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At least 973 records · Page 54Linked to original sources
PubMed2006

Brain structure predicts the learning of foreign speech sounds.

Previous work has shown a relationship between parietal lobe anatomy and nonnative speech sound learning. We scanned a new group of phonetic learners using structural magnetic resonance imaging and diffusion tensor imaging. Voxel-based morphometry indicated higher white matter (WM) density in left Heschl's gyrus (HG) in faster compared with slower learners, and manual segmentation of this structure confirmed that the WM volume of left HG is larger in the former compared with the latter group. This finding was replicated in a reanalysis of the original groups tested in Golestani and others (2002, Anatomical correlates of learning novel speech sounds. Neuron 35:997-1010). We also found that faster learners have a greater asymmetry (left > right) in parietal lobe volumes than slower learners and that the right insula and HG are more superiorly located in slower compared with faster learners. These results suggest that left auditory cortex WM anatomy, which likely reflects auditory processing efficiency, partly predicts individual differences in an aspect of language learning that relies on rapid temporal processing. It also appears that a global displacement of components of a right hemispheric language network, possibly reflecting individual differences in the functional anatomy and lateralization of language processing, is predictive of speech sound learning.

Adolescent↗
PubMed1999

Relationship between nailfold plexus visibility and clinical, neuropsychological, and brain structural measures in schizophrenia.

BACKGROUND: Although all published studies investigating the association between nailfold plexus visibility and schizophrenia have found the subpapillary plexus (the vascular network into which capillaries drain) to be unusually visible in many schizophrenia patients, little else is known about this putative marker for schizophrenia liability. METHODS: Plexus visibility was rated in 63 chronic schizophrenia, 67 first-episode schizophrenia, 9 schizophreniform, and 66 unipolar and bipolar depressed patients, all with psychosis, and 119 nonpsychiatric controls. Smooth-pursuit eye tracking, clinical features, neuropsychological performance, and lateral ventricle size were assessed. RESULTS: Approximately 21% of chronic schizophrenia, 22% of first-episode schizophrenia, and 22% of schizophreniform patients had highly visible plexus compared to only 8% of unipolar, bipolar, and nonpsychiatric controls. Schizophrenia patients with visible plexus had worse oculomotor performance. Additionally, chronic schizophrenia patients with visible plexus had more negative symptoms, worse course, more severe illness, worse occupational functioning, and worse neuropsychological performance on tasks thought to be sensitive to frontal dysfunction. An inverse relationship between plexus visibility and lateral ventricle size was found. CONCLUSIONS: This study provides evidence that schizophrenia patients with plexus visibility are characterized by oculomotor dysfunction, negative symptoms, severe symptomatology, chronic course, neuropsychological dysfunction, and an absence of enlarged ventricles.

Adult↗
PubMed1987

Comparison of brain structure volumes in Insectivora and primates. VI. Paleocortical components.

Volumes of the main structures of the 'paleocortical complex' were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of nonhuman simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to decrease in the lateral olfactory tract (TRL), its nucleus (NTO), and in the olfactory cortices (RB, PRPI, TOL) and to increase in the anterior commissure (COA) and substantia innominata (SIN). The reduction in the olfactory cortices is strongest for the retrobulbar region (RB, = anterior olfactory nucleus in Anglo-American terminology), and least for the olfactory tubercle (TOL). In prosimians, the reduction clearly parallels that of the main olfactory bulb (BOL); in simians and especially in man, the indices of PRPI and TOL are clearly larger than those of BOL. Possible reasons for these growing deviations were discussed: (1) increasing difficulties in clearly homologizing and delineating the olfactory cortices in the microsmatic simians, and (2) non-olfactory functional influences.

Animals↗
PubMedDate not supplied

[The influence of chronic neurotization on the monoaminergic systems of various brain structures in rats with various typological characteristics].

