230 research outputs found
A NWB-based dataset and processing pipeline of human single-neuron activity during a declarative memory task
A challenge for data sharing in systems neuroscience is the multitude of different data formats used. Neurodata Without Borders: Neurophysiology 2.0 (NWB:N) has emerged as a standardized data format for the storage of cellular-level data together with meta-data, stimulus information, and behavior. A key next step to facilitate NWB:N adoption is to provide easy to use processing pipelines to import/export data from/to NWB:N. Here, we present a NWB-formatted dataset of 1863 single neurons recorded from the medial temporal lobes of 59 human subjects undergoing intracranial monitoring while they performed a recognition memory task. We provide code to analyze and export/import stimuli, behavior, and electrophysiological recordings to/from NWB in both MATLAB and Python. The data files are NWB:N compliant, which affords interoperability between programming languages and operating systems. This combined data and code release is a case study for how to utilize NWB:N for human single-neuron recordings and enables easy re-use of this hard-to-obtain data for both teaching and research on the mechanisms of human memory
Star-galaxy separation in the AKARI NEP Deep Field
Context: It is crucial to develop a method for classifying objects detected
in deep surveys at infrared wavelengths. We specifically need a method to
separate galaxies from stars using only the infrared information to study the
properties of galaxies, e.g., to estimate the angular correlation function,
without introducing any additional bias. Aims. We aim to separate stars and
galaxies in the data from the AKARI North Ecliptic Pole (NEP) Deep survey
collected in nine AKARI / IRC bands from 2 to 24 {\mu}m that cover the near-
and mid-infrared wavelengths (hereafter NIR and MIR). We plan to estimate the
correlation function for NIR and MIR galaxies from a sample selected according
to our criteria in future research. Methods: We used support vector machines
(SVM) to study the distribution of stars and galaxies in the AKARIs multicolor
space. We defined the training samples of these objects by calculating their
infrared stellarity parameter (sgc). We created the most efficient classifier
and then tested it on the whole sample. We confirmed the developed separation
with auxiliary optical data obtained by the Subaru telescope and by creating
Euclidean normalized number count plots. Results: We obtain a 90% accuracy in
pinpointing galaxies and 98% accuracy for stars in infrared multicolor space
with the infrared SVM classifier. The source counts and comparison with the
optical data (with a consistency of 65% for selecting stars and 96% for
galaxies) confirm that our star/galaxy separation methods are reliable.
Conclusions: The infrared classifier derived with the SVM method based on
infrared sgc- selected training samples proves to be very efficient and
accurate in selecting stars and galaxies in deep surveys at infrared
wavelengths carried out without any previous target object selection.Comment: 8 pages, 8 figure
Addressing the Language Binding Problem With Dynamic Functional Connectivity During Meaningful Spoken Language Comprehension
During speech, how does the brain integrate information processed on different timescales and in separate brain areas so we can understand what is said? This is the language binding problem. Dynamic functional connectivity (brief periods of synchronization in the phase of EEG oscillations) may provide some answers. Here we investigate time and frequency characteristics of oscillatory power and phase synchrony (dynamic functional connectivity) during speech comprehension. Twenty adults listened to meaningful English sentences and non-sensical “Jabberwocky” sentences in which pseudo-words replaced all content words, while EEG was recorded. Results showed greater oscillatory power and global connectivity strength (mean phase lag index) in the gamma frequency range (30–80 Hz) for English compared to Jabberwocky. Increased power and connectivity relative to baseline was also seen in the theta frequency range (4–7 Hz), but was similar for English and Jabberwocky. High-frequency gamma oscillations may reflect a mechanism by which the brain transfers and integrates linguistic information so we can extract meaning and understand what is said. Slower frequency theta oscillations may support domain-general processing of the rhythmic features of speech. Our findings suggest that constructing a meaningful representation of speech involves dynamic interactions among distributed brain regions that communicate through frequency-specific functional networks
Implantable photonic neural probes for light-sheet fluorescence brain imaging
Significance: Light-sheet fluorescence microscopy (LSFM) is a powerful technique for highspeed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. We demonstrate that these constraints can be surmounted using a new class of implantable photonic neural probes.Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components.Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200-mm-diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed, in vitro, and in vivo mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose.Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses Conclusions: The neural probes can lead to new variants of LSFM for deep brain imaging and experiments in freely moving animals
