The zona incerta modulates spontaneous spike - wave discharges in the rat 1 2 3 4

32 The contribution of the zona incerta (ZI) of the thalamus upon spike-wave discharges (SWDs) 33 was investigated. Chronic recordings of bilateral cortices, bilateral vibrissa muscle and unilateral ZI 34 were performed in Long-Evans rats in order to examine the functional role of SWDs. Rhythmic ZI 35 activity appeared at the beginning of SWD and accompanied by higher-oscillation frequencies and 36 larger spike magnitudes. Bilateral lidocaine injections into the mystacial pads led to a decreased 37 oscillation frequency of SWDs, but the phenomenon of ZI-related spike magnitude enhancement 38 was preserved. Moreover, 800-Hz ZI microstimulation terminates most of the SWDs and whisker 39 twitching (WT) (> 80%). In contrast, 200-Hz ZI microstimulation selectively stops WTs but not 40 SWDs. Stimulation of the thalamic ventroposteriomedial nucleus showed no obvious effect on 41 terminating SWDs. An unilateral ZI lesion resulted in a significant reduction of 7-12-Hz power of 42 the both ipsilateral cortical and contralateral vibrissae muscle activities during SWDs. Intraincertal 43 microinfusion of muscimol showed a significant inhibition on SWDs. Our present data suggest that 44 the ZI actively modulates the SWD magnitude and WT behavior. 45 46