Connections between the zona incerta and superior colliculus in the monkey and squirrel

Abstract

The zona incerta contains GABAergic neurons that project to the superior colliculus in the cat and rat, suggesting that it plays a role in gaze changes. However, whether this incertal connection represents a general mammalian pattern remains to be determined. We used neuronal tracers to examine the zona incerta connections with the midbrain tectum in the gray squirrel and macaque monkey. Collicular injections in both species revealed that most incertotectal neurons lay in the ventral layer, but anterogradely labeled tectoincertal terminals were found in both the dorsal and ventral layers. In the monkey, injections of the pretectum also produced retrograde labeling, but mainly in the dorsal layer. The dendritic fields of incertotectal and incertopretectal cells were generally contained within the layer inhabited by their somata. The macaque, but not the squirrel, zona incerta extended dorsolaterally, within the external medullary lamina. Zona incerta injections produced retrogradely labeled neurons in the superior colliculus of both species. In the squirrel, most cells inhabited the lower sublamina of the intermediate gray layer, but in the monkey, they were scattered throughout the deeper layers. Labeled cells were present among the pretectal nuclei in both species. Labeled terminals were concentrated in the lower sublamina of the intermediate gray layer of both species, but were dispersed among the pretectal nuclei. In summary, an incertal projection that is concentrated on the collicular motor output layers and that originates in the ventral layer of the ipsilateral zona incerta is a common mammalian feature, suggesting an important role in collicular function.

Functional Organisation and Connectivity of the Dorsal Column Nuclei Complex Reveals a Sensorimotor Integration and Distribution Hub

“…Neurons in ZI have a variety of efferent projection targets throughout the neuraxis, of which the SC seems dominant (May & Basso, 2018;Mitrofanis, 2005;Nicolelis et al, 1992;Ricardo, 1981;Romanowski, Mitchell, & Crossman, 1985). The ZI has been associated with diverse functions including appetite and visceral regulation, sleep, attention, locomotion and postural control, and pain regulation (Huang & Mogenson, 1974;K.…”

The mouse cortico-tectal projectome

“…The SC zones also receive topographic inputs from hypothalamic structures, including zona incerta (ZI), and ventromedial nucleus of hypothalamus (VMH) 33,34 . The output patterns of ZI to SC support the topographic organization of medial visuomotor and lateral somatic sensorimotor subnetworks.…”

The Dorsal Column Nuclei Complex Neuroanatomy Reveals a Complex Sensorimotor Integration and Distribution Hub

“…Neurons in ZI have a variety of efferent projection targets throughout the neuraxis, of which the SC seems dominant (May & Basso, 2018;Mitrofanis, 2005;Nicolelis et al, 1992;Ricardo, 1981;Romanowski, Mitchell, & Crossman, 1985). The ZI has been associated with diverse functions including appetite and visceral regulation, sleep, attention, locomotion and postural control, and pain regulation (Huang & Mogenson, 1974;K.…”