Visual Shape Recognition Research Articles

Individual Differences Offer Insight Into Clinical Recommendations for Directional and Remote Microphone Technology Use in Children.

Purpose This study sought to evaluate the effects of common hearing aid microphone technologies on speech recognition and listening effort, and to evaluate potential predictive factors related to microphone benefits for school-age children with hearing loss in a realistic listening situation. Method Children (n = 17, ages 10-17 years) with bilateral, sensorineural hearing loss were fitted with hearing aids set to include three programs: omnidirectional, adaptive directional, and omnidirectional + remote microphone. Children completed a dual-task paradigm in a moderately reverberant room. The primary task included monosyllabic word recognition, with target speech presented at 60 dB A from 0° (front) or 180° (back) azimuth. The secondary task was a "go/no-go," visual shape-recognition task. Multitalker babble noise created a +5 dB SNR. Children were evaluated in two speaker conditions (front, back) using all three hearing aid programs. The remote microphone transmitter remained at the front speaker throughout testing. Speech recognition performance was calculated from the primary task while listening effort was measured as response time during the secondary task. Results Speech presented from the back significantly increased listening effort and caused a reduction in speech perception when directional and remote microphones were used. Considerable variability was found in pattern of benefit across microphones and source location. Clinical measures did not predict benefit patterns with directional or remote microphones; however, child age and performance with omnidirectional microphones did. Conclusions When compared to a traditional omnidirectional setting, the directional and remote microphone configurations evaluated in this study have the potential to provide benefit for some children and increase difficulty for others when used in dynamic environments. A child's performance with omnidirectional hearing aids could be used to better inform clinical recommendations for these technologies.

A biphasic effect of cross-modal priming on visual shape recognition

We used a cross-modal priming paradigm to evoke a biphasic effect in visual short-term memory. Participants were required to match the memorandum (a visual shape, either spiky or curvy) to a delayed probe (a shape belonging to the same category). In two-thirds of trials the sequence of shapes was accompanied by a task-irrelevant sound (either tzk or upo, cross-modally correspondent to spiky and curvy shape categories, respectively). The biphasic effect occurred when a congruent vs. incongruent sound was presented 200ms after the memorandum, while it did not occur when the sound was presented 200ms before or simultaneously with it. The biphasic pattern of recognition sensitivities was revealed by an interaction between cross-modal congruency and probe delay, such that sensitivity was higher for visual shapes paired with a congruent rather than incongruent sound with a 300-ms delay, while the opposite was true with a 1300-ms delay. We suggest that this biphasic pattern of recognition sensitivities was dependent on the task-irrelevant sound activating different levels of shape processing as a function of the relative timing of sound, memorandum, and probe.

Visual Shape Recognition in Crayfish as Revealed by Habituation

Visual Shape Recognition in Crayfish as Revealed by Habituation

Linear and Non-Linear Visual Feature Learning in Rat and Humans.

The visual system processes visual input in a hierarchical manner in order to extract relevant features that can be used in tasks such as invariant object recognition. Although typically investigated in primates, recent work has shown that rats can be trained in a variety of visual object and shape recognition tasks. These studies did not pinpoint the complexity of the features used by these animals. Many tasks might be solved by using a combination of relatively simple features which tend to be correlated. Alternatively, rats might extract complex features or feature combinations which are nonlinear with respect to those simple features. In the present study, we address this question by starting from a small stimulus set for which one stimulus-response mapping involves a simple linear feature to solve the task while another mapping needs a well-defined nonlinear combination of simpler features related to shape symmetry. We verified computationally that the nonlinear task cannot be trivially solved by a simple V1-model. We show how rats are able to solve the linear feature task but are unable to acquire the nonlinear feature. In contrast, humans are able to use the nonlinear feature and are even faster in uncovering this solution as compared to the linear feature. The implications for the computational capabilities of the rat visual system are discussed.

