Posterior Corona Radiata Research Articles

Falta de integridad de la sustancia blanca en la depresión bipolar como posible marcador estructural de la enfermedad

Background Diffusion tensor imaging allows the study of integrity of white matter (WM) tracts. Literature suggests that WM integrity could be altered in bipolar disorder. Heterogeneity of brain imaging methods, the studied samples, and drug treatments make localization, nature, and severity of the WM abnormalities unclear. Methods We applied tract-based spatial statistics of diffusion tensor imaging measures to compare fractional anisotropy (FA), mean, and radial diffusivity of the WM skeleton in a group of 40 consecutively admitted inpatients affected by a major depressive episode without psychotic features with a diagnosis of bipolar disorder type I and 21 unrelated healthy volunteers from the general population. Results Compared with control subjects, patients showed lower FA in the genu of the corpus callosum and in anterior and right superior-posterior corona radiata and higher values of radial diffusivity in WM tracts of splenium, genu and body of corpus callosum, right mid-dorsal part of the cingulum bundle, left anterior and bilateral superior and posterior corona radiata, bilateral superior longitudinal fasciculus, and right posterior thalamic radiation. Patients had no brain areas with higher FA or lower diffusivity values than control subjects. Conclusions Reduced FA with increased mean and radial diffusivity suggests significant demyelination and/or dysmyelination without axonal loss. Comparing our findings with other observations in homogeneous samples of euthymic and manic patients, it can be hypothesized that changes in measures of WM integrity might parallel illness phases of bipolar illness.

An anatomical account of somatoparaphrenia

Somatoparaphrenia is a delusional belief whereby a patient feels that a paralyzed limb does not belong to his body; the symptom is typically associated with unilateral neglect and most frequently with anosognosia for hemiplegia. This association of symptoms makes anatomical inference based on single case studies not sufficiently specific. On the other hand, the only three anatomical group studies on somatoparaphrenia are contradictory: the right posterior insula, the supramarginal gyrus and the posterior corona radiata, or the right medial or orbito-frontal regions were all proposed as specific lesional correlates.We compared 11 patients with and 11 without somatoparaphrenia matched for the presence and severity of other associated symptoms (neglect, motor deficits and anosognosia). To take into account the frequent association of SP and neglect and hemiplegia, patients with and without somatoparaphrenia were also compared with a group of fifteen right brain damage patients without neglect and hemiplegia. We found a lesion pattern involving a fronto-temporo-parietal network typically associated with spatial neglect, hemiplegia and anosognosia. Somatoparaphrenic patients showed an additional lesion pattern primarily involving white matter and subcortical grey structures (thalamus, basal ganglia and amygdala). Further cortical damage was present in the middle and inferior frontal gyrus, postcentral gyrus and hippocampus.We propose that somatoparaphrenia occurs providing that a distributed cortical lesion pattern is present together with a subcortical lesion load that prevents most sensory input from being processed in neocortical structures; involvement of deep cortical and subcortical grey structures of the temporal lobe may contribute to reduce the sense of familiarity experienced by somatoparaphrenic patients for their paralyzed limb.

High Connectivity Between Reduced Cortical Thickness and Disrupted White Matter Tracts in Long-Standing Type 1 Diabetes

