Cerebral lateralization of olfactory-mediated affective processes in rats

To determine whether processing of information is lateralized in the brain of non-human mammalian species, rats that had undergone ablation of the left or right olfactory bulb were compared to sham-operated animals and to bilaterally bulbectomized animals in their response to emotionally positive or negative social odours. Left-bulbectomized rats were impaired in their behavioural reaction but not in their hormonal response to an odour from a stressed conspecific. They fully retained, however, their ability to recognize a nonstressed juvenile conspecific on the basis of its olfactory characteristics. These results suggest that hemispheric asymmetries develop in mammals not for recognition of emotional stimuli but for association of emotional experiences with appropriate adaptive behaviour.