Research on input and output connections and amplitude control of saccadic eye movement by multiple electrode recording.

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A simultaneous and continuous recording system of multi-channel digital signals of neural unitary activities was developed in order to analyze spatial and temporal activity of the superior colliculus that has two-dimensional retinotopical map. The system is composed of hand-made circuits of digital ICs and a computer and has advantages such as limitless channel number, and continuous long-time recording or triggered intermittent repetitive recording. Concerning the speed, 5 kHz sampling can be done with 256 channels in the continuous recording mode until the computere hard disk becomes full.A method of three-dimensional reconstruction of single axons by tracing with biotinylated dextran amine labeling was developed in order to analyze afferent and efferent connections in different areas in the retinotopical map in the superior colliculus. In advance, I tried to establish the methods in experiments in the rat cerebellum. I found that single axons originating from the inferior olivary nucleus and the lateral reticular nucleus frequently innervate the cerebellar nucleus. Branchings and innervation patterns of these single axons in the cerebellar cortex and cerebellar nucleus were clarified. A new afferent axons selective to the cerebellar nucleus that barely projected to the cerebellar cortex was found. These axons originated from the paramedian reticular formation in the rostral medulla. During the experiments in the cerebellum, methods for gelatin embedding and histochemical treatment and fabrication of tissue reaction chamber were improved and experimental protocol was established. Concerning superior collicular connections, it is was found that the ventromedial portion of the caudal part of the medial accessory olive, which was shown to receive afferent from the superior colliculus, then projected to lobule VI and VII in the rat cerebellar vermis.