Typological behavioral features of Wistar rats were tested in the open field and in Porsolt test. Rats were assigned to groups with high (HAct), medium (MAct), and low (LAct) behavioral activities. The same rats were assigned to high (HDep), medium (MDep) and low depressive (LDep) groups. The release of norepinephrine, dopamine, serotonin and their metabolites in homogenates obtained from the hypothalamus, hippocampus, frontal cortex and amygdala was assessed by microdialysis and HPLC. In these groups, the monoamine concentrations were different: the level of serotonin was higher in the hypothalamus and norepinephrine and 5-HIAA levels were lower in the hippocampus of MAct - MDep rats as compared to LAct - HDep. Chronic neurotization caused changes in monoamine concentrations in the hypothalamus and amygdala in rats of all groups, whereas in the hippocampus and frontal cortex monoamine changes were observed in HAct - LDep and LAct -HDep rats. The most prominent changes in monoamines levels in neurotized rats with different types of behavior were found in the frontal cortex, amygdala and hippocampus. The results show a correlation between the typological of behavioral characteristics and the reaction to stress of monoaminergic systems of the hypothalamus, hippocampus, frontal cortex and amygdala.

Amygdala↗
PubMed2000

Evidence for progression of brain structural abnormalities in schizophrenia: beyond the neurodevelopmental model.

OBJECTIVE: Clinical, neuroimaging, neuropathological and neuropsychological evidence suggests that, in schizophrenia, there is structural and functional disturbance of the hippocampus. The purpose of this paper is to present published findings concerning the nature, timing and course of these putative disturbances of hippocampal function and the pathophysiological mechanisms involved, and to explore whether schizophrenia is a disorder of neurodevelopment, neurodegeneration or a combination of both processes. METHOD: The available cross-sectional and longitudinal evidence for hippocampal involvement in schizophrenia is reviewed and a model of hippocampal involvement in this disorder, which derives from our own cross-sectional and longitudinal hippocampal imaging data, is described. RESULTS: We propose a three-hit model in which an early neurodevelopmental lesion renders the hippocampus vulnerable to further insult later in life during the transition phase to active illness. The available evidence suggests that the left hippocampus is particularly vulnerable during these early stages, while further insult involving the hippocampus bilaterally occurs in those who develop a chronic form of the illness. CONCLUSIONS: Intervention strategies should target the most vulnerable stages of the illness, in particular the transition phase to psychosis, when novel treatments may prevent the illness or ameliorate its effects.

Brain↗
PubMedDate not supplied

Changes in the constant potential in brain structures in rats during focal ischemia and systemic hypoxia.

The functional consequences of spreading depression (SD) during the evolution of ischemic damage was studied in two models: focal cortical ischemia induced by photothrombosis of the middle cerebral artery (MCA) and systemic hypoxia induced by 0.8% carbon monoxide (CO). These studies showed that cortical waves of SD, arising spontaneously during MCA thrombosis and after arterial occlusion delayed thrombus formation and promoted the establishment of a collateral blood supply in the perifocal zone of ischemic lesions. The underlying mechanism consisted of episodes of intense vasodilation at the decay phase of every wave of SD. Respiration of 0.8% CO increased the blood carboxyhemoglobin level to 50-60%. In lightly anesthetized rats (pentobarbital 20 mg/kg), cortical and subcortical spontaneous waves of SD were transformed into stable hypoxic depolarization, leading to death of 60% of the animals or severe lesions of the central nervous system, in 20% of animals. Increases in the level of anesthesia (50 mg/kg anesthetic) prevented the spontaneous appearance of SD during long-lasting exposure to CO. In these conditions, experimentally induced waves of SD demonstrated that the hippocampus has a high sensitivity to moderate levels of hypoxia. The duration of hypoxic depolarization of the hippocampus, provoking a single SD wave, reached 30-60 min. Selective neuron damage in field CA1 was seen 30 days after hypoxia. Additionally, the left hippocampus of rats frequently showed profound morphological lesions in the form of "granules." Cerebrolysine (2.5 ml/kg daily for 10 days) completely prevented the formation of these lesions.

Amino Acids↗
PubMed1993

Molecules and cognition: the latterday lessons of levels, language, and lac. Evolutionary overview of brain structure and function in some vertebrates and invertebrates.

