Evidence for physiological asymmetries in the intertectal connections of the pigeon (Columba livia) and their potential role in brain lateralisation.

In pigeons, visual object processing is lateralised with a dominance of the left tectofugal system. To test the hypothesis, that avian visual lateralisation may arise, at least in part, from asymmetric interhemispheric inhibition, the intertectal modulation was quantified in 19 pigeons. Field potentials were recorded from intratectal electrodes in response to a stroboscope flash to the contralateral eye. Electrical stimulation of the contralateral tectum changed these flash-evoked potentials. This change was taken as a measure of intertectal modulation. It was found that the left-to-right tectotectal modulation was more pronounced than vice versa, supporting the hypothesis of an asymmetric modulation between the tecta of both hemispheres. It is conceivable that this lateralised interhemispheric crosstalk could constitute an important component of asymmetric visual processing.