Efficient dynamics in the space of contact maps

In a stereoscopic system, both eyes or cameras have a slightly different view. As a consequence, small variations between the projected images exist ('disparities') which are spatially evaluated in order to retrieve depth information (Sanger 1988; Fleet et al. 1991). A strong similarity exists between the analysis of visual disparities and the determination of the azimuth of a sound source (Wagner and Frost 1993). The direction of the sound is thereby determined from the temporal delay between the left and right ear signals (Konishi and Sullivan 1986). Similarly, here we transpose the spatially defined problem of disparity analysis into the temporal domain and utilize two resonators implemented in the form of causal (electronic) filters to determine the disparity as local temporal phase differences between the left and right filter responses. This approach permits real-time analysis and can be solved analytically for a step function contrast change, which is an important case in all real-world applications. The proposed theoretical framework for spatial depth retrieval directly utilizes a temporal algorithm borrowed from auditory signal analysis. Thus, the suggested similarity between the visual and the auditory system in the brain (Wagner and Frost 1993) finds its analogy here at the algorithmical level. We will compare the results from the temporal resonance algorithm with those obtained from several other techniques like cross-correlation or spatial phase-based disparity estimation showing that the novel algorithm achieves performances similar to the 'classical' approaches using much lower computational resources.     

Clinical and pharmacological spectral maps of the neuroleptics

Forty-seven patients with Graves' disease, 73 with thyroiditis and 128 controls drawn from the same geographical area of Newfoundland were HLA typed. The frequency of HLA-B8 was significantly increased in the Graves' disease patients when compared to the control group giving a relative risk of 3.9. There were no significant HLA differences between the thyroiditis and control groups. Homozygosity for the HLA haplotype, which is common in this island population, was more common in Graves' disease patients (12.8%) than in controls (5.5%) but did not reach statistical significance in this sample. Homozygosity was due in five of the six cases to either an A1;B8 haplotype or an A2;B8 haplotype. This contrasted with an apparently random assortment of haplotypes in the control and thyroiditis groups. Calculations suggest that homozygosity for a B8 haplotype confers an additional risk over heterozygosity for B8 of about 3.5 fold; however, homozygosity had no observable influence on the severity of the disease. These results strengthen the idea that B8, or an allele in linkage disequilibrium with it, determines in part the susceptibility of an individual to developing Graves' disease.     

Mental organization of maps.

Previous studies deconfounding spatial and temporal proximity during map learning have found a temporal influence on mental map organization. The authors explored whether this observed priming effect reflected the manner in which a map was learned by having people either name objects or point to them during learning. Naming objects resulted in temporal organization but pointing to objects resulted in spatial organization, suggesting that mental map organization is sensitive to emphasizing different types of map information during learning. The authors also explored whether the temporal organization observed in the naming group was influenced by the ease of using spatial information during learning, such as when the expectancy to use spatial information was made explicit or when a consistent temporal order was absent. When naming map objects, evidence for a spatial organization was weak, whereas a temporal organization was observed when a consistent temporal order was present. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Registration of neural maps through value-dependent learning: modeling the alignment of auditory and visual maps in the barn owl's optic tectum

In the optic tectum (OT) of the barn owl, visual and auditory maps of space are found in close alignment with each other. Experiments in which such alignment has been disrupted have shown a considerable degree of plasticity in the auditory map. The external nucleus of the inferior colliculus (ICx), an auditory center that projects massively to the tectum, is the main site of plasticity; however, it is unclear by what mechanisms the alignment between the auditory map in the ICx and the visual map in the tectum is established and maintained. In this paper, we propose that such map alignment occurs through a process of value-dependent learning. According to this paradigm, value systems, identifiable with neuromodulatory systems having diffuse projections, respond to innate or acquired salient cues and modulate changes in synaptic efficacy in many brain regions. To test the self-consistency of this proposal, we have developed a computer model of the principal neural structures involved in the process of auditory localization in the barn owl. This is complemented by simulations of aspects of the barn owl phenotype and of the experimental environment. In the model, a value system is activated whenever the owl carries out a foveation toward an auditory stimulus. A term representing the diffuse release of a neuromodulator interacts with local pre- and postsynaptic events to determine synaptic changes in the ICx. Through large-scale simulations, we have replicated a number of experimental observations on the development of spatial alignment between the auditory and visual maps during normal visual experience, after the retinal image is shifted through prismatic goggles, and after the reestablishment of normal visual input. The results suggest that value-dependent learning is sufficient to account for the registration of auditory and visual maps of space in the OT of the barn owl, and they lead to a number of experimental predictions.     

Dynamic contact maps of protein structures

The two-dimensional contact map of interresidue distances is a visual analysis technique for protein structures. We present two standalone software tools designed to be used in combination to increase the versatility of this simple yet powerful technique. First, the program Structer calculates contact maps from three-dimensional molecular structural data. The contact map matrix can then be viewed in the graphical matrix-visualization program Dotter. Instead of using a predefined distance cutoff, we exploit Dotter's dynamic rendering control, allowing interactive exploration at varying distance cutoffs after calculating the matrix once. Structer can use a number of distance measures, can incorporate multiple chains in one contact map, and allows masking of user-defined residue sets. It works either directly with PDB files, or can use the MMDB network API for reading structures.