The characteristics of the nervous systems of a number of organisms in different phyla are examined at the recombinant DNA, protein, neuroanatomic, neurophysiological, and cognitive levels. Among the invertebrates, special attention is paid to the advantages as well as the shortcomings of the fly Drosophila melanogaster, the worm Caenorhabditis elegans, the honey bee Apis mellifera, the sea hare Aplysia californica, the octopus Octopus vulgaris, and the squid Loligo pealei. Among vertebrates, the focus is on Homo sapiens, the mouse Mus musculus, the rat Rattus norvegicus, the cat Felis catus, the macaque monkey Macaca fascicularis, the barn owl Tyto alba, and the zebrafish Brachydanio rerio. Vertebrate nervous systems have also been compared in fossil vs. extant organisms. I conclude that complex nervous systems arose in the Early Cambrian via a big bang that was underpinned by a modular method of construction involving massive pleiotropy of gene circuits. This rapidity of construction had enormous implications for the degrees of freedom that were subsequently available to evolving nervous systems. I also conclude that at the level of neuronal populations and interactions of neuropiles there is no model system between phyla except at the basic macromolecular level. Further, I argue that to achieve a significant understanding of the functions of extant nervous systems we need to concentrate on fewer organisms in greater depth and manipulate genomes via transgenic technologies to understand the behavioral outputs that are possible from an organism. Finally, I analyze the concepts of "perceptual categorization" and "information processing" and the difficulties involved in the extrapolation of computer analogies to sophisticated nervous systems.

Animals↗
PubMed2000

The role of some brain structures in the switching of the descending influences in operantly conditioned rats.

A hypothesis was proposed according to which the switching of descending influences by the corticospinal and corticorubrospinal systems was associated with rubro-olivary projection involvement depending on the context of movement [Kennedy P. R. (1990) Trends Neurosci. 13, 474-479]. Our results confirmed and extended this hypothesis. It was shown that a preliminary transection of the dorsolateral funiculus (containing the rubrospinal tract) accelerated the compensatory rehabilitation process following lesions of the red nucleus and the ventrolateral thalamic nucleus in albino rats with learned instrumental reflexes on equilibrium. A preliminary lesion of the ventrolateral thalamic nucleus considerably hampered the switching process; nevertheless, performance of the reflexes suggested that the switching of cerebellar ascending influences to the cerebral cortex could be completed through other cerebellocortical pathways as well. Comparison of the results of electrolytic and chemical lesions of the red nucleus suggested a similar conclusion. It was established that the conditioning and recovery of already learned instrumental reflexes were impossible after complete neurotoxic destruction of the inferior olive. The data obtained emphasize the role of the inferior olive, ventrolateral thalamic nucleus and red nucleus in the switching of descending influences in operantly motor conditioned rats. Motor deficit and the compensatory rehabilitation process depended on the severity of inferior olive destruction combined with a high transection of the dorsolateral funiculus and a destroyed red nucleus. Long-lasting training improved compensation of motor deficit and stabilized instrumental reflexes to some extent in rats with incomplete destruction of the inferior olive. It has been suggested that these modifications occur because of collateral sprouting in the olivocerebellar system.

Animals↗
PubMed2003

Parametric analysis of rate-dependent hemodynamic response functions of cortical and subcortical brain structures during auditorily cued finger tapping: a fMRI study.

