Can the Default-Mode Network Be Described with One Spatial-Covariance Network?

The default-mode network (DMN) has become a well accepted concept in cognitive and clinical neuroscience over the last decade, and perusal of the recent literature attests to a stimulating research field of cognitive and diagnostic applications (for example, (Andrews-Hanna et al., 2010; Koch et al., 2010; Sheline et al., 2009a; Sheline et al., 2009b; Uddin et al., 2008; Uddin et al., 2009; Weng et al., 2009; Yan et al., 2009)). However, a formal definition of what exactly constitutes a functional brain network is difficult to come by. In recent contributions, some researchers argue that the DMN is best understood as multiple interacting subsystems (Buckner et al., 2008) and have explored modular components of the DMN that have different functional specialization and could to some extent be identified separately (Fox et al., 2005; Uddin et al., 2009). Such conception of modularity seems to imply an opposite construct of a 'unified whole', but it is difficult to locate proponents of the idea of a DMN who are supplying constraints that can be brought to bear on data in rigorous tests. Our aim in this paper is to present a principled way of deriving a single covariance pattern as the neural substrate of the DMN, test to what extent its behavior tracks the coupling strength between critical seed regions, and investigate to what extent our stricter concept of a network is consistent with the already established findings about the DMN in the literature. We show that our approach leads to a functional covariance pattern whose pattern scores are a good proxy for the integrity of the connections between a medioprefrontal, posterior cingulate and parietal seed regions. Our derived DMN network thus has potential for diagnostic applications that are simpler to perform than computation of pairwise correlational strengths or seed maps

Limits on τ lepton-flavor violating decays into three charged leptons

A search for the neutrinoless, lepton-flavor violating decay of the τ lepton into three charged leptons has been performed using an integrated luminosity of 468  fb^(-1) collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8–3.3)×10^(-8) at 90% confidence level

Contrasting Visual Working Memory for Verbal and Non-Verbal Material with Multivariate Analysis of fMRI

We performed a Delayed-Item-Recognition task to investigate the neural substrates of non-verbal visual working memory with event-related fMRI ('Shape task'). 25 young subjects (mean age: 24.0 years; STD=3.8 years) were instructed to study a list of either 1, 2 or 3 unnamable nonsense line drawings for 3s ('stimulus phase' or STIM). Subsequently, the screen went blank for 7s ('retention phase' or RET), and then displayed a probe stimulus for 3s in which subjects indicated with a differential button press whether the probe was contained in the studied shape-array or not ('probe phase' or PROBE). Ordinal Trend Canonical Variates Analysis (Habeck et al., 2005a) was performed to identify spatial covariance patterns that showed a monotonic increase in expression with memory load during all task phases. Reliable load-related patterns were identified in the stimulus and retention phase (p<0.01), while no significant pattern could be discerned during the probe phase. Spatial covariance patterns that were obtained from an earlier version of this task (Habeck et al., 2005b) using 1, 3, or 6 letters ('Letter task') were also prospectively applied to their corresponding task phases in the current non-verbal task version. Interestingly, subject expression of covariance patterns from both verbal and non-verbal retention phases correlated positively in the non-verbal task for all memory loads (p<0.0001). Both patterns also involved similar frontoparietal brain regions that were increasing in activity with memory load, and mediofrontal and temporal regions that were decreasing. Mean subject expression of both patterns across memory load during retention also correlated positively with recognition accuracy (d(L)) in the Shape task (p<0.005). These findings point to similarities in the neural substrates of verbal and non-verbal rehearsal processes. Encoding processes, on the other hand, are critically dependent on the to-be-remembered material, and seem to necessitate material-specific neural substrates

Study of B → Xγ decays and determination of |V_(td)/V_(ts)|

Using a sample of 471×10^6 BB̅[overbar] events collected with the BABAR detector, we study the sum of seven exclusive final states B→X_(s(d))γ, where X_(s(d)) is a strange (nonstrange) hadronic system with a mass of up to 2.0  GeV/c^2. After correcting for unobserved decay modes, we obtain a branching fraction for b→dγ of (9.2±2.0(stat)±2.3(syst))×10^(-6) in this mass range, and a branching fraction for b→sγ of (23.0±0.8(stat)±3.0(syst))×10^(-5) in the same mass range. We find B[script](b→dγ)/B[script](b→sγ)=0.040±0.009(stat)±0.010(syst), from which we determine |V_(td)/V_(ts)|=0.199±0.022(stat)±0.024(syst)±0.002(th)

