The projection of ocellar neurons within the brain of the Locust, Schistocerca gregaria

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Abstract
Summary Cobalt iontophoresis of the median and lateral ocellar nerves of Schistocerca gregaria, combined with silver impregnated sections of the brain, has demonstrated the projection areas of the large and medium-sized ocellar afferent neurons. These neurons terminate within the brain and their cell bodies lie within the protocerebrum. Ocellar neurons project to two discrete areas on each side of the brain, each area receiving input from a different set of fibres. Both postero-dorsal complexes receive an input from two large ipsilateral and two large median fibres. Their dendritic fields maintain an ordered spatial array relative to one another. The two antero-lateral complexes receive an input from one large ipsilateral fibre and medium-sized ipsilateral and median small-field afferent fibres. Each lateral ocellus has two large fibres in common with the median ocellus. These lateromedial fibres receive photoreceptor input from both ocelli but form no major arborisations within the brain. The lateral ocellar tracts appear to form a third ocellar association area since higher-order neurons branch amongst the lateral and latero-medial fibres within the tract. The axons of the higher-order neurons descend to the ventral cord via the circum-oesophageal commissures.