Fig. 7. The primary visual pathways of the chick and patterns of teneurin expression. (A) There are two primary visual circuits in birds, the tectofugal pathway and the thalamofugal pathway. (B) Teneurin 1 is expressed by neurons in at least two of the three major parts of the tectofugal pathway (expression in the telencephalon has not been examined). Teneurin 2 is expressed by the neurons of the thalamofugal visual pathway. See text for details and abbreviations.