A Prototype Smart Materials Warehouse Application Implemented Using Custom Mobile Robots and Open Source Vision Technology Developed Using EmguCV

Customized mobile robots are commonplace in manufacturing and material handling applications. One class of mobile robots, known as Automatic Guided Vehicles (AGV), follow a fixed path along the floor using tracks, RFID tags, or magnetic tape. These robots typically travel along predetermined routes and offer limited flexibility for changes to be made or for their use in environments like hospitals or military installations. Moving away from traditional fixed AGV systems to wireless and dynamic control and monitoring presents some distinct advantages and new opportunities. This type of robot is known as an Autonomous AGV. A prototype smart materials warehouse is presented in this paper as a platform to explore some particular aspects of this technology. First, four multi-purpose mobile robots were built using off-the-shelf BattleBot kits, wireless Arduino controls, and fabricated components. Secondly, a Microsoft Kinect camera was installed on one robot for visual feedback, obstacle avoidance, and shape recognition. Lastly, a ceiling mounted IP camera was used with software developed using Visual Studio .NET and the C# wrapper for OpenCV (EmguCV) to facilitate robot path development, video processing and real-time tracking. Testing of the completed system was done in a 2000 sq. ft. mock warehouse set up with stations for shipping/receiving, storage, staging areas, and processes including cutting, milling, and turning for preparing raw stock to be used in production. As cyber-physical systems research continues to grow, the integration of computational algorithms, physical systems, wireless controls, and custom user interfaces will undoubtedly lead to their increased use throughout society. This work was completed as part of the Northwest Manufacturing Initiative at the Oregon Institute of Technology. Possibilities for applying the results of this work in the military, retail and service sectors are also identified. All hardware and software for the project was developed to facilitate future work.

Preserved Haptic Shape Processing after Bilateral LOC Lesions.

The lateral occipital complex (LOC) is a brain region regarded to be critical for recognizing object shape, both in vision and in touch. However, causal evidence linking LOC with haptic shape processing is lacking. We studied recognition performance, psychophysical sensitivity, and brain response to touched objects, in a patient (M.C.) with extensive lesions involving LOC bilaterally. Despite being severely impaired in visual shape recognition, M.C. was able to identify objects via touch and she showed normal sensitivity to a haptic shape illusion. M.C.'s brain response to touched objects in areas of undamaged cortex was also very similar to that observed in neurologically healthy controls. These results demonstrate that LOC is not necessary for recognizing objects via touch.

Aging and solid shape recognition: Vision and haptics

The ability of 114 younger and older adults to recognize naturally-shaped objects was evaluated in three experiments. The participants viewed or haptically explored six randomly-chosen bell peppers (Capsicum annuum) in a study session and were later required to judge whether each of twelve bell peppers was “old” (previously presented during the study session) or “new” (not presented during the study session). When recognition memory was tested immediately after study, the younger adults’ (Experiment 1) performance for vision and haptics was identical when the individual study objects were presented once. Vision became superior to haptics, however, when the individual study objects were presented multiple times. When 10- and 20-min delays (Experiment 2) were inserted in between study and test sessions, no significant differences occurred between vision and haptics: recognition performance in both modalities was comparable. When the recognition performance of older adults was evaluated (Experiment 3), a negative effect of age was found for visual shape recognition (younger adults’ overall recognition performance was 60% higher). There was no age effect, however, for haptic shape recognition. The results of the present experiments indicate that the visual recognition of natural object shape is different from haptic recognition in multiple ways: visual shape recognition can be superior to that of haptics and is affected by aging, while haptic shape recognition is less accurate and unaffected by aging.

Perception of biological motion from size-invariant body representations.

The visual recognition of action is one of the socially most important and computationally demanding capacities of the human visual system. It combines visual shape recognition with complex non-rigid motion perception. Action presented as a point-light animation is a striking visual experience for anyone who sees it for the first time. Information about the shape and posture of the human body is sparse in point-light animations, but it is essential for action recognition. In the posturo-temporal filter model of biological motion perception posture information is picked up by visual neurons tuned to the form of the human body before body motion is calculated. We tested whether point-light stimuli are processed through posture recognition of the human body form by using a typical feature of form recognition, namely size invariance. We constructed a point-light stimulus that can only be perceived through a size-invariant mechanism. This stimulus changes rapidly in size from one image to the next. It thus disrupts continuity of early visuo-spatial properties but maintains continuity of the body posture representation. Despite this massive manipulation at the visuo-spatial level, size-changing point-light figures are spontaneously recognized by naive observers, and support discrimination of human body motion.

