scholarly journals Asymmetric transcallosal conduction delay leads to finer bimanual coordination

2020 ◽  
Author(s):  
Marta Bortoletto ◽  
Laura Bonzano ◽  
Agnese Zazio ◽  
Clarissa Ferrari ◽  
Ludovico Pedullà ◽  
...  
Keyword(s):  
Information Transfer ◽  
Bimanual Coordination ◽  
Diffusion Tensor ◽  
Silent Period ◽  
Hemispheric Dominance ◽  
Conduction Delay ◽  
Dominant Hemisphere ◽  
Interhemispheric Communication ◽  
Temporal Features ◽  
Motor Areas

AbstractIt has been theorized that hemispheric dominance and a more segregated information processing have evolved to overcome long conduction delay through the corpus callosum (TCD) but that this may still impact behavioral performance mostly in tasks requiring high timing accuracy. Nevertheless, a thorough understanding of the temporal features of interhemispheric communication is missing due to methodological shortcomings. Here, we show in the motor system that TCD can be measured from transcranial magnetic stimulation (TMS) -evoked potentials (TEPs): by integrating TEPs with diffusion tensor imaging (DTI) and peripheral measures of interhemispheric inhibition (i.e., the ipsilateral silent period-iSP), we show that P15 TEP component reflects TCD between motor areas. Importantly, we report that better bimanual coordination is achieved when TCD between motor areas is asymmetric. These results suggest that interhemispheric communication can be optimized through asymmetric connectivity, in which information transfer is faster from the dominant hemisphere to the non-dominant hemisphere.

Visualization of the frontotemporal language fibers by tractography combined with functional magnetic resonance imaging and magnetoencephalography

2007 ◽  
Vol 106 (1) ◽  
pp. 90-98 ◽  
Author(s):  
Kyousuke Kamada ◽  
Tomoki Todo ◽  
Yoshitaka Masutani ◽  
Shigeki Aoki ◽  
Kenji Ino ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Diffusion Tensor ◽  
Tumor Resection ◽  
Awake Surgery ◽  
Hemispheric Dominance ◽  
Dominant Hemisphere ◽  
Functional Magnetic Resonance ◽  
Accurate Identification ◽  
Generation Task ◽  
Language Functions

Object There is continuous interest in the monitoring of language function during tumor resection around the fron-totemporal regions of the dominant hemisphere. The aim of this study was to visualize language-related subcortical connections, such as the arcuate fasciculus (AF) by diffusion tensor (DT) imaging–based tractography. Methods Twenty-two patients with brain lesions adjacent to the AF in the frontotemporal regions of the dominant hemisphere were studied. The AF tractography was accomplished by placing initiation and termination sites (seed and target points) in the frontal and temporal regions, which were functionally identified by using functional magnetic resonance (fMR) imaging in conjunction with a verb generation task and magnetoencephalography (MEG) in conjunction with a reading task. The combination of fMR imaging and MEG data clearly demonstrated the hemispheric dominance of language functions, which was confirmed by an intracranial amobarbital test (Wada procedure). In all 22 patients, the authors were able to consistently visualize the AF by DT imaging–based tractography, using the functionally identified seed and target points and a fractional anisotropy value of 0.16. In two of 22 cases investigated, the functional information, including the results of AF tractography, fMR imaging, and MEG, was imported to a neuronavigation system and was validated by bipolar electric stimulation of the cortical and subcortical areas during awake surgery. The cortical stimulation to the gyrus that included the area of activation identified in fMR imaging with the language task evoked speech arrest, while the subcortical stimulation close to the AF reproducibly caused paranomia without speech arrest. Postoperative AF tractography showed that the distances between the stimulus points and the AF were within 6 mm. Conclusions The combination of these techniques facilitated accurate identification of the location of the AF and verification of the language fibers.

scholarly journals Language hemispheric dominance analyzed with magnetic resonance DTI: correlation with the Wada test

