Hemispheric Asymmetry and Positive Emotions

(taken from The Clinical Guide to Sound and Light
By Thomas Budzynski, Ph. D.; with emphasis added)

Frontal Brain Asymmetry Predicts Infants' Response to Maternal Separation:

The EEG as recorded from the left and right frontal and parietal scalp regions of 13 normal 10 month-old infants showed greater activation of the right frontal area in infants that cried during a brief period of maternal separation. Infants that did not cry showed significantly less activation over this region (Davidson & Fox, 1989). Conclusion: Frontal EEG activation asymmetry may be a state-independent marker for individual differences in threshold of reactivity to stressful events and vulnerability to particular emotions.

Approach-Withdrawal and Cerebral Asymmetry:

Scalp EEG measures of activation were found to be associated with the facial expressions of approach-avoidance. Disgust was found to be associated with right-sided activation in the frontal and anterior temporal regions compared with the happy condition. In contrast, happiness was accompanied by
left-sided activation in the anterior temporal region compared with the disgust condition (Davidson, Ekman, Saron, Senulis & Friesen, 1990).

Can Brain Asymmetry Predict Emotional Response to Films?

The answer to this question is YES. Resting alpha power asymmetry in the left/right frontal areas significantly predicted self-reported global negative affect in response to film clips eliciting positive and negative affect (Tomarken, Davidson & Henriques, 1990). Conclusion: Resting anterior asymmetry may be a state-independent index of the individual's predisposition to respond affectively.

Can Brain EEG Asymmetry Discriminate Previously Depressed and Healthy Control Subjects?

This study showed that previously depressed (normothymic) individuals had less left-sided anterior and less right-sided posterior activation (i.e., more
alpha activity) than did never depressed subjects. The previously depressed subjects had no history of pharmacological treatment and did not differ from the controls in emotional state at the time of testing (Henriques & Davidson, 1990).
Conclusion: The pattern of anterior and posterior asymmetry in the previously depressed subjects is similar to that found in acutely depressed subjects and suggests that this may be a state-independent marker for depression.