1.Afferent information from the neck plays an important role in the regulation of posture and the control of head and eye movements. The present series of experiments was designed in order to characterize the cerebellar projections of neck afferents in the cat. Both anesthetized and decerebrate animals were used, and recordings were obtained following electrical stimulation of the second cervical dorsal root (C2).2.Following electrical stimulation of C2 dorsal root, field potentials were recorded in lobules V and VI. Amplitude was maximum in the lateral third of the ipsilateral lobule V. These field potentials were produced by combined mossy and climbing fiber (MF and CF) volleys arriving at the cerebellar cortex with different latencies: 8 msec for MF and 24 msec for CF (mean values). The threshold for electrical stimulation was lower for MF than for CF activation; CF responses were evoked by high threshold afferents from muscle and joint receptors.3.A comparison was made between the latencies of cerebellar responses evoked by electrical stimulation of nuchal and other afferents (vestibular nerve, fore-and hindpaw). The latencies of MF responses vary widely, while those of the CF responses show a much smaller variation.4.Projection of the afferents from the neck was also demonstrated in the pars intermedia at the limit of the caudal folium of lobule V and of lobule VI (lobule simplex). A study of the convergence to this portion of pars intermedia demonstrated that stimulation of extraocular muscle nerves, trigeminal nerve, and fore-and hindpaws, as well as the neck afferents, generates a strong localized CF response with actual convergence onto single Purkinje cells. The recordings suggest that this area of wide convergence on CFs is not restricted to the superficial cortex, but extends through the depth of the fissura prima. Implications of these findings, in relation to the functional organization of lobule VI and the fissura prima, are discussed.
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