2020 ◽  
pp. 1-8
Author(s):  
Juan Delgado-Fernández ◽  
Maria Ángeles García-Pallero ◽  
Rafael Manzanares-Soler ◽  
Pilar Martín-Plasencia ◽  
Guillermo Blasco ◽  
...  
Keyword(s):  
Epilepsy Surgery ◽  
Diffusion Tensor ◽  
Hemispheric Dominance ◽  
Uncinate Fasciculus ◽  
Arcuate Fasciculus ◽  
Dominant Hemisphere ◽  
Wada Test ◽  
Pharmacoresistant Epilepsy ◽  
Linear Discriminant ◽  
Dominance Testing

OBJECTIVELanguage lateralization is a major concern in some patients with pharmacoresistant epilepsy who will face surgery; in these patients, hemispheric dominance testing is essential to avoid further complications. The Wada test is considered the gold standard examination for language localization, but is invasive and requires many human and material resources. Functional MRI and tractography with diffusion tensor imaging (DTI) have demonstrated that they could be useful for locating language in epilepsy surgery, but there is no evidence of the correlation between the Wada test and DTI MRI in language dominance.METHODSThe authors performed a retrospective review of patients who underwent a Wada test before epilepsy surgery at their institution from 2012 to 2017. The authors retrospectively analyzed fractional anisotropy (FA), number and length of fibers, and volume of the arcuate fasciculus and uncinate fasciculus, comparing dominant and nondominant hemispheres.RESULTSTen patients with temporal lobe epilepsy were reviewed. Statistical analysis showed that the mean FA of the arcuate fasciculus in the dominant hemisphere was higher than in the nondominant hemisphere (0.369 vs 0.329, p = 0.049). Also, the number of fibers in the arcuate fasciculus was greater in the dominant hemisphere (881.5 vs 305.4, p = 0.003). However, no differences were found in the FA of the uncinate fasciculus or number of fibers between hemispheres. The length of fibers of the uncinate fasciculus was longer in the dominant side (74.4 vs 50.1 mm, p = 0.05). Volume in both bundles was more prominent in the dominant hemisphere (12.12 vs 6.48 cm3, p = 0.004, in the arcuate fasciculus, and 8.41 vs 4.16 cm3, p = 0.018, in the uncinate fasciculus). Finally, these parameters were compared in patients in whom the seizure focus was situated in the dominant hemisphere: FA (0.37 vs 0.30, p = 0.05), number of fibers (114.4 vs 315.6, p = 0.014), and volume (12.58 vs 5.88 cm3, p = 0.035) in the arcuate fasciculus were found to be statistically significantly higher in the dominant hemispheres. Linear discriminant analysis of FA, number of fibers, and volume of the arcuate fasciculus showed a correct discrimination in 80% of patients (p = 0.024).CONCLUSIONSThe analysis of the arcuate fasciculus and other tract bundles by DTI could be a useful tool for language location testing in the preoperative study of patients with refractory epilepsy.

scholarly journals Structural and Functional Imaging in Glioma Management

Neurosurgery ◽  
2020 ◽  
Author(s):  
Bledi C Brahimaj ◽  
Ryan B Kochanski ◽  
John J Pearce ◽  
Melike Guryildirim ◽  
Carter S Gerard ◽  
...  
Keyword(s):  
Diffusion Tensor ◽  
Imaging Modalities ◽  
Hemispheric Dominance ◽  
Tumor Control ◽  
Histopathological Diagnosis ◽  
Glioma Surgery ◽  
Multiple Modalities ◽  
Advantages And Disadvantages ◽  
Multiple Imaging