Herschel-ATLAS/GAMA: A difference between star formation rates in strong-line and weak-line radio galaxies
We have constructed a sample of radio-loud objects with optical spectroscopy from the Galaxy and Mass Assembly (GAMA) project over the Herschel Astrophysical Terahertz Large Area Survey (Herschel-ATLAS) Phase 1 fields. Classifying the radio sources in terms of their optical spectra, we find that strong-emission-line sources ('high-excitation radio galaxies') have, on average, a factor of ~4 higher 250-μm Herschel luminosity than weak-line ('lowexcitation') radio galaxies and are also more luminous than magnitude-matched radio-quiet galaxies at the same redshift. Using all five H-ATLAS bands, we show that this difference in luminosity between the emission-line classes arises mostly from a difference in the average dust temperature; strong-emission-line sources tend to have comparable dust masses to, but higher dust temperatures than, radio galaxies with weak emission lines. We interpret this as showing that radio galaxies with strong nuclear emission lines are much more likely to be associated with star formation in their host galaxy, although there is certainly not a one-to-one relationship between star formation and strong-line active galactic nuclei (AGN) activity. The strong-line sources are estimated to have star formation rates at least a factor of 3-4 higher than those in the weak-line objects. Our conclusion is consistent with earlier work, generally carried out using much smaller samples, and reinforces the general picture of high-excitation radio galaxies as being located in lower-mass, less evolved host galaxies than their low-excitation counterparts.Peer reviewe
AzTEC millimeter survey of the COSMOS field - III. Source catalog over 0.72 sq. deg. and plausible boosting by large-scale structure
We present a 0.72 sq. deg. contiguous 1.1mm survey in the central area of the
COSMOS field carried out to a 1sigma ~ 1.26 mJy/beam depth with the AzTEC
camera mounted on the 10m Atacama Submillimeter Telescope Experiment (ASTE). We
have uncovered 189 candidate sources at a signal-to-noise ratio S/N >= 3.5, out
of which 129, with S/N >= 4, can be considered to have little chance of being
spurious (< 2 per cent). We present the number counts derived with this survey,
which show a significant excess of sources when compared to the number counts
derived from the ~0.5 sq. deg. area sampled at similar depths in the Scuba HAlf
Degree Extragalactic Survey (SHADES, Austermann et al. 2010). They are,
however, consistent with those derived from fields that were considered too
small to characterize the overall blank-field population. We identify
differences to be more significant in the S > 5 mJy regime, and demonstrate
that these excesses in number counts are related to the areas where galaxies at
redshifts z < 1.1 are more densely clustered. The positions of optical-IR
galaxies in the redshift interval 0.6 < z < 0.75 are the ones that show the
strongest correlation with the positions of the 1.1mm bright population (S > 5
mJy), a result which does not depend exclusively on the presence of rich
clusters within the survey sampled area. The most likely explanation for the
observed excess in number counts at 1.1mm is galaxy-galaxy and galaxy-group
lensing at moderate amplification levels, that increases in amplitude as one
samples larger and larger flux densities. This effect should also be detectable
in other high redshift populations.Comment: 21 pages, 17 figures, accepted for publication in MNRA
HerMES: spectral energy distributions of submillimeter galaxies at z > 4.
We present a study of the infrared properties for a sample of seven spectroscopically confirmed submillimetre galaxies (SMGs) at z > 4.0. By combining ground-based near-infrared, Spitzer IRAC and MIPS, Herschel SPIRE, and ground-based submillimetre / millimeter photometry, we construct their spectral energy distributions (SEDs) and a composite model to fit the SEDs. The model includes a stellar emission component at λ rest 50μm. Six objects in the sample are detected at 250 and 350μm. The dust temperatures for the sources in this sample are in the range of 40–80 K, and their L FIR ∼ 10 13 Lo qualifies them as hyper-luminous infrared galaxies. The mean FIR-radio index for this sample is around (q) = 2.2 indicating no radio excess in their radio emission. Most sources in the sample have 24μmdetections corresponding to a rest-frame 4.5μm luminosity of Log 10 (L 4.5 /L ? )=11 ∼ 11.5. Their L 4.5 /L FIR ratios are very similar to those of starburst-dominated SMGs at z ∼ 2. The L CO − L FIR relation for this sample is consistent with that determined for local ULIRGs and SMGs at z ∼ 2. We conclude that SMGs at z > 4 are hotter and more luminous in the FIR but otherwise very similar to those at z ∼ 2. None of these sources show any sign of the strong QSO phase being triggered
The Spitzer Infrared Nearby Galaxies Survey: A High-Resolution Spectroscopy Anthology
High resolution mid-infrared spectra are presented for 155 nuclear and
extranuclear regions from the Spitzer Infrared Nearby Galaxies Survey (SINGS).
