Biomedical subjects

Trevor J Hine

Publications and source records attributed to Trevor J Hine.

6 recordsLinked to original sources

PubMed2006

Attention 'capture' by the flash-lag flash.

We report data from eight participants who made alignment judgements between a moving object and a stationary, continuously visible 'landmark'. A reversing object had to overshoot the landmark by a significant amount in order to appear to reverse aligned with it. In addition, an adjacent flash irrelevant to the judgment task reliably increased this illusory 'foreshortening'. This and other results are most simply explained by a model in which the flash causes attentional capture, complemented by processes of temporal integration, or backward inhibition, and object representation. A flash used to probe the perception of a moving object's position disrupts that very perception.

Adolescent↗

PubMed2006

Reflexive optokinetic nystagmus in younger and older observers under photopic and mesopic viewing conditions.

PURPOSE: To investigate the effect of age on optokinetic nystagmus (OKN) in response to stimuli designed to preferentially stimulate the M-pathway. METHOD: OKN was recorded in 10 younger (32.3 +/- 5.98 years) and 10 older (65.6 +/- 6.53) subjects with normal vision. Vertical gratings of 0.43 or 1.08 cpd drifting at 5 degrees /s or 20 degrees /s and presented at either 8% or 80% contrast were displayed on a large screen as full-field stimulation, central stimulation within a central Gaussian-blurred window of 15 degrees diameter, or peripheral stimulation outside this window. All conditions apart from the high-contrast condition were presented in a random order at two light levels, mesopic (1.8 cdm(-2)) and photopic (71.5 cdm(-2)). RESULTS: Partial-field data indicated that central stimulation, mesopic light levels, and lower temporal frequency each significantly increased slow-phase velocity (SPV). Although there was no overall difference between groups for partial-field stimulation, full-field stimulation, or low-contrast stimulation, a change in illumination revealed a significant interaction with age: there was a larger decrease in SPV going from photopic to mesopic conditions for the older group than the younger group, especially for higher temporal frequency stimulation. CONCLUSIONS: OKN becomes reflexive in conditions conducive to M-pathway stimulation, and this rOKN response is significantly diminished in older healthy adults than in younger healthy adults, indicative of decreased M-pathway sensitivity.

Adult↗

PubMed2004

Events before the flash Do influence the flash-lag magnitude.

The flash-lag effect occurs when a flash abreast of a smoothly moving object is perceived to spatially lag the moving object. The postdiction accounts of this effect assume either that the flash "resets" motion detectors [Science 287 (2000) 2036], or that position information is not computed for moving objects until it is needed [Trends in the Neurosciences 25 (2002) 293], the latter view having also been proposed by Brenner and Smeets [Vision Research 40 (2000) 1645]. According to these accounts, events occurring before the flash should not change the magnitude of the flash-lag effect. In our experiment, pre-exposure of the moving object as a stationary stimulus, for as little as 50 ms before the flash occurred, significantly reduced the flash-lag effect.

Cues↗

PubMed2003

Is there an auditory-visual flash-lag effect?

A flash adjacent to the path of a moving object appears behind the moving object: the 'flash-lag effect'. We sought to test the flash-lag effect with a 'click' instead of a flash: a white triangle horizontally traversed the screen at a constant 12 degrees /s passing through a fixation cross in the presence of a quiet click. The subject judged whether the click occurred before or after the triangle passed through the cross. To be perceived as co-instantaneous events, the click had to be presented 127 ms after the moving triangle reached the cross (a 'click-lead' effect, providing falsification of predictive accounts of the flash-lag effect), as opposed to a standard flash-lag effect condition where a flashed triangle replaced the click and had to appear 60 ms before the moving triangle to appear aligned. With the auditory versus visual processing speed advantage considered, the neural time required to calculate a moving object's position is constant, independent of the modality of the flag.

Acoustic Stimulation↗

PubMed2002

The flash-lag effect and equiluminance.

An object briefly flashed adjacent to the path of another moving object appears to spatially lag the moving object in the direction of its motion: the 'flash-lag effect'. A simple differential lag model account of this effect suggests that it occurs because the moving object activates motion detectors in the faster magnocellular pathway, whereas the flashed object does not. This model was tested by reducing M-pathway involvement using isoluminant stimuli. All four participants, who were university undergraduate students, were exposed to eight conditions, involving all possible combinations of moving and flashing objects coloured either white or green, shown against either a grey or a black background. Green objects were equiluminant with the grey background. The magnitude of the flash-lag effect was found using the method of constant stimuli. No reliable support was found for the hypothesis that equiluminance of the moving object reduces the flash-lag effect. Instead an interaction was found where there was an effect of equiluminance on the flash, but only when the moving object was not equiluminant. Such data is problematic for this and other simple differential lag models of the flash-lag effect.

Adolescent↗

PubMed2002

Ratio model serves suprathreshold color--luminance discrimination.

We extended earlier results [J. Opt. Soc. Am. A 16, 2625 (1999)] to examine how the responses of the three postreceptoral mechanisms are combined to subserve discrimination of suprathreshold stimuli. Test thresholds were obtained in the presence of suprathreshold pedestals selected in different quadrants of the red-green/luminance and blue-yellow/luminance planes of cardinal color space. We showed that (1) test threshold was directly proportional to pedestal contrast for pedestal contrasts exceeding five times pedestal contrast threshold, and (2) there were exceptions to this proportionality, notably when the test and pedestal directions were fixed in the cardinal directions. Results support a ratio model of suprathreshold color-luminance discrimination, in which discrimination depends on a ratio of outputs of the postreceptoral mechanisms. We also observed that when test threshold was measured as a function of test color-space direction, masking by the achromatic component of the pedestal was less than that by the chromatic component. In addition, masking by a dark (negative luminance component) pedestal was lower than masking by a light (positive luminance) pedestal of a similar contrast. Our results demonstrated that (1) there is no fundamental difference between discrimination in the isoluminant and in the two chromoluminant cardinal planes, (2) there exists the possibility that discrimination in cardinal directions differs from that in noncardinal (intermediate) directions, and (3) suprathreshold discrimination of luminance differences may be more sensitive than that of chromatic differences for a given suprathreshold pedestal.

Adult↗