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Results for “FORM PERCEPTION”

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PubMedDate not supplied

PET reveals occipitotemporal pathway activation during elementary form perception in humans.

To define brain regions involved in feature extraction or elementary form perception, regional cerebral blood flow (rCBF) was measured using positron emission tomography (PET) in subjects viewing two classes of achromatic textures. Textures composed of local features (e.g. extended contours and rectangular blocks) produced activation or increased rCBF along the occipitotemporal pathway relative to textures with the same mean luminance, contrast, and spatial-frequency content but lacking organized form elements or local features. Significant activation was observed in striate, extrastriate, lingual, and fusiform cortices as well as the hippocampus and brain stem. On a scan-by-scan basis, increases in rCBF shifted from the occipitotemporal visual cortices to medial temporal (hippocampus) and frontal lobes with increased exposure to only those textures containing local features. These results suggest that local feature extraction occurs throughout the occipitotemporal (ventral) pathway during extended exposure to visually salient stimuli, and may indicate the presence of similar receptive-field mechanisms in both occipital and temporal visual areas of the human brain.

Adult↗
PubMed1998

Form perception with a 49-point electrotactile stimulus array on the tongue: a technical note.

Form perception with the tongue was studied with a 49-point electrotactile array. Five sighted adult human subjects (3M/2F) each received 4 blocks of 12 tactile patterns, approximations of circles, squares, and vertex-up equilateral triangles, sized to 4x4, 5x5, 6x6, and 7x7 electrode arrays. Perception with electrical stimulation of the tongue is better than with fingertip electrotactile stimulation, and the tongue requires 3% (5-15 V) of the voltage. The mean current for tongue subjects was 1.612 mA. Tongue shape recognition performance across all sizes was 79.8%. The approximate dimensions of the electrotactile array and the dimensions of compartments built into dental retainers have been determined. The goal is to develop a practical, cosmetically acceptable, wireless system for blind persons, with a miniature TV camera, microelectronics, and FM transmitter built into a pair of glasses, and the electrotactile array in a dental orthodontic retainer.

Adult↗
PubMed1983

Haptic dominance in form perception with blurred vision.

Three experiments are reported in which subjects were exposed to discrepant visual and haptic form information. Stained glass was used to blur vision and lower its accuracy close to the level of touch. Haptic dominance occurred with the large intersensory conflicts under study. It is proposed that touch may be dominant in form perception when vision is peripheral and blurry .

Discrimination Learning↗
PubMed1989

Necessary considerations for a theory of form perception: a theoretical and empirical reply to Boselie and Leeuwenberg (1986)

Boselie and Leeuwenberg (1986) recently defended their version of the minimum principle, called structural information theory or SIT, against a varied set of criticisms. Two of the most notable of these criticisms are (i) that perceptual organization can proceed as a piecemeal, rather than as a global, process (as demonstrated by partially-biased Necker cubes and 'impossible' figures), and (ii) that perceptual organization is influenced by subjective variables as well as by stimulus variables (Peterson and Hochberg 1983). The second criticism was acknowledged by Boselie and Leeuwenberg but not addressed. The first criticism was addressed by the introduction of two new variables into SIT in order to argue that the perceived organization of partially-biased Necker cubes and impossible figures can be predicted by a global coding scheme, thereby supporting rather than refuting global minimum principles. It is argued here that the criticisms cannot be dismissed by this rebuttal, which is focused narrowly on single examples rather than on the general principles embodied by the demonstrations. The implications of piecemeal perception and subjective mediation are spelled out, and both old and new data showing that the applicability of global minimum principles must be reexamined, not merely defended, are discussed. Finally, the argument for a richer, more interacting, theory of form perception is presented.

Attention↗
PubMed2004

An fMRI study of the cerebral macro network involved in 'cue invariant' form perception and how it is influenced by stimulus complexity.

