Biomedical subjects

K Kalfane

Publications and source records attributed to K Kalfane.

4 recordsLinked to original sources

PubMed1999

[From vestibular nystagmus to the transfer function of the vestibulo-ocular reflex].

A new method for the separation of the two phases of the vestibular nystagmus (slow eye velocity and fast eye velocity) is presented. The aim is to calculate the transfer coefficients of the human vestibulo-ocular reflex (VOR). With a combination of thresholds on the eye velocity and the eye acceleration signals, the different phases of fast eye velocity in the vestibular nystagmus can be located with a good accuracy. So this phases which are not of vestibular origin can be eliminated. The dependence of the transfer function and of the coherence function from the values of the thresholds is studied. This study shows that our method is very robust and that the consequence of the systematic errors occurring with the preceding methods, we have used, is a bad estimation of the gain of the VOR. The values of the coherence function we obtained show that the VOR has a linear behaviour within the range of frequencies we studied (0.01-0.5 Hz).

Electronystagmography↗

PubMed1998

Pseudorandom rotational stimuli of the vestibulo-ocular reflex in humans: normal values of the transfer function.

Pseudorandom binary rotatory stimulation is used to study the vestibulo-ocular reflex (VeOR) frequency response (from 0.01 to 0.64 Hz). Fifty-two normal subjects volunteered for this test. The transfer function's gain and phase, and the corresponding coherence function between slow phase eye velocity and head velocity were computed. According to the linearity hypothesis, the results match the sinusoidal stimulation studies. In both cases, the variability of the gain was higher than that of the phase shift. Identification of some parameters of the VeOR's mathematical model were performed, using the experimental results.

Adult↗

PubMed1991

[Vestibular test in Menière's disease].

When it is well known that the electronystagmographic examination cannot diagnose the Meniere's disease, it is very useful to ensure that no other pathology is involved and for the follow up of the patients. The vestibulo-oculogram, on the other hand, suggests the presence of hydrops, according to the mechanical model.

Electronystagmography↗

PubMed1988

[Computer-assisted vestibular tests].

The labyrinth is a sensor of vibration. Therefore, multifrequency vestibular stimulation proves indispensable in obtaining a more accurate study of the VOR. We chose to use a pseudo-random binary sequence, generated on a mini computer. The angular velocity instructions are made up of eight repetitive sequences, the spectrum of energy in which is adapted to the frequency range of VOR. A process eliminating the quick phases, the blinking and other artefacts is applied to the nystagmic response, in order to observe only the slow phase velocity. The velocity of eye and chair are compared and the transfer function of VOR is performed. Gain, phase, coherence function and predominance of the mean slow phase velocity between left and right responses are the four indices which define VOR function. The multifrequency rotatory test is interesting for topographic diagnosis, and makes out three diagnostic ranges: a mechanical peripheral, a neurosensory peripheral and a central one. Two practical measures could help the propagation of this method: a simpler vestibular stimulation in order to suppress the rotatory chair, a simplified method of data processing using a personal computer.

Diagnosis, Computer-Assisted↗