Structural Descriptions Of Objects Research Articles

Using Prosopagnosia to Test and Modify Visual Recognition Theory.

Biederman's contemporary theory of basic visual object recognition (Recognition-by-Components) is based on structural descriptions of objects and presumes 36 visual primitives (geons) people can discriminate, but there has been no empirical test of the actual use of these 36 geons to visually distinguish objects. In this study, we tested for the actual use of these geons in basic visual discrimination by comparing object discrimination performance patterns (when distinguishing varied stimuli) of an acquired prosopagnosia patient (LB) and healthy control participants. LB's prosopagnosia left her heavily reliant on structural descriptions or categorical object differences in visual discrimination tasks versus the control participants' additional ability to use face recognition or coordinate systems (Coordinate Relations Hypothesis). Thus, when LB performed comparably to control participants with a given stimulus, her restricted reliance on basic or categorical discriminations meant that the stimuli must be distinguishable on the basis of a geon feature. By varying stimuli in eight separate experiments and presenting all 36 geons, we discerned that LB coded only 12 (vs. 36) distinct visual primitives (geons), apparently reflective of human visual systems generally.

Algorithm A* in logical-structure recognition of objects on raster images

In this paper we put forward a logical-structure method for recognition of objects on high resolution satellite images. This approach is based on logical reasoning with the use of structural description of objects. A search for object boundaries on an image is implemented as a unification of the built-in predicate line with account for the set of constraints given in the description. Algorithm A* is used to reduce the complexity.

Unification of the predicate line in the logic-syntactic recognition of raster images

A logic-syntactic method of object recognition on images is proposed that is based on logical inference with use of the structural description of objects. The search for boundaries of objects on the image is performed as unification of the built-in predicate line with account of the set of constraints specified by the description.

Apperceptive agnosia and the visual recognition of object categories in dementia of the Alzheimer type

This paper reports the case of a woman (NA) with a clinical diagnosis of Alzheimer's disease and a modality-specific disorder affecting the visual recognition of living things. Investigations revealed early visual processing deficits suggestive of visual apperceptive agnosia. Visually related naming errors were numerous, but NA's ability to describe the physical properties of visually similar objects suggested that the structural descriptions of objects were preserved. There were no effects of structural similarity, visual complexity, concept familiarity, name frequency or age of acquisition on her naming of visual objects, and her ability to define the names of objects was normal. Errors were consistent over repeated tests. Purely visual errors were particularly likely to occur (a) when the object was presented from a non-canonical view, (b) when parts of objects were presented out of context and (c) when objects could be readily segmented into separate parts; the latter were particularly common for man-made objects. In contrast, category-related visual errors were more likely to reflect the overall shape of the object, and were most common to living things. The results are argued to show that category-specific deficits, usually considered to be semantic in origin, can arise from perceptual impairments occurring at an early stage of visual processing.

Intact Perceptual Priming in a Patient with Damage to the Anterior Inferior Temporal Lobes

We conducted three experiments to examine whether the anterior portion of the inferior temporal (IT) lobe is involved in the processing of visual objects in humans. In monkeys, damage to this region results in severe deficits in perception and in memory for visual objects. Our study was designed to examine both these processes in a patient (DM) with bilateral damage to the anterior portion of the inferior temporal lobe. Neuropsychological examination revealed a significant semantic impairment and a mild deficit in the discrimination of familiar objects from nonobjects. Despite these difficulties, the results of several studies indicated that DM was able to form and retain descriptions of the structure of objects. Specifically, DM showed normal perceptual priming for familiar and novel objects on implicit memory tests, even when the objects were transformed in size and left-right orientation. These results suggest that the anterior IT is not'involved in (1) the storage of pre-existing structural descriptions of known objects, (2) the ability to create new structural descriptions for novel objects, and (3) the ability to compute descriptions that are invariant with respect to changes in size and reflection. Instead, the anterior IT appears to provide the interface between structural descriptions of objects and their meanings.

Category-specific semantic impairment in Alzheimer's disease and temporal lobe dysfunction: A comparative study

In this paper we report an in-depth case study of a patient suffering from Alzheimer's disease who presented with a category-specific disorder relating to processing of knowledge about animate objects in the presence of spared knowledge of inanimate objects. Impairments appeared not only in a confrontation naming task but also on a range of visual knowledge tasks, such as drawing from memory or part-whole matching. The pattern of impairment was compared to that shown by a post-encephalitic patient who manifested a well-documented category-specific deficit for animate objects. Both patients' performance was compatible with an interpretation in terms of impairment at the level of the structural description of objects within the semantic system, as general encyclopaedic knowledge was largely preserved. Temporal lobe damage may be the cause of memory breakdown in both patients.

MATCHING OF STRUCTURAL SHAPE DESCRIPTIONS WITH HOPFIELD NET

Structural description of objects comprised descriptions of the parts and spatial relations between the parts. This paper presents a Hopfield net based scheme for matching structural shape descriptions. The current formulation of the matching scheme is general enough to take care of partial mismatch between the individual parts and spatial constraints between these parts. In addition, a transformation of the shape descriptions has been suggested with which shape descriptions containing asymmetrical spatial constraints between the parts can be matched using symmetric interconnection weights for the Hopfield net. The Hopfield net based formulation has been extended to consider the problem of finding the best match of the test shape descriptions with one of the stored prototypes. The matching scheme has been experimentally applied for recognition of hand-tools and symbols. In both cases, the network produced encouraging recognition results.