Short temporal asynchrony disrupts visual object recognition.

Humans can recognize objects and scenes in a small fraction of a second. The cascade of signals underlying rapid recognition might be disrupted by temporally jittering different parts of complex objects. Here we investigated the time course over which shape information can be integrated to allow for recognition of complex objects. We presented fragments of object images in an asynchronous fashion and behaviorally evaluated categorization performance. We observed that visual recognition was significantly disrupted by asynchronies of approximately 30 ms, suggesting that spatiotemporal integration begins to break down with even small deviations from simultaneity. However, moderate temporal asynchrony did not completely obliterate recognition; in fact, integration of visual shape information persisted even with an asynchrony of 100 ms. We describe the data with a concise model based on the dynamic reduction of uncertainty about what image was presented. These results emphasize the importance of timing in visual processing and provide strong constraints for the development of dynamical models of visual shape recognition.

Haptic Shape Processing in Visual Cortex

Humans typically rely upon vision to identify object shape, but we can also recognize shape via touch (haptics). Our haptic shape recognition ability raises an intriguing question: To what extent do visual cortical shape recognition mechanisms support haptic object recognition? We addressed this question using a haptic fMRI repetition design, which allowed us to identify neuronal populations sensitive to the shape of objects that were touched but not seen. In addition to the expected shape-selective fMRI responses in dorsal frontoparietal areas, we observed widespread shape-selective responses in the ventral visual cortical pathway, including primary visual cortex. Our results indicate that shape processing via touch engages many of the same neural mechanisms as visual object recognition. The shape-specific repetition effects we observed in primary visual cortex show that visual sensory areas are engaged during the haptic exploration of object shape, even in the absence of concurrent shape-related visual input. Our results complement related findings in visually deprived individuals and highlight the fundamental role of the visual system in the processing of object shape.

Integration of texture and color cues for visual shape recognition

Integration of texture and color cues for visual shape recognition

Integration of texture and color cues for visual shape recognition

Integration of texture and color cues for visual shape recognition

Breaking the symmetry: Mirror discrimination for single letters but not for pictures in the Visual Word Form Area

Humans and primates can quickly recognize mirror images of previously exposed pictures. This spontaneous mirror invariance, though advantageous for visual recognition, makes it difficult to distinguish the orientation of letters (e.g. to differentiate a “b” from a “d”), and may result in classical mirror reading and writing errors in preschoolers. Mirror invariance must therefore be overcome during reading acquisition. The Visual Word Form Area (VWFA), a region in the ventral stream that develops with reading expertise, was previously shown to discriminate words from their mirror images in literate adults. Here we investigate whether this region underlies mirror-image discrimination at the most elementary level of the orthographic code, the single-letter level. Using an fMRI priming paradigm, we demonstrate that the VWFA distinguishes the left–right orientation of single letters in skilled readers, and yet exhibits mirror invariance for simple pictures of matched complexity. These results clarify how letter shapes, after reading acquisition, escape the process of mirror invariance which is a basic property of the ventral visual shape recognition pathway.

Density codes and shape spaces

This paper presents an algorithm that allows for encoding probability density functions associated to samples of points of R n . The resulting code is a sequence of points of R n whose density function approximates that of the set of data points. However, contrarily to sampled data points, code points associated to two different density functions can be matched, which allows to efficiently compare such functions. Moreover, the comparison of two codes can be made invariant to a wide variety of geometrical transformations of the support coordinates, provided that the Jacobian matrix of the transformation be everywhere triangular, with a strictly positive diagonal. Such invariances are commonly encountered in visual shape recognition, for example. Thus, using this tool, one can build spaces of shapes that are suitable input spaces for pattern recognition and pattern analysis neural networks. Moreover, a parallel neural implementation of the encoding algorithm is available for 2D image data.

