Awake Reactivation of Prior Experiences Consolidates Memories and Biases Cognition.

After experiences are encoded into memory, post-encoding reactivation mechanisms have been proposed to mediate long-term memory stabilization and transformation. Spontaneous reactivation of hippocampal representations, together with hippocampal-cortical interactions, are leading candidate mechanisms for promoting systems-level memory strengthening and reorganization. While the replay of spatial representations has been extensively studied in rodents, here we review recent fMRI work that provides evidence for spontaneous reactivation of nonspatial, episodic event representations in the human hippocampus and cortex, as well as for experience-dependent alterations in systems-level hippocampal connectivity. We focus on reactivation during awake post-encoding periods, relationships between reactivation and subsequent behavior, how reactivation is modulated by factors that influence consolidation, and the implications of persistent reactivation for biasing ongoing perception and cognition

Finite element analysis of footings and embankment dam cores

Imperial Users onl

Brief targeted memory reactivation during the awake state enhances memory stability and benefits the weakest memories.

Reactivation of representations corresponding to recent experience is thought to be a critical mechanism supporting long-term memory stabilization. Targeted memory reactivation, or the re-exposure of recently learned cues, seeks to induce reactivation and has been shown to benefit later memory when it takes place during sleep. However, despite recent evidence for endogenous reactivation during post-encoding awake periods, less work has addressed whether awake targeted memory reactivation modulates memory. Here, we found that brief (50 ms) visual stimulus re-exposure during a repetitive foil task enhanced the stability of cued versus uncued associations in memory. The extent of external or task-oriented attention prior to re-exposure was inversely related to cueing benefits, suggesting that an internally-orientated state may be most permissible to reactivation. Critically, cueing-related memory benefits were greatest in participants without explicit recognition of cued items and remained reliable when only considering associations not recognized as cued, suggesting that explicit cue-triggered retrieval processes did not drive cueing benefits. Cueing benefits were strongest for associations and participants with the poorest initial learning. These findings expand our knowledge of the conditions under which targeted memory reactivation can benefit memory, and in doing so, support the notion that reactivation during awake time periods improves memory stabilization

Existential Absurdity and Alienation in Kafka’s the Metamorphosis and Hedayat’s the Blind Owl

This study intended to illustrate and compare the specific existential elements such as absurdity and alienation portrayed by Hedayat and Kafka in The Metamorphosis and The Blind Owl. Elucidating how the two authors portrayed these notions in similar or different ways led to the idea that the selected works were similar to each other in terms of existential notions such as absurdity and alienation. The method utilized in this thesis was based on the comparative literature and the two works were treated as the surreal fictions since the characters and incidents were not real. In addition, this study delineated the fact that Hedayat and Kafka employed philosophy of existentialism to testify the perplexed situation of human being’s condition in the contemporary world. Both authors, Kafka and Hedayat, suffered from the modern society’s complexities and tortures that captured their daily lives and also they endured the lack of mutual love and relationship among the members of their families and societies; thereby, they reflected all these concerns in the same way showing how contemporary man tolerates hardships imposed by alienation and world absurdity in a similar way and on the basis of existentialism

Similarity Breeds Proximity: Pattern Similarity within and across Contexts Is Related to Later Mnemonic Judgments of Temporal Proximity

SummaryExperiences unfold over time, but little is known about the mechanisms that support the formation of coherent episodic memories for temporally extended events. Recent work in animals has provided evidence for signals in hippocampus that could link events across temporal gaps; however, it is unknown whether and how such signals might be related to later memory for temporal information in humans. We measured patterns of fMRI BOLD activity as people encoded items that were separated in time and manipulated the presence of shared or distinct context across items. We found that hippocampal pattern similarity in the BOLD response across trials predicted later temporal memory decisions when context changed. By contrast, pattern similarity in lateral occipital cortex was related to memory only when context remained stable. These data provide evidence in humans that representational stability in hippocampus across time may be a mechanism for temporal memory organization

Effect of the presence of corpus luteum on the ovary and the new oocyte recovery method on the oocyte recovery rate and meiotic competence of ovine oocytes

