Cerebral asymmetries in vertebrates are implemented as differences in the preferential encoding strategies of the two brain halves. These differences require mechanisms entailing the dominance of one hemisphere controlling response selection and behavioral output in case of conflicting information processing. This metacontrol is mediated by intra- and/ or interhemispheric neuronal mechanisms, which presumably differ depending on cognitive complexity of the particular tasks. For a deeper understanding of the underlying mechanisms, we explored metacontrol in pigeons when confronted with an ambiguous categorization task.
We trained pigeons simultaneously on two categories (cats or dogs) whereby each hemisphere learnt only one of the stimulus classes. After training, the pigeons displayed equal discrimination and transfer performances with the left and right eyes indicating comparable categorization abilities of both brain sides. During the critical tests, the binocularly seeing pigeons were confronted with ambiguous stimulus pairs combining positive items from both categories. Thereby stimuli could be trained (memory-based decision) or new (category-based decision). Pecking onto one of the stimuli indicated the hemisphere taking charge of the response selection and hence, dominated choice behavior. Pigeons displayed individual metacontrol when confronted with a memory- or category-based conflict. Response latencies indicate that dominance for memory-based decisions is mediated by intrahemispheric mechanisms while category-based choices involve interhemispheric processes. Ongoing optogenetic manipulations during conflict choices prove the critical role of these interhemispheric mechanisms. These experiments contribute to our understanding how the hemispheres interact in a lateralized brain.