Table of contents

The following subjects are considered in this review: anatomy and functional characteristics of the vestibular apparatus (including the semicircular canals; dynamics of otolith behaviour); the vestibulo-ocular reflex mechanisms (including; neurophysiology; dynamic response of the canal-occular reflex); the vestibulo-spinal reflex mechanisms (including: neurophysiology; the nature of vestibular myoneural control).

A method is described which will allow a number of small-angle stimulus visual evoked responses to be measured simultaneously, thus providing the practical possibility for mapping the responses from different retinal sites for patients suspected of patchy optic nerve demyelination. The technique consists of stimulating four different retinal locations concurrently with small emitting diodes (LEDS) and time-locking a computer data buffer to each stimulus. Tests showed that if all four LEDS were flashed randomly, the evoked response to any given LED was as though this LED was the only stimulus present.

Regular amplitude variations have frequently been observed in the slow-wave electrical signals recorded from the human duodenum. The amplitude variations could be the result of amplitude modulation of a single frequency signal, or the result of the summation of two signals at different frequencies. Signals were recorded from the serosal surface of the human duodenum. Frequency analysis of the signals, using both Fast Fourier Transform and Auto-Regressive Modelling techniques, shows that the predominant cause of the amplitude variations is the summation of two signals. The implications that the results have for models of the electrical activity of the human duodenum are discussed, and it is shown that an estimate of the degree of electrical coupling between cells can be inferred.

Laboratory and clinical tests were conducted to determine whether any one type of surgical diathermy electrode was technically superior to another. In order to do this it was necessary to develop a model of the method of working of indifferent electrodes and the electrode-tissue interface for a range of frequencies. Performances were compared by measuring the impedance between the electrode under test and the body, and possible variations of impedance with diathermy load current, duration of study, and the physiological variables of the patient were considered. A correlation between electrode area and performance was observed. The consequences of using dry or gelled electrodes and of re-using electrodes were also considered, and the importance of consistent performance was noted. Possible effects of current developments in electrode design are discussed, and a technical assessment of each electrode used is included.

Using the maximum frequency envelope obtained from the sonogram of the Doppler shifted frequencies a mathematical feature extraction technique has been used to provide an objective identification of the significant waveform features. The technique described is that of principal component factor analysis. The data used were taken from an eighteen month programme in which techniques based on the use of directional Doppler ultrasound were evaluated in comparison with direct percutaneous carotid angiography and arch aortography. A tracing of the vessel outlined based on the anterior-posterior view of the angiogram was used to classify each vessel segment studied. Two groups only are considered in this initial study, a normal group (25 vessel segments) and a stenosis group (18 vessel segments). The principal component analysis technique was shown to provide a superior classification of the vessel segments when compared with the more familiar A/B ratio. Nevertheless the principal diagnostic feature is shown to be the A/B ratio.

A system is described which enables recordings from metatarsal heads and the toe to be made simultaneously while the subject is walking bare-foot, and with a variety of footware to test their effect in modifying and redistributing the shear forces. The system involves placing a centre-tapped magneto resistor in a bridge configuration, with a magnet placed centrally above it. By applying an elastic self-centring force to the magnet, the degree of movement is made proportional to the shearing force applied.

Measurements were made on 10 children who had finger tip amputations. They were made at 1 to 7 day intervals until 2 successive zero readings were obtained. The injured finger was immersed in physiologically normal saline for approximately ²/₃ of its length, and the probe was moved across the surface of the wound. The currents recorded a remarkable similarity to those obtained by Borgens et al. (1977) on salamanders, rising to a peak average current density of 22 mu A cm^-2 after an average of 8 days.