Abstract The goal of glioma surgery is maximal safe resection in order to provide optimal tumor control and survival benefit to the patient. There are multiple imaging modalities beyond traditional contrast-enhanced magnetic resonance imaging (MRI) that have been incorporated into the preoperative workup of patients presenting with gliomas. The aim of these imaging modalities is to identify cortical and subcortical areas of eloquence, and their relationship to the lesion. In this article, multiple modalities are described with an emphasis on the underlying technology, clinical utilization, advantages, and disadvantages of each. functional MRI and its role in identifying hemispheric dominance and areas of language and motor are discussed. The nuances of magnetoencephalography and transcranial magnetic stimulation in localization of eloquent cortex are examined, as well as the role of diffusion tensor imaging in defining normal white matter tracts in glioma surgery. Lastly, we highlight the role of stimulated Raman spectroscopy in intraoperative histopathological diagnosis of tissue to guide tumor resection. Tumors may shift the normal arrangement of functional anatomy in the brain; thus, utilization of multiple modalities may be helpful in operative planning and patient counseling for successful surgery.

scholarly journals White matter abnormalities in the corpus callosum with cognitive impairment in Parkinson disease

Neurology ◽  
2018 ◽  
Vol 91 (24) ◽  
pp. e2244-e2255 ◽  
Author(s):  
Ian O. Bledsoe ◽  
Glenn T. Stebbins ◽  
Doug Merkitch ◽  
Jennifer G. Goldman
Keyword(s):  
Cognitive Impairment ◽  
White Matter ◽  
Corpus Callosum ◽  
Parkinson Disease ◽  
Information Transfer ◽  
Diffusion Tensor ◽  
Anterior Segment ◽  
Mean Diffusivity ◽  
Cognitive Domain ◽  
White Matter Abnormalities

ObjectiveTo evaluate microstructural characteristics of the corpus callosum using diffusion tensor imaging (DTI) and their relationships to cognitive impairment in Parkinson disease (PD).MethodsSeventy-five participants with PD and 24 healthy control (HC) participants underwent structural MRI brain scans including DTI sequences and clinical and neuropsychological evaluations. Using Movement Disorder Society criteria, PD participants were classified as having normal cognition (PD-NC, n = 23), mild cognitive impairment (PD-MCI, n = 35), or dementia (PDD, n = 17). Cognitive domain (attention/working memory, executive function, language, memory, visuospatial function) z scores were calculated. DTI scalar values, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), were established for 5 callosal segments on a midsagittal plane, single slice using a topographically derived parcellation method. Scalar values were compared among participant groups. Regression analyses were performed on cognitive domain z scores and DTI metrics.ResultsParticipants with PD showed increased AD values in the anterior 3 callosal segments compared to healthy controls. Participants with PDD had significantly increased AD, MD, and RD in the anterior 2 segments compared to participants with PD-NC and most anterior segment compared to participants with PD-MCI. FA values did not differ significantly between participants with PD and participants with HC or among PD cognitive groups. The strongest associations for the DTI metrics and cognitive performance occurred in the most anterior and most posterior callosal segments, and also reflected fronto-striatal and posterior cortical type cognitive deficits, respectively.ConclusionsMicrostructural white matter abnormalities of the corpus callosum, as measured by DTI, may contribute to PD cognitive impairment by disrupting information transfer across interhemispheric and callosal–cortical projections.

scholarly journals Magnetoencephalographic mapping of the language-specific cortex

1998 ◽  
Vol 5 (5) ◽  
pp. E2 ◽  
Author(s):  
Andrew C. Papanicolaou ◽  
Panagiotis G. Simos ◽  
Joshua I. Breier ◽  
George Zouridakis ◽  
L. James Willmore ◽  
...  
Keyword(s):  
Receptive Language ◽  
Cortical Stimulation ◽  
Hemispheric Dominance ◽  
Mapping Technique ◽  
Dominant Hemisphere ◽  
Language Mapping ◽  
Valuable Adjunct ◽  
Simple Language ◽  
Noninvasive Mapping ◽  
Further Development