OBJECTIVEPrevious studies have observed disruptions in brain white and gray matter structure in individuals with type 1 diabetes, and these structural differences have been associated with neurocognitive testing deficiencies. This study investigated the relationship between cerebral cortical thickness reductions and white matter microstructural integrity loss in a group of patients with type 1 diabetes and in healthy control subjects using diffusion tensor imaging (DTI).RESEARCH DESIGN AND METHODSTwenty-five subjects with type 1 diabetes for at least 15 years and 25 age- and sex-matched control subjects underwent structural T1 and proton-density and DTI on a 3.0 Tesla scanner. Fractional anisotropy measurements were made on major cerebral white matter tracts, and DTI tractography was performed to identify cortical regions with high connectivity to these tracts.RESULTSPosterior white matter tracts with reduced fractional anisotropy (optic radiations, posterior corona radiata, and the splenium region of the corpus callosum) were found to have high connectivity with a number of posterior cortical regions, including the cuneus, precuneus, fusiform, and posterior parietal cortical regions. A significant reduction in cortical thickness in the diabetic group was observed in the regions with high connectivity to the optic radiations and posterior corona radiata tracts (P < 0.05).CONCLUSIONSThe direct relationship between white and gray matter structural pathology has not been previously demonstrated in subjects with long-standing type 1 diabetes. The relationship between posterior white matter microstructural integrity disruption and lower cortical thickness demonstrated using a novel DTI connectivity technique suggests a common or interrelated pathophysiological mechanism in type 1 diabetes.

White Matter Correlates of Apathy in HIV-Positive Subjects: A Diffusion Tensor Imaging Study

White Matter Correlates of Apathy in HIV-Positive Subjects: A Diffusion Tensor Imaging Study

Thalamic integrity underlies executive dysfunction in traumatic brain injury

To quantify the effects of traumatic brain injury on integrity of thalamocortical projection fibers and to evaluate whether damage to these fibers accounts for impairments in executive function in chronic traumatic brain injury. High-resolution (voxel size: 0.78 mm x 0.78 mm x 3 mm(3)) diffusion tensor MRI of the thalamus was conducted on 24 patients with a history of single, closed-head traumatic brain injury (TBI) (12 each of mild TBI and moderate to severe TBI) and 12 age- and education-matched controls. Detailed neuropsychological testing with an emphasis on executive function was also conducted. Fractional anisotropy was extracted from 12 regions of interest in cortical and corpus callosum structures and 7 subcortical regions of interest (anterior, ventral anterior, ventral lateral, dorsomedial, ventral posterior lateral, ventral posterior medial, and pulvinar thalamic nuclei). Relative to controls, patients with a history of brain injury showed reductions in fractional anisotropy in both the anterior and posterior corona radiata, forceps major, the body of the corpus callosum, and fibers identified from seed voxels in the anterior and ventral anterior thalamic nuclei. Fractional anisotropy from cortico-cortico and corpus callosum regions of interest did not account for significant variance in neuropsychological function. However, fractional anisotropy from the thalamic seed voxels did account for variance in executive function, attention, and memory. The data provide preliminary evidence that traumatic brain injury and resulting diffuse axonal injury results in damage to the thalamic projection fibers and is of clinical relevance to cognition.

Disrupted white matter integrity of corticopontine-cerebellar circuitry in schizophrenia

Evidence for white matter abnormalities in patients with schizophrenia is increasing. Decreased fractional anisotropy (FA) in interhemispheric commissural fibers as well as long-ranging fronto-parietal association fibers belongs to the most frequent findings. The present study used tract-based spatial statistics to investigate white matter integrity in 35 patients with schizophrenia and 35 healthy volunteers. We found that patients exhibited significantly decreased FA relative to healthy subjects in the corpus callosum, the cerebral peduncle, the left inferior fronto-occipital fasciculus, the anterior thalamic radiation, the right posterior corona radiata, the middle cerebellar peduncle, and the right superior longitudinal fasciculus. Increased FA was detectable in the inferior sections of the corticopontine-cerebellar circuit. Present data indicate extended cortical-subcortical alterations of white matter integrity in schizophrenia using advanced data analysis strategies. They corroborate preceding findings of white matter structural deficits in mainly long-ranging association fibers and provide first evidence for neuroplastic changes in terms of an increased directionality in more inferior fiber tracts.

