bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern Learning and the Control of Behaviour by All-Inhibitory Neural Network Hierarchies
Authors: Dobson Vernon 
Published: January 2007

An all-inhibitory network which learns by selective disconnection of synapses is described. This is similar to an ‘associative net'; however, it is simpler in that its neurons do not need to perform arithmetical operations, and the net does not require additional threshold modulating neurons in order to cope with input patterns which are incomplete, or of differing sizes. This fundamental simplicity permits a greater variety and density of connections. These can multiply the capacity of the nets to learn complex sequences of patterns without being saturated. An “all-connected‘’ net is described which has the holograph-like capacity to reconstruct the whole of an input pattern from part patterns without involving delays or threshold devices. All of these inhibitory nets can construct themselves by means of simple random growth processes, without incurring any loss of learning capacity of holographic properties. Similarly, synapses can be allowed to potentiate with use, so that reaction times are progressively reduced by practice, without any reduction in the quality of the performance. Inhibitory connections between arrays can give patterns in one array control over the allocation of channels in which lower arrays store learned information. A description is given of a model, decentralised, inhibitory hierarchy consisting of inter-connected arrays which can learn to execute goal-directed TOTE-type programs of behaviour by means of a simple ‘putting-through’ procedure.
The Perception of Familiar Stimuli
Authors: Pickering John 
Published: January 2007

A model is described for the processing of word-like (regular) and nonword-like (irregular) letter strings in a situation where either type of string may occur. It is proposed that each type of string is processed by specialised routines which are deployed contingently on an initial decision about the regularity of an item. Three experiments involving word/nonword and same/different responses investigate how the processing of a string is affected by the brief exposure of a prior string. It is shown that processing is interfered with less when both strings are of the same degree of regularity than when they are not. The model is revised and extended in the light of the results obtained as well as some theoretical considerations.
Pattern Structure and Relational Discrimination Learning
Authors: Dodwell Peter C 
Published: January 2007

McGonigle and Jones take exception to Dodwell's explanation of anomalous transfer (AT) as the outcome of relational discriminations among a set of stimulus patterns which vary along a single dimension of orientational salience, from ‘horizontal’ to ‘vertical’. In particular they do not think that the continuum is generated by units with Hubel-and-Wiesel type retinal receptive fields. Instead, they invoke Garner's notions about stimulus structure to explain Dodwell's results, as well as their own finding of two situations where AT fails to occur. It seems that McGonigle and Jones missed the point of the relational discrimination explanation of AT. In fact, it is shown that AT is not predicted by this model for the conditions in which they failed to obtain it. The relational model makes definite predictions about conditions under which AT will occur; as this is not true of their invocation of Garner's ideas, the former is to be preferred. Whether or not outputs are coded by Hubel-and-Wiesel type units is not particularly relevant to the main point, that AT is a result of relational learning. In fact, the model is an instance of how structure, in Garner's sense, can be generated.
Gross Failure to Utilise Alignment Cues in Children's Drawing of Three-Dimensional Relationships
Authors: Freeman Norman , Hayton Claire 
Published: January 2007

There are two major ways of classifying the development of children's attempts to represent three-dimensional relationships on the page. One is in terms of discrete drawing systems and the other is in terms of local decisions that have to be taken within more than one system. An observation is made which appears paradoxical from each of these approaches. Nonetheless, study of the observation reveals a systematic relationship with a systems approach. But this cannot be explained without extending the assumptions of a systems approach.
Distinguishing Two Classes of Impossible Objects
Authors: Thro E Broydrick 
Published: January 2007