A multitude of functional imaging studies revealed a mass activation effect at the level of the sensorimotor cortex during repetitive finger-tapping or finger-to-thumb opposition tasks in terms of either a stepwise or a monotonic relationship between movement rate and hemodynamic response. With respect to subcortical structures of the centralmotor system, there is, by contrast, some preliminary evidence for nonlinear rate/response functions within basal ganglia and cerebellum. To further specify these hemodynamic mechanisms, functional magnetic resonance imaging (fMRI) was performed during a finger-tapping task in response to acoustic stimuli (six different frequencies: 2.0, 2.5, 3.0, 4.0, 5.0 and 6.0 Hz; applied via headphones). Passive listening to the same auditory stimuli served as a control condition. Statistical evaluation of the obtained data considered two approaches: categorical and parametric analysis. As expected, the magnitude of the elicited hemodynamic response within left sensorimotor cortex (plateau phase at frequencies above 4 Hz) and mesiofrontal cortex paralleled movement rate. The observed bipartite mesial response pattern, most presumably, reflects functional compartmentalization of supplementary motor area (SMA) in a rostral component (pre-SMA) and in a caudal (SMA proper) component. At the level of the cerebellum, two significant hemodynamic responses within the hemisphere ipsilateral to the hand engaged into finger tapping (anterior/posterior quadrangular lobule and posterior quadrangular lobule) could be observed. Both activation foci exhibited a stepwise rate/response function. In accordance with clinical data, these data indicate different cerebellar contributions to motor control at frequencies below or above about 3 Hz, respectively. Caudate nucleus, putamen, and external pallidum of the left hemisphere displayed, by contrast, a negative linear rate/response relationship. The physiological significance of these latter findings remains to be clarified.

Adult↗
PubMed1976

[Nature of the curves of the cranial vault and their relationship with various brain structures].

A radiometric investigation for various angles of two dry craniums and of the encephalographic or cerebral arteriographic pictures of 250 subjects has revealed the following facts: The architectural lines of the dome of the skull found by orthogonal projection of the profile, from the front, and in vertical projection, are hyperbolic spirals starting from the base of the skull and converging on the sphenoid. These lines join up in the parietal region forming a hyperbole. The frontal spiral is a simple hyperbolic spiral. The temporal spiral is of the lituus type. The axes of these lines converge in a frontal plane on the epiphysis. The axis of the parietal hyperbole on a projection of the profile passes through the epiphysis and is followed by the parietal artery. Central cranio-encephalic formations follow the same spiral path. The contour of the upper edge of the cerebellum is a lituus spiral. The outline of the lower part of the cerebellum is a simple hyperbolic spiral. The right side of the polar origins of a spiral plotted in the plane of the insula coincides with the right side of the opercula. It can always be plotted, in theory, and forms an angle of 22 degrees 30' with the right side of the median frontal spiral. It cuts the axis of the parietal hyperbole at the apex of the insular triange. The bissector of the angle formed by the two right sides of the polar origins bissects the axis of the parietal hyperbole at a point corresponding to the epiphysis. The temporal hyperbolic lituus spiral has its focal point under the anterior, clinoid, at the junction of the segments CII and CIII of the carotid siphon the curve of which follows the convolutions of the temporal spiral. The right side of the polar origins of this curve indicates the mean direction of the posterior cerebral. The contours of the corpus callosum are homothetic with those of the dome of the skull as far as the axis of the parietal hyperbole. The frontal and parietal curves converge according to four types in the main Pacchionian granulations. The sections of the frontal spiral are often marked by bone abnormalities on the internal table. This analytic test is invariably valid whatever the constants of the spirals or the eccentricities of the hyperboles. Combinations between spirals with different constants and hyperboles of various eccentricities amount to very many types which call for separate study.

Brain↗
PubMed1986

Postmortem evidence of structural brain changes in schizophrenia. Differences in brain weight, temporal horn area, and parahippocampal gyrus compared with affective disorder.

The brains of 232 patients with a case-note diagnosis of schizophrenia or affective disorder who died in one mental hospital over a period of 22 years were weighed, and were assessed in a coronal section at the level of the interventricular foramina. From this sample were eliminated the brains of patients whose illnesses did not meet the Washington University criteria for a diagnosis of definite schizophrenia or primary affective disorder and those brains that showed significant histopathologic evidence of Alzheimer's-type change or cerebrovascular disease. This left a sample of 41 patients with schizophrenia and 29 patients with affective disorder. With age, sex, and year of birth controlled for, the brains of the patients with schizophrenia were 6% lighter, had lateral ventricles that were larger in the anterior (by 19%), and particularly in the temporal, (by 97%) horn cross section, and had significantly thinner parahippocampal cortices (by 11%). The findings provide postmortem confirmation of reports of ventricular enlargement in radiological studies and suggest that such enlargement is associated with tissue loss in the temporal lobe. The changes in schizophrenia were of a lesser degree than those seen in a sample of brains of patients with Alzheimer's-type dementia and Huntington's chorea.

