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Longitudinal Fascicles (longitudinal + fascicle)
Selected AbstractsDifferential modulation by monoamine membrane receptor agonists of reticulospinal input to lamina VIII feline spinal commissural interneuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Ingela Hammar Abstract Noradrenaline and serotonin have previously been demonstrated to facilitate the transmission between descending reticulospinal tracts fibres and commissural interneurons coordinating left,right hindlimb muscle activity. The aim of the present study was to investigate the contribution of subclasses of monoaminergic membrane receptors to this facilitation. The neurons were located in Rexed lamina VIII in midlumbar segments and identified by their projections to the contralateral gastrocnemius,soleus motor nuclei and by lack of projections rostral to the lumbosacral enlargement. The effects of ionophoretically applied membrane receptor agonists [phenylephrine (noradrenergic ,1), clonidine (noradrenergic ,2), 8-OH-DPAT (5-HT1A, 5-HT7), 2-me-5-HT (5-HT3), 5-me-5-HT (5-HT2) and ,-me-5-HT (5-HT2)] were examined on extracellularly recorded spikes evoked monosynaptically by electric stimulation of descending reticulospinal fibres in the medial longitudinal fascicle. Application of ,1 and 5-HT2 agonists resulted in a facilitation of responses in all investigated neurons while application of ,2, 5-HT1A/7 and 5-HT3 agonists resulted in a depression. These opposite modulatory effects of different agonists suggest that the facilitatory actions of noradrenaline and serotonin on responses of commissural interneurons reported previously following ionophoretic application are the net outcome of the activation of different subclasses of monoaminergic membrane receptors. As these receptors may be distributed predominantly, or even selectively, at either pre- or postsynaptic sites their differential modulatory actions could be compatible with a presynaptically induced depression and a postsynaptically evoked enhancement of synaptic transmission between reticulospinal neurons and commissural interneurons. [source] Rey Visual Design Learning Test performance correlates with white matter structureACTA NEUROPSYCHIATRICA, Issue 2 2009Stefan Begré Objective:, Studies exploring relation of visual memory to white matter are extensively lacking. The Rey Visual Design Learning Test (RVDLT) is an elementary motion, colour and word independent visual memory test. It avoids a significant contribution from as many additional higher order visual brain functions as possible to visual performance, such as three-dimensional, colour, motion or word-dependent brain operations. Based on previous results, we hypothesised that test performance would be related with white matter of dorsal hippocampal commissure, corpus callosum, posterior cingulate, superior longitudinal fascicle and internal capsule. Methods:, In 14 healthy subjects, we measured intervoxel coherence (IC) by diffusion tensor imaging as an indication of connectivity and visual memory performance measured by the RVDLT. IC considers the orientation of the adjacent voxels and has a better signal-to-noise ratio than the commonly used fractional anisotropy index. Results:, Using voxelwise linear regression analyses of the IC values, we found a significant and direct relationship between 11 clusters and visual memory test performance. The fact that memory performance correlated with white matter structure in left and right dorsal hippocampal commissure, left and right posterior cingulate, right callosal splenium, left and right superior longitudinal fascicle, right medial orbitofrontal region, left anterior cingulate, and left and right anterior limb of internal capsule emphasises our hypothesis. Conclusion:, Our observations in healthy subjects suggest that individual differences in brain function related to the performance of a task of higher cognitive demands might partially be associated with structural variation of white matter regions. [source] Heritability of regional and global brain structure at the onset of puberty: A magnetic resonance imaging study in 9-year-old twin pairsHUMAN BRAIN MAPPING, Issue 7 2009Jiska S. Peper Abstract Puberty represents the phase of sexual maturity, signaling the change from childhood into adulthood. During childhood and adolescence, prominent changes take place in the brain. Recently, variation in frontal, temporal, and parietal areas was found to be under varying genetic control between 5 and 19 years of age. However, at the onset of puberty, the extent to which variation in brain structures is influenced by genetic factors (heritability) is not known. Moreover, whether a direct link between human pubertal development and brain structure exists has not been studied. Here, we studied the heritability of brain structures at 9 years of age in 107 monozygotic and dizygotic twin pairs (N = 210 individuals) using volumetric MRI and voxel-based morphometry. Children showing the first signs of secondary sexual characteristics (N = 47 individuals) were compared with children without these signs, based on Tanner-stages. High heritabilities of intracranial, total brain, cerebellum, and gray and white matter volumes (up to 91%) were found. Regionally, the posterior fronto-occipital, corpus callosum, and superior longitudinal fascicles (up to 93%), and the amygdala, superior frontal and middle temporal cortices (up to 83%) were significantly heritable. The onset of secondary sexual characteristics of puberty was associated with decreased frontal and parietal gray matter densities. Thus, in 9-year-old children, global brain volumes, white matter density in fronto-occipital and superior longitudinal fascicles, and gray matter density of (pre-)frontal and temporal areas are highly heritable. Pubertal development may be directly involved in the decreases in gray matter areas that accompany the transition of our brains from childhood into adulthood. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Asynchrony of the early maturation of white matter bundles in healthy infants: Quantitative landmarks revealed noninvasively by diffusion tensor imagingHUMAN BRAIN MAPPING, Issue 1 2008Jessica Dubois Abstract Normal cognitive development in infants follows a well-known temporal sequence, which is assumed to be correlated with the structural maturation of underlying functional networks. Postmortem studies and, more recently, structural MR imaging studies have described qualitatively the heterogeneous spatiotemporal progression of white matter myelination. However, in vivo quantification of the maturation phases of fiber bundles is still lacking. We used noninvasive diffusion tensor MR imaging and tractography in twenty-three 1,4-month-old healthy infants to quantify the early maturation of the main cerebral fascicles. A specific maturation model, based on the respective roles of different maturational processes on the diffusion phenomena, was designed to highlight asynchronous maturation across bundles by evaluating the time-course of mean diffusivity and anisotropy changes over the considered developmental period. Using an original approach, a progression of maturation in four relative stages was determined in each tract by estimating the maturation state and speed, from the diffusion indices over the infants group compared with an adults group on one hand, and in each tract compared with the average over bundles on the other hand. Results were coherent with, and extended previous findings in 8 of 11 bundles, showing the anterior limb of the internal capsule and cingulum as the most immature, followed by the optic radiations, arcuate and inferior longitudinal fascicles, then the spinothalamic tract and fornix, and finally the corticospinal tract as the most mature bundle. Thus, this approach provides new quantitative landmarks for further noninvasive research on brain-behavior relationships during normal and abnormal development. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [source] Metastatic cutaneous leiomyosarcoma from primary neoplasm of the mesenteryINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 8 2001Kyoung Jin Kim MD A 31-year-old South Korean woman was referred to the dermatology department from the oncology department for the evaluation of a subcutaneous nodular lesion on the back. Three years before, she noted a palpable, fingertip-sized, nontender mass on her right lower abdomen. The mass had increased in size slowly. One year ago, she visited a local clinic and physical examination revealed a 7 × 8 × 7 cm, slightly tender, deep-seated mass on the right lower quadrant of the abdomen. The mass on the ilial mesentery was resected by surgical exploration and tissue examination revealed leiomyosarcoma. She refused adjuvant chemotherapy. Approximately 3 months later, she re-visited the clinic with a tender, subcutaneous nodule on the back. Cutaneous examination revealed a solitary, 2 × 2 cm, well-defined, hard, movable, subcutaneous nodule on the upper back without skin color change (Fig. 1). She complained of tenderness on touching the lesion. Histologic examination of a biopsy specimen showed irregularly arranged spindle cells scattered throughout the dermis. They were arranged in haphazardly oriented or interweaving fascicles. Most of the spindle cells possessed elongated nuclei with blunt ends and some cells had a polygonal outline with irregularly shaped nuclei (Fig. 2). There were many mitoses: 3,4 per high-power (× 400) field. Immunohistochemically, smooth muscle actin and desmin were positive in most of the tumor cells (Fig. 3). S-100 reactivity was not observed. A diagnosis of metastatic leiomyosarcoma was made. About 1 month later, computed tomography showed two, ill-defined, heterogeneous, low attenuation masses in the right lobe of the liver, suggesting liver metastasis. The patient was treated with chemotherapy for 2 months and remains in good condition. Figure 1. 2 × 2 cm, solitary, well-defined, hard, movable, subcutaneous nodule without any overlying skin change Figure 2. (a) Characteristic findings of cutaneous leiomyosarcoma with markedly high cellularity and densely packed transverse and longitudinal fascicles of cells (hematoxylin and eosin, × 40). (b) High magnification of the neoplasm revealing spindle cells with blunt-ended nuclei, pleomorphism, and mitotic figures (hematoxylin and eosin, × 200) Figure 3. Dense cytoplasmic reactivity for smooth muscle actin is apparent (smooth muscle actin, × 200) [source] | |||||||||||||