Development of temporal response properties and contrast sensitivity of V1 and V2 neurons in macaque monkeys

The temporal contrast sensitivity of human infants is reduced compared to that of adults. It is not known which neural structures of our visual brain sets limits on the early maturation of temporal vision. In this study we investigated how individual neurons in the primary visual cortex (V1) and visual area 2 (V2) of infant monkeys respond to temporal modulation of spatially optimized grating stimuli and a range of stimulus contrasts. As early as 2 wk of age, V1 and V2 neurons exhibited band-pass temporal frequency tuning. However, the optimal temporal frequency and temporal resolution of V1 neurons were much lower in 2- and 4-wk-old infants than in 8-wk-old infants or adults. V2 neurons of 8-wk-old monkeys had significantly lower optimal temporal frequencies and resolutions than those of adults. Onset latency was longer in V1 at 2 and 4 wk of age and was slower in V2 even at 8 wk of age than in adults. Contrast threshold of V1 and V2 neurons was substantially higher in 2- and 4-wk-old infants but became adultlike by 8 wk of age. For the first 4 wk of life, responses to high-contrast stimuli saturated more readily in V2. The present results suggest that although the early development of temporal vision and contrast sensitivity may largely depend on the functional maturation of precortical structures, it is also likely to be limited by immaturities that are unique to V1 and V

Effects of perceptual learning on local stereopsis and neuronal responses of V1 and V2 in prism-reared monkeys.

Visual performance improves with practice (perceptual learning). In this study, we sought to determine whether or not adult monkeys reared with early abnormal visual experience improve their stereoacuity by extensive psychophysical training and testing, and if so, whether alterations of neuronal responses in the primary visual cortex (V1) and/or visual area 2 (V2) are involved in such improvement. Strabismus was optically simulated in five macaque monkeys using a prism-rearing procedure between 4 and 14 wk of age. Around 2 yr of age, three of the prism-reared monkeys ( trained monkeys) were tested for their spatial contrast sensitivity and stereoacuity. Two other prism-reared monkeys received no training or testing ( untrained monkeys). Microelectrode experiments were conducted around 4 yr of age. All three prism-reared trained monkeys showed improvement in stereoacuity by a factor of 7 or better. However, final stereothresholds were still approximately 10-20 times worse than those in normal monkeys. In V1, disparity sensitivity was drastically reduced in both the trained and untrained prism-reared monkeys and behavioral training had no obvious effect. In V2, the disparity sensitivity in the trained monkeys was better by a factor of approximately 2.0 compared with that in the untrained monkeys. These data suggest that the observed improvement in stereoacuity of the trained prism-reared monkeys may have resulted from better retention of disparity sensitivity in V2 and/or from learning by upstream neurons to more efficiently attend to residual local disparity information in V1 and V

Changes in global ocean bottom properties and volume transports in CMIP5 models under climate change scenarios

Changes in bottom temperature, salinity and density in the global ocean by 2100 for CMIP5 climate models are investigated for the climate change scenarios RCP4.5 and RCP8.5. The mean of 24 models shows a decrease in density in all deep basins except the North Atlantic which becomes denser. The individual model responses to climate change forcing are more complex: regarding temperature, the 24 models predict a warming of the bottom layer of the global ocean; in salinity, there is less agreement regarding the sign of the change, especially in the Southern Ocean. The magnitude and equatorward extent of these changes also vary strongly among models. The changes in properties can be linked with changes in the mean transport of key water masses. The Atlantic Meridional Overturning Circulation weakens in most models and is directly linked to changes in bottom density in the North Atlantic. These changes are due to the intrusion of modified Antarctic Bottom Water, made possible by the decrease in North Atlantic Deep Water formation. In the Indian, Pacific and South Atlantic, changes in bottom density are congruent with the weakening in Antarctic Bottom Water transport through these basins. We argue that the greater the 1986-2005 meridional transports, the more changes have propagated equatorwards by 2100. However, strong decreases in density over 100 years of climate change cause a weakening of the transports. The speed at which these property changes reach the deep basins is critical for a correct assessment of the heat storage capacity of the oceans as well as for predictions of future sea level rise

Cold-induced changes in gene expression in brown adipose tissue, white adipose tissue and liver

