SUMMARY1. In anaesthetized albino rabbits, the occurrence of Purkinje cell inhibition on canal-ocular reflexes was surveyed with a reflex testing method.2. Test reflexes were elicited by electrical stimulation of the semicircular canals. The results were appraised by recording potentials and tension from extraocular muscles. Twelve reflexes were defined in terms of the receptor canal and the effector muscle.3. Conditioning electrical stimuli were applied to the flocculus, the inferior olive, and optic pathways at the retinae, optic chiasm, pretectal area and upper medulla.4. The conditioning stimulation at the ipsilateral flocculus induced depression in six of the twelve canal-ocular reflexes; four of the six arose from the anterior canal and the remaining two from the horizontal canal.5. The effect of stimulation of the contralateral inferior olive was similar to that of the ipsilateral flocculus, though less clear in two of the four reflexes from the anterior canal because of a contaminating effect. 6. The two reflexes from the horizontal canal were depressed by stimulation of the ipsilateral optic pathway which reached the ipsilateral flocculus via the contralateral pretectal area and inferior olive.7. The four reflexes from the anterior canal were affected by stimulation of optic pathways in a different manner from each other. One was depressed from the contralateral retina via the ipsilateral pretectal area, while another was depressed from the ipsilateral retina via the contralateral pretectal area, though only occasionally. The third reflex was depressed from the ipsilateral pretectal area but not from the retina. The fourth was affected from neither the retina nor the pretectal area.8. On the basis of latency measurements, it was concluded that the depression of canal-ocular reflexes was due to inhibition of relay neurones of the testing reflexes by flocculus Purkinje cells which were activated either directly, or indirectly through olivocerebellar climbing fibre afferents.MASAO ITO AND OTHERS 9. The above conclusion was supported by the observation that the depression induced by stimulation of the inferior olive and optic pathways was abolished by acute destruction of the ipsilateral flocculus.10. The possible functional significance of the specific patterns of connexions from flocculus Purkinje cells to canal-ocular reflex pathways is discussed, and specialization among flocculus Purkinje cells in relationship with vestibulo-ocular reflexes is postulated.

The effects of the baroceptor reflex on sympathetic nerve activity (SNA) to spleen, kidney, and heart were analyzed in anesthetized cats. The baroceptor reflex times of SNA to the spleen, kidney, and heart were 292, 199, and 164 msec, respectively. SNA to these organs changed almost inversely to changes in the absolute mean aortic pressure between 100 and 150 mm Hg. Within this pressure range the gain of baroceptor-sympathetic systems to the spleen,

ings must be evaluated with caution because the possible spread of stimulating currents to outside the cerebellum was not accurately controlled at that time.During the past four to five decades, research on the cerebellum has advanced markedly and our knowledge about its functional involvements and neuronal mechanisms has been conspicuously improved [6][7][8][9][10]. A new concept regarding the cerebellum has thus developed. The cerebellum has a unique modular structure, including a cortical microzone, a small group of nuclear neurons and a small group of inferior olive neurons, which are mutually interconnected to form a cerebellar corticonuclear microcomplex (hereafter, abbreviated as microcomplex). Each microcomplex contains a uniform neuronal circuit that is capable of learning based on activity-dependent synaptic plasticity. And each one is attached to an

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