Evidence for interhemispheric conflict during meta-control in pigeons.

In birds each hemisphere receives visual input from the contralateral eye. Since birds have no corpus callosum, avian brains are often seen as 'natural split brains'. How do birds cope with situations, when both hemispheres are brought into conflict? If under such conditions one hemisphere completely determines the response, this is called meta-control. This phenomenon has recently been demonstrated in pigeons. The aim of the current study is to test, if meta-control results from an interhemispheric conflict that would require interhemispheric interaction, possibly via the commissura anterior. To this end, we trained pigeons in a forced-choice color discrimination task under monocular condition such that each hemisphere was trained with a different pair of colors. Subsequently, pigeons were binocularly tested with conflicting and non-conflicting stimulus patterns. Conflicting stimuli indeed produced a delayed reaction time as expected when two divergent decisions create a conflict. In addition, we sometimes observed a pecking pattern that seemed to represent the average of two discrepant and hemisphere-specific movements. Thus, pigeons possibly undergo interhemispheric conflict during meta-control even without a corpus callosum. However, also when having decided to peck a certain color, the planned movement trajectory of the other hemisphere sometimes compromises the final pecking movement.