White matter architecture rather than cortical surface area correlates with the EEG alpha rhythm

There are few studies on the neuroanatomical determinants of EEG spectral properties that would explain its substantial inter-individual variability in spite of decades of biophysical modeling that predicts this type of relationship. An exception is the negative relation between head size and the spectral position of the alpha peak (Pα) reported in Nunez et al. (1978)—proposed as evidence of the influence of global boundary conditions on slightly damped neocortical waves. Here, we attempt to reexamine this finding by computing the correlations of occipital Pα with various measures of head size and cortical surface area, for 222 subjects from the EEG/MRI database of the Cuban Human Brain Mapping Project. No relation is found (p>0.05). On the other hand, biophysical models also predict that white matter architecture, determining time delays and connectivities, could have an important influence on Pα. This led us to explore relations between Pα and DTI fractional anisotropy by means of a multivariate penalized regression. Clusters of voxels with highly significant relations were found. These were positive within the Posterior and Superior Corona Radiata for both hemispheres, supporting biophysical theories predicting that the period of cortico-thalamocortical cycles might be modulating the alpha frequency. Posterior commissural fibers of the Corpus Callosum present the strongest relationships, negative in the inferior part (Splenium), connecting the inferior occipital lobes and positive in the superior part (Isthmus and Tapetum), connecting the superior occipital cortices. We found that white matter architecture rather than neocortical area determines the dynamics of the alpha rhythm.

Voxel-based analysis of T2 hyperintensities in white matter during treatment of childhood leukemia.

White matter (WM) hyperintensities on T2-weighted MR imaging are the most common imaging manifestation of neurotoxic effects of therapy for central nervous system (CNS) prophylaxis in childhood acute lymphoblastic leukemia (ALL). This study uses voxel-based analyses (VBA) of T2-weighted imaging of patients during treatment to identify which WM regions are preferentially damaged. Two sets of conventional T2-weighted axial images were acquired on a 1.5T MR imaging scanner from 197 consecutive patients (85 female, 112 male; aged 1.0-18.9 years) enrolled on an institutional ALL treatment protocol. Images were acquired after completion of induction therapy and after the final of the 4 courses of intravenous high-dose methotrexate in consolidation therapy (3.9 +/- 0.8 months apart). Voxel-wise statistical testing of the incremental change between normalized longitudinal T2 images was performed with radiologist reading (normal or abnormal) and treatment risk-group as covariates. Two highly significant bilateral clusters of T2 signal intensity change were identified in both 1-group and 2-group analyses. The regions were symmetric in size, shape, and average signal intensity. Increased T2-weighted signal intensity from these regions both within and between examinations were nonlinear functions of age at examination, and the difference between the examinations was greater for older subjects who received more intense therapy. These analyses identified specific WM tracts involving predominantly the anterior, superior, and posterior corona radiata and superior longitudinal fasciculus, which were at increased risk for the development of T2-weighted hyperintensities during therapy for childhood ALL. These vulnerable regions may be the cause of subsequent cognitive difficulties consistently observed in survivors.

Brain regional lesion burden and impaired mobility in the elderly

This study investigated the relationship of brain white matter (WM) lesions affecting specific neural networks with decreased mobility in ninety-nine healthy community-dwelling subjects ≥75 years old prospectively enrolled by age and mobility status. We assessed lesion burden in the genu, body and splenium of corpus callosum; anterior, superior and posterior corona radiata; anterior and posterior limbs of internal capsule; corticospinal tract; and superior longitudinal fasciculus. Burden in the splenium of corpus callosum (SCC) demonstrated the highest correlation particularly with walking speed (r=0.4, p<10(-4)), and in logistic regression it was the best regional predictor of low mobility performance. We also found that independent of mobility, corona radiata has the largest lesion burden with anterior (ACR) and posterior (PCR) aspects being the most frequently affected. The results suggest that compromised inter-hemispheric integration of visuospatial information through the SCC plays an important role in mobility impairment in the elderly. The relatively high lesion susceptibility of ACR and PCR in all subjects may obscure the importance of these lesions in mobility impairment.

