PubMed Health⌕ Search

Biomedical subjects

R H Day

Publications and source records attributed to R H Day.

At least 55 records · Page 3Linked to original sources
PubMed1987

The representation of uniform motion in vision.

For veridical detection of object motion any moving detecting system must allocate motion appropriately between itself and objects in space. A model for such allocation is developed for simplified situations (points of light in uniform motion in a frontoparallel plane). It is proposed that motion of objects is registered and represented successively at four levels within frames of reference that are defined by the detectors themselves or by their movements. The four levels are referred to as retinocentric, orbitocentric, egocentric, and geocentric. Thus the retinocentric signal is combined with that for eye rotation to give an orbitocentric signal, and the left and right orbitocentric signals are combined to give an egocentric representation. Up to the egocentric level, motion representation is angular rather than three-dimensional. The egocentric signal is combined with signals for head and body movement and for egocentric distance to give a geocentric representation. It is argued that although motion perception is always geocentric, relevant registrations also occur at the three earlier levels. The model is applied to various veridical and nonveridical motion phenomena.

Concept Formation↗
PubMed1986

Separation and properties of rabbit buccal mucosal wound hyaluronidase.

This study establishes the existence of a mammalian buccal mucosal wound hyaluronidase (hyaluronate 4-glycohydrolase; EC 3.2.1.35) having properties distinct from those of the endogenous lysosomal hyaluronidase of normal (uninjured) buccal mucosa. A time-dependent change in hyaluronidase activity was measured, with the highest specific activity occurring on post-wound day 4 (7.7 +/- 1.3 units/mg protein), followed by consecutive decreases until activity was no longer discernible by day 21. Mucosal wound hyaluronidase closely resembled a previously described integumentary wound endoglycosidase in terms of a high pH optimum (5.0-6.0), distinct (but non-exclusive) substrate preference for hyaluronic acid, and ability to generate saturated depolymerization products by an endoglycosidic hydrolysis.

Animals↗
PubMed1986

Spatial localization in infancy: position constancy in a square and circular room with and without a landmark.

The ability of 8-month-old infants to localize an event from a new direction of facing was tested in a square and a circular room with and without a landmark. Subjects were trained to anticipate the site from 2 directions of facing and then tested in a new direction of facing. The number of trials to a criterion of learning, the number of subjects looking first at the event site after reorientation, and the time spent in doing so were recorded. Taken together, the results show that at 8 months ability to identify the site of an event after reorientation is based on the spatial relationship between the event and environmental features. The latter include features associated with room shape as well as a landmark at the site of the event.

Attention↗
PubMed1985

Familiarity, spatial frequency and task determinants in processing laterally presented representations of faces.

Laterally presented portraits were judged as familiar or unfamiliar (Experiments 1 and 2), or were processed in a target matching task (Experiment 3). Exposure durations (100 or 190 msec.) were varied between (Experiments 1 and 2) or within (Experiment 3) the experiments. Clear and degraded faces appeared either randomly intermingled (Experiment 1) or in blocked sequences (Experiments 2 and 3). In Experiment 3 familiar and unfamiliar stimuli also appeared in blocks. Stimulus degradation was achieved by coarse quantization of the image into blocks, so replacing relevant high-spatial-frequencies (the features) by spurious information, preserving only the original lower-spatial-frequency components. Left hemisphere mediation was strongest and most consistent with long exposures and random sequences of clear and degraded stimuli. Right hemisphere mediation tended to appear with shorter exposures and degraded stimuli presented in blocks. Though the interactions were often complex, the general pattern of results was consistent with the analytic-holistic processing dichotomy.

Discrimination Learning↗
PubMed1983

On the Morinaga Misalignment Illusion.

The Morinaga illusion is the apparent misalignment of the aligned apexes of oppositely facing angles. It is also called the Morinaga paradox because its direction is opposite to that intuitively expected from the Müller-Lyer illusion. Six experiments are reported. The first showed that the illusion is greater when the apexes are aligned obliquely than when aligned vertically or horizontally (the oblique effect); the second showed that the illusion is undiminished when the two outer angles are replaced with single lines coincident with the arms of the angles; and the third showed that the illusion is undiminished when the central apex is replaced by a dot but diminished by about half when the two outer apexes are each replaced by dots. The fourth experiment showed that the illusion also occurs with the aligned ends of parallel lines and edges of squares but not with the aligned tangential points of circles of about the same size. Experiments 5 and 6 showed that the effect is markedly greater with small, widely spaced elements. Explanations in terms of perceptual normalization to a line and perceptual assimilation have been considered. The latter explanation is the more plausible of the two, although it is conceivable that both processes contribute to the effect.

Female↗
PubMed1983

Illusory contours in line patterns with apparent depth due to either perspective or overlay.

An illusory contour along a partially delineated border in the form of an apparent 'outside' corner due to perspective was as strong as one along a similarly delineated border in the form of an edge due to overlay. An illusory contour along a border in the form of an apparent 'inside' corner, due probably to both perspective and overlay, was stronger than either. These outcomes suggest that apparent stratification from overlay is not necessary for the occurrence of illusory contours. They also accord with the view that apparent depth due to overlay or to perspective is equally effective in rendering partially delineated borders more prominent and, in consequence, the illusory contours that form along them stronger.

Depth Perception↗
PubMed1981

Effects of the similarity and dissimilarity between familiarization and test objects on recognition memory in infants following unimodal and bimodal familiarization.

Recognition memory for the shape of an object following unimodal (visual) and bimodal (visual and haptic) familiarization was investigated in 2 experiments. In both experiments, 6-month-old infants were familiarized either unimodally or bimodally with simple objects. In the first experiment the subjects were tested unimodally after familiarization, and in the second the subjects were tested bimodally. Visual recognition memory was only evident when the conditions of familiarization and testing were identical. 2 possible explanations of the data are presented, and the implications of these for the conclusions generated by previous studies are discussed.

Attention↗
PubMed1980

Visual aftereffects derived from inspection of orthogonally moving patterns.

Alternate inspection of patterns moving in orthogonal directions induces an aftereffect in which a stationary test pattern seems to move in a new direction. This direction is the resultant of the two directions of aftereffect that would have arisen from separately inspecting each of the moving patterns. The direction in which objects appear to move, like their color and depth, can thus depend on a synthesis of unperceived components.

Afterimage↗