Object In this paper the authors introduce a novel use of magnetoencephalography (MEG) for noninvasive mapping of language-specific cortex in individual patients and in healthy volunteers. Methods The authors describe a series of six experiments in which normative MEG data were collected and the reliability, validity, and topographical accuracy of the data were assessed in patients who had also undergone the Wada procedure or language mapping through intraoperative cortical stimulation. Conclusions Findings include: 1) receptive language-specific areas can be reliably activated by simple language tasks and this activation can be readily recorded in short MEG sessions; 2) MEG-derived maps of each individual are reliable because they remain stable over time and are independent of whether auditory or visual stimuli are used to activate the brain; and 3) these maps are also valid because they concur with results of the Wada procedure in assessing hemispheric dominance for language and with the results of cortical stimulation in identifying the precise topography of receptive language regions within the dominant hemisphere. Although the MEG mapping technique should be further refined, it has been shown to be efficacious by correctly identifying the language-dominant hemisphere and specific language-related regions within this hemisphere. Further development of the technique may render it a valuable adjunct for routine presurgical planning in many patients who harbor tumors or have epilepsy.

Inhibition of Manual Movements at Speech Arrest Sites in the Posterior Inferior Frontal Lobe

Neurosurgery ◽  
2018 ◽  
Vol 85 (3) ◽  
pp. E496-E501 ◽  
Author(s):  
Jonathan D Breshears ◽  
Derek G Southwell ◽  
Edward F Chang
Keyword(s):  
Frontal Lobe ◽  
Functional Relationship ◽  
Inferior Frontal Gyrus ◽  
Hand Movement ◽  
Language Function ◽  
Motor Inhibition ◽  
Dominant Hemisphere ◽  
Intraoperative Localization ◽  
Stimulation Of ◽  
Motor Areas

Abstract BACKGROUND Intraoperative stimulation of the posterior inferior frontal lobe (IFL) induces speech arrest, which is often interpreted as demonstration of essential language function. However, prior reports have described “negative motor areas” in the IFL, sites where stimulation halts ongoing limb motor activity. OBJECTIVE To investigate the spatial and functional relationship between IFL speech arrest areas and negative motor areas (NMAs). METHODS In this retrospective cohort study, intraoperative stimulation mapping was performed to localize speech and motor function, as well as arrest of hand movement, hand posture, and guitar playing in a set of patients undergoing awake craniotomy for dominant hemisphere pathologies. The incidence and localization of speech arrest and motor inhibition was analyzed. RESULTS Eleven patients underwent intraoperative localization of speech arrest sites and inhibitory motor areas. A total of 17 speech arrest sites were identified in the dominant frontal lobe, and, of these, 5 sites (29.4%) were also identified as NMAs. Speech arrest and arrest of guitar playing was also evoked by a single IFL site in 1 subject. CONCLUSION Inferior frontal gyrus speech arrest sites do not function solely in speech production. These findings provide further evidence for the complexity of language organization, and suggest the need for refined mapping strategies that discern between language-specific sites and inhibitory motor areas.

Interhemispheric Connectivity in Idiopathic Cervical Dystonia and Spinocerebellar Ataxias: A Transcranial Magnetic Stimulation Study

2020 ◽  
pp. 155005942095748 ◽  
Author(s):  
Tommaso Bocci ◽  
Davide Baloscio ◽  
Roberta Ferrucci ◽  
Lucia Briscese ◽  
Alberto Priori ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Cervical Dystonia ◽  
Magnetic Stimulation ◽  
Silent Period ◽  
Cortical Inhibition ◽  
Common Disease ◽  
Conduction Time ◽  
Mutational Load ◽  
Spinocerebellar Ataxias ◽  
Interhemispheric Communication

