modified by three processes: (1) the addition of new behaviors to the response repertoire of the "affect program"; (2) regulation in the forms of inhibition and appraisal; and (3) blending. We reviewed our own and other evidence indicating that the emotions of interest and disgust are reliably elicited in the neonate. We proposed that these emotions are under unilateral hemispheric control since little functional interconnection between the hemispheres exists at birth. The emergence of fear and sadness toward the end of the first year was considered in relation to changes in interhemispheric communication. The onset of locomotion, a behavior which is associated with commissural transfer, is tightly coupled to the emergence of fear. The expression of sadness is often associated with alternating sequences of approach and avoidance again implicating a critical role for interhemispheric communication. The capacity to inhibit negative affective responses which emerges during the second year was also linked to the functional integrity of the commissural system. We proposed that the left hemisphere inhibits regions in the right hemisphere through transcallosal connections and this results in the attenuation of negative emotion. Finally, we ended by suggesting that the specification of neural correlates of affective change does not imply that we have identified the causes of these developmental shifts. We believe that the parameters of hemispheric function to which we refer are candidates for a mechanism or a proximal cause of affective change. Clearly, both maturational and experiential factors both play important roles in the development of emotion and hemispheric interaction.
We believe that while speculative, our model does contain a number of empirically testable hypotheses concerning relations between hemispheric asymmetry, interhemispheric transfer, and affective development. We are currently pursuing a number of these questions using electrophysiological measures of both activation asymmetry as well as interhemispheric transfer and relating these indices to well-defined parameters of affective response.
Preparation of this chapter was supported in part by a grant from the Foundation for Child Development to RJD and NAF and by a grant from the John D. and Catherine T. MacArthur Foundation to RJD. We would like to thank Diana Angelini for her patient secretarial support.
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