The fluxes for nine atomic forbidden and three molecular hydrogen mid-infrared
emission lines are also provided, along with upper limits in key lines for
infrared-faint targets. The SINGS sample shows a wide range in the ratio of
[SIII]18.71um/[SIII]33.48um, but the average ratio of the ensemble indicates a
typical interstellar electron density of 300-400 cm^{-3} on ~23"x15" scales and
500-600 cm^{-3} using ~11"x9" apertures, independent of whether the region
probed is a star-forming nuclear, a star-forming extranuclear, or an AGN
environment. Evidence is provided that variations in gas-phase metallicity play
an important role in driving variations in radiation field hardness, as
indicated by [NeIII]15.56um/[NeII]12.81um, for regions powered by star
formation. Conversely, the radiation hardness for galaxy nuclei powered by
accretion around a massive black hole is independent of metal abundance.
Furthermore, for metal-rich environments AGN are distinguishable from
star-forming regions by significantly larger [NeIII]15.56um/[NeII]12.81um
ratios. Finally, [FeII]25.99um/[NeII]12.81um versus [SiII]34.82um/[SIII]33.48um
also provides an empirical method for discerning AGN from normal star-forming
sources. However, similar to [NeIII]15.56um/[NeII]12.81um, these mid-infrared
line ratios lose their AGN/star-formation diagnostic powers for very low
metallicity star-forming systems with hard radiation fields.Comment: Accepted for publication in Ap
The origin of dust in galaxies revisited: the mechanism determining dust content
The origin of cosmic dust is a fundamental issue in planetary science. This
paper revisits the origin of dust in galaxies, in particular, in the Milky Way,
by using a chemical evolution model of a galaxy composed of stars, interstellar
medium, metals (elements heavier than helium), and dust. We start from a review
of time-evolutionary equations of the four components, and then, we present
simple recipes for the stellar remnant mass and yields of metal and dust based
on models of stellar nucleosynthesis and dust formation. After calibrating some
model parameters with the data from the solar neighborhood, we have confirmed a
shortage of the stellar dust production rate relative to the dust destruction
rate by supernovae if the destruction efficiency suggested by theoretical works
is correct. If the dust mass growth by material accretion in molecular clouds
is active, the observed dust amount in the solar neighborhood is reproduced. We
present a clear analytic explanation of the mechanism for determining dust
content in galaxies after the activation of accretion growth: a balance between
accretion growth and supernova destruction. Thus, the dust content is
independent of the uncertainty of the stellar dust yield after the growth
activation. The timing of the activation is determined by a critical metal mass
fraction which depends on the growth and destruction efficiencies. The solar
system formation seems to have occurred well after the activation and plenty of
dust would have existed in the proto-solar nebula.Comment: 12 pages, 11 figure
AzTEC Millimetre Survey of the COSMOS Field - II. Source Count Overdensity and Correlations with Large-Scale Structure
We report an over-density of bright sub-millimetre galaxies (SMGs) in the
0.15 sq. deg. AzTEC/COSMOS survey and a spatial correlation between the SMGs
and the optical-IR galaxy density at z <~ 1.1. This portion of the COSMOS field
shows a ~ 3-sigma over-density of robust SMG detections when compared to a
background, or "blankfield", population model that is consistent with SMG
surveys of fields with no extragalactic bias. The SMG over-density is most
significant in the number of very bright detections (14 sources with measured
fluxes S(1.1mm) > 6 mJy), which is entirely incompatible with sample variance
within our adopted blank-field number densities and infers an over-density
significance of >> 4. We find that the over-density and spatial correlation to
optical-IR galaxy density are most consistent with lensing of a background SMG
population by foreground mass structures along the line of sight, rather than
physical association of the SMGs with the z <~ 1.1 galaxies/clusters. The SMG
positions are only weakly correlated with weak-lensing maps, suggesting that
the dominant sources of correlation are individual galaxies and the more
tenuous structures in the region and not the massive and compact clusters.
These results highlight the important roles cosmic variance and large-scale
structure can play in the study of SMGs.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in MNRA
- …