-
11. Quantitative assessment of sensorimotor performance affected by motion sickness inducing stimulation
- Hong Kong University Press, HKU
- Chapter
- Additional Information
Basic and Applied Aspects ofVestibular Function J.C. Hwang, N.G. Daunton and V.I. Wilson (Eds.)© Hong Kong University Press, Hong Kong, 1988 QUANTITATIVE ASSESSMENT OF SENSORIMOTOR PERFORMANCE AFFECTED BY MOTION SICKNESS INDUCING STIMULATION J.C. Hwang, P.W.F. Poon and N.Y.S. Tan Department ofPhysiology, Faculty ofMedicine, University ofHong Kong, Sassoon Road, Hong Kong. Abstract Sensorimotor performance of consicous cats was studied by analysing the head orienting response (HOR) to a 70 dB SPL sound presented suddenly in an azimuthal plane. The same animals were then subjected to sinusoidal vertical accelerations for 30 minutes. The onset latency, end latency and the end direction of HOR were analysed within one minute after exposure to the vestibular perturbance which elicited various degrees of motion sickness. Results indicate that after exposure to this mode of motion sicknessinducing (MSI) stimulation, both the onset latency and end latency of head movement were prolonged. The accuracy ofend direction was adversely affected and the velocity of the orienting response was slowed down. Without MSI stimulation, comparable mean values of the affected parameters could be obtained when the acoustic signal was attenuated to 60 dB. Apparently, the unique effect of vestibular challenge was to increase the variance of these paramenters. No correlation was found between the severity of performance impairment and the Suri motion-sickness scores. The HOR is considered to be a useful means of assessing motion sickness and could well be used to defme motion sickness in terms of sensorimotor modifications. Introduction Motion sickness is commonly defined in terms of autonomic signs and symptoms such as pallor, cold sweating and vomiting. The act of vomiting is often considered as the most direct and reliable indicator of motion sickness in both human subjects and experimental animals (Borison, 1983). Keywords: motion sickness, vestibular system, sensorimotor performance, head orienting response, auditory stimuli, cat 100 Hwang etal. On the other hand, drowsiness and mental depression have also been regarded as cardinal symptoms. Graybiel and Knepton (1976) described a symptom-complex centering around drowsiness, the 'sopite complex', based primarily on sensations and reports of the experimental subject. Thus, motion sickness signs and symptoms have been divided largely into 'gut syndrome' and 'head syndrome' (Graybiel et al.• 1968; Thornton et al., 1987). Both of these are difficult to quantify objectively. In 1964, McCabe and Gillingham showed that cats become sick when subjected to vertical accelerations of appropriate sinusoidal wave forms. Since then Suri et al. (1979) have developed a symptom rating scale for evaluating the severity of motion sickness in cats based on manifestations such as salivation, urination and retching. We were interested in studying a sensorimotor performance which could be accurately and quantitatively evaluated in an experimental animal with or without motion sicknessinducing stimuli (MSI). Such studies may shed light on the basic mechanisms or neural substrates implicated in motion sickness. It is well known that both human subjects and many animals show a series of audiomotor responses to a suddenly presented sound, including orientation of the head towards the source of this sound. For such orienting or localizing responses movement trajectories, onset latency, end latency and end direction can all be accurately recorded with the use of a closed circuit television system (CCTV) and analysed frame by frame (pang et al., 1984). The study of the head orienting response (HOR) towards a target is of interest in vestibular physiology for at least three reasons: 1. It implicates the vestibular reflexes. 2. It involves midbrain and cortical structures (Thompson and Masterson, 1978). 3. It is well documented that head movements aggravate symptoms of space or motion sickness (Matsnev et al., 1983; Lackner and Graybiel, 1987). This paper describes an approach to the quantitative assessment of motion sickness in terms of modifications of sensorimotor performance, i.e. the head orienting response. The response involves a motor act more complex than reflexes, such as the vestibulo-ocular reflex, optokinetic reflex, or H-reflex. It also involves some aspects of central neural processing, since the superior colliculus and cortex are known to be involved in localization of sensory stimuli. Yet, the head orienting response, unlike some other types of sensorimotor performance, can be measured without subjective report (cf. Ross et al.• 1987). Methods Adult, conscious cats of either sex were first tested for their orienting response to a concealed sound source 60-70 dB SPL (500 ms train of five tone pips at 3.5 kHz; rise/fall time: 3 ms; plateau: 64 ms; interpip interval: 30 ms) directed some...