Patterns Of Brain Organization Research Articles

Language and spatial attention can lateralize to the same hemisphere in healthy humans.

Disorders of language classically occur after left brain lesions, and disorders of spatial attention after right brain lesions. It is unclear whether the hemispheric dissociation of functions is a fixed pattern of brain organization. The authors determined whether lateralization of language and lateralization of spatial attention also dissociate in people with atypical (i.e., right hemispheric) language dominance. The authors selected 10 subjects with typical, i.e., left hemispheric, and 10 with atypical, i.e., right hemispheric, language representation on a random basis from a sample of 326 healthy volunteers examined with functional transcranial Doppler sonography (fTCD) for language dominance. In these subjects, hemispheric lateralization of cerebral perfusion during a line bisection task was determined with fTCD. The authors found a dissociation between dominance for language and spatial attention in all but four subjects. In the latter subjects, there was a significant lateralization to the right hemisphere for both tasks. The four subjects showed normal intellectual, linguistic, and spatial performance, with normal EEG and MRI scans of the brain. Even in the absence of brain pathology, the same hemisphere can be dominant in control of both language and spatial attention.

The neurobiology of dyslexia

Within the last two decades overwhelming evidence from many laboratories has converged to indicate the cognitive basis for dyslexia: dyslexia represents a disorder within the language system and more specifically within a particular subcomponent of that system, phonological processing. Recent advances in imaging technology and the development of tasks which sharply isolate the subcomponent processes of reading now allow the localization of phonological processing in brain, and, as a result, provide for the first time, the potential for elucidating a biological signature for reading and reading disability. Converging evidence from a number of laboratories using functional brain imaging indicates a pattern of brain organization in dyslexia different from that seen in nonimpaired readers; specifically these studies show a disruption of left hemisphere posterior brain systems in adult dyslexic readers while performing reading tasks with an additional suggestion for an associated increased reliance on frontal lobe circuits. The discovery of neural systems serving reading has significant implications. At the most fundamental level, it is now possible to investigate specific hypotheses regarding the neural substrate of dyslexia, and to verify, reject or modify suggested cognitive models. From a more clinical perspective, the identification of neural systems for reading offers the promise for more precise identification and diagnosis of dyslexia in children, adolescents and adults.

Williams syndrome: an exploration of neurocognitive and genetic features

We report here on significant attempts to forge links between neurodevelopmental disorders, development of specific neuropsychological abilities, and the functional establishment of patterns of brain organization. Such research programs are providing converging evidence for the coherence or dissociability of components of cognition (e.g. language, spatial cognition) and will allow development of theoretical explanations for the underlying architecture of human cognition. Williams syndrome involves focal rather than generalized cognitive deficits, and offers an important opportunity for linking brain findings to specific atypical cognitive profiles. The unusual neurocognitive profile of Williams syndrome makes it a compelling model of the pathways between genes and human cognition. It is becoming clear that the syndrome's unique genomic organization may also make it an important model of human chromosomal evolution and disease. These studies with a specific neurodevelopmental disorder that presents a rare dissociation of higher cortical functioning may provide opportunities to explore some of the central issues of cognitive neuroscience that tie cognitive functions to brain organization and ultimately to the human genome.

Salivary testosterone concentrations in left-handers: An association with cerebral language lateralization.

The level of testosterone exposure in early brain development may influence the direction or degree of cerebral language lateralization. Possible links between individual differences in testosterone levels and patterns of speech representation were investigated in 180 healthy young adults (97 left handed, 83 right handed) using the Fused Dichotic Words Test (T. Halwes, 1991). Among left-handed participants, significantly higher testosterone concentrations were observed in individuals with a left-ear advantage on dichotic listening than in individuals with a right-ear advantage. Among right-handed participants, the pattern of group differences in testosterone tended to be reversed, resulting in a statistically significant interaction. Results extend prior findings by S. D. Moffat and E. Hampson (1996a) and raise the possibility that higher testosterone is associated with patterns of brain organization in which speech and praxic functions are lateralized to the same hemisphere.

The developing dorsal ganglion of the salp Thalia democratica, and the nature of the ancestral chordate brain