Aged↗
PubMed1989

Genetic and perinatal determinants of structural brain deficits in schizophrenia.

Using a subsample from the Copenhagen schizophrenia high-risk project, we examined the contributions of schizophrenic genetic liability and perinatal complications to computed tomographic (CT) measurements of ventricular enlargement and cortical and cerebellar abnormalities. A factor analysis of six CT measurements yielded two significant factors. One factor reflected multisite neural deficits as evidenced by abnormality of the cerebellar vermis and widening of the sylvian and interhemispheric fissures and cortical sulci. The other factor reflected periventricular damage as evidenced by enlargement of the third and lateral ventricles. Because all of the subjects had schizophrenic mothers, the major source of genetic variation is contributed by the diagnostic status of their fathers. In a stepwise multiple-regression analysis, it was determined that the multisite neural deficits factor was significantly related to genetic risk for schizophrenia (as measured by schizophrenia spectrum illness in the subjects' fathers) but was unrelated to pregnancy or delivery complications or to weight at birth. Periventricular damage was highly and significantly correlated with the number of complications suffered at delivery, but only among subjects with an elevated genetic risk. Although limited by a small sample size, these results suggest that the two types of CT abnormalities in schizophrenia may reflect partially independent processes based on different combinations of genetic and perinatal influences.

Adolescent↗
PubMed2006

Sensorineural deafness, hydrocephalus and structural brain abnormalities in two sisters: the Chudley-McCullough syndrome.

We describe an Italian family in which two sisters have macrocephaly due to hydrocephalus, and sensorineural hearing loss in addition to other brain abnormalities demonstrated by Magnetic resonance imaging (MRI). The girls, born to healthy non-consanguineous parents, have borderline psychomotor development delay (probably due to hearing defect) and minor dysmorphisms. The clinical picture fits the Chudley-McCullough syndrome, an autosomal recessive condition, to date described in only five families. Our data, in particular the neuroradiological findings, include all brain anomalies variably reported in previous works (hydrocephalus, corpus callosum partial agenesis, interhemispheric cyst, cerebral and cerebellar cortex dysplasia), thus illustrating the full phenotype of the syndrome.

Abnormalities, Multiple↗
PubMed2000

Dual voxel proton magnetic resonance spectroscopy in the healthy elderly: subcortical-frontal axonal N-acetylaspartate levels are correlated with fluid cognitive abilities independent of structural brain changes.

The published literature suggests that degeneration of the subcorticofrontal networks may underlie cognitive ageing, but appropriate methods to examine this in vivo have been lacking. Proton Magnetic Resonance Spectroscopy ((1)H-MRS) has now been used in a number of clinical studies to assess cerebral pathophysicochemistry and recently has been utilized to examine the relationship between neurochemical markers and cognitive functioning in normal individuals. Results have been somewhat conflicting and difficult to interpret. To further clarify the role of the cognitive spectroscopy technique, we measured N-acetylaspartate (NAA) levels in the frontal subcortical white matter and the occipitoparietal grey matter and correlated them with performance in different cognitive domains in a group of twenty healthy elderly individuals. Subjects underwent whole brain T(1)- and T(2)-weighted magnetic resonance imaging (MRI), dual voxel short echo-time (1)H-MRS, and a comprehensive neuropsychological assessment. Individual tests of executive and attentional abilities, and a principal components composite score reflecting these skills, but not measures of memory or verbal abilities, were correlated with NAA concentration in the frontal white matter only. These relationships were independent of other neurocognitive predictors of executive impairment such as age, midventricular dilation, frontal white matter disease, and presenescent verbal proficiency. This study suggests the ability of (1)H-MRS to differentiate anatomically distinct neurochemical markers related to specific cognitive abilities. In particular, neurometabolic fitness of the frontal subcortical-cortical axonal fibers may be important in mediating fluid intellectual processing. Longitudinal MRS studies are required to determine if the present results reflect different rates of neurocellular degeneration or preexisting individual differences in neuronal density.

Aged↗