasoconstrictor nerves regulate heat retention, and are activated by falls in skin or core temperature. The efferent pathways controlling this process originate within the preoptic area. A descending GABAergic pathway, activated by warm skin or core, indirectly inhibits sympathetic premotor neurons in the medullary raphé. Those premotor neurons drive cutaneous vasoconstriction via excitatory glutamatergic and serotonergic connections to spinal preganglionic neurons. Cold skin and/or cold core temperatures activate a direct preoptic-to-raphé excitatory pathway. The balance of inhibitory and excitatory influences reaching the medullary raphé determines cutaneous blood flow. During fever, prostaglandin E2 inhibits preoptic GABAergic neurons, resulting in disinhibition of the excitatory preoptic-to-raphé pathway, and hence, cutaneous vasoconstriction. A weaker, parallel source of descending excitatory drive reaches cutaneous preganglionic neurons from the rostral ventrolateral medulla. Sweating follows local heating of the preoptic area in cats and monkeys, and heated humans show sweating-related activation of this same region in functional magnetic resonance imaging (fMRI) studies. A descending pathway that drives sweating has been traced in cats from the hypothalamus to putative premotor neurons in the parafacial region at the pontomedullary junction. The homologous parafacial region in humans also shows sweating-related activation in fMRI studies. The central pathways that drive active vasodilatation in human nonacral skin remain unknown.

Multi-objective particle swarm optimization for postoperative deep brain stimulation targeting of subthalamic nucleus pathways.

OBJECTIVE: The effectiveness of deep brain stimulation (DBS) therapy strongly depends on precise surgical targeting of intracranial leads and on clinical optimization of stimulation settings. Recent advances in surgical targeting, multi-electrode designs, and multi-channel independent current-controlled stimulation are poised to enable finer control in modulating pathways within the brain. However, the large stimulation parameter space enabled by these technologies also poses significant challenges for efficiently identifying the most therapeutic DBS setting for a given patient. Here, we present a computational approach for programming directional DBS leads that is based on a non-convex optimization framework for neural pathway targeting. APPROACH: The algorithm integrates patient-specific pre-operative 7 T MR imaging, post-operative CT scans, and multi-objective particle swarm optimization (MOPSO) methods using dominance based-criteria and incorporating multiple neural pathways simultaneously. The algorithm was evaluated on eight patient-specific models of subthalamic nucleus (STN) DBS to identify electrode configurations and stimulation amplitudes to optimally activate or avoid six clinically relevant pathways: motor territory of STN, non-motor territory of STN, internal capsule, superior cerebellar peduncle, thalamic fasciculus, and hyperdirect pathway. MAIN RESULTS: Across the patient-specific models, single-electrode stimulation showed significant correlations across modeled pathways, particularly for motor and non-motor STN efferents. The MOPSO approach was able to identify multi-electrode configurations that achieved improved targeting of motor STN efferents and hyperdirect pathway afferents than that achieved by any single-electrode monopolar setting at equivalent power levels. SIGNIFICANCE: These results suggest that pathway targeting with patient-specific model-based optimization algorithms can efficiently identify non-trivial electrode configurations for enhancing activation of clinically relevant pathways. However, the results also indicate that inter-pathway correlations can limit selectivity for certain pathways even with directional DBS leads.

White-matter structural connectivity predicts short-term melody and rhythm learning in non-musicians.

Music learning has received increasing attention in the last decades due to the variety of functions and brain plasticity effects involved during its practice. Most previous reports interpreted the differences between music experts and laymen as the result of training. However, recent investigations suggest that these differences are due to a combination of genetic predispositions with the effect of music training. Here, we tested the relationship of the dorsal auditory-motor pathway with individual behavioural differences in short-term music learning. We gathered structural neuroimaging data from 44 healthy non-musicians (28 females) before they performed a rhythm- and a melody-learning task during a single behavioural session, and manually dissected the arcuate fasciculus (AF) in both hemispheres. The macro- and microstructural organization of the AF (i.e., volume and FA) predicted the learning rate and learning speed in the musical tasks, but only in the right hemisphere. Specifically, the volume of the right anterior segment predicted the synchronization improvement during the rhythm task, the FA in the right long segment was correlated with the learning rate in the melody task, and the volume and FA of the right whole AF predicted the learning speed during the melody task. This is the first study finding a specific relation between different branches within the AF and rhythmic and melodic materials. Our results support the relevant function of the AF as the structural correlate of both auditory-motor transformations and the feedback-feedforward loop, and suggest a crucial involvement of the anterior segment in error-monitoring processes related to auditory-motor learning. These findings have implications for both the neuroscience of music field and second-language learning investigations.

Risk of Postoperative Performance Status Worsening after Resection of Lesions Involving the Motor Pathway: A Multinomial Logistic Regression Model.

BACKGROUND AND STUDY OBJECTIVE: In surgery for gliomas and brain metastases, preservation of neurologic functions is essential to ensure a good quality of life and the eligibility for adjuvant therapies. This article assesses which factors could influence the functional outcome in patients with lesions located in the motor pathways. MATERIALS AND METHODS: A total of 92 patients with gliomas and metastases involving the motor pathways were studied for concerns regarding quality of life (Karnofsky performance status [KPS] and modified Rankin scale [mRS]) before and after surgical treatment supported by intraoperative neuromonitoring. Patient-related, surgery-related, and lesion-related data were recorded to identify the relationships with postoperative performance status. The relationship between lesions and the corticospinal tract were investigated with preoperative magnetic resonance imaging sequences and tractographic reconstructions. RESULTS: Means of preoperative mRS and KPS were 1.91 ± 1.34 and 80.8 ± 20, and at 30 days postoperatively they were 1.93 ± 1.63 and 79.8 ± 24.4, respectively. The better preoperative performance status was a predictor of better outcome in terms of quality of life. Gender showed a statistical association with ∆KPS (p = 0.033) and ∆mRS (p = 0.031). A recurrent lesion was a predictor of poor functional outcome (p= 0.045 for KPS at 30 days).A left-sided lesion showed a statistical association with a lesser improvement with respect to right sided. Complications were associated with a lesser functional improvement (∆mRS, ∆KPS, and clinical improvement: p = 0.001, p = 0.006, and p = 0.003, respectively). Hemorrhagic complications were associated with the worst functional prognosis. CONCLUSIONS: In our experience, factors associated with worse functional prognosis and quality of life were a poor preoperative performance status, female gender, operating on a recurrent lesion, involvement of the left corticospinal tract, and surgical or medical postoperative complications.

