SOMATOSENSORY AND VISUAL CORRELATION IN THE OPTIC TECTUM OF A PYTHON,PYTHON REGIUS - A HORSERADISH-PEROXIDASE AND GOLGI-STUDY

In snakes with infrared receptors the optic tectum receives infrared i nput in addition to visual and general somatosensory inputs. In order to observe their tectal termination patterns in ball pythons, Python r egius, we injected horseradish peroxidase (HRP) into the nucleus of th e lateral descending trigeminal tract (LTTD) which mediates infrared i nformation, the optic nerve, and the nucleus of the trigeminal descend ing tract (TTD) which relays general somatosensory information. Fibers from LTTD were found in layers 5-13 of the contralateral optic tectum , and were especially dense in layers 7a-8. Optic nerve fibers termina ted in layers 7a-13 of the contralateral tectum, and mainly in layers 12-13. TTD fibers were few, and could be seen in only the rostral half of the contralateral tectum. These fibers were found in layers 5-7b, but mainly in layers 6-7a. Among various types of neurons stained by t he Golgi-Cox method, we focused on six types of neurons whose dendriti c arborization overlapped with the distribution of the terminals of th ese sensory afferents described above. It is possible that these diffe rent sensory modalities converge on a single neuron of the various typ es.