Cold exposure imposes a metabolic challenge to mammals that is met by a coordinated response in different tissues to prevent hypothermia. This study reports a transcriptomic analysis in brown adipose tissue (BAT), white adipose (WAT) and liver of mice in response to 24 h cold exposure at 8°C. Expression of 1895 genes were significantly (P<0.05) up- or down-regulated more than two fold by cold exposure in all tissues but only 5 of these genes were shared by all three tissues, and only 19, 14 and 134 genes were common between WAT and BAT, WAT and liver, and BAT and liver, respectively. We confirmed using qRT-PCR, the increased expression of a number of characteristic BAT genes during cold exposure. In both BAT and the liver, the most common direction of change in gene expression was suppression (496 genes in BAT and 590 genes in liver). Gene ontology analysis revealed for the first time significant (P<0.05) down regulation in response to cold, of genes involved in oxidoreductase activity, lipid metabolic processes and protease inhibitor activity, in both BAT and liver, but not WAT. The results reveal an unexpected importance of down regulation of cytochrome P450 gene expression and apolipoprotein, in both BAT and liver, but not WAT, in response to cold exposure. Pathway analysis suggests a model in which down regulation of the nuclear transcription factors HNF4α and PPARα in both BAT and liver may orchestrate the down regulation of genes involved in lipoprotein and steroid metabolism as well as Phase I enzymes belonging to the cytochrome P450 group in response to cold stress in mice. We propose that the response to cold stress involves decreased gene expression in a range of cellular processes in order to maximise pathways involved in heat production

The End of the Rainbow: What Can We Say About the Extragalactic Sub-Megahertz Radio Sky?

The Galactic disc is opaque to radio waves from extragalactic sources with frequencies nu less than ~3 MHz. However, radio waves with kHz, Hz, and even lower frequencies may propagate through the intergalactic medium (IGM). I argue that the presence of these waves can be inferred by using the Universe as our detector. I discuss possible sub-MHz sources and set new non-trivial upper limits on the energy density of sub-MHz radio waves in galaxy clusters and the average cosmic background. Limits based on five effects are considered: (1) changes in the expansion of the Universe from the radiation energy density (2) heating of the IGM by free-free absorption; (3) radiation pressure squeezing of IGM clouds by external radio waves; (4) synchrotron heating of electrons in clusters; and (5) Inverse Compton upscattering of sub-MHz radio photons. Any sub-MHz background must have an energy density much smaller than the CMB at frequencies below 1 MHz. The free-free absorption bounds from the Lyman-alpha forest are potentially the strongest, but are highly dependent on the properties of sub-MHz radio scattering in the IGM. I estimate an upper limit of 6 * 10^4 L_sun Mpc^-3 for the emissivity within Lyman-alpha forest clouds in the frequency range 5 - 200 Hz. The sub-MHz energy density in the Coma cluster is constrained to be less than ~10^-15 erg cm^-3. At present, none of the limits is strong enough to rule out a maximal T_b = 10^12 K sub-MHz synchrotron background, but other sources may be constrained with a better knowledge of sub-MHz radio propagation in the IGM.Comment: Accepted by MNRAS, 4 figures, 20 pages

SIVA1 directs the E3 ubiquitin ligase RAD18 for PCNA monoubiquitination

published_or_final_versio

CO2 emissions reduction of Chinese light manufacturing industries:a novel RAM-based global Malmquist-Luenberger productivity index

Climate change has become one of the most challenging issues facing the world. Chinese government has realized the importance of energy conservation and prevention of the climate changes for sustainable development of China's economy and set targets for CO2 emissions reduction in China. In China industry contributes 84.2% of the total CO2 emissions, especially manufacturing industries. Data envelopment analysis (DEA) and Malmquist productivity (MP) index are the widely used mathematical techniques to address the relative efficiency and productivity of a group of homogenous decision making units, e.g. industries or countries. However, in many real applications, especially those related to energy efficiency, there are often undesirable outputs, e.g. the pollutions, waste and CO2 emissions, which are produced inevitably with desirable outputs in the production. This paper introduces a novel Malmquist-Luenberger productivity (MLP) index based on directional distance function (DDF) to address the issue of productivity evolution of DMUs in the presence of undesirable outputs. The new RAM (Range-adjusted measure)-based global MLP index has been applied to evaluate CO2 emissions reduction in Chinese light manufacturing industries. Recommendations for policy makers have been discussed

A framework for measuring global Malmquist–Luenberger productivity index with CO2 emissions on Chinese manufacturing industries

China has achieved significant progress in terms of economic and social developments since implementation of reform and open policy in 1978. However, the rapid speed of economic growth in China has also resulted in high energy consumption and serious environmental problems, which hindering the sustainability of China's economic growth. This paper provides a framework for measuring eco-efficiency with CO2 emissions in Chinese manufacturing industries. We introduce a global Malmquist-Luenberger productivity index (GMLPI) that can handle undesirable factors within Data Envelopment Analysis (DEA). This study suggested after regulations imposed by the Chinese government, in the last stage of the analysis, i.e. during 2011–2012, the contemporaneous frontier shifts towards the global technology frontier in the direction of more desirable outputs and less undesirable outputs, i.e. producing less CO2 emissions, but the GMLPI drops slightly. This is an indication that the Chinese government needs to implement more policy regulations in order to maintain productivity index while reducing CO2 emissions

Activation of the mTOR signalling pathway is required for pancreatic growth in protease-inhibitor-fed mice

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65924/1/jphysiol.2006.106914.pd