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To study the effects of senescence on the vestibular nuclear complex twenty brainstems from male golden hamsters between 3 and 27 months-old were used and the possible variations in the number of neurons, neuronal morphology and nuclear volume were studied. The neuron profiles were drawn with a camera lucida and Abercrombie's method was used to estimate the total number of neurons. The test of Kolmogorov-Smirnov with the correction of Lilliefors was used to evaluate the fit of our data to a normal distribution and a regression analysis was done to decide if the variation of our data with age was statistically significant. The results of the present study are relevant only for male animals and the effect of senescence could be different in female vestibular nuclear complex. Aging affects the volume of the superior and lateral vestibular nuclei, as well as the nuclear neuronal diameter of the medial vestibular nucleus, but no significant neuronal loss has been appreciated in vestibular nuclear complex related with age. During the aging process we have observed that the distribution of neurons within the vestibular nuclei of the golden hamster does not show important changes and most of their morphometric parameters do not vary significantly.

2 populations of cells were found in the Deiters' nucleus responsive to direct electrical stimulation of the ipsilateral saccule. Only those Deiters' neurons activated monosynaptically from the saccule could be driven antidromically from the oculomotor nucleus. Such an intracellular study provides strong evidence for a tri-neuronal arc in the sacculo-ocular reflex for vertical eye movements.

A simple, low cost interspike interval analyzer for the analysis of trains of nerve impulses is described. The analyzer is built with readily available integrated circuits and has been used to analyze spike trains in the lateral vestibular nucleus of cats.