Diffusion Tensor Imaging Identifies Deficits in White Matter Microstructure in Subjects With Type 1 Diabetes That Correlate With Reduced Neurocognitive Function

OBJECTIVE—Long-standing type 1 diabetes is associated with deficits on neurocognitive testing that suggest central white matter dysfunction. This study investigated whether diffusion tensor imaging (DTI), a type of magnetic resonance imaging that measures white matter integrity quantitatively, could identify white matter microstructural deficits in patients with long-standing type 1 diabetes and whether these differences would be associated with deficits found by neurocognitive tests.RESEARCH DESIGN AND METHODS—Twenty-five subjects with type 1 diabetes for at least 15 years and 25 age- and sex-matched control subjects completed DTI on a 3.0 Tesla scanner and a battery of neurocognitive tests. Fractional anisotropy was calculated for the major white matter tracts of the brain.RESULTS—Diabetic subjects had significantly lower mean fractional anisotropy than control subjects in the posterior corona radiata and the optic radiation (P < 0.002). In type 1 diabetic subjects, reduced fractional anisotropy correlated with poorer performance on the copy portion of the Rey-Osterreith Complex Figure Drawing Test and the Grooved Peg Board Test, both of which are believed to assess white matter function. Reduced fractional anisotropy also correlated with duration of diabetes and increased A1C. A history of severe hypoglycemia did not correlate with fractional anisotropy.CONCLUSIONS—DTI can detect white matter microstructural deficits in subjects with long-standing type 1 diabetes. These deficits correlate with poorer performance on selected neurocognitive tests of white matter function.

P3-151: White matter hyperintensities within cholinergic pathways in Alzheimer's disease affecting the clock drawing test performance

Cerebral white matter hyperintensities (WMH) are common findings on MRI in elderly people. Two possible mechanisms have been suggested: 1) by disruption of corticocortical association fibers or fronto-subcortical neuronal networks; 2) interference with cholinergic projecting pathway. The purpose of this study is to evaluate how WMH can affect on the Clock Drawing Test in Alzheimer disease (AD). One hundred twenty seven patients with AD were enrolled for this study. Subjects met the National Institute of Neurological Communicative Disorders and Stroke-Alzheimer Disease and Related Disorders Association (NINCDS-ADRDA) research criteria for possible or probable AD. All subjects were taken MRI to measure the severity of WMH based on visual inspection of T2-weighted and proton-density MRI. Subjects underwent standardized neuropsychological testing, including Korean versions of the Mini-Mental State Exam (MMSE) and the modified MMSE (3MS) to assess cognitive domains of interest (attention, memory, executive function) as well as general level of cognition. Clock Drawing Test (CDT) was given to all patients to analyze the level of performance and error-types. Manos scoring protocol was adopted for the evaluation of CDT results. Cognitive measures and the CDT were assessed independently by a neuropsychologist and a neurologist who were not aware of clinical information. The Age-Related White Matter Changes (ARWMC) rating scale of the European Task Force was used as a general measure of WMH severity. WMH involved in cholinergic pathways were measured by the Cholinergic Pathways Hyperintensities Scale (CHIPS). Performance of the CDT as well as overall level of cognition showed significant relation with the WMC severity. Temporal WMH in ARWMC had stronger relationship with the CDT performance than other areas. WMH of the posterior corona radiata in CHIPS showed significant correlation with the CDT performance. Interference in the cholinergic projecting pathway as well as disruption of cortico-subcortical neural networks by WMH may contribute to the impaired CDT performance in AD.

White matter integrity and cognition in chronic traumatic brain injury: a diffusion tensor imaging study

