PubMed Health⌕ Search

Biomedical subjects

M Juhola

Publications and source records attributed to M Juhola.

8 recordsLinked to original sources
PubMed1992

Evaluation of some nonrecursive digital filters for signals of auditory evoked responses.

Auditory brain stem evoked responses are routinely used in audiology and otoneurology. Because recordings include more or less noise, the signals of evoked responses need digital filtering to suppress the noise. Nonrecursive digital filters are often the best since they can be organized to have no phase shift, which is essential in order not to distort sensitive parameters, as latency, in evoked responses. We have studied effects of some nonrecursive digital filters on the latency parameters of evoked responses. It turned out that digital filtering can have considerable influence on latencies, and thus the choice of appropriate filters is crucial.

Evaluation Studies as Topic↗
PubMed1992

On identification of saccades from sinusoidal eye movement signals.

Sinusoidal eye movements and potential saccadic eye movements are examined using the syntactic pattern recognition method presented previously. A few computer tests are presented for the verification of potential saccades from signals of sinusoidal eye movements. The technique was developed and tested with electro-oculographic signals. The verification of saccades consists of three tests: the estimation of average noise peaks in an eye movement signal; an angular velocity threshold; and the comparison between a sinusoidal eye movement signal and the corresponding stimulus signal. The technique is also efficient for noisy signals of eye movements, which were stimulated by both predictive and non-predictive sinusoidal stimulus movements.

Calibration↗
PubMed1991

A syntactic analysis method for sinusoidal tracking eye movements.

A syntactic method for the recognition of sinusoidal eye movements is presented. The method is based on a piecewise transformation of an eye movement signal to strings of a formal language and use of a formal grammar which generates the formal language. Gain and phase parameters of sinusoidal eye movements between a stimulus and its response are computed after the recognition of eye movements and after removing corrective saccades from the transformed signal. The method is used at an otoneurological laboratory.

Diagnosis, Computer-Assisted↗
PubMed1991

Median filtering is appropriate to signals of saccadic eye movements.

In this paper we show nonlinear standard and hybrid median filters are appropriate to the filtering of signals of saccadic eye movements. Although these filters effectively attenuate noise, they do not harm the parameters of saccades, particularly the maximum velocity which is an important indicator of certain diseases and disorders in man. The filters have been tested by simulation as well as actual eye movement signals recorded electro-oculographically and photoelectrically.

Algorithms↗
PubMed1991

Postural control in blinds and in Usher's syndrome.

The postural control mechanisms were evaluated in 10 blinds and in 10 subjects with Usher's syndrome. The results were compared with 27 age matched healthy volunteers. In visual conditions the subjects with Usher's syndrome performed worse, but in nonvisual condition they performed equally well as the controls. The results were the same irrespective of whether the tests were performed on a rigid surface or foam rubber covered surface. The blinds and controls performed equally well on the bare surface, but the blinds performed significantly better on the foam rubber covered surface. The results indicate that in subjects with Usher's syndrome the vestibulo-cochlear degeneration is well compensated but the postural stability aggravated due to retinal degeneration. Blind subjects have a better postural control than their seeing referents, but the difference is only evident in situations in which the postural control is hampered by surface perturbation.

Adolescent↗
PubMed1991

Effects of digital low pass filtering on the parameters of nystagmus eye movements.

We examined how lowpass filtering has an influence on nystagmus parameters: durations, amplitudes, and mean velocities of its slow and fast phases. We experimented with two types of common linear digital filters by using both nonrecursive and recursive filters, and with two types of nonlinear digital filters by using so-called standard median and hybrid median filters. We concluded that 70 Hz as strict cutoff frequency is high enough not to cause errors in the nystagmus parameters when information content in nystagmus signals is filtered above that cutoff frequency with linear filters. Using nonlinear filters good window lengths of filtering are equal to or less than about nine samples for a sampling frequency of 400 Hz which we applied.

Analog-Digital Conversion↗
PubMed1991

A microcomputer system for assessment of peripheral blood flow. An example of nasal blood flow.

We have designed and implemented a microcomputer system for studying the effect of various mediator substances on the nasal blood flow. The system uses an IBM PC/AT microcomputer, which is connected with a Laser Doppler Flowmeter (LDF) and an iontophoretic drug application system. The LDF measures flux from the tissue that in the example is the inferior nasal turbinate. The flux is converted to digital form by an analog-digital converter of 12 bits. The program is implemented in the Pascal language. In the analysis, a flux level, amplitude, rise time and decay time of the pulse wave are determined. The effect of drugs on the flux can be studied by applying them iontophoretically. In the program the length and number of the drug application periods as well as the recording period are user-driven. In the nasal blood flow iontophoretically administered adrenaline reduced significantly the flux parameters and histamine canceled this effect. Tachyphylalaxis was a frequent observation in repeated measurements. The system can be used to evaluate the role of different transmitters in the etiology of chronic rhinitis.

Adult↗