This study was designed to identify the effects of the presence of corpus luteum (CL) on the meiotic competence of the ewe oocytes. In addition, due to the pivotal roles of oocyte recovery methods on efficiency of in vitro maturation and in vitro fertilization, this study considered the new oocyte recovery method “Oocyte Recovery with Centrifuge” (ORC); Ovine ovaries were obtained from local abattoir at Karaj, Iran. The ovaries were placed in 0.9% saline which was supplemented with penicillin/streptomycin in thermo flask at 37°C and transported to the laboratory within 1 to 2 h of slaughter. The ovaries were assigned to two groups; group-1 with functional CL and group-2 without CL. The oocytes were recovered by means of aspiration pump or ORC. After oocyte recovery, they were cultured in TCM-199 for 24 h. The mean number of oocyte recovery per ovary in group 1 ovaries (1.8 ± 0.01 via aspiration and 3.84 ± 0.05 via ORC) was lower (P<0.05) than group 2 ovaries (2.2 ± 0.00 via aspiration and 5.43 ± 0.01 via ORC). There were no significant differences (P>0.05) between percentage of nuclear maturation in oocytes which were recovered from group 2 ovaries via aspiration and ORC (75.20 ± 0.00 vs. 74.95 ± 0.00, metaphase II; M-II) method. The nuclear maturation in oocytes which were obtained via ORC from group 2 ovaries was higher (P<0.05) than group 1 ovaries (74.95 ± 0.00 vs. 60.07 ± 0.00b). Nuclear maturation for oocytes obtained via ORC from group 1 ovaries was (P<0.05) lower than oocytes obtained via aspiration (60.07 ± 0.00 vs. 74.70 ± 0.00). Result of the present study showed that the presence of CL on ovaries lead to decrease in the quality and the quantity of oocytes. ORC method increased the quantity and quality of recovered oocytes.Key words: Aspiration, corpus luteum, in vitro maturation (IVM), oocyte recovery

Lagrangian formalism and Lie group approach for commutative semigroup of differential equations

A set of linear second-order differential equations is converted into a semigroup, whose algebraic structure is used to generate many novel equations. Two independent methods that can be used to derive the equations of the semigroup are considered, namely, the Lagrangian formalism and the Lie group approach. The advantages and disadvantages of each method are discussed, and it is shown that the Lagrangian formalism can be established for all equations of the semigroup, however, the Lie group approach is only limited to a certain sub-semigroup . The obtained results are discussed in the context of their applications in mathematical physics.Comment: 17 page

Special Functions of Mathematical Physics: A Unified Lagrangian Formalism

Lagrangian formalism is established for differential equations with special functions of mathematical physics as solutions. Formalism is based on either standard or non-standard Lagrangians. This work shows that the procedure of deriving the standard Lagrangians leads to Lagrangians for which the Euler--Lagrange equation vanishes identically, and that only some of these Lagrangians become the null Lagrangians with the well-defined gauge functions. It is also demonstrated that the non-standard Lagrangians require that the Euler--Lagrange equations are amended by the auxiliary conditions, which is a new phenomenon in the calculus of variations. The~existence of the auxiliary conditions has profound implications on the validity of the Helmholtz conditions. The obtained results are used to derive the Lagrangians for the Airy, Bessel, Legendre and Hermite equations. The presented examples clearly demonstrate that the developed Lagrangian formalism is applicable to all considered differential equations, including the Airy (and other similar) equations, and that the regular and modified Bessel equations are the only ones with the gauge functions. Possible implications of the existence of the gauge functions for these equations are~discussed.Comment: 22 page

Distortion and Signal Loss in Medial Temporal Lobe

Background: The medial temporal lobe (MTL) contains subregions that are subject to severe distortion and signal loss in functional MRI. Air/tissue and bone/tissue interfaces in the vicinity of the MTL distort the local magnetic field due to differences in magnetic susceptibility. Fast image acquisition and thin slices can reduce the amount of distortion and signal loss, but at the cost of image signal-to-noise ratio (SNR). Methodology/Principal Findings: In this paper, we quantify the severity of distortion and signal loss in MTL subregions for three different echo planar imaging (EPI) acquisitions at 3 Tesla: a conventional moderate-resolution EPI (36363 mm), a conventional high-resolution EPI (1.561.562 mm), and a zoomed high-resolution EPI. We also demonstrate the advantage of reversing the phase encode direction to control the direction of distortion and to maximize efficacy of distortion compensation during data post-processing. With the high-resolution zoomed acquisition, distortion is not significant and signal loss is present only in the most anterior regions of the parahippocampal gyrus. Furthermore, we find that the severity of signal loss is variable across subjects, with some subjects showing negligible loss and others showing more dramatic loss. Conclusions/Significance: Although both distortion and signal loss are minimized in a zoomed field of view acquisition with thin slices, this improvement in accuracy comes at the cost of reduced SNR. We quantify this trade-off between distortion and SNR in order to provide a decision tree for design of high-resolution experiments investigating the functio