Feature-Specific Information Processing Precedes Concerted Activation in Human Visual Cortex

Current knowledge about the precise timing of visual input to the cortex relies largely on spike timings in monkeys and evoked-response latencies in humans. However, quantifying the activation onset does not unambiguously describe the timing of stimulus-feature-specific information processing. Here, we investigated the information content of the early human visual cortical activity by decoding low-level visual features from single-trial magnetoencephalographic (MEG) responses. MEG was measured from nine healthy subjects as they viewed annular sinusoidal gratings (spanning the visual field from 2 to 10° for a duration of 1 s), characterized by spatial frequency (0.33 cycles/degree or 1.33 cycles/degree) and orientation (45° or 135°); gratings were either static or rotated clockwise or anticlockwise from 0 to 180°. Time-resolved classifiers using a 20 ms moving window exceeded chance level at 51 ms (the later edge of the window) for spatial frequency, 65 ms for orientation, and 98 ms for rotation direction. Decoding accuracies of spatial frequency and orientation peaked at 70 and 90 ms, respectively, coinciding with the peaks of the onset evoked responses. Within-subject time-insensitive pattern classifiers decoded spatial frequency and orientation simultaneously (mean accuracy 64%, chance 25%) and rotation direction (mean 82%, chance 50%). Classifiers trained on data from other subjects decoded the spatial frequency (73%), but not the orientation, nor the rotation direction. Our results indicate that unaveraged brain responses contain decodable information about low-level visual features already at the time of the earliest cortical evoked responses, and that representations of spatial frequency are highly robust across individuals.Peer reviewe

Vertical propagation characteristics and seasonal variability of tidal wind oscillations in the MLT region over Trivandrum (8.5° N, 77° E): first results from SKiYMET Meteor Radar

Tidal activity in the Mesospheric Lower Thermosphere (MLT) region over Trivandrum (8.5° N, 77° E) is investigated using the observations from newly installed SKiYMET Meteor Radar. The seasonal variability and vertical propagation characteristics of atmospheric tides in the MLT region are addressed in the present communication. The observations revealed that the diurnal tide is more prominent than the semi/terdiurnal components over this latitude. It is also observed that the amplitudes of meridional components are stronger than that of zonal ones. The amplitude and phase structure shows the vertical propagation of diurnal tides with vertical wavelength of ~25 km. However, the vertical wavelength of the semidiurnal tide showed considerable variations. The vertical propagation characteristics of the terdiurnal tide showed some indications of their generating mechanisms. The observed features of tidal components are compared with Global Scale Wave Model (GSWM02) values and they showed a similar amplitude and phase structure for diurnal tides. Month-to-month variations in the tidal amplitudes have shown significant seasonal variation. The observed seasonal variation is discussed in light of the variation in tidal forcing and dissipation

Early Cenozoic rapid flight enigma of the Indian subcontinent resolved: roles of topographic top loading and subcrustal erosion

Intrinsic magmatic processes are considered as critical operators of plate movements. Here we demonstrate the role of extrinsic processes consequent to intrinsic processes as a catalyst for anomalous rapid plate movement. The rapid and accelerated flight of the Indian subcontinent since Deccan volcanism until its collision with Eurasia remains as one of the geological conundrums. Data on seismic tomography, peninsular geomorphology and inferences on continuum of subcrustal structures are utilized to address this enigma. We propose geomorphic isostasy as the mechanism that has driven this fastest drift ever recorded in geological history. It was initiated by sudden instability after the Deccan volcanism and resultant extensive accumulation of lava pile over continental lithosphere of northern India, northern-eastern tilt due to crustal thickness heterogeneity and subcrustal thermal stratification. The drift was sustained by Carlsberg and Central Indian ridge-push until collision and sediment top loading at northeast thenceforth. These inferences and geomorphic isostasy as a catalytic mechanism necessitate variability of drift rates as integral inputs for any continental scale modeling.Muthuvairavasamy Ramkumar, David Menier, Manoj Mathew, M. Santosh, Numair A. Siddiqu

Fishery and Exploitation of Malabar Grouper, Epinephelus malabaricus (Bloch & Schneider 1801) from Andaman Islands

