Visual and nonvisual units recorded from the optic tectum of Gallus domesticus.

Units recorded from the optic tectum of Gallus domesticus were tested for responses to visual, auditory and somesthetic and stimuli. Units recorded from the superficial tectal layers (stratum opticum, stratum griseum et fibrosum superficiale) responded only to visual stimuli. On the basis of the unit's responsiveness to the directionality of a moving visual stimulus, three unit types referred to as pandirectional, unidirectional, and multidirectional units were identified. In the deeper layers (stratum griseum centrale, stratum album centrale) unimodal and bimodal units were encountered. These units responded to visual, auditory, and/or somesthetic stimuli. These results indicate that the tectal cortex of Gallus domesticus is subdivided into two functional divisions: the superficial layers which correlate visual information and the deep layers which correlate visual and nonvisual information.