Background and Rationale Hyperkinetic movement disorders represent a heterogeneous group of diseases, different from a genetic and clinical perspective. In the past, neurophysiological approaches provided different, sometimes contradictory findings, pointing to an impaired cortical inhibition as a common electrophysiological marker. Our aim was to evaluate changes in interhemispheric communication in patients with idiopathic cervical dystonia (ICD) and spinocerebellar ataxias (SCAs). Materials and Methods Eleven patients with ICD, 7 with genetically confirmed SCA2 or SCA3, and 10 healthy volunteers were enrolled. The onset latency and duration of the ipsilateral silent period (iSPOL and iSPD, respectively), as well as the so-called transcallosal conduction time (TCT), were then recorded from the abductor pollicis brevis of the right side using an 8-shaped focal coil with wing diameters of 70 mm; all these parameters were evaluated and compared among groups. In SCAs, changes in neurophysiological measures were also correlated to the mutational load. Results iSPD was significantly shorter in patients with SCA2 and SCA3, when compared both to control and ICD ( P < .0001); iSPOL and TCT were prolonged in SCAs patients ( P < .001). Changes in iSPD, iSPOL, and TCT in SCAs are significantly correlated with the mutational load ( P = .01, P = .02, and P = .002, respectively). Discussion This is the first study to assess changes in interhemispheric communication in patients with SCAs and ICD, using a transcranial magnetic stimulation protocol. Together with previous data in Huntington’s disease, we suggest that these changes may underlie, at least in part, a common disease mechanism of polyglutamine disorders.

scholarly journals Dynamic response of microglia/macrophage polarization following demyelination in mice

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Tianci Chu ◽  
Yi Ping Zhang ◽  
Zhisen Tian ◽  
Chuyuan Ye ◽  
Mingming Zhu ◽  
...  
Keyword(s):  
Diffusion Tensor ◽  
Macrophage Polarization ◽  
Functional Decline ◽  
Oligodendrocyte Progenitor Cells ◽  
Spatial Features ◽  
Lesion Pattern ◽  
Temporal Features ◽  
Temporal And Spatial ◽  
Highly Correlated ◽  
Focal Demyelination

Abstract Background The glial response in multiple sclerosis (MS), especially for recruitment and differentiation of oligodendrocyte progenitor cells (OPCs), predicts the success of remyelination of MS plaques and return of function. As a central player in neuroinflammation, activation and polarization of microglia/macrophages (M/M) that modulate the inflammatory niche and cytokine components in demyelination lesions may impact the OPC response and progression of demyelination and remyelination. However, the dynamic behaviors of M/M and OPCs during demyelination and spontaneous remyelination are poorly understood, and the complex role of neuroinflammation in the demyelination-remyelination process is not well known. In this study, we utilized two focal demyelination models with different dynamic patterns of M/M to investigate the correlation between M/M polarization and the demyelination-remyelination process. Methods The temporal and spatial features of M/M activation/polarization and OPC response in two focal demyelination models induced by lysolecithin (LPC) and lipopolysaccharide (LPS) were examined in mice. Detailed discrimination of morphology, sensorimotor function, diffusion tensor imaging (DTI), inflammation-relevant cytokines, and glial responses between these two models were analyzed at different phases. Results The results show that LPC and LPS induced distinctive temporal and spatial lesion patterns. LPS produced diffuse demyelination lesions, with a delayed peak of demyelination and functional decline compared to LPC. Oligodendrocytes, astrocytes, and M/M were scattered throughout the LPS-induced demyelination lesions but were distributed in a layer-like pattern throughout the LPC-induced lesion. The specific M/M polarization was tightly correlated to the lesion pattern associated with balance beam function. Conclusions This study elaborated on the spatial and temporal features of neuroinflammation mediators and glial response during the demyelination-remyelination processes in two focal demyelination models. Specific M/M polarization is highly correlated to the demyelination-remyelination process probably via modulations of the inflammatory niche, cytokine components, and OPC response. These findings not only provide a basis for understanding the complex and dynamic glial phenotypes and behaviors but also reveal potential targets to promote/inhibit certain M/M phenotypes at the appropriate time for efficient remyelination.

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