[Comments on the topography of the crossed isthmo-tectal projection in the frog].

In this work, we show that cortical cells of the contralateral nucleus isthmi remain unlabelled when HRP deposits are made in the monocular zone of the optic tectum. On the other hand, labelling is present with deposits made in the binocular tectal region. This result would confirm that in frogs the crossed isthmo-tectal pathway is only concerned with ipsilateral retinotectal messages.