Direct motor cortex projections to the interstitial nucleus of Cajal in the cat demonstrated by autoradiographic technique.

Szentagothai (1943) hypothesized that the interstitial nucleus of Cajal and nucleus of Darkschewitsch take part in vertical and rotatory eye movements, as a relay center for cortical and vestibular inputs. Hassler and Hess (1954) reported that low frequency stimulation of the interstitial nucleus of Cajal results in rotatory movements around the longitudinal axis of the body. On the other hand, using a stimulation technique according to Hess in the cortical premotor and motor areas, the head-raising effects were seen on the dorsal part of the lateral wall of gyrus proreus and the rotation, separated from ipsiversive turning, on the lower lip of the cruciate sulcus (Hassler 1966). Three midbrain nuclei, the nucleus prestitialis, nucleus precommissuralis (nucleus cornmissurae posterioris) and nucleus interstitialis of Cajal, were described by Hassler (1966) concerning the direction of specific movements (raising, lowering and rotatory movements), and the frontal cortical connections to these nuclei were speculated (see his Figure 13). Although frontal cortical projections to the mesencephalo-diencephalic region have been studied in a variety of carnivores and primates, direct cortico-interstitial connections have not been demonstrated. Only Szentagothai (1943) reported an extensive cortical input to the interstitial nucleus using the Gross-Bielschowsky