Traumatic brain injury (TBI) is a serious public health problem. Even injuries classified as mild, the most common, can result in persistent neurobehavioural impairment. Diffuse axonal injury is a common finding after TBI, and is presumed to contribute to outcomes, but may not always be apparent using standard neuroimaging. Diffusion tensor imaging (DTI) is a more recent method of assessing axonal integrity in vivo. The primary objective of the current investigation was to characterize white matter integrity utilizing DTI across the spectrum of chronic TBI of all severities. A secondary objective was to examine the relationship between white matter integrity and cognition. Twenty mild, 17 moderate to severe TBI and 18 controls underwent DTI and neuropsychological testing. Fractional anisotropy, axial diffusivity and radial diffusivity were calculated from the DTI data. Fractional anisotropy was the primary measure of white matter integrity. Region of interest analysis included anterior and posterior corona radiata, cortico-spinal tracts, cingulum fibre bundles, external capsule, forceps minor and major, genu, body and splenium of the corpus callosum, inferior fronto-occipital fasciculus, superior longitudinal fasciculus and sagittal stratum. Cognitive domain scores were calculated from executive, attention and memory testing. Decreased fractional anisotropy was found in all 13 regions of interest for the moderate to severe TBI group, but only in the cortico-spinal tract, sagittal stratum and superior longitudinal fasciculus for the mild TBI group. White Matter Load (a measure of the total number of regions with reduced FA) was negatively correlated with all cognitive domains. Analysis of radial and axial diffusivity values suggested that all severities of TBI can result in a degree of axonal damage, while irreversible myelin damage was only apparent for moderate to severe TBI. The present data emphasize that white matter changes exist on a spectrum, including mild TBI. An index of global white matter neuropathology (White Matter Load) was related to cognitive function, such that greater white matter pathology predicted greater cognitive deficits. Mechanistically, mild TBI white matter changes may be primarily due to axonal damage as opposed to myelin damage. The more severe injuries impact both. DTI provides an objective means for determining the relationship of cognitive deficits to TBI, even in cases where the injury was sustained years prior to the evaluation.

P.3.041 Clinical and neurophysiologicalefficacy of neurofeedback in the combined therapy of anxiety disorders resistant to psychopharmacotherapy

Anxiety sensitivity (AS) refers to a fear of anxiety-related sensations and is a dispositional variable especially elevated in patients with panic disorder (PD). Although several functional imaging studies of AS in patients with PD have suggested the presence of altered neural activity in paralimbic areas such as the insula, no study has investigated white matter (WM) alterations in patients with PD in relation to AS. The objective of this study was to investigate the WM correlates of AS in patients with PD.One–hundred and twelve right-handed patients with PD and 48 healthy control (HC) subjects were enrolled in this study. The Anxiety Sensitivity Inventory-Revised (ASI-R), the Panic Disorder Severity Scale (PDSS), the Albany Panic and Phobia Questionnaire (APPQ), the Beck Anxiety Inventory (BAI), and the Beck Depression Inventory (BDI) were administered. Tract-based spatial statistics were used for diffusion tensor magnetic resonance imaging analysis.Among the patients with PD, the ASI-R total scores were significantly correlated with the fractional anisotropy values of the WM regions near the insula, the splenium of the corpus callosum, the tapetum, the fornix/stria terminalis, the posterior limb of the internal capsule, the retrolenticular part of the internal capsule, the posterior thalamic radiation, the sagittal striatum, and the posterior corona radiata located in temporo-parieto-limbic regions and are involved in interoceptive processing (p<0.01; threshold-free cluster enhancement [TFCE]-corrected). These WM regions were also significantly correlated with the APPQ interoceptive avoidance subscale and BDI scores in patients with PD (p<0.01, TFCE-corrected). Correlation analysis among the HC subjects revealed no significant findings.There has been no comparative study on the structural neural correlates of AS in PD.The current study suggests that the WM correlates of AS in patients with PD may be associated with the insula and the adjacent temporo-parieto-limbic WM regions, which may play important roles in interoceptive processing in the brain and in depression in PD.

Diffusion tensor MRI visualizes decreased subcortical fiber connectivity in focal cortical dysplasia

Diffusion tensor imaging (DTI) was applied to 12 patients with focal cortical dysplasia (FCD) in frontal or occipital cortex. Fiber tractography was obtained from seeding points in superior longitudinal fasciculus or posterior corona radiata. Mean fractional anisotropy of fiber bundles around the affected cortex was decreased in comparison to the contralateral hemisphere with statistical significance (paired t test, P = 0.0274). On visual analysis, tractography depicted decreased volume of fiber bundles connected to the dysplastic cortex invariably even in those with a normal T2 signal intensity of underlying white matter adjacent to FCD. DTI has high potential to be applied to localize the FCD and to provide a better understanding of the pathological changes in the white matter.