Measurement of CP observables in B^± → D_(CP)K^± decays and constraints on the CKM angle γ

Using the entire sample of 467×10^6 Υ(4S)→BB[overbar] decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, we perform an analysis of B^± → DK^± decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A_(CP+) = 0.25±0.06±0.02 and A_(CP-) = -0.09±0.07±0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A_(CP+) is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, R_(CP+) = 1.18±0.09±0.05 and R_(CP-) = 1.07±0.08±0.04. We infer frequentist confidence intervals for the angle γ of the unitarity triangle, for the strong phase difference δ_B, and for the amplitude ratio r_B, which are related to the B^- → DK^- decay amplitude by r_(B)e^(i(δB-γ)) = A(B^- → D[overbar]^(0)K^-)/A(B^- → D^(0)K^-). Including statistical and systematic uncertainties, we obtain 0.24 < r_B < 0.45 (0.06 < r_B <0.51) and, modulo 180°, 11.3° < γ < 22.7° or 80.8° < γ <99.2° or 157.3° <γ < 168.7° (7.0°<γ<173.0°) at the 68% (95%) confidence level

Analysis of the D^+ → K^-π^+e^+ν_e decay channel

Using 347.5  fb^(-1) of data recorded by the BABAR detector at the PEP-II electron-positron collider, 244×10^3 signal events for the D^+ → K^-π^+e^+ν_e decay channel are analyzed. This decay mode is dominated by the K̅ ^*(892)^0 contribution. We determine the K̅ ^*(892)^0 parameters: m_(K^*(892)^0)=(895.4±0.2±0.2)  MeV/c^2, Γ_(K^*(892)^0)=(46.5±0.3±0.2)  MeV/c^2, and the Blatt-Weisskopf parameter r_(BW) =2.1±0.5±0.5  (GeV/c)^-1, where the first uncertainty comes from statistics and the second from systematic uncertainties. We also measure the parameters defining the corresponding hadronic form factors at q^2 = 0 (r_V = ^(V(0))/_(A1(0)) = 1.463 ± 0.017 ± 0.031, r_2 = _(A1(0)) ^(A2(0))= 0.801±0.020±0.020) and the value of the axial-vector pole mass parametrizing the q^2 variation of A_1 and A_2: m_A=(2.63±0.10±0.13)  GeV/c^2. The S-wave fraction is equal to (5.79±0.16±0.15)%. Other signal components correspond to fractions below 1%. Using the D^+ → K^-π^+π^+ channel as a normalization, we measure the D^+ semileptonic branching fraction: B(D^+ → K^-π^+e^+ν_e)=(4.00±0.03±0.04±0.09)×10^(-2), where the third uncertainty comes from external inputs. We then obtain the value of the hadronic form factor A_1 at q^2=0: A_1(0)=0.6200±0.0056±0.0065±0.0071. Fixing the P-wave parameters, we measure the phase of the S wave for several values of the Kπ mass. These results confirm those obtained with Kπ production at small momentum transfer in fixed target experiments

Measurement of the B → D̅ ^((*))D^((*))K branching fractions

We present a measurement of the branching fractions of the 22 decay channels of the B^0 and B+ mesons to D̅ ^((*))D^((*))K, where the D^((*)) and D̅ ^((*)) mesons are fully reconstructed. Summing the 10 neutral modes and the 12 charged modes, the branching fractions are found to be B(B^0→D̅6((*))D^((*))K)=(3.68 ± 0.10 ± 0.24)% and B(B^+→D̅ ^((*))D^((*))K)=(4.05 ± 0.11 ± 0.28)%, where the first uncertainties are statistical and the second systematic. The results are based on 429  fb^(-1) of data containing 471 × 10^6BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory

Measurement of partial branching fractions of inclusive charmless B meson decays to K^+, K^0, and π^+

We present measurements of partial branching fractions of B → K^+X, B → K^0X, and B → π^+X, where X denotes any accessible final state above the endpoint for B decays to charmed mesons, specifically for momenta of the candidate hadron greater than 2.34 (2.36) GeV for kaons (pions) in the B rest frame. These measurements are sensitive to potential new-physics particles which could enter the b → s(d) loop transitions. The analysis is performed on a data sample consisting of 383 × 10^6B B̅ pairs collected with the BABAR detector at the PEP-II e^+e^- asymmetric energy collider. We observe the inclusive B→π+X process, and we set upper limits for B → K^+X and B → K^0X. Our results for these inclusive branching fractions are consistent with those of known exclusive modes, and exclude large enhancements due to sources of new physics