The traditional verbal/nonverbal dichotomy is inadequate for completely describing cerebral lateralization. Musical functions are not necessarily mediated by the right hemisphere; evidence for a specialist left-hemisphere mechanism dedicated to the encoded speech signal is weakening, and the right hemisphere possesses considerable comprehensional powers. Right-hemisphere processing is often said to be characterized by holistic or gestalt apprehension, and face recognition may be mediated by this hemisphere partly because of these powers, partly because of the right hemisphere's involvement in emotional affect, and possibly through the hypothesized existence of a specialist face processor or processors in the right. The latter hypothesis may, however, suffer the same fate as the one relating to a specialist encodedness processor for speech in the left. Verbal processing is largely the province of the left because of this hemisphere's possession of sequential, analytic, time-dependent mechanisms. Other distinctions (e.g., focal/diffuse and serial/parallel) are special cases of an analytic/holistic dichotomy. More fundamentally, however, the left hemisphere is characterized by its mediation of discriminations involving duration, temporal order, sequencing, and rhythm, at the sensory (tactual, visual, and, above all, auditory) level, and especially at the motor level (for fingers, limbs, and, above all, the speech apparatus). Spatial aspects characterize the right, the mapping of exteroceptive body space, and the positions of fingers, limbs, and perhaps articulators, with respect to actual and target positions. Thus there is a continuum of function between the hemispheres, rather than a rigid dichotomy, the differences being quantitative rather than qualitative, of degree rather than of kind.

The nature of hemispheric specialization in man

Two visual search experiments were carried out using as stimuli large letters made of small identical letters presented in right, or left, or central visual fields. Considering the spatial frequency contents of the stimuli as the critical variable, Experiment 1 showed that a left-field superiority could be obtained whenever a decision had to be made on a large (low frequency) letter alone, and a right-field advantage emerged when a small (high frequency) letter had to be processed. Experiment 2 showed that the two levels of structure of the stimulus were not encoded at the same rate and that at very brief exposure, only the large letter could be accurately identified. This was accompanied by a left-field superiority, whether or not the stimulus contained the target. These results are interpreted as revealing a differential sensitivity of the hemispheres to the spatial frequency contents of a visual image, the right hemisphere being more adept at processing early-available low frequencies and the left hemisphere operating more efficiently on later-available low frequencies. From these and other experiments reviewed, it is suggested that (a) cerebral lateralization of cognitive functions results from differences in sensorimotor resolution capacities of the hemispheres; (b) both hemispheres can process verbal and visuospatial information, analytically and holistically; (c) respective hemispheric competence is a function of the level of sensorimotor resolution required for processing the information available. Language: en

The cerebral balance of power: confrontation or cooperation?

Functional specialization in the lower and upper visual fields in humans is analyzed in relation to the origins of the primate visual system. Processing differences between the vertical hemifields are related to the distinction between near (peripersonal) and far (extrapersonal) space, which are biased toward the lower and upper visual fields, respectively. Nonlinear/global processing is required in the lower visual field in order to pergeive the optically degraded and diplopic images in near vision, whereas objects in far vision are searched for and recognized primarily using linear/local perceptual mechanisms. The functional differences between near and far visual space are correlated with their disproportionate representations in the dorsal and ventral divisions of visual association cortex, respectively, and in the magnocellular and parvocellular pathways that project to them. Advances in far visual capabilities and forelimb manipulatory skills may have led to a significant enhancement of these functional specializations.

Functional Specialization in the Lower and Upper Visual Fields in Humans: Its Ecological Origins and Neurophysiological Implications

This paper describes a novel theoretical framework of how the position of a letter within a string is encoded, the SERIOL model (sequential encoding regulated by inputs to oscillations within letter units). Letter order is represented by a temporal activation pattern across letter units, as is consistent with current theories of information coding based on the precise timing of neural spikes. The framework specifies how this pattern is invoked via an activation gradient that interacts with subthreshold oscillations and how it is decoded via contextual units that activate word units. Using mathematical modeling, this theoretical framework is shown to account for the experimental data from a wide variety of string-processing studies, including hemispheric asymmetries, the optimal viewing position, and positional priming effects.

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How the brain encodes the order of letters in a printed word: The SERIOL model and selective literature review

Hemisphere differences in the acquisition and use of descriptive systems.

Developmental aspects of visual hemifield differences in perception of verbal material.

Displacement of albumin-bound bilirubin by free fatty acids. Implications for neonatal hyperbilirubinemia

Congeni ta l d iaphragmat ic defects have been classified by Bingham (1959) into posterolateral defects (foramina of Bochdalek) retrosternal defects ( foramina of Morgagni) , and the rare extensive defects involving most or all of the hemidiaphragm (agenesis). Famil ial occurrence of d iaphragmat ic hernia is rare and in most families in which this has been reported the pat ients have died from extensive defects within a few days of bir th (Daent l and Passarge, 1972). Daent l and Passarge summarized nine reported families in whom 20 of 29 siblings were affected with agenesis of the diaphragm. In view of the rari ty of d iaphragmat ic agenesis it was suggested that this lesion might be etiologically different f rom the other two types of the defect, which do not show increased familial incidence (Passarge et al., 1968). The role of genetic factors in the etiology of familial agenesis of the d iaphragm is unclear. Autosomal recessive and mult ifactorial inheri tance have been suggested (Passarge et al., 1968; ten Kate and Anders, 1970; Jensen and Altrogge, 1971; Daent l and Passarge, 1972). No parenta l consanguin i ty has been reported. In this report we present two affected sisters who are the offspring of a consanguineous marriage.

Ruth Starinsky

Papers

Developmental aspects of visual hemifield differences in perception of verbal material.

Displacement of albumin-bound bilirubin by free fatty acids. Implications for neonatal hyperbilirubinemia

Diaphragmatic defects in children of consanguineous parents