The fishery and population dynamics of groupers from Andaman Islands were studied from Jan 2010 to Dec 2011 with a special emphasis on Malabar grouper, Epinephelus malabaricus (Bloch & Schneider 1801). The average annual catch of Malabar grouper was 1,296 tonnes contributing to 21.6% of annual grouper landings. Length-weight relationship of Malabar grouper showed that growth was allometric (b=2.96) and relative condition factor (Kn) was 1 and the growth parameters viz., L∞, K and t0 were 124.60 cm, 0.80 and -0.05 respectively. The recruitment pattern was unimodal with one major peak during April to July throughout the study period. The natural mortality (M), fishing mortality (F) and total mortality (Z) were 1.05, 1.48 and 2.53 respectively and exploitation rate (E) was 0.58. The M/K ratio (1.31) was found to be well within the normal range of 1to 2.5. Catch per unit effort varied from 4 to16.5 kg.h-1. The maximum sustainable yield (MSY) was 1,107 tonnes which was lower than the average annual catch (1,296 tonnes), indicating over exploitation. The current study calls for further research in identifying the grouper fishing and spawning aggregation grounds and introduce measures for reducing fishing efforts with input and output controls to sustain the Malabar grouper fishery in Andaman waters

Interaction of JLP with Plk1 recruits FoxK1 to interact and form a ternary complex

JLP (JNK associated Leucine zipper protein) is a scaffolding protein, which has been shown to interact with and activate JNK/p38MAPK pathway. Its interaction with various signaling proteins is associated with coordinated regulation of cellular process such as endocytosis, motility, neurite outgrowth, cell proliferation and apoptosis. Here we identified a mitotic Serine/Threonine kinase, Polo like kinase 1 (Plk1), as a novel interaction partner of JLP through a mass spectrometry based approach. We show that the N-terminal domain of JLP interacts with the polo-box domain (PBD) of Plk1 in a phosphorylation-dependent manner. Our results indicate that, JLP is phospho-primed on Thr 351 residue on its Nterminus, which is recognized by the PBD of Plk1 leading to phosphorylation of JLP at additional sites. Moreover, treatment of cells with the Plk1 inhibitor, BI2536 affects the interaction demonstrating the importance of Plk1 kinase activity in this process. Since JLP is a scaffolding protein that recruits proteins to mediate specific cell signaling events, we hypothesized that the interaction of JLP with Plk1 might result in the recruitment of other proteins to this complex. To test this hypothesis, we carried out SILAC labeling of proteins in mitotic cells in the presence or absence of BI2536. Through mass-spectrometry we identified the transcription factor, FoxK1 as a Plk1-dependent JLP-interacting protein. Furthermore, we show that JLP, Plk1 and FoxK1 form a ternary complex, which occurs only during mitosis. Knockdown of Plk1 and not JLP, affected the interaction between JLP and FoxK1 indicating that the formation of the ternary complex is dependent on Plk1. FoxK1 has been previously characterized as a transcriptional repressor of cyclin dependent kinase inhibitor, p21/WAF1. We observed that knockdown of JLP in U2OS cells results in increased protein levels of FoxK1 and a reduction of p21 expression. Moreover, immunofluorescence studies in asynchronous cells showed that FoxK1 is excluded from the nucleus during mitosis. Based on our observations, we propose that formation of the ternary complex between JLP, Plk1 and FoxK1 regulates the stability and/or localization of FoxK1

Invariance and plasticity in the Drosophila melanogaster metabolomic network in response to temperature

BACKGROUND: Metabolomic responses to extreme thermal stress have recently been investigated in Drosophila melanogaster. However, a network level understanding of metabolomic responses to longer and less drastic temperature changes, which more closely reflect variation in natural ambient temperatures experienced during development and adulthood, is currently lacking. Here we use high-resolution, non-targeted metabolomics to dissect metabolomic changes in D. melanogaster elicited by moderately cool (18°C) or warm (27°C) developmental and adult temperature exposures. RESULTS: We find that temperature at which larvae are reared has a dramatic effect on metabolomic network structure measured in adults. Using network analysis, we are able to identify modules that are highly differentially expressed in response to changing developmental temperature, as well as modules whose correlation structure is strongly preserved across temperature. CONCLUSIONS: Our results suggest that the effect of temperature on the metabolome provides an easily studied and powerful model for understanding the forces that influence invariance and plasticity in biological networks. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12918-014-0139-6) contains supplementary material, which is available to authorized users