Psychologists disagree about what is wrong with the fork. R L Gregory says that its spatial orientation is impossible. J M Kennedy claims that it lacks the intact boundaries characteristic of solid objects. In fact, the fork possesses both these flaws. It cannot be made out of wires because the rectangular/trapezoidal shapes representing its conjoined middle plate and prong create a self-contradictory angle between planes. Further, the fork cannot be cut from a flat sheet of paper because figural contours delineating its boundaries show us self-contradictory transformations of surfaces into air space. The fork is important because its two flaws form the bases of distinct classes into which all the recognized impossibles fall. Different arrangements of the fork's critical rectangle/trapezoid shapes are the sole source of paradox in ‘depth impossibles’—for instance, the triangle and staircase drawings by R and L S Penrose, the window design published anonymously in Aviation Week & Space Technology in 1964, and Belvedere by M C Escher. And variations on the fork's self-contradictory boundary constitute the only source of paradox in ‘impossible solids’—for instance, Escher's Day and Night, Victor Vasarely's Study in Axonometric Perspective, and Escher's Convex and Concave.
Testing a Perceptual Constancy Model for Odor Strength: The Effects of Sniff Pressure and Resistance to Sniffing
Authors: Teghtsoonian Robert , Teghtsoonian Martha 
Published: January 2007

The rate at which odorous vapor flows over the receptor surface is reflected in olfactory nerve activity, but the evidence for a corresponding effect on odor strength is scant and inconsistent. A perceptual constancy model for odor strength resolves this apparent contradiction: The effect of flow rate at the receptor site may be perceptually discounted when there is sensory feedback, in the form of perceived effort, from the action of sniffing responsible for changes in flow rate. Previous evidence shows that observers experience change in perceived effort when sniffing at various pressures against fixed resistance but not when sniffing with fixed pressure against varying resistance. Thus the model predicts both that odor strength varies when flow rate is manipulated by changes in olfactory resistance and that odor strength is invariant when flow rate is manipulated by changes in sniff pressure. In the present study, in which subjects made magnitude estimates of the odor strength of pyridine and n-butanol, an earlier finding for the effects of resistance change was confirmed and extended. Further, within the framework of a single experiment in which both pressure and resistance were independently manipulated, the odor strength of n-butanol conformed to the predictions of the constancy model.
Further Studies of the Café Wall and Hollow Squares Illusions
Authors: Woodhouse J Margaret , Taylor Steve 
Published: January 2007

The effect of varying the contrast on the apparent convergence is measured for both the Café Wall and the Hollow Squares (Taylor—Woodhouse) illusions. The apparent convergence is dependent on the contrast, and also on the size of the stimulus, and varies in the same way for both illusions. This strengthens the argument that the illusions are not independent, as Taylor and Woodhouse originally claimed. McCourt has discussed brightness induction as a basis of the Café Wall illusion. Consideration of this theory leads to some interesting examples of interactions of the two illusions, and to a further, very strong, variation of the illusion in a real-life situation.
Visual Illusory Productions with or without Amodal Completion
Authors: Bonaiuto Paolo , Giannini Anna Maria , Bonaiuto Marino 
Published: January 2007

A new type of illusory contour is presented whose appearance is generated by the graphic representation of groups of human figures interacting in a coordinated manner with external reality. When numerous pictorial indicators of cause-effect relationships are provided, and appropriate techniques and sufficiently ambiguous observation conditions are used, hallucinatory objects congruent with expectations linked to the meaning of the configurations appear. There is thus a high-level semantic component that is active in the formation of visual illusory contours and is even capable of interacting with other known factors: brightness contrast, the number of elements, the degree of alignment of the elements, etc. This new type of illusory contour fits current definitions and can be experimentally modified. The variations in subjective clarity scores are presented for a study in which twenty subjects observed nineteen experimental figures, certain variables of which were manipulated. The issue is worthy of further experimental investigation.
The Ceiling of the Church of St Ignatius and the Perception of Concave Surfaces
Authors: Massironi Manfredo , Savardi Ugo 
Published: January 2007

This research describes two hitherto unobserved phenomena in the frescoes of the seventeenth century architect and painter, Andrea Pozzo, painted on the vaulted ceiling of the central nave of the Church of St Ignatius in Rome. The present research also reports the results of two experimental studies on the problem of the perception of shapes projected on concave surfaces. A quantitative evaluation of the phenomena perceived from various points of observation is made by means of stimuli projected at various angles on a semicylindrical surface. The validity of the assumption of invariance, and in particular of the projective invariant called the cross-ratio, is discussed within the framework of ecological theories on perception.
Amodal Completion versus Induced Inhomogeneities in the Organization of Illusory Figures
Authors: Davi Marco , Pinna Baingio , Sambin Marco 
Published: January 2007

