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    Cerebellar Afferents from neurons in the extraocular motor nuclei: a fluorescent retrograde double-labeling study in the sheep

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    The fluorescent retrograde double labeling technique has been used to identify within the extraocular motor nuclei of the sheep the neurons projecting to the cerebellum and to provide evidence whether they are motor neurons sending collaterals to the cerebellum or a separate population of neurons. The study was performed on eight sheep. The fluorescent tracers used were Fast Blue and the diamidino yellow dihydrochloride. In one and the same animal a fluorescent tracer was injected into the extraocular muscles (EOMs) and the other into bilateral points of the vermal folia II-V and paramedian lobule, or into the vermal folia VI, VIIA and VIIB, or into the underlying fastigial nuclei. Within the oculomotor, trochlear, and abducens nuclei, almost all of the motor neurons were labeled by the tracer injected into the EOMs and only a few cells were fluorescent for the tracer infiltrated into the cerebellum. These latter labelings were present bilaterally, and their number and distribution did not show apparent differences after injecting the paramedian lobule and the vermal folia or the fastigial nucleus. Along the rostrocaudal extent of the oculomotor and trochlear nuclei, the neurons projecting to the cerebellum were intermingled with the motor neurons located in the nuclear area facing the medial longitudinal fasciculus. In the abducens nucleus they were restricted to the caudal pole of the nucleus, which is located ventrolaterally to the genu of the facial nerve. Double-labeled neurons were never found. The absence of double-labeled cells, in spite of the efficiency of the tracer infiltration into the EOMs and into the cerebellum, demonstrates that the cerebellar projections from the extraocular motor nuclei are not collaterals of the motor neurons, but axons of a separate population of neurons. [...

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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