11,084 research outputs found
Learning, memory, and transcranial direct current stimulation
Transcranial direct current stimulation (tDCS) has been the subject of many studies concerning its possible cognitive effects. One of the proposed mechanisms of action for neuromodulatory techniques, such as transcranial magnetic stimulation and tDCSis induction of long-term potentiation (LTP) and long-term depression (LTD)-like phenomena. LTP and LTD are also among the most important neurobiological processes involvedin memory and learning. This fact has led to an immediate interest _in the study of possible effects of tDCS on memory consolidation, retrieval, or learning of various tasks. This review analyses published articles describing beneficial or disruptive effects of tDCS on memory and learning in normal subjects. The most likely mechanisms underlying these effects are discussed
Plasticity of the human cerebral cortex as revealed by transcranial magnetic stimulation
Um velho dogma da biologia afirma que só existiria capacidade de reorganização
cortical (neuroplasticidade) em animais muito jovens; no adulto, tal capacidade
seria pequena ou mesmo inexistente.
Aqui, revisamos estudos realizados em animais e em humanos que demonstram
uma capacidade de reorganização cortical nos sistemas sensoriais e motores
em indivíduos adultos. Destacamos os estudos realizados com a técnica de estimulação magnética transcraniana. O córtex cerebral asulto é capaz de reorganização após lesões do sistema nervoso periférico ou central ou no contexto do aprendizado. ______________________________________________________________________________ ABSTRACTAn old biological dogma states that a potencial for cortical reorganization
(neuroplasticity) exists nly in young animals, being lost in adlt life.
Here we review studies carried out both in animals and humans, whixh
demonstrate cortical reorganization in sensory and motor systems in adult
subjects. We particulary emphasiza human studies carried out with the aid of
transcranial magnetic stimulation. The adult cortex is capable of reorganization
after peripheral or central nervous system lesions and as a result of learning
Angular Momentum of the BTZ Black Hole in the Teleparallel Geometry
We carry out the Hamiltonian formulation of the three- dimensional
gravitational teleparallelism without imposing the time gauge condition, by
rigorously performing the Legendre transform. Definition of the gravitational
angular momentum arises by suitably interpreting the integral form of the
constraint equation Gama^ik=0 as an angular momentum equation. The
gravitational angular momentum is evaluated for the gravitational field of a
rotating BTZ black hole.Comment: 17 pages, no figures, v2: some misprints corrected, Ref.s added, Eq.s
revised, submitted to General Relativity and Gravitatio
Motor Cortex Stimulation for pain relief : do corollary discharges play a role?
Both invasive and non-invasive motor cortex stimulation techniques have been successfully employed in the treatment of chronic pain, but the precise mechanism of action of such treatments is not fully understood. It has been hypothesized that a mismatch of normal interaction between motor intention and sensory feedback may result in central pain. Sensory feedback may come from peripheral nerves, vision and also from corollary discharges originating from the motor cortex itself. Therefore, a possible mechanism of action of motor cortex stimulation might be corollary discharge reinforcement, which could counterbalance sensory feedback deficiency. In other instances, primary deficiency in the production of corollary discharges by the motor cortex might be the culprit and stimulation of cortical motor areas might then be beneficial by enhancing production of such discharges. Here we review evidence for a possible role of motor cortex corollary discharges upon both the pathophysiology and the response to motor cortex stimulation of different types of chronic pain. We further suggest that the right dorsolateral prefrontal cortex (DLPC), thought to constantly monitor incongruity between corollary discharges, vision and proprioception, might be an interesting target for non-invasive neuromodulation in cases of chronic neuropathic pain
How hole defects modify vortex dynamics in ferromagnetic nanodisks
Defects introduced in ferromagnetic nanodisks may deeply affect the structure
and dynamics of stable vortex-like magnetization. Here, analytical techniques
are used for studying, among other dynamical aspects, how a small cylindrical
cavity modify the oscillatory modes of the vortex. For instance, we have
realized that if the vortex is nucleated out from the hole its gyrotropic
frequencies are shifted below. Modifications become even more pronounced when
the vortex core is partially or completely captured by the hole. In these
cases, the gyrovector can be partially or completely suppressed, so that the
associated frequencies increase considerably, say, from some times to several
powers. Possible relevance of our results for understanding other aspects of
vortex dynamics in the presence of cavities and/or structural defects are also
discussed.Comment: 9 pages, 4 page
Impurity states on the honeycomb lattice using the Green's function method
Using the Green's function method, we study the effect of an impurity
potential on the electronic structure of the honeycomb lattice in the one-band
tight-binding model that contains both the nearest neighbor () and the
second neighbor () interactions. The model is relevant to the case of the
substitutional vacancy in graphene. If the second neighbor interaction is large
enough (), then the linear Dirac bands no longer occur at the Fermi
energy and the electronic structure is therefore fundamentally changed. With
only the nearest neighbor interactions present, there is particle-hole
symmetry, as a result of which the vacancy induces a "zero-mode" state at the
band center with its wave function entirely on the majority sublattice, i. e.,
on the sublattice not containing the vacancy. With the introduction of the
second neighbor interaction, the zero-mode state broadens into a resonance peak
and its wave function spreads into both sublattices, as may be argued from the
Lippmann-Schwinger equation. The zero-mode state disappears entirely for the
triangular lattice and if is large for the honeycomb lattice as well. In
case of graphene, is relatively small, so that a well-defined zero-mode
state occurs in the vicinity of the band center.Comment: 8 pages, 9 figure
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