Spatially dynamic recurrent information flow across long-range dorsal motor network encodes selective motor goals.

Performing voluntary movements involves many regions of the brain, but it is unknown how they work together to plan and execute specific movements. We recorded high-resolution ultra-high-field blood-oxygen-level-dependent signal during a cued ankle-dorsiflexion task. The spatiotemporal dynamics and the patterns of task-relevant information flow across the dorsal motor network were investigated. We show that task-relevant information appears and decays earlier in the higher order areas of the dorsal motor network then in the primary motor cortex. Furthermore, the results show that task-relevant information is encoded in general initially, and then selective goals are subsequently encoded in specifics subregions across the network. Importantly, the patterns of recurrent information flow across the network vary across different subregions depending on the goal. Recurrent information flow was observed across all higher order areas of the dorsal motor network in the subregions encoding for the current goal. In contrast, only the top-down information flow from the supplementary motor cortex to the frontoparietal regions, with weakened recurrent information flow between the frontoparietal regions and bottom-up information flow from the frontoparietal regions to the supplementary cortex were observed in the subregions encoding for the opposing goal. We conclude that selective motor goal encoding and execution rely on goal-dependent differences in subregional recurrent information flow patterns across the long-range dorsal motor network areas that exhibit graded functional specialization.

Multimodal MRI quantification of the common neurostructural bases within the FTD-ALS continuum.

The continuum hypothesis linking the behavioral variant of frontotemporal dementia (bvFTD) and amyotrophic lateral sclerosis (ALS) is supported by clinical, pathological, genetic, and neuroimaging evidence. In the present multimodal magnetic resonance study, we characterized the site and extent of shared neurostructural changes in gray and white matter in 20 bvFTD and 19 ALS patients without dementia. We found an overlap of macrostructural and microstructural damage in both patient groups compared with healthy controls, involving the right orbital and the bilateral anterior cingulate cortices, the corticospinal tract and corpus callosum. The quantification of gray and white matter damage within the areas of shared alterations highlighted a higher degree of atrophy in orbitofrontal and frontomedial regions in patients with more severe executive and/or behavioral symptoms, and a higher degree of degeneration in the motor pathway in patients with more severe motor neuron disorders. Our finding provides additional evidence confirming the FTD-ALS continuum hypothesis and supports the notion of a bimodal but convergent pattern of neurostructural changes characterizing bvFTD and ALS.

Aggravation of an injured dentato-rubro-thalamic tract in a patient with mild traumatic brain injury: A case report.

RATIONALE: We report on a patient with mild traumatic brain injury (TBI) by follow-up diffusion tensor tractography (DTT), and observed for approximately nine monthsby serial diffusion tensor tractography (DTT). PATIENT CONCERNS: A 66-year-old male patient was injured in a car crash. Approximately four weeks after the crash, he developed a tremor in the right hand and leg. His symptoms worsened over time. DIAGNOSES: Approximately six months after the crash, he developed a mild tremor in the left hand. Nine months after the crash, he manifested severe tremor in his right hand, mild resting and intentional tremor in his left hand and both legs, and mild trunkal ataxia. INTERVENTIONS: N/A. OUTCOMES: On 3-week DTT, well reconstructed DRTTs were observed in both hemispheres, except for the thinned lower portion of the right DRTT. On 9-month DTT, the right lower DRTT had thinned compared with the 3-week DTT and showed a disruption at the upper portion. The left DRTT showed thinning in the lower portion and tearing in the upper portion compared with 3-week DTT. LESSONS: Aggravation of an injured DRTT was demonstrated in a patient with mild TBI, using serial DTT examination.

Interactions Between the Corticospinal Tract and Premotor-Motor Pathways for Residual Motor Output After Stroke.

BACKGROUND AND PURPOSE: Brain imaging has continuously enhanced our understanding how different brain networks contribute to motor recovery after stroke. However, the present models are still incomplete and do not fit for every patient. The interaction between the degree of damage of the corticospinal tract (CST) and of corticocortical motor connections, that is, the influence of the microstructural state of one connection on the importance of another has been largely neglected. METHODS: Applying diffusion-weighted imaging and probabilistic tractography, we investigated cross-network interactions between the integrity of ipsilesional CST and ipsilesional corticocortical motor pathways for variance in residual motor outcome in 53 patients with subacute stroke. RESULTS: The main finding was a significant interaction between the CST and corticocortical connections between the primary motor and ventral premotor cortex in relation to residual motor output. More specifically, the data indicate that the microstructural state of the connection primary motor-ventral premotor cortex plays only a role in patients with significant damage to the CST. In patients with slightly affected CST, this connection did not explain a relevant amount of variance in motor outcome. CONCLUSIONS: The present data show that patients with stroke with different degree of CST disruption differ in their dependency on structural premotor-motor connections for residual motor output. This finding might have important implications for future research on recovery prediction models and on responses to treatment strategies.