An analysis is presented of a phenomenological model of illusory contours. The model is based on amodal completion as the primary factor giving rise to the illusory figure. In the experiment, conducted by the method of paired comparisons, the same parameter was manipulated in two series of equivalent configurations. The first series yielded examples of amodal completion, the second examples of illusory figures. Three groups of subjects evaluated the magnitude of completion, the brightness contrast of the illusory figure, and the contour clarity of the illusory figure. A control experiment was conducted, which demonstrated that in these configurations amodal completion and amodal continuation behave in the same way. Line displacement did not influence the brightness or the contour clarity of the illusory figures, though it influenced the magnitude of amodal completion. These results are in agreement with the energetic model developed by Sambin.
Guest Editorial: Perceptual Organisation and Object Recognition—POOR is the Acronym, Rich the Notion
Authors: Wagemans Johan , Kolinsky Régine 
Published: January 2007

Instead of studying perceptual organisation and object recognition in relative isolation, they can be viewed as two highly related sets of processes performed by the visual system to achieve its goal of acquiring information about the world. Fifteen papers devoted to specific subproblems within this active area of research have been brought together in two successive issues of Perception. Collectively they demonstrate that focusing on the functional interrelationships between perceptual organisation and object recognition will enrich our understanding of each of the subprocesses involved. The editorial provides an overview of the papers together with a discussion on how they relate to one another. If a general message is to be extracted from this set of papers, it is that the reported findings and the speculations offered to explain them suggest that the visual system's processes cannot be characterised in general by simple dichotomies such as analytic versus wholistic, bottom-up versus top-down, local versus global, low-level versus high-level, parallel versus serial, etc. Instead, it appears that a wide variety of mechanisms is available to the visual system. Therefore, a complete understanding of its functioning will require careful examination of the circumstances within which one processing mechanism seems to be selected over another, depending on the available information, the task demands, and perhaps even the observer's individual characteristics.
Mechanisms of Stereoscopic Processing: Stereoattention and Surface Perception in Depth Reconstruction
Authors: Tyler Christopher W , Kontsevich Leonid L 
Published: January 2007

Consideration of the range of phenomena from studies of human stereopsis suggests that a five-stage model is required to provide a complete account of the processes involved, within which any stereoattention mechanism must operate. The information from the disparity field of the optical projections to the two eyes (stage 1) goes to a set of parallel Keplerian arrays of disparity detectors, each array selective for a different spatiotemporal property of the visual images (stage 2). Global interactions produce a cyclopean depth image that is cleaned of the spurious ghost images in the Keplerian arrays (stage 3) and that may then be processed for its (hypercyclopean) form elements (stage 4). Finally, there must be a stage of integration of the stereoscopic depth cues with monocular and kinesthetic depth cues to form the overall map of perceived distance (stage 5). The fact that multiple cyclopean surfaces may be perceived as transparent implies that the stereoscopic system is not limited by a singular-surface constraint. However, it is unclear whether multiple surfaces can be seen simultaneously or whether only one surface is seen at a time by a selective-attention process, with the others perceived as a purely inchoate (qualitative) depth impression. New experiments on cueing of ambiguous stereocorrugations by singular flat planes suggest that selective stereoattention is a powerful mechanism. In fact, the results show that attention can be focused not just in horopteral planes but in a variety of depth configurations. Moreover, this attention focus may act as a tracking mechanism to allow perception of smooth cyclopean stereomotion, which has a frequency response up to ~ 5 Hz (in contrast to the ~15 Hz limit for detecting planar disparity shifts as jerky appearance and disappearance effects). Finally, the spatial limits of stereosurface reconstruction are explored with cyclopean targets to show some interesting asymmetries of the surface-wrapping process that may represent object-oriented constraints on depth reconstruction.
Shadows and Depth Illusions
Authors: Morris Reg C 
Published: January 2007

