Morphological aspects of the teleostean visual system: a review

This review is concerned with results of research carried out in the last two decades regarding visual pathways and centers in teleosts. It covers neither morphology of the retina nor development and plasticity. The optic nerve is considered in terms of axonal composition and retinotopic organization. The connections to the retina and from the retina are subsequently reviewed, and a general scheme is proposed for the retinofugal targets in thalamus and pretectum. The tectum opticum is then reviewed as regards its afferent connections from retina, telencephalon, diencephalon, mesencephalon and brainstem, with details on distribution of terminals, cell types contacted and synaptic structure. The efferent tectal connections are reviewed next, including their plausible cells of origin. Finally, a general diagram of the teleostean visual system is presented, and several circuits within this diagram are emphasized and discussed.