Recollection, Familiarity, and Cortical Reinstatement: A Multivoxel Pattern Analysis

SummaryEpisodic memory retrieval is thought to involve reinstatement of the neurocognitive processes engaged when an episode was encoded. Prior fMRI studies and computational models have suggested that reinstatement is limited to instances in which specific episodic details are recollected. We used multivoxel pattern-classification analyses of fMRI data to investigate how reinstatement is associated with different memory judgments, particularly those accompanied by recollection versus a feeling of familiarity (when recollection is absent). Classifiers were trained to distinguish between brain activity patterns associated with different encoding tasks and were subsequently applied to recognition-related fMRI data to determine the degree to which patterns were reinstated. Reinstatement was evident during both recollection- and familiarity-based judgments, providing clear evidence that reinstatement is not sufficient for eliciting a recollective experience. The findings are interpreted as support for a continuous, recollection-related neural signal that has been central to recent debate over the nature of recognition memory processes

An Approximate Procedure for Determining Prediction Error Variances of Sire Evaluations

Prediction errors of sire evaluations can be obtained directly from the inverse of the appropriate coefficient matrix. Considerably more effort is required to obtain the inverse in practical situations than can be justified for publication of a confidence figure. An approximate prediction error variance, k/(n + 20), is used currently in the Northeast Artificial Insemination Sire Comparison where n is the number of daughters and k is an appropriate breed constant corresponding to the residual variance. This procedure, however, does not account for distribution of sires across herds nor several lactations per daughter. Thus, the diagonal elements of the sire equations after absorption of cow, sire-by-herd, natural service sire, and herd-year-season equations were chosen as likely indicators of the prediction error variance for this more complicated model. Simple regression was used to relate prediction error variance obtained from the inverse to the diagonal after absorption. The coefficient of determination was .995 or greater in all cases. A single approximate prediction error variance of sire evaluation (group plus sire solution) could be used for Ayrshire, Guernsey, Jersey, and Brown Swiss bulls (and probably for Holsteins, which were not studied). The approximate prediction error variance is [-.0014 + 1.08/diagonal] times the appropriate residual variance. An approximation comparable to repeatability for herdmate comparisons also was derived as [1.01 - 9/diagonal]

Nonequilibrium probe of paired electron pockets in the underdoped cuprates

We propose an experimental method that can be used generally to test whether the cuprate pseudogap involves precursor pairing that acts to gap out the Fermi surface. The proposal involves angular-resolved photoemission spectroscopy (ARPES) performed in the presence of a transport current driven through the sample. We illustrate this proposal with a specific model of the pseudogap that contains a phase-incoherent paired electron and unpaired hole Fermi surfaces. We show that even a weak current tilts the paired band and reveals parts of the previously gapped electron Fermi surface in ARPES if the binding energy is smaller but close to the pseudogap. Stronger currents can also reveal the Fermi surface through direct suppression of pairing. The proposed experiment is sufficiently general such that it can be used to reveal putative Fermi surfaces that have been reconstructed from other types of periodic order and are gapped out due to pairing. The observation of the predicted phenomena should help resolve the central question about the existence of pairs in the enigmatic pseudogap regime.Comment: 5 pages, 3 figures (published version

Modeling of complex oxide materials from the first principles: systematic applications to vanadates RVO3 with distorted perovskite structure

"Realistic modeling" is a new direction of electronic structure calculations, where the main emphasis is made on the construction of some effective low-energy model entirely within a first-principle framework. Ideally, it is a model in form, but with all the parameters derived rigorously, on the basis of first-principles electronic structure calculations. The method is especially suit for transition-metal oxides and other strongly correlated systems, whose electronic and magnetic properties are predetermined by the behavior of some limited number of states located near the Fermi level. After reviewing general ideas of realistic modeling, we will illustrate abilities of this approach on the wide series of vanadates RVO3 (R= La, Ce, Pr, Nd, Sm, Gd, Tb, Yb, and Y) with distorted perovskite structure. Particular attention will be paid to computational tools, which can be used for microscopic analysis of different spin and orbital states in the partially filled t2g-band. We will explicitly show how the lifting of the orbital degeneracy by the monoclinic distortion stabilizes C-type antiferromagnetic (AFM) state, which can be further transformed to the G-type AFM state by changing the crystal distortion from monoclinic to orthorhombic one. Two microscopic mechanisms of such a stabilization, associated with the one-electron crystal field and electron correlation interactions, are discussed. The flexibility of the orbital degrees of freedom is analyzed in terms of the magnetic-state dependence of interatomic magnetic interactions.Comment: 23 pages, 13 figure

