The Implications of Discharge Regularity: My Forty-Year Peek into the Vestibular System

Abstract

The chapter traces my research in the vestibular system starting in the late 1960s when César Fernández and I collaborated in a study of the discharge properties of the mammalian vestibular nerve. In this chapter, I have taken advantage of Arthur Popper and Richard Fay’s invitation to write an account that “might be very personal.” The scientific literature emphasizes the orderly progress of knowledge. But research advances by fits and starts, with crucial clues coming not only from well-thought-out experiments, but also from experiments undertaken for purposes that, in retrospect, might be ill conceived. In this chapter I emphasize those intellectual way stations, both accidental and well conceived, that drove my own research. The theme that dominates the research is the discovery, made in our early studies, that afferents differing in their discharge regularity differ in many other respects as well. Later research showed that results first found in mammals were confirmed in other vertebrate classes. Regular and irregular units differ in their terminal morphology and their neuroepithelial locations. Beginning with studies of galvanic responses in the 1980s and confirmed more recently in intracellular recordings of the subthreshold events leading to spike discharge, the cellular basis of discharge regularity and associated properties are now well understood. Mutual-information calculations imply that regular and irregular units are optimized in the encoding, respectively, of low- and high-frequency head motions.