Visual responses of morphologically identified tectal neurons in the crucian carp.

Tectal neurons of the crucian carp were functionally and morphologically identified by recording their electrical activity and simultaneously injecting dye (Procion yellow). Among intrinsic tectal neurons, visual neurons successfully stained with dye were pyramidal, pyriform and uncategorized neurons. The stained intrinsic tectal neurons were classified into 4 types, according to their visual response properties, i.e. sustained, dimming, transient and other response types. In 23 stained neurons we studied, no correlation was established between response properties and morphology of tectal neurons. In stained pyramidal neurons, the following receptive field (RF) organization could be recognized: (1) on-center, off-surround; off-center, on-surround; both with a small RF; and (2) excitatory or inhibitory center only, with a large RF.