Dendrites of deep layer, somatosensory superior collicular neurons extend into the superficial laminae

Intracellular recording and horseradish peroxidase (HRP) injection techniques were used to delineate the structural and functional properties of superior collicular (SC) neurons in hamsters. Of 34 cells recovered from the deep laminae (those ventral to the stratum opticum--SO), 26 were exclusively somatosensory and 10 of these extended dendrites into the superficial layers, the stratum griseum superficiale (SGS) and SO. In 2 instances, dendrites extended only to the SO, but in 8 others they reached the SGS. Three of the latter cells had dendrites which terminated just beneath the pial surface. These findings show that an anatomical substrate for communication from superficial to deep layer cells exists in the hamster SC, but that such communication may not necessarily be reflected in the response of deep layer neurons.