The development of the dorsal ganglion of the salp,Thalia democratica, is described from electron microscope reconstructions up to the stage of central neuropile formation. The central nervous system (CNS) rudiment is initially tubular with an open central canal. Early developmental events include: (i) the formation of a thick dorsal mantle of neuroblasts from which paired dorsal paraxial neuropiles arise; (ii) the differentiation of clusters of primary motor neurons along the ventral margin of the mantle; and (iii) the development from the latter of a series of peripheral nerves. The dorsal paraxial neuropiles ultimately connect to the large central neuropile, which develops later. Direct contact between neuroblasts and muscle appears to be involved in the development of some anterior nerves. The caudal nerves responsible for innervating more distant targets in the posterior part of the body develop without such contacts, which suggests that a different patterning mechanism may be employed in this part of the neuromuscular system.The results are compared with patterns of brain organization in other chordates. Because the salp CNS is symmetrical and generally less reduced than that of ascidian larvae, it is more easily compared with the CNS of amphioxus and vertebrates. The dorsal paraxial centres in the salp resemble the dorsolateral tectal centres in amphioxus in both position and organization; the central neuropile in salps likewise resembles the translumenal system in amphioxus. The neurons themselves are similar in that many of their neurites appear to be derived from the apical surface instead of the basal surface of the cell. Such neurons, with extensively developed apical neurites, may represent a new cell type that evolved in the earliest chordates in conjunction with the formation of translumenal or intralumenal integrative centres. In comparing the salp ganglion with vertebrates, we suggest that the main core of the ganglion is most like the mes–etencephalic region of the vertebrate brain, i.e. the zone occupied by the midbrain, isthmus, and anterior hindbrain. Counterparts of more anterior regions (forebrain) and posterior ones (segmented hindbrain) appear to be absent in salps, but are found in other tunicates, suggesting that evolution has acted quite differently on the main subdivisions of the CNS in different types of tunicates.

From first words to grammar in children with focal brain injury

The effects of focal brain injury were investigated in the first stages of language development, during the passage from first words to grammar. Parent report, free‐speech data, or both are reported for 53 infants and preschool children between 10 and 44 months of age. All children had suffered a single, unilateral brain injury to the left or right hemisphere, incurred before 6 months of age (usually in the pre‐ or perinatal period). This is the period in which one would expect to see maximal plasticity, but it is also the period in which the initial specializations of particular cortical regions ought to be most evident. In direct contradiction of hypotheses based on the adult aphasia literature, results from 10 to 17 months suggest that children with right‐hemisphere injuries are at greater risk for delays in word comprehension and in the gestures that normally precede and accompany language onset. Although there were no differences between left‐ and right‐hemisphere injury per se on expressive language, children whose lesions included the left‐temporal lobe showed significantly greater delays in expressive vocabulary and grammar throughout the period from 10 to 44 month s. No specific deficits were associated with left‐frontal damage, but there was a significant effect of frontal lobe injury to either hemisphere in the period from 16 to 31 months, when normal children usually show a burst in vocabulary and grammar. This bilateral effect of frontal damage is independent of motor impairment. Hence, there are specific effects of lesion site in early language development, but they are consistent neither with the lesion‐syndrome correlations observed in adults with homologous injuries nor with the literature on acquired lesions in older children. Results are used to argue against innate localization of linguistic representations, and in favor of an alternative view in which innate regional biases in style of information processing lead to familiar patterns of brain organization for language under normal conditions and permit alternative patterns to emerge in children with focal brain injury.

As the Twig Is Bent - The Biology and Socialization of Gender-Roles in Women

The present study supports the view that biological predisposition interacts with perceived parental influences to affect cross-gender role identity. Geschwind and colleagues have identified two patterns of brain organization (anomalous and standard dominance) assessed through individual and familial handedness. Anomalous dominant women who perceived their parents as definitely giving them permission for cross-gender behavior demonstrated high masculine/low feminine characteristics on the Bem Sex Role Inventory. The cross-gender role identity in this group differed significantly from the traditional gender role identity found in all other groups of females (including anomalous dominant women whose parents were perceived as less permissive and the women with standard dominance reporting both styles of parenting).

Human growth hormone may differentially influence the grasp reflex in human neonates on the basis of genetically predetermined neural pattern of brain organization in utero.

The relations of the grasp-reflex strengths from right (R) and left (L) hands to human growth hormone (hGH) levels were studied in human neonates within the first day after birth. In right-handed (RH) males without familial sinistrality (-FS), grasp reflex from right and left hands directly correlated with hGH. In RH, -FS females, grasp reflex from right and left hands inversely correlated with hGH. In -FS, LH males, grasp reflex from right and left inversely correlated with hGH (no significant correlations in LH, -FS females). The R-L grasp reflex decreased linearly with hGH, only in RH, -FS males. These results indicated that hGH may affect cerebral development according to genetically predetermined neural patterns in utero.

