[Neuron group of rostral midbrain associated with selective vertical gaze palsy in alert cats]

The neural and anatomical basis for selective vertical gaze palsy (isolated failure of upward or downward gaze) is still not completely understood. To study a new class of cells which is possibly related to selective vertical gaze near or in the INC (Interstitial-nucleus of Cajal), single cell recordings were performed in the vicinity of the INC of alert cats. We found 25 upward and 50 downward burster-driving neurons (BDN), which have very similar characteristics as those of previously reported horizontal BDNs. The activity of these vertical BDNs gradually increased during the downward slow phase and the upward slow phase, respectively, and this increased activity was further followed by a burst discharge shortly before and during the quick phase. These cells also showed burst discharge shortly before and during on-direction saccade. Downward BDNs were recorded mainly in the INC. Upward BDNs were found in the surrounding area of the INC. Deactivation by GABA agonist of each of the recorded sites produced selective upward and downward gaze palsy. Taken together, these results suggest that the deactivation of vertical BDNs involve some aspect of the selective vertical gaze palsy.