Lateralization Of Cerebral Function Research Articles

Sex-specific effects of maternal testosterone on lateralization in a cichlid fish

Lateralization of cerebral functions is a fundamental aspect of the organization of brain and behaviour in vertebrates. Sex differences in human lateralization have inspired researchers to postulate several hypotheses concerning the effect of prenatal testosterone on lateralization, but few experimental studies have examined these hypotheses. We investigated whether prenatal testosterone affects strength or direction of lateralization in a cichlid fish, Aequidens rivulatus. Eggs were given a control or testosterone treatment immediately after spawning, mimicking elevated maternal androgen concentrations towards the high end of the natural range. After 7 months the fish were tested in two rotational preference tests. As expected from earlier studies, control fish showed (nonsignificant) right-eye preference while viewing a predator and (significant) left-eye preference while viewing their mirror image, but no clear sex differences were apparent. A sex-specific effect of our treatment was found in the first test. Only females exposed to elevated prenatal levels of testosterone significantly shifted in direction of lateralization. In the second test no effect of the treatment was found. Our results suggest that mothers have a stronger influence on the lateralization pattern of their daughters than on their sons, but do not support any of the current hypotheses about prenatal testosterone and development of lateralization. (C) 2011 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Handedness and speech: a critical reappraisal of the role of genetic and environmental factors in the cerebral lateralization of function.

Functional predominance of the left cerebral hemisphere with regard to both handedness and speech has usually been assumed to be due to some underlying neural specialization that is predetermined and inborn. However, data from left-handed individuals and animal experiments, together with a consideration of the effects of natural selection on brain and behaviour during hominid evolution, are incompatible with such an explanation. A critical reexamination of the relevant nonhuman and human evidence suggests that although the development of a cerebral lateralization for speech and handedness is dependent on both genetic and environmental factors, the specific role of inborn and postnatal influences is very different. This has significant implications for a fundamental revision of current theory and research orientation.

Handedness and speech: A critical reappraisal of the role of genetic and environmental factors in the cerebral lateralization of function.

Handedness and speech: A critical reappraisal of the role of genetic and environmental factors in the cerebral lateralization of function.

Relationships between specific and general tests of cerebral functioning

Abstract This study compared a group of control subjects with a group of brain-damaged subjects to determine whether “specific” neuropsychological measures were more sensitive to cerebral damage than “general” neuropsychological tests. The historical interest in localization and lateralization of cerebral functions has produced a strong emphasis on specific deficits, while general deficits, characterized by more complex functions, have received less directed attention. The results indicated that the general measures were significantly more sensitive to cerebral damage than were the specific measures. These findings identify the need for further investigation of the relationships between specific and general neuropsychological tests, since both types of tests are of value in comprehensive evaluations of individual subjects.

Cerebral lateralization of function: From infancy through childhood.

Cerebral lateralization of function: From infancy through childhood.

Cerebral lateralization of function: From infancy through childhood.

Cerebral lateralization of function: From infancy through childhood.

Lateralization of function in the rat brain: Basic mechanisms may be operative in humans

Lateralization of cerebral function has, in the last decade, been documented in the brains of several animal species. The present review summarizes recent findings concerning lateralized processes in the rat brain and considers their implications for understanding similar or the same processes in the human brain. Lateralization of the rat brain is present at birth, changes during development and is sexually dimorphic. This asymmetry exists in several brain regions. For example, as in the human, affective processes appear to be lateralized and, in both species, a dopaminergic asymmetry in basal ganglia function appears to underlie the mechanism of spatial preferences.

Cerebral lateralization of function and bilingual decision processes: Is thinking lateralized?

Four experiments utilizing tachistoscopic presentation of verbal and spatial stimuli to visual half-fields are presented. Three experiments failed to find any cerebral lateralization effect of the type predicted from existing models of cerebral lateralization processes. One experiment found marked lateralization effects. Since the experiments differ only in the ratio of trials to experimental stimuli, it is argued that cerebral lateralization experiments are detecting only a memory process occurring after subjects have learned all the stimuli to be presented. When new stimuli are presented on each trial, no cerebral lateralization effects are found, suggesting that active ongoing cognitive processing is independent of lateralization.

The Effect of Cerebral Dominance on Time Sharing between Speaking and Tapping by Preschool Children

48 kindergartners tapped as fast as they could with either the right index finger or the left, either alone or while reciting or repeating verbal material. The secondary tasks diminished tapping rate on both sides, but disproportionately on the right. This result was predicted by a model that postulates greater interference between concurrent activities when both are programmed by the same cerebral hemisphere. Children appear to be more vulnerable to this type of interference than adults. This attribute of immature motor development can be used as an indicator of cerebral lateralization of function in children.

Asymmetries in the CNV over left and right hemispheres while subjects await numeric information

The contingent negative variation (CNV) was recorded from frontal and central electrodes in one left-handed and 12 right-handed subjects. The CNV was elicited by tachistoscopically exposed visual stimuli comprising a warning spot followed by a numeral. Numerals so exposed had to be memorized (cumulative condition), added (arithmetic condition), or checked to ensure that all were zeros (repetitive condition). The arithmetic and cumulative tasks were designed to potentiate any expectancy mechanisms in the hemisphere dominant for verbal processes. The repetitive task was intended as a neutral control. All three tasks elicited CNVs whose amplitude was greater over the hemisphere contralateral to the preferred hand. The results are discussed in terms of possible relationships with handedness and the lateralization of cerebral function.

Lateralization of cerebral functions.

Lateralization of cerebral functions.