Verbal asomatognosia

Verbal asomatognosia is a form of neglect in which a patient denies ownership of a limb contralateral to a brain lesion. To establish the neuroanatomic substrate of this syndrome, we analyzed the CTs of 12 right-hemisphere stroke patients with neglect and verbal asomatognosia and 4 patients with neglect but without asomatognosia. Of 16 cortical and subcortical brain regions analyzed, supramarginal gyrus and its subcortical connections within posterior corona radiata were most consistently involved in the asomatognosia cases. One or both of these regions were spared in all cases of neglect without asomatognosia. Our data confirm Nielsen's localization of asomatognosia to the right supramarginal gyrus and thalamoparietal peduncle. Converging lines of evidence from experiments in humans and monkeys suggest that damage to area PF may be necessary for the production of personal neglect of a limb.

The cranial computed tomographic findings in patients with pure sensory stroke

We reported three patients compatible with the clinical syndrome of pure sensory stroke (PSS). The computed tomography (CT) scan suggested the lesions responsible for the deficits were posterior thalamus, corona radiata, and parietal lobe. PSS could conceivably arise anywhere along the sensory systems and CT scan is reliable method for discussing the lesion responsible for PSS.

Computed tomographic studies of the basis pedunculi in chronic hemiplegic patients: topographic correlation between cerebral lesion and midbrain shrinkage.

A computed tomographic method for analyzing the shrinkage of the basis pedunculi (BP) due to the secondary degeneration of the descending fibers was applied in correlation to the site of cerebral lesions in 89 chronic hemiplegic patients. Cerebral lesions in the anterior corona radiata or the anterior limb of the capsula interna caused shrinkage of the medial BP. Lesions in the central corona radiata or the genu and posterior limb of the capsula interna caused shrinkage of the central BP, while lesions of the posterior corona radiata or the posterior limb of the capsula interna caused shrinkage of the lateral BP. These results suggested that CT images are able to reveal the principle sites of atrophy of the descending fiber tracts in chronic hemiplegia.

Intracellular study of lemniscal and non-specific synaptic interactions in thalamic ventrobasal neurons

The effects of low frequency repetitive stimulation of medial thalamic (MTh) non-specific nuclei have been examined in intracellular studies of neurons of the ventrobasal (VB) thalamic complex. VB relay cells identified by medial lemniscus (ML) stimulation were relatively uninfluenced during recruiting responses elicited by MTh stimulation. VB neurons exhibiting long latency EPSPs or IPSP-EPSP sequences in response to ML stimulation were more consistently affected by MTh stimulation. Interactions observed in these elements were characteristically inhibitory in nature although in some cells facilitation of discharge without significant change in membrane potential occurred during MTh stimulation. Potentiation or enhancement of ML evoked IPSPs was observed in a small proportion of identified VB relay cells during 3nd as an after-effect of MTh stimulation. Spontaneosly developing 6–12/sec spindle waves in posterior sigmoid gyrus were associated with prominent IPSP and EPSP-IPSP sequences in VB relay cells. Stimulation of posterior sigmoid gyrus, corona radiata or internal capsule elicited prominent, variable latency, IPSPs or EPSP-IPSP sequences in relay cells and other neurons of the VB complex. The characteristics of these PSPs suggest the operation of complex interneuronal systems acting on VB relay cells via corticofugal projections. The intracellular data indicate marked differences in the distribution of synaptic pathways to VB relay and non-relay cells from medial non-specific nuclei. These results are considered in the light of previous findings on the effects of medial thalamic stimulation on specific neurons of the ventrolateral thalamic nucleus.