Visual shape recognition with contour propagation

A neural architecture is presented that encodes the visual space inside and outside of a shape. The contours of a shape are propagated across an excitable neuronal map and fed through a set of orientation columns, thus creating a pattern which can be viewed as a vector field. This vector field is then burned as synaptic, directional connections into a propagation map, which will serve as a "shape map". The shape map identifies its own, preferred input when it is translated, deformed, scaled and fragmented, and discriminates other shapes very distinctively. Encoding visual space is much more efficient for shape recognition than determining contour geometry only.

Shape representation in area V4: position-specific tuning for boundary conformation.

Visual shape recognition in primates depends on a multi-stage pathway running from primary visual cortex (V1) to inferotemporal cortex (IT). The mechanisms by which local shape signals from V1 are transformed into selectivity for abstract object categories in IT are unknown. One approach to this issue is to investigate shape representation at intermediate stages in the pathway, such as area V4. We studied 109 V4 cells that appeared sensitive to complex shape in preliminary tests. To achieve a more complete picture of shape representation in V4, we tested each cell with a set of 366 stimuli, constructed by systematically combining convex and concave boundary elements into closed shapes. Using this large, diverse stimulus set, we found that all the cells in our sample responded to a wide variety of shapes and did not appear to encode any single type of global shape. However, for most cells the shapes evoking strongest responses were characterized by a consistent type of boundary conformation at a specific position within the stimulus. For example, a given cell might be tuned for shapes containing concave curvature at the right, with other parts of the shape having little or no effect on responses. Many cells were tuned for more complex boundary configurations (e.g., a convex angle adjacent to a concave curve). We quantified this kind of shape tuning with Gaussian functions on a curvature x position domain. These tuning functions fit the neural responses much better than tuning functions based on edge or axis orientation. Thus individual V4 cells appear to encode moderately complex boundary information at specific locations within larger shapes. This finding suggests that, at intermediate stages in the V1-IT transformation, complex objects are represented at least partly in terms of the configurations and positions of their contour components.

Visual object recognition in multiple sclerosis

Deficits in tasks measuring visual processing have been earlier reported in studies of MS. Yet, the nature and severity of visual-processing deficits in MS remains unclear. We used a new method in order to measure the different stages of visual processing in object recognition: shape recognition, familiarity recognition, semantic categorization, and identification with naming. Six two-choice reaction-time tasks were presented to 30 MS patients and 15 healthy controls. The patients were divided into cognitively preserved and cognitively deteriorated study groups according to their cognitive status. The purpose was to find out whether deficits at specific stages of visual processing can be found in cognitively deteriorated MS patients. Cognitively deteriorated MS patients did not perform as well as cognitively preserved MS patients or healthy controls. They were slower already at the early stage of visual processing where discrimination of whole objects from scrambled ones was required. They also had higher error rates in tasks requiring object familiarity detection and object identification with naming. Thus, cognitively deteriorated MS patients had difficulties in visual shape recognition and semantic–lexical processing. However, variation of performances was large within both of the patient groups indicating that even patients without a generalized cognitive decline may have deficits in some stages of the visual processing. We suggest that because of the heterogeneity of the patients, every single case needs to be examined separately in order to identify the possible deficits in visual processing.

A model for visual shape recognition.

A model for visual shape recognition.

Visual and stereognostic shape recognition in normal children and mongol and non-mongol imbeciles.

Visual and stereognostic shape recognition in normal children and mongol and non-mongol imbeciles.

Recognition of shapes by normal and subnormal children.

Normal and subnormal children, matched for mental age, were compared on visual and stereognostic shape recognition. While some subjects were required to explore and recognize the items in the same sensory modality, others had to recognize them in the opposite modality from the one in which they were initially presented.No differences between the conditions were observed in normal children. The imbeciles obtained results similar to those of the normals, except with the like modality stereognostic procedure. This resulted in significantly higher recognition scores than were obtained under the other conditions.It is suggested that absence of verbal coding in the cross modality tests, and relatively intact stereognostic discrimination ability in imbeciles may explain the results.