Search PubMed⌕ Search

Biomedical subjects

S Magnussen

Publications and source records attributed to S Magnussen.

52 records · Page 3Linked to original sources
PubMed1981

Photopic and scotopic flicker sensitivity of a rod monochromat.

The sensitivity to sine-wave flicker of a rod monochromat was compared with that of a normal subject at photopic and scotopic levels of luminance. The sensitivity of the rod monochromat in the low-frequency region (below 3 Hz at scotopic levels and below 12 to 14 Hz at photopic levels) was found to be superior to that of the control. This superiority was most pronounced at photopic levels, where the rod monochromat frequently showed a two-peak sensitivity curve.

Adult↗
PubMed1980

Adapting to two orientations: disinhibition in a visual aftereffect.

The tilt aftereffect of adapating to two different orientations simultaneously is weaker than the aftereffect of adapting to the more effective of the two orientations alone. This finding is consistent with explanations of orientational after-effects in terms of lateral inhibition between cortical orientation detectors, but not with explanations in terms of neural "fatigue" from excitation.

Adaptation, Physiological↗
PubMed1980

Rod monochromat sensitivity to sine wave flicker at luminances saturating the rods.

The flicker sensitivity (temporal modulation transfer function) of a rod monochromat was measured at luminances in the range of 8 to 782 scotopic td. The results could be fitted by a single curve shifted vertically, suggesting that rod saturation is independent of the temporal properties of the stimulus. This is consistent with the hypothesis that rod saturation is a pure receptor phenomenon.

Adult↗
PubMed1979

A test for contrast-polarity selectivity in the tilt aftereffect.

The tilt aftereffect (TAE) was studied with adapting and test stimuli consisting of black or white bars (experiment 1), and of luminance edges (experiment 2). Both experiments failed to demonstrate selectivity of the TAE to the polarity of luminance contrast.

Adaptation, Ocular↗
PubMed1975

Temporal frequency characteristics of spatial interaction in human vision.

In psychophyscial experiments the bright-dark contrast effects observed in a steady test-field were measured as a function of the temporal frequency of an inducing-field modulated symmetrically about the test-field luminance. The frequency-contrast functions obtained from these measurements were interpreted as reflecting the temporal frequency characteristics of the lateral pathways within the B and D systems (the on-center and off-center neurons) in human vision. Psychophysical evidence is further presented that the lateral neural pathways have lower temporal cut-off frequencies than the "straight-through" pathways. The results are discussed in terms of the frequency characteristics of the center and surround of the receptive fields of on-center and off-center neurons. It is doubtful, however, whether the psychophysical results can be fully explained by the properties of the single-unit receptive field mechanisms.

Humans↗