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Biomedical subjects

R H Day

Publications and source records attributed to R H Day.

At least 19 recordsLinked to original sources
PubMed2000

Cautery-assisted palatal stiffening operation.

Outpatient surgical therapy of habitual snoring and mild obstructive sleep apnea has evolved significantly in recent years. We introduce the cautery-assisted palatal stiffening operation (CAPSO) and detail its important advantages over uvulopalatopharyngoplasty, laser-assisted uvulopalatoplasty, and palatal radiofrequency ablation. CAPSO is critically analyzed with regard to extent of surgery, need for repetition of procedure, results, complications, predictors of success, and cost analysis. CAPSO is a mucosal surgery that induces a midline palatal scar that stiffens the floppy palate. Two hundred six consecutive patients underwent CAPSO over an 18-month period, followed by office examination and telephone evaluation. The success rate was initially 92% and dipped to 77% after 1 year. CAPSO eliminates excessive snoring caused by palatal flutter and has success rates that were comparable with those of traditional palatal surgery. CAPSO is a simple and safe office procedure that avoids the need for multiple-stage operations and does not rely on expensive laser systems or radiofrequency generators and hand pieces.

Adult↗
PubMed1999

Visual perception of human activity and gender in biological-motion displays by individuals with mental retardation.

By examining perception of biological-motion in three experiments, we investigated whether limitations in perceptual ability by individuals with mental retardation may extend to learning perceptual categories based on elements of actions. In two experiments individuals with mental retardation and age- and gender-matched controls reported gender and activity in randomly ordered point-light displays. In Experiment 2 decision times were measured and in Experiment 3, the effect of training with feedback on discriminating gender was assessed. Individuals with mental retardation identified walking, running, and stair-climbing without error but were less proficient in identifying throwing, had slower decision times for activity identification, and could not identify gender. For both groups feedback training improved gender identification in the short- and long-term. Improvements represented above-chance responding for the retarded group. Experimental outcomes are discussed in terms of capacity to classify perceptual stimuli as actions.

Adult↗
PubMed1997

Loss of 3-D shape constancy in interior spaces: the basis of the Ames-room illusion.

The apparently rectangular form of the irregularly shaped Ames room is explained in terms of a loss of interior 3-D shape constancy consequent on viewing the room with one eye through a small specifically positioned aperture. In the absence of retinal disparity and motion parallax the appearance of the room is held to shift markedly toward the rectangular dimensions of its retinal image. Three experiments designed to test this explanation with a miniature (one-tenth size) version of the Ames room No 1 with the matched 2-D shape of the back wall and as an index of interior 3-D shape are reported. The experiments showed that interior constancy was almost fully restored with binocular viewing of the room (experiment 1). The effect with a 'skeletal' version of the room was about the same as that with the conventional version and was clearly evident when the back wall or its frame version was presented alone (experiment 2), and it varied according to whether the interior perspective corresponded with that of the Ames or a rectangular room (experiment 3). Experiment 3 also showed that a rectangular room is significantly distorted when the interior perspective accords with that of the Ames room. These outcomes are construed as supporting the loss-of-constancy explanation and as showing that the Ames-room effect is one of a class of illusions attributable to the absence of stimulus correlates that normally sustain visual shape constancy.

Adult↗
PubMed1997

Visual discrimination and motor reproduction of movement by individuals with mental retardation.

Visual discrimination and motor reproduction tasks involving computer-simulated arm movements were administered to 12 adults with mental retardation and a gender-matched control group to examine whether inadequacies in visual perception account for the poorer motor performance of individuals with mental retardation. In the discrimination phase subjects judged whether simulated arm movements were either of greater or lesser extent or shorter or longer in duration, respectively, than those of a standard display. In the reproduction phase accuracy in reproducing the movement in the standard display was measured. Results indicate that error in discriminating extent and duration was significantly greater for the individuals with mental retardation, who were also less accurate and more variable in matching the extent and duration of the standard displays. These outcomes implicate both perceptual and motor-reproduction inadequacies in skill acquisition for these individuals.

Adult↗
PubMed1996

Anticipatory reaching by infants and adults: the effect of object features and apertures in opaque and transparent screens.

Perception of the manner in which objects may be grasped was examined in a series of experiments with adults and 10-month-old infants; visuomotor adjustment in hand orientation before making contact with objects served as the index throughout. In the first experiment, infants modified their hand orientation to match more closely the long axis of an object. They did so even though the target object could have been grasped by either end with hands oriented orthogonally to the long axis of the object. In two subsequent experiments involving reaching through narrow apertures to grasp the target, anticipatory adjustments in hand posture were evident for adults but not for infants. However, anticipatory adjustments by infants, sometimes appropriate and sometimes inappropriate, were made when the object was of such a size that it could neither be grasped nor retrieved through the aperture. In the final experiment, infants directed their hands first toward a handle, the only graspable part of an object, and oriented their hands so as to be nearly parallel with it prior to contact. This was the only orientation in which a grasp was possible. It was concluded that infants at 10 months respond more appropriately to object properties than to surface apertures that place limitations on how an object may be grasped.

