( Robinson et al., 1981). In other cases, it appears that the right hemisphere is intrinsically overactive, as in clinically-depressed adults, where EEG activation for the right is greater than for the left hemisphere ( Davidson et al., 1979). Possibly, the important factor lies more in the relative levels, as opposed to absolute levels, of activity.
If the balance of activation across the hemispheres is important in depression, it may be possible to explain why younger children are more resistant to depression, and why diagnoses of depression increase around the age of puberty ( Cantor , 1983). Around puberty, the corpus callosum and other neural pathways become mature. One possible scenario is that in younger children, overactivation of the right hemisphere does not result in a concomitant inhibition of the left hemisphere, since callosal pathways are immature. As a result, depressed mood is less likely to be experienced.
Currently, it is not known how anterior/posterior pathways influence the overall balance of activation in the brain. Although evidence has been reviewed that in older children and adults right parietal activation is associated with mood changes, it is not known how activity in this region influences the dynamic balance of the entire system or how the relationship between parietal and frontal areas is mediated. Perhaps variations in right parietal activation have specific effects upon the relationships among other structures in the system, with concomitant correlates in emotional behavior. These matters, however, are subjects for future research.
Current research in neuropsychology suggests that it may be possible to differentiate specific patterns of cerebral arousal that characterize different emotional states. In this chapter, I have proposed that emotional states are associated with the activity of two neurological systems. One, localized in the frontal lobes, is involved in determining emotional valence along a dimension of pleasure/displeasure. The other, localized in the parietal lobe and particularly in the right hemisphere, is involved in determining the level of overall cerebral and autonomic arousal. Emotional states can be characterized by the relative activation of these two neurological systems, which correspond to the psychological dimensions that people use to describe emotions, as revealed by multidimensional scaling studies.
When the neuropsychological mechanisms of emotion are conceived in this manner, a number of issues become moot. As discussed by Leventhal and Tomarken ( 1986), such a perspective diminishes the attractiveness of arguments that require the pairing of a cognitive label with an autonomic state to produce an emotional experience. Unique patterns of neural activity could be produced in