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S L Buck

Publications and source records attributed to S L Buck.

5 recordsLinked to original sources
PubMed1991

Test-additivity experiments: different procedures, different results.

Test-additivity experiments reveal the combination rules for separate contributions to visual detection. The measured degree of additivity and the shape and symmetry of the additivity function have been used to design or evaluate theories about the underlying visual pathways. However, all these characteristics can be distorted if measured by means of a variable-proportion procedure, in which the amount of one primary is held constant while the amount of the other is varied in order to measure threshold. A fixed-proportion procedure, in which the amounts of each primary are varied together in constant proportion in order to measure threshold, is preferable. These differences in results were found by using the method of adjustment but may also apply to the method of limits and other psychophysical procedures.

Color Perception↗
PubMed1987

Rod-cone interaction in monocular but not binocular pathways.

Photopic background stimulation elevates scotopic increment thresholds (rod-cone interaction) at moderate background levels when both test and concentric disk-background stimuli enter the same eye (monocular condition) but not when they enter different eyes (dichoptic condition). Only when background levels are made extremely high is there any measurable dichoptic interaction, and this interaction does not resemble that observed monocularly. Rod-cone interaction, as usually studied, is a property of monocular pathways in human vision.

Cell Communication↗
PubMed1985

Determinants of the spatial properties of cone-rod interaction.

Photopic increment thresholds can be elevated by 0.2-1.9 log units, depending on the diameter of a concentric scotopic background. This cone-rod interaction displays spatial properties that resemble the spatial sensitization (Westheimer effect) observed in the isolated scotopic and photopic systems. This raises the possibility that the spatial properties of the interaction are determined by the same mechanisms or pathways that determine the spatial properties of either scotopic or photopic vision. When annulus backgrounds are used, the spatial properties of interaction match those of the scotopic system but not the photopic system. When disk backgrounds are used, the spatial properties of interaction match those of neither photopic nor scotopic systems. Thus, under some conditions, the scotopic visual system alone is sufficient to determine the spatial properties of cone-rod interaction. Under other conditions, additional complications arise. The results are discussed in terms of the center-surround model that has previously been applied to cone-rod interaction.

Adaptation, Ocular↗
PubMed1985

Cone-rod interaction over time and space.

Scotopic background stimulation can elevate photopic increment thresholds by more than 2 log units. This cone-rod interaction is greatest on small backgrounds (less than 1 degree diameter), but is found consistently on large backgrounds as well. Interaction develops and disappears quickly as backgrounds are turned on or off, respectively. The onset, and in some cases the offset, of a background stimulus can produce an additional, transitory interaction that augments the interaction that is maintained by continued presentation of the same background. The majority of the present findings lend support to a simple center-surround model of cone-rod interaction: nearby scotopic excitation raises photopic thresholds and more distant scotopic stimulation primarily antagonizes this interaction.

Cell Communication↗