Aiming at exploring the brain’s structural organisation underlying successful second language learning, we investigate the anatomy of the perisylvian language network in a group of healthy adults,... Show moreAiming at exploring the brain’s structural organisation underlying successful second language learning, we investigate the anatomy of the perisylvian language network in a group of healthy adults, consisting of participants with high and average language analytical abilities. Utilising deterministic tractography, six tracts per participant (left and right long direct segment, left and right indirect anterior segment and left and right indirect posterior segment) were virtually dissected and measurements pertaining to their microstructural organisation were collected. Our results obtained by means of linear discriminant analysis pointed to mean diffusivity (MD) values of three tracts (right anterior, left long and left anterior segments) as best discriminating between the two groups. By far the highest coefficient was obtained for the MD values of the right anterior segment, pointing to the role of the right white matter fronto-parietal connectivity for superior language learning abilities. The results imply the importance of attentional processes and reasoning abilities for successful L2 acquisition, and support previous findings concerning right-hemispheric involvement in language learning. Show less
Kraima, A.C.; Schaik, J. van; Susan, S.; Velde, C.J.H. van de; Hamming, J.F.; Lakke, E.A.J.F.; DeRuiter, M.C. 2015
Object. Accuracy of reinnervation is an important factor that determines outcome after nerve injury and repair. Type grouping-the clustering of muscle fibers of the same type after reinnervation... Show moreObject. Accuracy of reinnervation is an important factor that determines outcome after nerve injury and repair. Type grouping-the clustering of muscle fibers of the same type after reinnervation-can be used to investigate the accuracy of reinnervation. In this study, the degree of type grouping after crush injury in rats was compared with the clustering of muscle fibers after autografting or single-lumen nerve grafting. Methods. Twelve weeks after sciatic nerve crush injury in rats, clustering of Type I muscle fibers was analyzed in the target muscle with adenosine 5'-triphosphatase staining. In addition, the number of regenerated axons was determined in the nerve distal to the crush injury. Results were compared with that of the authors' previous study. Results. Type grouping was more abundant after crush injury than after autograft or single-lumen nerve graft repair. Conclusions. Crush injury leads to more clustered innervation of muscle fibers, probably because the Schwann cell basal lamina tubes are not interrupted as they are in autograft or artificial nerve graft repair. This finding adds to understanding the processes playing a role in nerve regeneration. (DOI: 10.3171/2010.9.JNS091656) Show less
Hyperactivity of the hypothalamic pituitary adrenal (HPA) axis is one of the most consistent findings in major depressive disorder (MDD). Impaired HPA feedback may be due to the lower... Show moreHyperactivity of the hypothalamic pituitary adrenal (HPA) axis is one of the most consistent findings in major depressive disorder (MDD). Impaired HPA feedback may be due to the lower glucocorticoid receptor (GR) or mineralocorticoid receptor (MR) levels in the forebrain. GR levels are transcriptionally controlled by multiple untranslated alternative first exons, each with its own promoter providing a mechanism for tissue-specific fine-tuning of GR levels. Recently epigenetic methylation of these GR promoters was shown to modulate hippocampal GR levels. Here we investigate in post-mortem brain tissues whether in MDD HPA axis hyperactivity may be due to epigenetic modulation of GR transcript variants. Levels of GR alpha, GR beta and GR-P transcripts were homogeneous throughout the limbic system, with GR alpha being the most abundant (83%), followed by GR-P (5-6%) while GR beta was barely detectable (0.02%). Among the alternative first exons, 1B and 1C were the most active, while 1E and 1J showed the lowest expression and transcript 1F expressed intermediate levels of about 1%. In MDD, total GR levels were unaltered, although GRa was decreased in the amygdala and cingulate gyrus ( p < 0.05); transcripts containing exons 1B, 1C and 1F were lower, and 1D and 1J were increased in some regions. NGFI-A, a transcription factor of exon 1F was down-regulated in the hippocampus of MDD patients; concomitantly exon 1F expression was reduced. Bisulphite sequencing of the alternative promoters showed low methylation levels in both MDD and control brains. Promoter 1F was uniformly unmethylated, suggesting that reduced 1F transcript levels are not linked to promoter methylation but to the observed dearth of NGFI-A. Previous studies showed high methylation levels in the 1F promoter, associated with childhood abuse. Provided our donors were not abused, our results suggest that the pathomechanism of MDD is similar but nevertheless distinct from that of abuse victims, explaining the clinical similarity of both conditions and that susceptibility to depression may be either predisposed by early trauma or developed independent of such a condition. However, this should be further confirmed in dedicated studies in larger cohorts. (C) 2009 Elsevier Ltd. All rights reserved. Show less