You are in sync with me:neural correlates of interpersonal synchrony with a partner

Interpersonal synchrony is characterized by a temporary alignment of periodic behaviors with another person. This process requires that at least one of the two individuals monitors and adjusts his/her movements to maintain alignment with the other individual (the referent). Interestingly, recent research on interpersonal synchrony has found that people who are motivated to befriend an unfamiliar social referent tend to automatically synchronize with their social referents, raising the possibility that synchrony may be employed as an affiliation tool. It is unknown, however, whether the opposite is true; that is, whether the person serving as the referent of interpersonal synchrony perceives synchrony with his/her partner or experiences affiliative feelings toward the partner.To address this question, we performed a series of studies on interpersonal synchrony with a total of 100 participants. In all studies, participants served as the referent with no requirement to monitor or align their behavior with their partners. Unbeknown to the participants, the timings of their “partner’s” movements were actually determined by a computer program based on the participant’s (i.e., referent’s) behavior.Overall, our behavioral results showed that the referent of a synchrony task expressed greater perceived synchrony and greater social affiliation toward a synchronous partner (i.e., one displaying low mean asynchrony and/or a narrow asynchrony range) than with an asynchronous partner (i.e., one displaying high mean asynchrony and/or high asynchrony range). Our neuroimaging study extended these results by demonstrating involvement of brain areas implicated in social cognition, embodied cognition, self-other expansion, and action observation as correlates of interpersonal synchrony (vs. asynchrony). These findings have practical implications for social interaction and theoretical implications for understanding interpersonal synchrony and social coordination

Pseudogap formation of four-layer BaRuO3_3 and its electrodynamic response changes

We investiaged the optical properties of four-layer BaRuO$_{3}$, which shows a fermi-liquid-like behavior at low temperature. Its optical conductivity spectra clearly displayed the formation of a pseudogap and the development of a coherent peak with decreasing temperature. Temperature-dependences of the density $n$ and the scattering rate $1/\tau$ of the coherent component were also derived. As the temperature decreases, both $n$ and $1/\tau$ decrease for four-layer BaRuO$_{3}$. These electrodynamic responses were compared with those of nine-layer BaRuO$_{3}$, which also shows a pseudogap formation but has an insulator-like state at low temperature. It was found that the relative rates of change of both $n$ and $1/\tau$ determine either metallic or insulator-like responses in the ruthenates. The optical properties of the four-layer ruthenate were also compared with those of other pseudogap systems, such as high $T_{c}$ cuprates and heavy electron systems.Comment: 7 figures. submitted to Phys. Rev.

The Fueling and Evolution of AGN: Internal and External Triggers

In this chapter, I review the fueling and evolution of active galactic nuclei (AGN) under the influence of internal and external triggers, namely intrinsic properties of host galaxies (morphological or Hubble type, color, presence of bars and other non-axisymmetric features, etc) and external factors such as environment and interactions. The most daunting challenge in fueling AGN is arguably the angular momentum problem as even matter located at a radius of a few hundred pc must lose more than 99.99 % of its specific angular momentum before it is fit for consumption by a BH. I review mass accretion rates, angular momentum requirements, the effectiveness of different fueling mechanisms, and the growth and mass density of black BHs at different epochs. I discuss connections between the nuclear and larger-scale properties of AGN, both locally and at intermediate redshifts, outlining some recent results from the GEMS and GOODS HST surveys.Comment: Invited Review Chapter to appear in LNP Volume on "AGN Physics on All Scales", Chapter 6, in press. 40 pages, 12 figures. Typo in Eq 5 correcte