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Biomedical subjects

B Mapperson

Publications and source records attributed to B Mapperson.

7 recordsLinked to original sources
PubMed1997

Dissociation of visual and spatial processing in working memory.

Although models of working memory originally included visuo-spatial memory as an undifferentiated component, recent work indicates that spatial location is separable from other visual characteristics. The evidence which is derived from interference, however, typically requires the division of conscious attention between primary and interference tasks. In the present experiments the differential effects of an unattended flickering surround upon serial recall of a central stimulus presentation were investigated. Colour changes in the surround created more interference than achromatic flicker when the task was to report either the colours or the patterns presented in the target. When the locations of the targets were required, however, the situation was reversed and the achromatic flicker created more interference than did the colour flicker. It is suggested that this double dissociation of identification and location is best understood in terms of differential involvement of the magnocellular and parvocellular pathways.

Adult↗
PubMed1984

The dependence of monocular rivalry on spatial frequency: some interaction variables.

The effect of spatial frequency upon the rate of monocular rivalry has been investigated on several occasions, with conflicting results. With increases in spatial frequency the rivalry rate has been variously reported as declining monotonically, increasing slightly and briefly before declining sharply, or showing a sharp increase before a sharp decrease. Experiments are reported which show that all three functions may be obtained depending on whether the number of cycles of the gratings is held constant across spatial frequency, or the field size is held constant (and, if the latter, what field size is used). The point at which any high-frequency decline occurs is also shown to increase with increasing luminance. All functions obtained correspond to visual sensitivity functions obtained under comparable conditions.

Dominance, Cerebral↗
PubMed1983

Instability in triangular-wave gratings: a role for perceptual inferences?

Recently it has been reported that a grating with a triangular-wave luminance profile may fluctuate between being perceived veridically , and as a percept which more closely resembles a square wave, and is itself bistable. Several additional percepts which may be experienced are reported. It is also noted that the relative dominance of two of these percepts can be altered by either physically present or inferred cues as to the probable direction of illumination. It is suggested that these observations implicate higher-level processes in this new form of perceptual instability.

Discrimination Learning↗
PubMed1979

The effect of spatial frequency and contrast on visual persistence.

The visual persistence of sinusoidal gratings of varying spatial frequency and contrast was measured. It was found that the persistence of low-contrast gratings was longer than that of high-contrast stimuli for all spatial frequencies investigated. At higher contrast levels of 1 and 4 cycles deg-1 gratings, a tendency for persistence to be independent of contrast was observed. For 12 cycles deg-1 gratings, however, persistence continued to decrease with increasing contrast. These results are compared with recently published data on other temporal responses, and are discussed in terms of the different properties of sustained and transient channels.

Afterimage↗