Temporal dynamics of the neural representation of hue and luminance contrast

Hue and luminance contrast are the most basic visual features, emerging in early layers of convolutional neural networks trained to perform object categorization. In human vision, the timing of the neural computations that extract these features, and the extent to which they are determined by the same or separate neural circuits, is unknown. We addressed these questions using multivariate analyses of human brain responses measured with magnetoencephalography. We report four discoveries. First, it was possible to decode hue tolerant to changes in luminance contrast, and luminance contrast tolerant to changes in hue, consistent with the existence of separable neural mechanisms for these features. Second, the decoding time course for luminance contrast peaked 16-24 ms before hue and showed a more prominent secondary peak corresponding to decoding of stimulus cessation. These results are consistent with the idea that the brain uses luminance contrast as an updating signal to separate events within the constant stream of visual information. Third, neural representations of hue generalized to a greater extent across time, providing a neural correlate of the preeminence of hue over luminance contrast in perceptual grouping and memory. Finally, decoding of luminance contrast was more variable across participants for hues associated with daylight (orange and blue) than for anti-daylight (green and pink), suggesting that color-constancy mechanisms reflect individual differences in assumptions about natural lighting

Genome-wide identification and phenotypic characterization of seizure-associated copy number variations in 741,075 individuals

Copy number variants (CNV) are established risk factors for neurodevelopmental disorders with seizures or epilepsy. With the hypothesis that seizure disorders share genetic risk factors, we pooled CNV data from 10,590 individuals with seizure disorders, 16,109 individuals with clinically validated epilepsy, and 492,324 population controls and identified 25 genome-wide significant loci, 22 of which are novel for seizure disorders, such as deletions at 1p36.33, 1q44, 2p21-p16.3, 3q29, 8p23.3-p23.2, 9p24.3, 10q26.3, 15q11.2, 15q12-q13.1, 16p12.2, 17q21.31, duplications at 2q13, 9q34.3, 16p13.3, 17q12, 19p13.3, 20q13.33, and reciprocal CNVs at 16p11.2, and 22q11.21. Using genetic data from additional 248,751 individuals with 23 neuropsychiatric phenotypes, we explored the pleiotropy of these 25 loci. Finally, in a subset of individuals with epilepsy and detailed clinical data available, we performed phenome-wide association analyses between individual CNVs and clinical annotations categorized through the Human Phenotype Ontology (HPO). For six CNVs, we identified 19 significant associations with specific HPO terms and generated, for all CNVs, phenotype signatures across 17 clinical categories relevant for epileptologists. This is the most comprehensive investigation of CNVs in epilepsy and related seizure disorders, with potential implications for clinical practice

<span style="mso-ansi-language:EN-US" lang="EN-US">Electrostatics and tailoring for aggregation of small linear molecules: An <i style="mso-bidi-font-style:normal">ab initio</i> study </span>

1019-1030Features of the molecular electrostatic potential (MESP) for three linear triatomic molecules, viz., CO2, CS2 and OCS are utilized for a comparative study of their aggregation into small clusters. Trial structures of clusters upto tetramers, generated by using the MESP insights, are subjected to geometry optimization employing second-order Møller-Plesset (MP2) theory, with correlation consistent aug-cc-pvTZ (aTZ) basis set. Single point energies at MP2/aQZ levels are calculated for the estimation of binding energies at complete basis set (CBS) limit. Calculations at the coupled cluster singles and doubles with perturbative triples (CCSD(T)) level are also reported for the most favorable tetramers using the molecular tailoring approach (MTA). Geometrical parameters such as rotational constants thus obtained are found to be in good agreement with the corresponding experimental ones. Minimal nature of the reported structures is confirmed by the vibrational frequency calculations at MP2/aDZ level of theory. The current work offers some hints towards the patterns in the oligomer formation for these molecules and a comparison of the motifs found in the corresponding crystal structure is made. </span

Electrophilic Additions to a 2-Methylenebicyclo[2.1.1 hexane System: Probing \pi-Face Selectivity for Electrostatic and Orbital Effects

5-exo-Bicyclo[2.1.1]hexane derivatives with remote electron-withdrawing substituents exhibit very modest face selectivity during electrophilic additions due to interplay of several electronic factors. These experimental results have been probed through ab initio MESP maps, bond density calculations, and energetics involved in pre-reaction complexation

Exploring Structures and Energetics of Large OCS Clusters by Correlated Methods

An extensive minima search based on accurate estimation of binding energies in (OCS)_<i>n</i> clusters for <i>n</i> = 2–5 is carried out employing MP2 and CCSD­(T) levels of theory. Features of the molecular electrostatic potential of the OCS monomer are utilized for building the laterally shifted and linear aggregates of OCS. Trial structures generated through cluster building algorithm are subjected to geometry optimization at MP2 level using aug-cc-pvTZ (TZ) basis set. Molecular tailoring approach (MTA)-based single-point energies at MP2/QZ and CCSD­(T)/TZ levels are calculated for the estimation of binding energy at complete basis set (CBS) limit. For a comparative study, benchmark calculations employing the dispersion-corrected B2PLYPD functional with TZ basis set are effected. The resulting geometrical parameters from which are found to be in excellent agreement with the experimental findings. With increasing cluster size, the calculated vibrational frequency at the MP2/DZ level of theory shows a substantial blue shift for the asymmetric C–O stretch. The results from the present study clearly bring out the feasibility of carrying out ab initio calculations on large-sized clusters on limited hardware with a minimal loss of accuracy