Trial manufacture of visual field specific stimulator by means of computer image frame memory and an application to brain metabolic mapping.

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We obtained two major results in this research project; first was to manufacture a visual stimulator and to show its effectiveness in an electrophysiological single-unit recording. Second was to apply it to the metabolic mapping of the brain.We had already shown merits of using "fractal patterns" in the research of visual memory. In this project our visual stimulator was constructed by modifying the FBX24 (Texnai) image frame memory system. The stimulator utilized the zoom, pan and scroll functions of FBX24 and succeeded in generating fractal patterns and presenting them at any position of the visual field in any size within 17msec. By using this stimulator we found that a shape-selective neural activity in the temporal cortex was highly selective for the pictorial information and was independent of the physical attributes such as size, orientation, color or position of the presented stimulus. In the hippocampus we found neuronal activity related to the place in which a stimulus was shown. This finding supports the hypothesis that the hippocampus contributes to the place memory. In the second application to metabolic mapping of the brain, local glucose utilization rates (LGU) were measured by 2-deoxyglucose autoradiography method after unilateral visual stimulation. We found that the cerebellar flocculus, especially in the contralateral side, exhibited high LGU during the visual stimulation. In the middle one-third of the contralateral flocculus we found patch-like high LGU areas, which may correspond to the cerebellar microzones.In 1989 a positron emission tomography (PET) was introduced in the Tokyo University Hospital and the Department of Radiology asked us to modify our visual stimulator for the PET system. It is important to further develop our results for a clinical diagnosis.