Prenatal malnutrition and development of the brain

In this review, we have summarized various aspects as to how prenatal protein malnutrition affects development of the brain and have attempted to integrate several broad principles, concepts, and trends in this field in relation to our findings and other studies of malnutrition insults. Nutrition is probably the single greatest environmental influence both on the fetus and neonate, and plays a necessary role in the maturation and functional development of the central nervous system. Prenatal protein malnutrition adversely affects the developing brain in numerous ways, depending largely on its timing in relation to various developmental events in the brain and, to a lesser extent, on the type and severity of the deprivation. Many of the effects of prenatal malnutrition are permanent, though some degree of amelioration may be produced by exposure to stimulating and enriched environments. Malnutrition exerts its effects during development, not only during the so-called brain growth spurt period, but also during early organizational processes such as neurogenesis, cell migration, and differentiation. Malnutrition results in a variety of minimal brain dysfunction-type syndromes and ultimately affects attentional processes and interactions of the organism with the environment, in particular producing functional isolation from the environment, often leading to various types of learning disabilities. In malnutrition insult, we are dealing with a distributed, not focal, brain pathology and various developmental failures. Quantitative assessments show distorted relations between neurons and glia, poor formation of neuronal circuits and alterations of normal regressive events, including cell death and axonal and dendritic pruning, resulting in modified patterns of brain organization. Malnutrition insult results in deviations in normal age-related sequences of brain maturation, particularly affecting coordinated development of various cell types and, ultimately, affecting the formation of neuronal circuits and the commencing of activity of neurotransmitter cell types and, ultimately, affecting the formation of neuronal circuits and the commencing of activity of neurotransmitter systems. It is obvious that such diffuse type "lesions" can be adequately assessed only by interdisciplinary studies across a broad range of approaches, including morphological, biochemical, neurophysiological, and behavioral analyses.

New evidence for distinct patterns of brain organization in rats differentiated on the basis of inherent laterality

The purpose of the present study was to search for possible relationships among diverse measures of behavioral laterality in a non-human species or to identify an index of laterality that was predictive of other non-lateralized functions. Several indices of behavioral laterality and open field activity were assessed in male and female rats before and after asymmetric neocortical ablations. Plasma adrenocorticotropin, corticosterone, and prolactin were measured following stress at sacrifice. Sex-dependent population-level lateral biases were observed preoperatively in the choice of arms in a T-maze and initial direction out of a corner of an open field. Unilateral left neocortical ablation induced a leftward bias in the T-maze in both male and female rats. The direction of rotation following the peripheral administration of amphetamine was correlated with: (a) the degree of sensitization to amphetamine; (b) preoperative open field activity in females; (c) the induction of hyperactivity following right neocortical ablation in males; (d) rotational responses to amphetamine in male rats sustaining bilateral ablations; and (e) the effect of left neocortical ablation on prolactin levels in males. We propose that these data provide new evidence for distinct patterns of brain organization in rats differentiated by a measure of inherent cerebral laterality.

Task-related EEG alpha asymmetry in schizophrenic patients prior to and after neuroleptic treatment

EEG was recorded from bilateral frontal, central, temporal, and parietal leads (referenced to or transformed to a vertex reference) during cognitive activity in 13 normal controls, ten schizophrenics, and eight patients with affective disorders. All subjects were male and right-handed, and patients had been free of psychotropic medications for at least 2 weeks. A verbal (copying text) and spatial (copying shapes) task were matched for stimulus presentation and motor output. The number and rate of correct responses were recorded for each normal subject and 11 of the patients. As reported by others, normal subjects manifested a significant difference in alpha asymmetry between the tasks, reflecting relatively greater alpha suppression over the left hemisphere during the verbal task compared to the spatial task ( P<0.05). This effect was not significant in either patient group. However, analysis of seven schizophrenics after neuroleptic treatment revealed robust effects of task on alpha asymmetry similar to that present in the normal control group ( P<0.02). The results suggest that abnormal task-related brain lateralization may be present in untreated schizophrenic patients, but it is state dependent and does not reflect permanent patterns of brain organization.

A palaeoecological model for Ouranopithecus macedoniensis

It has been argued that changes in the relative sizes of visual system structures predated an increase in brain size and provide evidence of brain reorganization in hominins. However, data about the volume and anatomical limits of visual brain structures in the extant taxa phylogenetically closest to humans–the apes–remain scarce, thus complicating tests of hypotheses about evolutionary changes. Here, we analyze new volumetric data for the primary visual cortex and the lateral geniculate nucleus to determine whether or not the human brain departs from allometrically-expected patterns of brain organization. Primary visual cortex volumes were compared to lunate sulcus position in apes to investigate whether or not inferences about brain reorganization made from fossil hominin endocasts are reliable in this context. In contrast to previous studies, in which all species were relatively poorly sampled, the current study attempted to evaluate the degree of intraspecific variability by including numerous hominoid individuals (particularly Pan troglodytes and Homo sapiens). In addition, we present and compare volumetric data from three new hominoid species–Pan paniscus, Pongo pygmaeus, and Symphalangus syndactylus. These new data demonstrate that hominoid visual brain structure volumes vary more than previously appreciated. In addition, humans have relatively reduced primary visual cortex and lateral geniculate nucleus volumes as compared to allometric predictions from other hominoids. These results suggest that inferences about the position of the lunate sulcus on fossil endocasts may provide information about brain organization.