The visual system uses shadows to compute perceived depth of features on an uneven surface, and in doing so makes the assumption of a single light source in most circumstances. Three illusory depth effects are described (depth reversal, accentuation, and flattening) that can be demonstrated with 3-D materials, and all of which are based on the single-source assumption. Ambiguous lighting conditions may produce moment-to-moment depth reversals and/or the subjective sensation of textural ‘strangeness’. It is suggested that these are both subjective experiences which occur when the system cannot compute depth with certainty.
Shading and Stereo in Early Perception of Shape and Reflectance
Authors: Sun Jennifer , Perona Pietro 
Published: January 2007

Recent experiments involving shaded 2-D stimuli have shown that early-vision mechanisms are capable of interpreting 3-D shape from shading. In particular, target discrimination tasks suggest that a target ‘pops out’ when background distractors, but not the target, can be interpreted as convex and lit from above or top-left. Since the problem of extracting 3-D shape from shading is intrinsically ill-defined, early vision may need to make these twin assumptions of convexity and top-left lighting in order to constrain the problem. Would these assumptions be recognized as unnecessary and consequently discarded when 3-D shape could be unambiguously defined by some other cue, like stereo disparity? A 2AFC stimulus onset asynchrony paradigm with masking was used in target discrimination experiments. The performance of five naive subjects on tasks where only shading cues were present was compared with that on tasks involving shading as well as stereo cues that define shape unambiguously. The results show that although stereo disparity information is incorporated by early-vision 3-D mechanisms, it is not used to overturn the default assumptions of lighting and shape. Stereo information is interpreted within the framework of top-left lighting, and a consistent preference for convexity is seen over concavity.
Effects of cyclization on conformational dynamics and binding properties of Lys48‐linked di‐ubiquitin
Authors: Dickinson Bryan C. , Varadan Ranjani , Fushman David 
Published: January 2007

AbstractIn solution, Lys48‐linked di‐ubiquitin exists in dynamic equilibrium between closed and open conformations. To understand the effect of interdomain motion in polyubiquitin chains on their ability to bind ligands, we cyclized di‐ubiquitin by cross‐linking the free C terminus of the proximal ubiquitin with the side chain of residue 48 in the distal ubiquitin, using a chemical cross‐linker, 1,6‐Hexane‐bis‐vinylsulfone. Our NMR studies confirm that the cyclization affects conformational dynamics in di‐ubiquitin by restricting opening of the interface and shifting the conformational equilibrium toward closed conformations. The cyclization, however, did not rigidly lock di‐ubiquitin in a single closed conformation: The chain undergoes slow exchange between at least two closed conformations, characterized by interdomain contacts involving the same hydrophobic patch residues (Leu8‐Ile44‐Val70) as in the uncyclized di‐ubiquitin. Lowering the pH changes the relative populations of these conformations, but in contrast with the uncyclized di‐ubiquitin, does not lead to opening of the interface. This restriction of domain motions inhibits direct access of protein molecules to the hydrophobic patch residues located at the very center of the interdomain interface in di‐ubiquitin, although the residual motions are sufficient to allow access of small molecules to the interface. This renders di‐ubiquitin unable to bind protein molecules (e.g., UBA2 domain) in the normal manner, and thus could interfere with Ub2 recognition by various downstream effectors. These results emphasize the importance of the opening/closing domain motions for the recognition and function of di‐ubiquitin and possibly longer polyubiquitin chains.
Crystal structure of human μ‐crystallin complexed with NADPH
Authors: Cheng Zhongjun , Sun Lihua , He Jianhua , Gong Weimin 
Published: January 2007

