Cerebral Asymmetry and Behavioral Laterality: Some Psychobiological Considerations
|Victor H. Denenberg|
|Michael J. Hofmann|
|Glenn D. Rosen|
|David A. Yutzey|
|University of Connecticut|
This chapter has four purposes. First, we review the literature showing that the brains of a variety of animals are asymmetrical with regard to anatomical structure and behavioral functions. We then show that early experiences can induce laterality or modify laterality already present in the rat. Next, we discuss the anatomical and physiological properties of the corpus callosurn and how those properties are changed by visual experience during development. Finally, we suggest a mechanism involving the corpus callosum by which early experiences may induce or modify cerebral laterality in animals.
Although affective behavior is our primary concern, the review includes other literature as well, in order to place the discussion of affective processes into their proper context. Before getting to our review, it is necessary to introduce a few general concepts concerning lateralization of brain-behavior processes.
There are important differences between laterality in an individual and laterality in a population. Population laterality occurs when more than half the organisms in that population are asymmetrically biased toward one side or the other. For example, the great majority of humans are right-handed. Also, whether right- or left-handed, most humans have the neural substrate for speech in their left hemisphere.
If the population is lateralized, then the individuals making up that population must possess brain-behavior asymmetry. However, the converse is not necessarily true: that is, organisms as individuals can be asymmetrical without the