Adult↗
PubMed1995

Visual accommodation as a cue for size.

Accommodation micropsia is examined in the general context of ocular accommodation as a cue for object size. The nature and limits of accommodation micropsia and arguments dealing with the possible contribution of accommodation to the perception of size are reviewed. Literature on the anomalous myopias, the intermediate-resting hypothesis, and theories of ciliary muscle innervation is examined critically in so far as it bears on the accommodation-micropsia hypothesis. The anomalous myopias and evidence for the intermediate-resting hypothesis are well documented, but without a mechanism for proprioceptive feedback from the ciliary complex about the state of accommodation it can only be concluded that such feedback would have to be indirect, either via the reflex link with vergence, or possibly through the agency of efference-copy neurones.

Accommodation, Ocular↗
PubMed1995

Apparent horizontal and vertical extents of patterns with and without a surround.

Following earlier informal observations, the first of two experiments confirmed that, whereas the vertical and horizontal extents of a printed passage are more or less veridically perceived when the passage is surrounded by margins as is usual on a page, they appear reduced when the margins are removed by cropping them close to the edges of the passage. In Exp. 2 with a horizontal-line grating a similar reduction occurred vertically but not horizontally, suggesting that the effect occurs for patterned regions but less or not at all for unpatterned, i.e., uniform, regions. The possible relationship between this effect and the Delboeuf illusion of size is discussed.

Female↗
PubMed1994

Pseudophakes experience apparent minification in an imaging display.

Apparent minification of virtual images has been attributed to accommodation micropsia, that is, a reduction in the apparent size of viewed objects accompanying an inward accommodation of the eyes. Thirteen bilateral pseudophakes incapable of accommodation but with good residual vision were tested monocularly for apparent minification in the viewfinder of a single-lens reflex camera. Apparent minification of about the same order as that typically found with normals occurred with the pseudophakic observers, demonstrating that pseudophakes are subject to distortions in apparent size with virtual-imaging displays in the same way as normals, thus establishing that visual accommodation is not a necessary condition for the effect.

Accommodation, Ocular↗
PubMed1994

On apparent misalignment of collinear edges and boundaries.

In two experiments, subjects adjusted various pairings of the top and bottom boundaries of two obliquely oriented outline bars (Experiment 1) and those of two similarly oriented complete and incomplete squares (Experiment 2) to apparent alignment. The data from the first experiment showed that the misalignment effects were determined jointly by the directional properties of the bar ends (vertical, oblique, and semicircular) and the pair of boundaries that were aligned (both top boundaries, top of upper bar with bottom of lower bar, bottom of upper bar with top of lower bar). The results from the second experiment showed that the misalignment effects were the same for the oblique boundaries of solid and outline squares and persisted when the squares were reduced to two parallel lines. The effect was undiminished when the ends of the parallels were aligned, but was markedly reduced when pairs of parallels themselves were aligned. The outcomes of the two experiments are explained in terms of the apparent positions of the oblique boundaries. It is proposed that these vary with the positions of the elements (bar or square) relative to the visual field, the position of the boundaries relative to the stimulus elements, and the positions of the boundaries relative to axes that are delineated by the parallel adjacent ends of bars and sides of squares. This relative-position basis for apparent misalignment is held to be the basis of misalignment effects in other figures.

Adult↗
PubMed1994

Apparent misalignment of oblique coplanar bars in depth.

Following preliminary observations of apparent misalignment of coplanar surfaces in a three-dimensional (3-D) form of the Poggendorff figure viewed in depth, the effect was investigated in five experiments and compared with the 2-D Poggendorff effect in the same object in a sixth. The effect in depth occurred with the complete object when it was viewed binocularly but did not do so with the oblique bars alone or when the object was viewed monocularly. The effect did not vary with oblique-parallel angles of 30 degrees, 45 degrees, and 60 degrees and was absent when the angle was 90 degrees. It varied as a function of the distance between the parallels, but was unaffected by a regular pattern on the oblique bars. A smaller 2-D Poggendorff effect occurred when the upper edges of the object were viewed from above. Although the depth effect was robust, its variance was high compared with that of the 2-D effect, indicating that acuity for misalignments of oblique elements in depth is poor. An explanation of apparent misalignment of oblique elements in 2-D and 3-D space in terms of a perceptual compromise between alignment in an oblique axis and separation relative to the axes of the parallels is proposed.

Adult↗
PubMed1994

Diagnosis and treatment of trigeminal nerve injuries.