AbstractHuman cytosolic 3,5,3′‐triiodo‐L‐thyronine‐binding protein, also called μ‐crystallin or CRYM, plays important physiological roles in transporting 3,5,3′‐triiodo‐L‐thyronine (T3) into nuclei and regulating thyroid‐hormone‐related gene expression. The crystal structure of human CRYM's bacterial homolog Pseudomonas putida ornithine cyclodeaminase and Archaeoglobus fulgidus alanine dehydrogenase have been available, but no CRYM structure has been reported. Here, we report the crystal structure of human CRYM bound with NADPH refined to 2.6 Å, and there is one dimer in the asymmetric unit. The structure contains two domains: a Rossmann fold–like NADPH‐binding domain and a dimerization domain. Different conformations of the loop Arg83–His92 have been observed in two monomers of human CRYM in the same asymmetric unit. The peptide bond of Val89–Pro90 is a trans‐configuration in one monomer but a cis‐configuration in the other. A detailed comparison of the human μ‐crystallin structure with its structurally characterized homologs including the overall comparison and superposition of active sites was conducted. Finally, a putative T3‐binding site in human CRYM is proposed based on comparison with structural homologs.
Site of deposition and absorption of an inhaled hydrophilic solute
Authors: Bondesson Eva , Bengtsson Thomas , Nilsson Lars‐Erik , Wollmer Per 
Published: January 2007

AimsTo characterize the absorption kinetics and bioavailability of an inhaled hydrophilic solute deposited at various sites within the airways.MethodsNine healthy nonsmokers received one intravenous, one oropharyngeal and two pulmonary doses of technetium‐99 m‐labelled diethylene triamine pentaacetic acid (99mTc‐DTPA) in an open and crossover fashion. Pulmonary doses were administered as nebulized large and fine droplet‐sized aerosols by Pari and UltraVent nebulizers at fairly rapid and slow inhalation flows, respectively. Plasma concentration‐time profiles and 24 h urinary excretion of radioactivity were determined. One dose of 99mTc‐labelled Nanocoll, as a marker of mucociliary clearance (MCC), was also administered by Pari for similar lung deposition as the 99mTc‐DTPA and followed by repeated chest γ‐imaging.ResultsIntrapulmonary deposition patterns of 99mTc‐DTPA differed significantly (the mean ratio of penetration index (Pari : UltraVent) was 76% with 95% CI 63%, 91%). However, no differences in rate or extent of 99mTc‐DTPA absorption were detected. Mean absorption time was 1.8 h (mean difference (Pari–UltraVent): −0.1 h with 95% CI −0.6 h, 0.3 h) and the bioavailability was 70% (mean ratio (Pari : UltraVent): 101% with 95% CI 90%, 115%). The pulmonary elimination half‐life of 99mTc‐Nanocoll (8 h and 45 min) was significantly longer than that of 99mTc‐DTPA (less than 2 h). The oral bioavailability of 99mTc‐DTPA was estimated to be 3.1%.ConclusionsThe main elimination pathway of the inhaled hydrophilic solute 99mTc‐DTPA from the lungs is trans‐epithelial absorption. Despite different intrapulmonary radioaerosol deposition patterns, as verified by gamma scintigraphy, no differences in 99mTc‐DTPA absorption kinetics or bioavailability were detected.
Fine needle aspiration cytology of solitary fibrous tumours of the pleura
Authors: Cho E. Y. , Han J. J. , Han J. , Oh Y. L. 
Published: January 2007

Objective:  To analyse fine needle aspirates from solitary fibrous tumour (SFT) of the pleura and to elucidate the cytological features unique to these tumours and differential diagnostic findings of benign and malignant SFTs.Methods:  Fine needle aspiration (FNA) cytology slides from eight cases of SFT of the pleura, including six benign and two malignant SFTs, were reviewed. The subsequent histological slides were also examined.Results:  Cytological diagnoses from six histologically proven cases of benign SFTs were low‐grade sarcoma (one), non‐small cell carcinoma (one), malignant tumour (1) and benign (three). Two cases of malignant SFTs were cytologically diagnosed as malignancy. The aspirates showed a varying degree of cellularity. Most smears were composed of single, scattered fusiform cells, and irregular loose aggregates of oval to spindle cells intimately admixed with dense collagenous stroma. Two malignant SFTs had a greater number of cells in clusters, and displayed mitotic activity, without significant cytological atypia.Conclusions:  The diagnosis of SFT may be suggested by a combination of cytological and radiological findings. The precise determination of malignancy for SFT, however, is not usually straightforward on the basis of cytological features alone. The findings of highly cellular clusters and mitotic activity in the FNA cytological smear can help differentiate malignant from benign SFTs.