Biomedical subjects

L Schlykowa

Publications and source records attributed to L Schlykowa.

4 recordsLinked to original sources

PubMed1990

The human motion VEP as a function of size and eccentricity of the stimulation field.

A 'motion onset VEP' was elicited by the onset of a pattern drift. The amplitude of the most distinct wave (AN200) was determined on the following stimulation conditions: eccentricity, 0 to 23 deg; velocity. 1.5 to 16 deg/s; spatial frequency, 0.19 to 2.1 c/deg; and stimulation field size, 0.2 to 160 deg2, AN200 remained constant at any degree of eccentricity if stimulation field size, velocity, and spatial frequency were M-scaled according to Rovamo-Virsu's M-equations. AN200 decreased as a function of eccentricity if field size and velocity were kept constant (spatial frequency had minimal effect). The size of the cortical representation field (Sc) in this case varied with change in eccentricity (stimulation field size constant). In another experiment, it varied by change in stimulation field size (eccentricity constant). For both conditions, AN200 was proportional to log Sc.

Electrodes↗

PubMed1988

[Topography of the movement visual evoked potential in the human].

The amplitudes of the motion VEP waves P100, N200 and P300 were investigated on 12 subjects at six electrode positions (2.5, 5, 7.5 and 10 cm above the inion and 5 cm bilaterally from the 2.5 cm midline point). The evaluation was performed on the basis of in general 45 (for P100 32) averaged potentials per subject. Each averaged potential was obtained from 40 single potentials. P100: The amplitudes were nearly equal at all electrodes. N200: The greatest amplitudes could be found at the lateral electrodes. The amplitudes decreased in the midline in occipito-frontal direction reaching the lowest value at the electrode most frontally situated. P300: This wave had its greatest amplitude at the most frontal lead position. The amplitude decreased systematically in occipital direction. The differences in the position of the amplitude maxima and in the topographical distribution of the remaining amplitude values suggest different generator structures of the waves N200 and P300.

Brain Mapping↗

PubMed1983

[Visual evoked potentials in pattern motion].

Our intention was to obtain a visual evoked potential (VEP) consisting only of a movement-related component for the purpose of further investigations of movement detection. This was attempted by selection of appropriate stimulus conditions. Evoked by initial movement a VEP with five typical waves was observed at the human occipital scalp. The N2-wave with a peak latency of 180-200 ms was most prominent. Following results were yielded in the experiments carried out: 1. Adaptation to a pattern movement: The amplitude of N2 and P1 is significantly reduced (Fig. 4). 2. Relation between amplitude and velocity: The experimental data could be approximated by a power function with an exponent of m = 0.3 for N2 and lower m for later waves (Fig. 5). 3. Pattern variation (grating, checkerboard, zig-zag) had no influence on N2 but on P1 and possibly also on later waves (Fig. 6). These results suggest that the wave N2 is movement-related under our experimental conditions. A pattern-related component may additionally be assumed in wave P2. Components, evoked by further reasons, may be included in the waves following N2. Their specification demands supplementary experiments.

Evoked Potentials, Visual↗

PubMed1983

[Effect of an alternating magnetic field on development and extinction of conditioned responses in rats].

This paper deals with the problem whether there is an effect of extremely low frequency electromagnetic fields on simple learning processes. The conditioned reaction upon an electromagnetic fields on simple learning processes. The conditioned reaction upon an acoustic stimulus (1000 Hz) reinforced by an electric painful stimulus was used. During the conditioning and extinction process 28 adult albino rats were put in a 10 Hz, 0,3 G magnetic field. Their learning and extinction behaviour was compared with that of a control group of 28 rats trained under normal laboratory conditions. The extinction schedule differs significantly between the experimental and control group: The extinction develops faster in the experimental group (p less than 0.05). In connection with the results of other authors our findings are discussed as a general amount of adaptability by the influence of the 10 Hz field.

Animals↗