Search results for "brain size"
showing 10 items of 24 documents
Heterozygous deletion of the LRFN2 gene is associated with working memory deficits
2016
International audience; Learning disabilities (LDs) are a clinically and genetically heterogeneous group of diseases. Array-CGH and high-throughput sequencing have dramatically expanded the number of genes implicated in isolated intellectual disabilities and LDs, highlighting the implication of neuron-specific post-mitotic transcription factors and synaptic proteins as candidate genes. We report a unique family diagnosed with autosomal dominant learning disability and a 6p21 microdeletion segregating in three patients. The 870 kb microdeletion encompassed the brain-expressed gene LRFN2, which encodes for a synaptic cell adhesion molecule. Neuropsychological assessment identified selective w…
Heterozygous Variants in KDM4B Lead to Global Developmental Delay and Neuroanatomical Defects
2020
International audience; KDM4B is a lysine-specific demethylase with a preferential activity on H3K9 tri/di-methylation (H3K9me3/2)-modified histones. H3K9 tri/di-demethylation is an important epigenetic mechanism responsible for silencing of gene expression in animal development and cancer. However, the role of KDM4B on human development is still poorly characterized. Through international data sharing, we gathered a cohort of nine individuals with mono-allelic de novo or inherited variants in KDM4B. All individuals presented with dysmorphic features and global developmental delay (GDD) with language and motor skills most affected. Three individuals had a history of seizures, and four had a…
Brain size and limits to adult neurogenesis
2015
The walls of the cerebral ventricles in the developing embryo harbor the primary neural stem cells from which most neurons and glia derive. In many vertebrates, neurogenesis continues postnatally and into adulthood in this region. Adult neurogenesis at the ventricle has been most extensively studied in organisms with small brains, such as reptiles, birds, and rodents. In reptiles and birds, these progenitor cells give rise to young neurons that migrate into many regions of the forebrain. Neurogenesis in adult rodents is also relatively widespread along the lateral ventricles, but migration is largely restricted to the rostral migratory stream into the olfactory bulb. Recent work indicates t…
Phylogenetic variation in cortical layer II immature neuron reservoir of mammals
2020
The adult mammalian brain is mainly composed of mature neurons. A limited amount of stem cell-driven neurogenesis persists in postnatal life and is reduced in large-brained species. Another source of immature neurons in adult brains is cortical layer II. These cortical immature neurons (cINs) retain developmentally undifferentiated states in adulthood, though they are generated before birth. Here, the occurrence, distribution and cellular features of cINs were systematically studied in 12 diverse mammalian species spanning from small-lissencephalic to large-gyrencephalic brains. In spite of well-preserved morphological and molecular features, the distribution of cINs was highly heterogeneou…
Re-thinking the effects of body size on the study of brain size evolution
2018
Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. …
Occurrence of new neurons in the piriform cortex
2015
In a recent mini-review (Yuan et al., 2015), support is given to the idea that neurons are generated during adulthood in the mammalian piriform cortex (PC), their periventricular origin being also discussed. It is known since long time that a subpopulation of cortical layer II cells in the adult PC of rodents express immature neuronal markers such as polysialylated NCAM (PSA-NCAM; Seki and Arai, 1991; Bonfanti et al., 1992) and doublecortin (DCX; Nacher et al., 2002). These immature neurons have been found in most mammals studied so far, their occurrence being restricted to the paleocortex in rodents (Seki and Arai, 1991; Bonfanti et al., 1992; Nacher et al., 2002), and extended to neocorti…
Association of 5′ end neuregulin-1 ( NRG1 ) gene variation with subcortical medial frontal microstructure in humans
2007
Animal data suggest that the gene neuregulin-1 (NRG1) is involved in neuronal myelination. A haplotype (deCODE) in the 5' end region of the gene was described to double the risk for schizophrenia in an Icelandic population (Stefansson, H., Sigurdsson, E., Steinthorsdottir, V., Bjornsdottir, S., Sigmundsson, T., Ghosh, S., Brynjolfsson, J., Gunnarsdottir, S., Ivarsson, O., Chou, T.T., Hjaltason, O., Birgisdottir, B., Jonsson, H., Gudnadottir, V.G., Gudmundsdottir, E., Bjornsson, A., Ingvarsson, B., Ingason, A., Sigfusson, S., Hardardottir, H., Harvey, R.P., Lai, D., Zhou, M., Brunner, D., Mutel, V., Gonzalo, A., Lemke, G., Sainz, J., Johannesson, G., Andresson, T., Gudbjartsson, D., Manolesc…
Brain density in depression: methodological and psychopathological aspects
1988
The relationship between brain density, measured by computerized tomography (CT), and severity of depression was investigated in 44 patients with a major depressive episode according to DSM-III. In order to limit methodological problems, correlations between both the Brief Psychiatric Rating Scale (BPRS) and the Bech-Rafaelsen Melancholia Scale (BRMS) with density values were controlled for age, different ventricle measurements, brain size, and density and size of the skull. The BRMS score correlated inversely with density of the right thalamus, the right head of the caudate, and with parietal grey matter and occipital regions of both hemispheres. Similar, but nonsignificant results, were o…
Early age of onset, brain morphological changes and non-consistent motor asymmetry in schizophrenic patients.
1999
Previous data suggest abnormalities in the consistence of motor dominance in schizophrenia (e.g. mixed-handedness, poor correlation between hand, eye and foot preferences and an increase of hand-eye crossed dominance). The aim of this work is to examine the clinical significance of hand-eye and hand-foot crossed dominance in a sample of 61 right-handed schizophrenic patients. The application of multivariate analysis revealed that 23 right-handed and non-right-eyed patients (crossed hand-eye dominant group) had a significant earlier clinical onset and smaller brain size, global and frontal area, than 38 right-handed and right-eyed schizophrenics (consistent hand-eye dominance group). These f…
Central nervous system involvement in late-onset Pompe disease: clues from neuroimaging and neuropsychological analysis
2018
Background and purpose Late-onset Pompe disease (LOPD) is a rare, multisystem disorder that is well established to mainly impair skeletal muscle function. Systematic studies exploring brain functions in LOPD are lacking. The aim of this study was to detect morphological and functional brain alterations as well as neuropsychological impairment in LOPD. Methods We studied 21 patients (10 male, mean age 49 ± 18.4 years) with defined diagnosis of LOPD, divided into two groups: one with pre-symptomatic hyperCKemia with no muscle weakness and the second with limb-girdle muscle weakness. All patients underwent 3T magnetic resonance imaging (MRI) to obtain morphological/angiographic evaluation as w…