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Biomedical subjects

W Lovegrove

Publications and source records attributed to W Lovegrove.

At least 19 recordsLinked to original sources
PubMed1998

The effects of visual discomfort and pattern structure on visual search.

Unpleasant somatic and perceptual side effects can be induced when viewing striped repetitive patterns, such as a square wave or a page of text. This sensitivity is greater in participants with higher scores on a scale of visual discomfort. In three experiments the effect that this sensitivity has on performance efficiency in a reading-like visual search task was investigated. In experiments 1 and 2, the 'global' structure of the patterns was manipulated to produce a square-wave, a checkerboard, and a plaid pattern. It was found that the group that suffered severe visual discomfort took significantly longer than other groups to perform the task, with interference greatest with presentation of the square-wave-like pattern. This supports the prediction of greatest distraction of visual attention from the local target elements with presentation of the pattern structure inducing greatest visual discomfort. In experiment 3, the internal pattern components were manipulated and task difficulty reduced. A no-interference and two interference patterns, one with a global characteristic only and the second made up of distracting line elements, containing global and local components were used. The global pattern structure produced interference effects on the visual-search task. All groups performed with the same speed and accuracy on the task involving the no-interference pattern, a finding attributed to reduced task difficulty. McConkie and Zola's model of visual attention was used to explain these results.

Asthenopia↗
PubMed1987

Flicker contrast sensitivity in normal and specifically disabled readers.

Temporal contrast sensitivity for counterphase flicker was determined for specifically disabled and normal readers to investigate whether the two groups differ in the functioning of their transient systems. In experiment 1, temporal contrast sensitivity was measured over a range of temporal frequencies with a spatial frequency of 2 cycles deg-1. Disabled readers were less sensitive than the control subjects at all temporal frequencies. In experiment 2, temporal contrast sensitivity was measured at a temporal frequency of 20 Hz over a range of spatial frequencies. Disabled readers were less sensitive than the controls at all spatial frequencies, with the differences between the groups increasing as spatial frequency increased. Both these findings are interpreted as supporting the hypothesis of a transient-system deficit in the visual systems of disabled readers.

Adolescent↗
PubMed1986

Contrast and phase processing in amblyopia.

Contrast-coding was investigated in amblyopic, fellow non-amblyopic and control eyes. Using a contrast-matching paradigm similar to Georgeson and Sullivan [J. Physiol. 252, 627-656 (1975)], amblyopic eyes were found to have a high frequency contrast-coding deficit not only at threshold but also at suprathreshold levels up to at least 0.45 contrast. The results do not support the claim of Hess and Bradley [Nature 287, 463-464 (1980)] and Hess, Bradley and Piotrowski [Proc. R. Soc. Lond. B217, 309-330 (1983)] that amblyopes have normal or near-to-normal suprathreshold contrast-coding. By taking this contrast-coding deficit into account we demonstrate that previously reported poor phase discrimination [Lawden, Hess and Campbell, Vision Res. 22, 1005-1016 (1982); Pass and Levi, Invest. Ophthal. Visual Sci. 23, 780-786 (1984)] in amblyopia may, in part, reflect a more basic deficit in contrast-coding across spatial frequencies. The possible involvement of contrast processing mechanisms in phase discrimination is discussed.

Adult↗
PubMed1984

The effects of field size and luminance on contrast sensitivity differences between specifically reading disabled and normal children.

Contrast sensitivity functions were measured for normal and specifically disabled readers in experiments which varied either field size or luminance level. The nature of the differences between groups was unaffected by field size, implying that spatial summation in specifically disabled readers is normal. Increasing luminance, however, increased the range over which disabled readers are less sensitive than normal readers. The results are discussed in terms of possible differences in underlying mechanisms.

Animals↗
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↗
PubMed1984

Flicker masking of spatial-frequency-dependent visible persistence and specific reading disability.

The effect of 6 Hz uniform-field flicker masking of visible persistence at a range of spatial frequencies was investigated in 12-year-old children with specific reading disabilities and a control group of average readers. This reduced differences in visible persistence between the two groups. The results suggest that children with specific reading disabilities experience a deficit in their transient system.

Child↗
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↗
PubMed1982

Contrast sensitivity functions and specific reading disability.

Contrast sensitivity functions for normal and specifically disabled readers were measured in two experiments. Each study showed that specifically disabled readers and controls differ in the pattern of relative sensitivity across spatial frequencies. Both studies provide evidence of differences between normal and disabled readers on measures of visual mechanisms fundamental to the reading process.

Child↗
PubMed1980

Visual persistence as a function of spatial frequency and age.

Duration of visual persistance of sine-wave gratings of 1,2,4,8,12, and 16 cycles deg-1 was determined for seven-year-old, ten-year-old, and thirteen-year-old children. It was found that there was a decrease in persistence duration with age but the slope of this function for the different age groups did not change.

Adolescent↗