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 laterali sation may arise, at least in part, from asymmetric interhemispheric inhibi tion, the intertectal modulation was quantified in 19 pigeons. Field potent ials were recorded from intratectal electrodes in response to a stroboscope flash to the contralateral eye. Electrical stimulation of the contralatera l tectum changed these flash-evoked potentials. This change was taken as a measure of intertectal modulation. It was found that the left-to-right tect otectal modulation was more pronounced than vice versa, supporting the hypo thesis of an asymmetric modulation between the tecta of both hemispheres. I t is conceivable that this lateralised interhemispheric crosstalk could con stitute an important component of asymmetric visual processing. (C) 2000 El sevier Science B.V. All rights reserved.