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Search Results: 1 - 10 of 325885 matches for " Mera S. Barr "
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The Effect of Repetitive Transcranial Magnetic Stimulation on Gamma Oscillatory Activity in Schizophrenia
Mera S. Barr, Faranak Farzan, Tamara Arenovich, Robert Chen, Paul B. Fitzgerald, Zafiris J. Daskalakis
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022627
Abstract: Background Gamma (γ) oscillations (30–50 Hz) have been shown to be excessive in patients with schizophrenia (SCZ) during working memory (WM). WM is a cognitive process that involves the online maintenance and manipulation of information that is mediated largely by the dorsolateral prefrontal cortex (DLPFC). Repetitive transcranial magnetic stimulation (rTMS) represents a non-invasive method to stimulate the cortex that has been shown to enhance cognition and γ oscillatory activity during WM. Methodology and Principal Findings We examined the effect of 20 Hz rTMS over the DLPFC on γ oscillatory activity elicited during the N-back task in 24 patients with SCZ compared to 22 healthy subjects. Prior to rTMS, patients with SCZ elicited excessive γ oscillatory activity compared to healthy subjects across WM load. Active rTMS resulted in the reduction of frontal γ oscillatory activity in patients with SCZ, while potentiating activity in healthy subjects in the 3-back, the most difficult condition. Further, these effects on γ oscillatory activity were found to be specific to the frontal brain region and were absent in the parieto-occipital brain region. Conclusions and Significance We suggest that this opposing effect of rTMS on γ oscillatory activity in patients with SCZ versus healthy subjects may be related to homeostatic plasticity leading to differential effects of rTMS on γ oscillatory activity depending on baseline differences. These findings provide important insights into the neurophysiological mechanisms underlying WM deficits in SCZ and demonstrated that rTMS can modulate γ oscillatory activity that may be a possible avenue for cognitive potentiation in this disorder.
Personality Goes a Long a Way: An Interhemispheric Connectivity Study
Sylco S. Hoppenbrouwers,Faranak Farzan,Mera S. Barr,Aristotle N. Voineskos,Dennis J.L.G. Schutter,Paul B. Fitzgerald,Zafiris J. Daskalakis
Frontiers in Psychiatry , 2010, DOI: 10.3389/fpsyt.2010.00140
Abstract: Throughout the development of psychology the delineation of personality has played a central role. Together with the NEO-PI-R, a questionnaire derived from the Five Factor Model of Personality, and recent advances in research technology it is now possible to investigate the relationship between personality features and neurophysiological brain processes. The NEO-FFI, the short version of the NEO-PI-R, reliably measures five main personality traits: Neuroticism, Extraversion, Openness to experience, Agreeableness, and Conscientiousness. As behavior and some psychiatric disorders have been related to interhemispheric connectivity, the present study used the combination of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to measure frontal interhemispheric connectivity and its association with personality as indexed by the NEO-FFI. Results demonstrated that prefrontal interhemispheric connectivity between the left and right dorsolateral prefrontal cortex correlates with Agreeableness in healthy subjects. This is the first study to relate personality features to interhemispheric connectivity through TMS–EEG and suggests that Agreeableness relates to the effectiveness of prefrontal communication between hemispheres.
Por una economía al servicio de todos
Manuel Mera Sánchez
Revista Galega de Economía , 2000,
Radiative Fermion Mass Hierarchy in a Non-supersymmetric Unified Theory
Barr, S. M.
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevD.76.105024
Abstract: In non-supersymmetric grand unified models a ``radiative fermion mass hierarchy" can be achieved in which the spectrum of quark and lepton masses is determined entirely by physics at the unification scale, with many relations following from the unified gauge symmetry, and with the masses of the lightest family arising from loops. A simple, realistic, and predictive model of this kind is presented. A "doubly lopsided" structure, known to lead to bilarge neutrino mixing, plays a crucial role in the radiative hierarchy.
A superweak solution of the Strong CP Problem
S. B. Barr
Physics , 1998, DOI: 10.1016/S0370-2693(98)01056-9
Abstract: A non-axion solution to the Strong CP Problem is proposed that works even in the context of gravity-mediated supersymmetry breaking. Both $\epsilon'/\epsilon$ and indirect CP violation in the $B-\bar{B}$ are predicted to be unobservably small. $\mu \longrightarrow e \gamma$ is predicted to arise, typically, with branching ration $3 \times 10^{-12}$. A new source of dark matter is also predicted in the model.
Supersymmetric Solutions to the Strong CP Problem
S. M. Barr
Physics , 1996, DOI: 10.1103/PhysRevD.56.1475
Abstract: It is argued that in the context of supersymmetry, the Strong CP Problem is most naturally seen as an aspect (particularly severe) of the whole complex of flavor-violating and CP-violating problems of supersymmetry. It is shown that certain approaches to solving these flavor problems also allow simple solutions to the Strong CP Problem. The idea of ``flavor alignment" suggested by Nir and Seiberg allows not only flavor violation to be controlled but supersymmetric contributions to the theta parameter to be made acceptably small. Another approach to the flavor-violation problem, namely low-energy supersymmetry breaking, allows another class of solutions to the Strong CP Problem to be viable.
Predictive Models of Large Neutrino Mixing Angles
S. M. Barr
Physics , 1996, DOI: 10.1103/PhysRevD.55.1659
Abstract: Several experimental results could be interpreted as evidence that certain neutrino mixing angles are large, of order unity. However, in the context of grand unified models the neutrino angles come out characteristically to be small, like the KM angles. It is shown how to construct simple grand-unified models in which neutrino angles are not only large but completely predicted with some precision. Six models are presented for illustration.
The Stability of the Gauge Hierarchy in $SU(5) \times SU(5)$
S. M. Barr
Physics , 1996, DOI: 10.1103/PhysRevD.55.6775
Abstract: It has been shown that the Dimopoulos-Wilczek (or missing-VEV) mechanism for doublet-triplet splitting can be implemented in $SU(5) \times SU(5)$ models, which requires no adjoint Higgs fields. This is an advantage from the point of view of string theory construction. Here the stability of the gauge hierarchy is examined in detail, and it is shown that it can be guaranteed much more simply than in $SO(10)$. In fact a $Z_2$ symmetry ensures the stability of the DW form of the expectation values to all orders in GUT-scale VEVs. It is also shown that models based on $SO(10) \times SU(5)$ have the advantages of $SU(5) \times SU(5)$ while permitting complete quark-lepton unification as in $SO(10)$.
Neutrino Oscillations: Some theoretical ideas
S. M. Barr
Physics , 2000,
Abstract: Talk given at Orbis Scientiae Conference, Coral Gables, FLA, Dec. 16-19, 1999. Talk surveys some recent three-neutrino models of neutrino masses and mixings.
Flavor without Flavor Symmetry
S. M. Barr
Physics , 2001, DOI: 10.1103/PhysRevD.65.096012
Abstract: Non-trivial patterns of quark and lepton masses and mixings can arise without there being any underlying flavor symmetry that distinguishes among the three families. Two realistic examples are given.
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