An autoregressive (AR) model applied to eye tremor movement, clinical application in schizophrenia.

In this study, we use a parametric autoregressive (AR) model to obtain descriptive features of eye tremor movement during fixation. The interest consists in analyzing model parameters to determine the information that can be used as indicator of specific pathophysiology underlying cerebral dysfunction in schizophrenic subjects. We have tested healthy volunteers and schizophrenic medicated and unmedicated patients, to evaluate the treatment effect. The AR model is applied to the eye tremor movement extracted from the eye position signal recorded when subjects are fixating a stationary target. The analysis of the model parameters shows distinct classes, corresponding to a population of subjects among the three kinds included in this study.

Performance of a computer system for recording and analysing eye gaze position using an infrared light device.

Our aim is to develop a computer system in order to study the visual scanning and eye fixation during exploration of image. The system uses an infrared device to detect the horizontal and vertical eye movements. In this paper, our interest is concentrated mainly on the calibration procedure. More precisely, on the correction of the nonlinearity in the oculomotor for individual subject's eyes. An adaptive calibration algorithm is developed. The algorithm uses a polynomial model and the optimal correction is obtained by using a mean square error criterion. The paper presents also a method to correct head movements. Experiments show that the proposed approach is fast and accurate for the study of visual perception and recognition processes.

Computer-assisted ABR interpretation using the automatic construction of the latency-intensity curve.

In this paper, we present a new computerised technique for the automatic construction of the latency intensity curve (LI curve). We take a pattern recognition approach determined by a priori information. We use knowledge gained from the audiogram and from physiological considerations. Therefore, we consider all recordings at different intensities as well as results from the extraction of a single auditory brainstem response (ABR) at a given stimulus intensity. We tested our method successfully: it allows us to prevent misrecognition errors in response detection or in latency measurements. Automatic recognition of the waves and recognition by the ear, nose and throat (ENT) specialist coincided in at least 90 per cent of cases. For wave V, the average deviation between the response thresholds given by our automatic recognition algorithm and those given by the ENT specialist was 5 dB, and the average deviation of the latencies was 0.05 ms.

Large band spectral analysis and harmful risks of dental turbines.

Previous studies have attributed harmful effects to ultrasonic frequencies and recently many have addressed the problem of early deafness among dentists caused by high-speed air turbines. In this study, we measured the spectra of the sounds generated by high-speed air turbines, ranging from audible to ultrasonic frequencies (0-70 kHz). The hypothesis advanced is that the ultrasound spectrum of high-speed air turbines reaches amplitudes that may be noxious. We performed continuous analyses of the spectra of three bands of turbines (n = 17). Measurements of frontal incidence were made using a Bruel & Kjaer microphone and sonometer. For spectral analysis we used the autoregressive parametric method. Using Akaike's criteria the model weights were fixed at 12. The method used in the present work led to an accuracy in the results of 10(-2) kHz within the same brand of turbine. Results show, in terms of frequencies, the presence of four main peaks: 5.6 kHz +/- 0.73 in the audible range, and 20.1 kHz +/- 2.16, 35.7 kHz +/- 2.56 and 46.5 kHz +/- 0.71 in the ultrasonic range. In a normalized spectrum, the amplitude of the ultrasonic component reaches 115 dBspl for 46.5 kHz and is 76% greater than that of the audible component. Such values, both in terms of frequencies and amplitude, reach levels which may provoke short- or long-term negative physiological disturbances and hearing-damage risk. Further research should be directed to determine to what extent they might induce noxious effects for the dental team.