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Biomedical subjects

G K Bijl

Publications and source records attributed to G K Bijl.

5 recordsLinked to original sources
PubMed1986

Minimum procedures for visual electrodiagnostic testing.

A set of procedures for the electroretinogram, electrooculogram, and pattern and luminance visual evoked cortical potentials was defined by representatives from all Dutch University Eye Clinics in order to promote standardization of procedures for routine diagnostic testing. The procedures have been selected to obtain an answer to most electrodiagnostic questions of frequent occurrence with a minimum of equipment and examination time. An individual examiner may add other procedures to the proposed program to extend and diagnostic possibilities.

Electrodiagnosis↗
PubMed1985

Neural conduction time and steady-state evoked potentials.

Signal processing in neural networks will inevitably include delays due to the finite conduction velocity of the neurones and their interconnections. Diamond proposed a method for finding these delays in the case of (visual) steady-state responses. Alignment of response features, when represented in a time domain plot, would, allegedly, yield the delay. We show that filter action, by introducing frequency-dependent phase shifts, is bound to distort the time domain plot considerably, thereby aligning the response features in such a way that a wrong value for the delay is found. This makes that analysis method of doubtful significance.

Evoked Potentials, Visual↗
PubMed1984

The visual electrically evoked potential (VEEP): steady-state responses.

The steady-state response of the visual system may provide us with complementary information about the system, when compared with transient EPs (Regan 1977). With our setup we could record such steady-state responses to electrical stimulation of the visual system for frequencies higher than about 20 Hz. We found comparatively little decline in amplitude with increasing frequency. We conclude that not much filtering is done by the system under study. The absence of pseudoflash related potentials substantiates this conclusion. Therefore it is likely that there is a constant latency for the frequencies under consideration. We also found that after some 10 cycles of the stimulating alternating current the steady-state seemed to be established. This indicates that by introducing silent periods after a limited number of stimulus cycles, recording during these periods and applying the analysis method of Diamond, the latency of the visual electrically evoked steady-state response can be determined.

Electroencephalography↗
PubMed1980

Recording the visual electrically evoked potential (VEEP).

A system for recording cortical responses to electrical stimulation of the visual system (electrical phosphene) is described. The system included a rotatable electrode pair for stimulation, with which artifacts caused by the relatively large stimulating currents could be reduced to suitable levels. Optical isolation on both the stimulating and recording sides of the equipment provided safety for the subject and made precise application of the stimulating current possible.

Electric Stimulation↗