The human magno and parvo systems and selective impairments of their functions.

The magno and parvo systems, consisting of large and small cells respectively and showing the greatest differences in temporospatial characteristics, are two of the most interesting channels in the organization of retinotopic input pathways of the human visual system. We tested the hypothesis that selective lesions of fibers of a specified diameter occurring in pathology of the conducting pathways, i.e.

[Human magno- and parvo-systems and selective disruptions in their function].

In psychophysical and electrophysiological investigations, we tested the hypothesis that in patients with multiple sclerosis at its early stage either phasic cells of the magnocellular pathway or tonic cells of the parvocellular pathway are disturbed. Healthy humans and patients with early stage of diseases have a contrast spatial-frequency sensitivity measure. The decrease in sensitivity at low, medium and high spatial frequency indicates changes in parvo- and magno-system activity.

[Visual potentials in humans with multiple sclerosis evoked by checkboard pattern of different contrast with additional noise].

A hypothesis is advanced of an effect of internal noise upon signal conduction along visual nerve in an early stage of multiple sclerosis. Visual evoked potentials in response to chess patterns against a homogeneous background and against a noise background were studied in healthy subjects and in patients with multiple sclerosis. Contrast between internal noise in the patients was found to be twice as great as in healthy subjects.