Responses of Cortical Extrastriate Area 21a Neurons Specialized in Motion Detection

According to a generally accepted concept, the stationary structure of the receptive field of a visually sensitive central neuron predetermines transformation and central processing of the incoming information, including that related to moving visual stimuli. We found, however, that a small group of visually sensitive neurons of the cat extrastriate cortical area 21a does not fit this statement and exhibits no responses to stationary visual stimuli while responding vigorously to moving images. The results of our experiments showed that response patterns of these neurons to moving stimuli display high degrees of diversification and processing of incoming visual information. We suppose that these neurons may be strictly specialized in the detection and central processing of visual information necessary for perception of moving images.Згідно із загальноприйнятою концепцією, стаціонарна структура рецептивного поля візуочутливого нейрона визначає специфіку трансформації та центральної обробки зорової інформації, що надходить, включно з інформацією про рухливі візуальні стимули. Ми, проте, виявили, що властивості невеликої групи візуочутливих нейронів у кортикальній екстрастріатній зоні 21a не узгоджуються з цим положенням; вони не генерують відповідей на пред’явлення стаціонарних зорових стимулів, але в той же час інтенсивно відповідають на пред’явлення рухомих зображень. Як показали результати наших експериментів, патерни відповідей даних нейронів на дію рухомих стимулів демонструють високі рівні диверсифікації та обробки візуальної інформації, що надходить. Ми вважаємо, що ці нейрони можуть бути високоспеціалізованими щодо детекції та центрального процесінгу зорової інформації, необхідної для перцепції рухомих зображень

Movement detection properties and structure of stationary receptive fields of single neurons in the cat extrastriate area 21a

Response patterns of single neurons in the extrastriate area 21a of the cat cortex to moving visual stimuli were studied, along with juxtaposition to the structure of their stationary receptive field. First, the precise mapping of stationary RFs was performed by flashing bright spots; then, moving visual stimuli of different shapes and sizes with two opposite contrasts were presented. We found that the majority of investigated neurons with a homogenous stationary RF organization demonstrate significant differences in their activity profiles depending on the size, shape, and contrast of the applied moving visual stimulus. The data obtained support a model in which the RF stationary structure undergoes specific dynamic changes due to simultaneous activation of the RF surround by the moving visual image; this provides more accurate incorporation of moving image information in movement detection.Досліджували патерни відповідей поодиноких нейронів екстрастріатного поля 21a кори великих півкуль кота на пред’явлення рухливих візуальних стимулів, одночасно беручи до уваги структуру стаціонарних рецептивних полів (РП) цих нейронів. Спочатку виконували прецизійне картування стаціонарних РП за допомогою пред’явлення яскравих плям, що спалахували; після цього пред’являли рухливі візуальні стимули різних форм та розмірів з двома протилежними контрастами. Значна більшість досліджених нейронів із гомогенною організацією стаціонарних РП демонстрували істотно відмінні профілі активності, залежні від величини, форми та контрасту рухливих зорових стимулів, що пред’являлися. Отримані дані узгоджуються з моделлю, в рамках якої стаціонарна структура РП піддається специфічним динамічним модифікаціям завдяки одночасній активації оточення РП під дією рухливого візуального образу. Це забезпечує точніше залучення інформації щодо руху зображення до процесу детекції такого руху

Mineralogical Transformations and Soil Development in Shale Across a Latitudinal Climosequence

To investigate factors controlling soil formation, we established a climosequence as part of the Susquehanna-Shale Hills Critical Zone Observatory (SSHCZO) in central Pennsylvania, USA. Sites were located on organic matter-poor, iron-rich Silurian-aged shale in Wales, Pennsylvania, Virginia, Tennessee, Alabama, and Puerto Rico, although this last site is underlain by a younger shale. Across the climosequence, mean annual temperature (MAT) increases from 7 to 24°C and mean annual precipitation (MAP) ranges from 100 to 250 cm. Variations in soil characteristics along the climosequence, including depth, morphology, particle-size distribution, geochemistry, and bulk and clay mineralogy, were characterized to investigate the role of climate in controlling mineral transformations and soil formation. Overall, soil horizonation, depth, clay content, and chemical depletion increase with increasing temperature and precipitation, consistent with enhanced soil development and weathering processes in warmer and wetter locations. Secondary minerals are present at higher concentrations at the warmest sites of the climosequence; kaolinite increases from \u3c5% at northern sites in Wales and Pennsylvania to 30% in Puerto Rico. The deepest observed weathering reaction is plagioclase feldspar dissolution followed by the transformation of chlorite and illite to vermiculite and hydroxy-interlayered vermiculite. Plagioclase, although constituting \u3c12% of the initial shale mineralogy, may be the profile initiating reaction that begins shale bedrock transformation to weathered regolith. Weathering of the more abundant chlorite and illite minerals (∼70% of initial mineralogy), however, are more likely controlling regolith thickness. Climate appears to play a central role in driving soil formation and mineral weathering reactions across the climosequence

Correction: Agricultural policies exacerbate honeybee pollination service supply-demand mismatches across Europe

The following information was missing from the funding section: BBSRC, DEFRA, NERC, the Scottish Government and the Wellcome Trust, under the Insect Pollinators Initiative crops project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Detector Description and Performance for the First Coincidence Observations between LIGO and GEO

For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial change

A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society