The objective of the present study was to investigate the relationship between emotion and hemispheric laterality in chickens. Regarding central monoamine laterality, the ratios of HVA/DA and 5-HIAA/5-HT in the right hemisphere were significantly higher than those in the left hemisphere of chickens on stress conditions. In addition, plasma CORT concentrations correlated positively with the laterality index of 5-HIAA/5-HT in the telencephalon of chickens. It has been suggested that emotional processing in the right hemisphere might be optimal with DAergic and/or serotonergic lateralization, whereas either a decrease or an increase in this lateralization might be reinstated in animals suffering stress. In addition, positive emotion-induced treatment tended to attenuate stressors, but we could not find the relationship between brain asymmetry and behavioral laterality.
