96 
Ebbesson 
Figure 4. Degeneration at level of tectum. 
likely, in view of the fact that direct spinal 
fibers also project to this cell group (Ebbes- 
son, 1966, 1967, 1969). 
Torus Semicircularis 
The dorsal column nuclei were, until very 
recently, thought to project only to the ven- 
trobasal complex in mammals. It is only 
recently that medial lemniscal fibers were 
also found to terminate in the inferior 
colliculus. In the cat, the three main divi- 
sions of this structure are known as the 
central, pericentral and external nucleus 
(Berman, 1968). Anatomical as well as 
electrophysiological studies have confirmed 
that the central nucleus serves as the main 
auditory area in the mesencephalon (Rose 
et al., 1963; Goldberg and Moore, 1967), 
whereas the external and pericentral nuclei, 
collectively usually described as intercollic- 
ular nuclei, receive direct projections from 
the spinal cord (Mehler et al., 1960; Jane 
and Scl^roeder, 1971; Schroeder and Jane, 
1971). Dorsal column nuclei projections to 