Microneurosurgery has become a valuable technique in the field of oral and maxillofacial surgery. It is now possible to microsurgically repair injuries to the inferior alveolar and lingual nerves resulting from routine oral surgery or dental or oncologic treatment. Sensation may be improved or restored, and painful pares thesias relieved, by timely, well-performed microsurgery.

Humans↗
PubMed1993

A Müller-Lyer-type illusion of egocentric distance with 3D convex and concave objects.

An illusion of egocentric distance with concave and convex objects at a distance of 135 cm is reported. When the centre of a concave object was viewed with both eyes its surface appeared nearer than the centre of the surface of a convex object at the same distance. The distortion was about two per cent of the viewing distance with right-angle objects and about five per cent with hemicylindrical objects. The distortion was slightly reduced when size cues for distance were attached to the surfaces of the objects, absent with monocular viewing, greater with convex than with concave objects, and occurred with the generally convex surface of a model human face. Possible explanations of the findings are discussed.

Defense Mechanisms↗
PubMed1993

The effect of edge orientation and movement direction on the apparent misalignment of collinear bars.

Four experiments on apparent misalignment of oblique collinear bars are reported. The data from the first three experiments showed that the misalignment was slight but significant when no direction other than that of the bars themselves was delineated and about double when the vertical was delineated by movements of the adjustable bar. When the vertical was delineated by both these movements and the ends of the bars (or by vertical parallel lines), the misalignment was more than six times greater. Conversely, it was reduced when the bar ends delineated the vertical and bar movements delineated the direction at right angles to the bars. The data from a fourth experiment showed that the inner pair of edges were closely involved in apparent misalignment and that the outer ends were not. The relationship between the misalignment effect with bars and the Poggendorff figure (oblique lines separated by parallels), the delineation of direction by edges and movement, and the implications of these data for an explanation are discussed.

Adult↗
PubMed1993

Effective action by infants to contact objects by reaching and leaning.

The ability of infants aged 8-12 months to coordinate their arm and trunk movements to contact an object located in different positions was investigated in 2 experiments. In the first, 8- and 10-month-old infants reached for near objects but both reached and leaned for more distant ones indicating that they perceived that forward leaning extends the range of contact beyond that of reaching alone. In addition, arm and trunk movements were initiated simultaneously; visual information concerning object distance was sufficient to activate an integrated reaching-and-leaning response. Object distances were increased and a mechanical aid was provided on half the trials in the second experiment with 10- and 12-month-old infants. For both age groups the degree of leaning was reduced for objects that were out of reach without the aid. Only older infants were able to use the aid to extend partially their range of contact. Overall the results support the conclusions that, by at least 8 months, infants perceive that leaning extends their effective reaching space; by 10 months they perceive the limits within which reaching together with leaning is likely to be effective; and by 12 months they begin to perceive how this space may be extended by a mechanical aid.

Child Development↗
PubMed1992

Two movement aftereffects: evidence for luminance- and color-movement pathways.

Two movement aftereffects (MAEs) that bear closely on the issue of visual processing of color and movement have been isolated. Following adaptation with a vertical luminance stimulus a strong MAE occurred with the same stationary test stimulus oriented horizontally and also in a perfectly uniform field. Neither effect occurred following adaptation with a color equiluminance stimulus. These aftereffects have not been reported before. It is concluded that there are at least three pathways for movement, a color, a color-plus-luminance, and a luminance pathway.

Adaptation, Ocular↗
PubMed1992

The Müller-Lyer illusion Mark II.

A new illusion of size is described. A passage of print occupying about half a standard A4 sheet appeared larger than the same passage when the sheet was cropped immediately above and below it. This illusion is demonstrated and explained in terms of perceptual compromise between the vertical extent of the printed passage and the sheet of which it is an intrinsic feature. In this sense it is held to be essentially the same as the Müller-Lyer illusion of extent in which the spaces between the apexes are intrinsic to the figure.

Attention↗
PubMed1992

The Poggendorff illusion and apparent interparallel extents.

An explanation of the Poggendorff misalignment effect in terms of apparent contraction of interparallel extent resulting from the Müller-Lyer illusion was tested in three experiments. Three of the eight stimulus figures had oblique transversals outside the parallels in the usual way, three had them inside, and two were controls consisting of the transversals only. Müller-Lyer forms were differently delineated between the parallels for the inside-transversal and outside-transversal figures, and were not delineated in the control figures. In the first experiment apparent misalignment occurred in four of the six parallel-line figures and in neither of the controls. In the second experiment oblique extent between the parallels was underestimated in six of the eight figures and right-angle extent was overestimated in all of them. The results of the third experiment showed that right-angle (horizontal) extent between the parallels without transversals is estimated without significant error. The data from the three experiments do not support the interparallel-extent explanation of apparent misalignment. Instead, the results are interpreted in terms of independent perceptual compromises, one involving alignment of the transversals and the other the distance between them.

Adult↗