1,629 research outputs found
Origin of Gamma Frequency Power during Hippocampal Sharp-Wave Ripples
Hippocampal sharp-wave ripples (SPW-Rs) support consolidation of recently acquired episodic memories and planning future actions by generating ordered neuronal sequences of previous or future experiences. SPW-Rs are characterized by several spectral components: a slow (5–15 Hz) sharp-wave, a high-frequency “ripple” oscillation (150–200 Hz), and a slow “gamma” oscillation (20–40 Hz). Using laminar hippocampal recordings and optogenetic manipulations, we dissected the origin of these spectral components. We show that increased power in the 20–40 Hz band does not reflect an entrainment of CA1 and CA3 neurons at gamma frequency but the power envelope of overlapping ripples. Spike-local field potential coupling between unit firing in CA1 and CA3 regions during SPW-Rs is lowest in the gamma band. Longer SPW-Rs are preceded by increased firing in the entorhinal cortex. Thus, fusion of SPW-Rs leads to lengthening of their duration associated with increased power in the slow gamma band without the presence of true oscillation
Enhancement of nematic order and global phase diagram of a lattice model for coupled nematic systems
We use an infinite-range Maier-Saupe model, with two sets of local
quadrupolar variables and restricted orientations, to investigate the global
phase diagram of a coupled system of two nematic subsystems. The free energy
and the equations of state are exactly calculated by standard techniques of
statistical mechanics. The nematic-isotropic transition temperature of system A
increases with both the interaction energy among mesogens of system B, and the
two-subsystem coupling . This enhancement of the nematic phase is manifested
in a global phase diagram in terms of the interaction parameters and the
temperature . We make some comments on the connections of these results with
experimental findings for a system of diluted ferroelectric nanoparticles
embedded in a nematic liquid-crystalline environment.Comment: 11 pages, 3 figures, to appear in Volume 42 of the Brazilian Journal
of Physic
Maternal aggression in Wistar rats: effect of 5-HT2A/2C receptor agonist and antagonist microinjected into the dorsal periaqueductal gray matter and medial septum
Índice funcional do ciático nas lesões por esmagamento do nervo ciático de ratos. Avaliação da reprodutibilidade do método entre examinadores
Spatial and temporal changes in Lutzomyia longipalpis abundance, a Leishmania infantum vector in an urban area in northeastern Argentina
Empresa social e economia solidária: perspectivas no campo da inserção laboral de portadores de transtorno mental
Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond
We review recent developments in the physics of ultracold atomic and
molecular gases in optical lattices. Such systems are nearly perfect
realisations of various kinds of Hubbard models, and as such may very well
serve to mimic condensed matter phenomena. We show how these systems may be
employed as quantum simulators to answer some challenging open questions of
condensed matter, and even high energy physics. After a short presentation of
the models and the methods of treatment of such systems, we discuss in detail,
which challenges of condensed matter physics can be addressed with (i)
disordered ultracold lattice gases, (ii) frustrated ultracold gases, (iii)
spinor lattice gases, (iv) lattice gases in "artificial" magnetic fields, and,
last but not least, (v) quantum information processing in lattice gases. For
completeness, also some recent progress related to the above topics with
trapped cold gases will be discussed.Comment: Review article. v2: published version, 135 pages, 34 figure
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