Basic and Applied Aspects of Vestibular Function

Foreword

FOREWORD It is a singular honour to have been invited to write a foreword to the proceedings of this fine symposium on Basic and Applied Aspects of Vestibular Function. In view of my personal commitment to the field it was particularly unfortunate that personal constraints prevented my joining the close knit family of friends and colleagues gathered together for the Hong Kong meeting. In overview, it is gratifying indeed to find such a wide variety of individuals and experimental approaches represented in the scientific content of the program. Not long ago, the Vestibular System was at risk of being relegated to the position of a vestigial relic, approaching redundancy in the phylogenetic march oftime. Indeed, even today the textbook treatment of vestibular sensation too often occupies a mere page or two of outdated notes, covertly embedded under chapterheadings such as 'motorcontrol' or 'visualand oculomotor functions'. On the contrary, as is well evidenced in this and allied contemporary scientific meetings, the vestibular sensory system ranks up front as one of the primary special senses of the nervous system. It is in fact a peculiar twist of fate that this tendency for historical understatement of 'vestibulation' has indirectly played a significant part in forwarding the progress of neuroscience generally. Thus the very variety ofroles in which Vestibular Function has been found to playa part has engendered broad new concepts of central integrative processes, building on earlier'Sherringtonian' foundations ofintegrative action in the nervous system. We find, for example, the evolving model ofa 'symbiotic' central neural network which systematically integrates the separate (but individually incomplete) vestibular and visual information aboutheadmovement. As aresult there emerges an entirely new, mathematically definable, central neural signal, which far better reflects the real physical event of head rotation than eitherofthe separateperipheral sensory inputs. We may hopethat this particular model, discovered within the vestibular-visual-oculomotor system, will prove seminal in the search for analogous symbiotic central integrative processes in other combinations of sensory-motor neural networks. Again, through studies ofadaptive plasticity in the vestibulo-ocular reflex, our attention has been drawn to an apparently ubiquitous potential for auto-adaptive control ofboth reflex and cognitive components of sensory-motor systems generally. Also, through vestibular research, we are broaching important components ofpuzzling problems raisedby the current phase of Ventures into Space. And last, but certainly not least, we find that recent advances in clinical 'vestibular' function testing are yielding powerful new insights into the etiology of neurological pathology far removed from the primary sources of vestibular information. Another feature ofgeneral import which stands out in these proceedings is the breaking down of traditional dividing lines which separate 'Basic' from 'Applied' approaches to research. Too often the former tends to imply 'things profound and fundamental', having little bearing on natural behaviour; whilst the latter tends to conjure up less erudite x Foreword impressions of behavioural studies on the intact organism. But to associate different value judgements with the 'bottom-up' and 'top down' approaches to research is quite unrealistic and indeed inhibitory to progress. Consider for example the penetrating basic insights uncovered by the non-invasive 'behavioural' studies of towering historical figures such as Helmholtz and Mach; or on the other hand the profound behaviourally significant implications of basic studies in, for example, neurochemistry or molecular biology. In the 'basic' sections of these proceedings we find amongst many other interesting topics, important new knowledge on the relevant roles of regularly and irregularly firing afferents in peripheral vestibular pathways. There is also a further unfolding of the intricate central neuralnetworks linking slow andquickphasecomponentsofvestibularly inducedeye movements. Today this kind of detailed elucidation of neuronal information processing is already throwing new light on clinical anomalies which disorganize internal components of intact sensory-motor systems. Intriguing also is the frequency of articles focussed on neurochemical aspects ofcentral vestibular pathways. Here too we find a lead into practical problems; for example, the etiology and treatment of motion sickness and the rationale for behaviourally induced clinical rehabilitation. Amongst the many interesting clinical contributions we read of the startling finding that labyrinthine defective children can apparently develop 'normal' vestibular nystagmus in the proven absence ofa peripheral canal system. How and where does the functional substitution operate? Here we see'applied' clinicalfindings calling for basic studies designed to elucidate further this phenomenal potential for sensory substitution. Other articles in this section continue to expand the armamentarium of the neurotologist for clinical vestibular function testing a field which is certainly ripe for entraining modem scientific advances in that field. These...