We investigated the influence of stimulus complexity on the macro network of visual areas involved in 'cue invariant' form perception. Functional MRI imaging on 14 healthy, adult volunteers was performed during a two alternative forced choice (2-AFC) form discrimination task. The functional load imposed onto the visual system was varied by using simple and complex shapes. The figures were defined using a luminance, a chromatic or a motion contrast cue. The three cues activated the same visual areas in the ventral pathway, including area 'LO'. Activation of visual area 'V3v' but not area 'KO' in the dorsal pathway was observed to the motion contrast cue. The simple shapes induced a larger BOLD response in BA18 than the complex shapes, reflecting the selectivity of this region for the features in the stimuli such as edges and vertices. The brain regions yielding a larger BOLD signal to the complex shapes were areas know to be selective to the orthographic content of our complex stimuli. The processing requirement was assessed by comparing the subjects' reaction time. We found no significant difference in the reaction times to the simple and complex shapes. The reaction times to the luminance contrast cue and the chromatic contrast cue were identical but that to the motion contrast cue were 200 ms longer. This finding concurs with neurophysiological studies, reporting a longer onset latency for motion contrast stimuli. It further lends support to the idea that the motion contrast cue requires auxiliary processing by the visual areas of the dorsal pathway before entry into the ventral pathway.

Adult↗
PubMed1981

The effect on form perception of change of orientation in the third dimension.

The experiments reported here concern the effect of change of orientation of figures in the third dimension on phenomenal shape. In one experiment, novel two-dimensional wire figures were first shown in one orientation in the sagittal plane, and recognition of them was then tested in an altered orientation in that plane. In another experiment, novel three-dimensional wire figures were first shown in one orientation, and recognition of them was tested following rotation about one of the three major axes of space. The guiding hypotheses were (a) form perception is the end result of a process of figural description; (b) orientation change that alters the perceived location of the top, bottom, and sides of a figure will affect this description; and (c) front-back reversal and rotations about the Y axis will not affect the description because front and back constitute the sides of a figure much as left and right do, and all figural sides are phenomenally equivalent. The findings support these hypotheses except for an unanticipated effect on recognition of 90 degrees rotations about the Y axis. This effect was seen as a hitherto unknown example of egocentrism in perception, since the description is governed by the retinal projection resulting from the particular vantage point of the observer.

Depth Perception↗
PubMed1978

An automated apparatus for the study of central variables in tactile form perception.

An apparatus which employs standard behavioral programming equipment is described. It enables the experimenter to program in advance with variables as auditory and visual instructional cues, delay intervals, and response mode, and to monitor response latency automatically. The apparatus is easily constructed, easily operated, and markedly increases the control of variables in tactile form perception experiments.

Computers↗
PubMed2000

A system for investigating 3-D form perception.

This paper describes a noninvasive, relatively inexpensive, and simple to use system developed by the authors for monitoring the visual inspection behavior of someone free to select any viewing angle of an object by moving about it while at the same time being able to rotate it. A demonstration experiment verifies the potential of the system to study 3-D form perception.

Adult↗
PubMed1977

Physiognomic form perception: mature or immature?

The hypothesis that physiognomic perception, rather than being an immature mode, characterizing, in particular, children, primitives, and schizophrenics, is, instead, a basic mode, was tested. Children of both Eastern and Western parentage in Grades 3, 5, 6, and 11 were given the Physiognomic Form Perception Test, an instrument specially developed for testing physiognimic perception. No decrease with age in such perception was noted. Although there was a tendency for scores to increase with age for girls of Eastern origin, in general the scores do not increase with age. Physiognomic perception is apparently not acquired. Sex differences were not significant.

Adolescent↗
PubMed1983

The spatial characteristics of tactile form perception.

The perceived orientation of a raised letterform indenting the skin of the finger reverses (from normal to its mirror-image) when the letter is held in contact with the finger and both are rotated through 180 degrees about the axis of the finger. Thus, though the pattern of stimulated skin receptors remains constant, the perceived orientation of the letter reverses. On the basis of this observation it is proposed that tactual perception of object form involves assignment of a spatial coordinate system within which the patterns of skin stimulation are interpreted. In experiments in which the orientations of letters and subjects are systematically varied within the environment, the occurrence or nonoccurrence of reversal in perceived orientation of letters has been used to investigate the origin of the proposed spatial coordinate system; that is, whether it is assigned with respect to the observer ( egocentrically ) or with respect to the environment ( geocentrically ). The results indicate that the assignment of coordinates is determined by both egocentric and geocentric factors. It is proposed that the reversal phenomena observed in these experiments, and in experiments of others which involve drawing characters on the skin, are consistent with Gibson's proposal that it is object form which is directly perceived, but that this involves interpretation of the patterns of skin stimulation within a framework of spatial coordinates.

Discrimination Learning↗