Search results for "homeostatic plasticity"
showing 10 items of 11 documents
Modulation of information processing by AMPA receptor auxiliary subunits
2020
AMPA-type glutamate receptors (AMPARs) are key molecules of neuronal communication in our brain. The discovery of AMPAR auxiliary subunits, such as proteins of the TARP, CKAMP and CNIH families, fundamentally changed our understanding of how AMPAR function is regulated. Auxiliary subunits control almost all aspects of AMPAR function in the brain. They influence AMPAR assembly, composition, structure, trafficking, subcellular localization and gating. This influence has important implications for synapse function. In the present review, we first discuss how auxiliary subunits affect the strength of synapses by modulating number and localization of AMPARs in synapses as well as their glutamate…
Synaptic scaling generically stabilizes circuit connectivity
2011
Neural systems regulate synaptic plasticity avoiding overly strong growth or shrinkage of the connections, thereby keeping the circuit architecture operational. Accordingly, several experimental studies have shown that synaptic weights increase only in direct relation to their current value, resulting in reduced growth for stronger synapses [1]. It is, however, difficult to extract from these studies unequivocal evidence about the underlying biophysical mechanisms that control weight growth. The theoretical neurosciences have addressed this problem by exploring mechanisms for synaptic weight change that contain limiting factors to regulate growth [2]. The effectiveness of these mechanisms i…
Transcranial direct current stimulation preconditioning modulates the effect of high-frequency repetitive transcranial magnetic stimulation in the hu…
2012
Experimental studies emphasize the importance of homeostatic plasticity as a mean of stabilizing the properties of neural circuits. In the present work we combined two techniques able to produce short-term (5-Hz repetitive transcranial magnetic stimulation, rTMS) and long-term (transcranial direct current stimulation, tDCS) effects on corticospinal excitability to evaluate whether and how the effects of 5-Hz rTMS can be tuned by tDCS preconditioning. Twelve healthy subjects participated in the study. Brief trains of 5-Hz rTMS were applied to the primary motor cortex at an intensity of 120% of the resting motor threshold, with recording of the electromyograph traces evoked by each stimulus o…
Combining tDCS with prismatic adaptation for non-invasive neuromodulation of the motor cortex
2017
Abstract Background Prismatic adaptation (PA) shifts visual field laterally and induces lateralized deviations of spatial attention. Recently, it has been suggested that prismatic goggles are also able to modulate brain excitability, with cognitive after-effects documented even in tasks not necessarily spatial in nature. Objective The aim of the present study was to test whether neuromodulatory effects obtained from tDCS and prismatic goggles could interact and induce homeostatic changes in corticospinal excitability. Methods Thirty-four subjects were submitted to single-pulse transcranial magnetic stimulation (TMS) over the right primary motor cortex to measure Input-Output (IO) curve as a…
Cyclical changes of cortical excitability and metaplasticity in migraine: evidence from a repetitive transcranial magnetic stimulation study.
2013
The primary brain dysfunctions leading to the onset of a migraine attack remain largely unknown. Other important open questions concern the mechanisms of initiation, continuation, and termination of migraine pain, and the changes in brain function underlying migraine transformation. Brief trains of high-frequency repetitive transcranial magnetic stimulation (rTMS), when applied to the primary motor cortex at suprathreshold intensity (⩾120% of resting motor threshold [RMT]), elicit in healthy subjects a progressive, glutamate-dependent facilitation of the motor evoked potentials (MEP). Conversely, in conditions of increased cortical excitability, the rTMS trains induce inhibitory MEP respons…
Abnormal facilitatory mechanisms in motor cortex of migraine with aura
2010
Experimental evidence suggests impairment of inhibitory intracortical circuits in migraine, while not much is known about activity of facilitatory intracortical circuits. In the present work we evaluated the effects of high frequency-repetitive transcranial magnetic stimulation (hf-rTMS) on the activity of facilitatory circuits of motor cortex in 18 patients affected by migraine with aura and 18 healthy subjects. Trains of 10 stimuli were applied to the motor cortex at 5-Hz frequency with recording of the EMG traces from the contralateral abductor pollicis brevis muscle (APB). Two intensities of stimulation (110% and 130% of resting motor threshold) were used in order to explore whether mot…
Reduced Threshold for Inhibitory Homeostatic Responses in Migraine Motor Cortex? A tDCS/TMS Study
2014
Background and Objective Neurophysiological studies in migraine have reported conflicting findings of either cortical hyper- or hypoexcitability. In migraine with aura (MwA) patients, we recently documented an inhibitory response to suprathreshold, high-frequency repetitive transcranial magnetic stimulation (hf-rTMS) trains applied to the primary motor cortex, which is in contrast with the facilitatory response observed in the healthy subjects. The aim of the present study was to support the hypothesis that in migraine, because of a condition of basal increased cortical responsivity, inhibitory homeostatic-like mechanisms of cortical excitability could be induced by high magnitude stimulati…
Synaptopodin regulates denervation-induced homeostatic synaptic plasticity
2013
Synaptopodin (SP) is a marker and essential component of the spine apparatus (SA), an enigmatic cellular organelle composed of stacked smooth endoplasmic reticulum that has been linked to synaptic plasticity. However, SP/SA-mediated synaptic plasticity remains incompletely understood. To study the role of SP/SA in homeostatic synaptic plasticity we here used denervation-induced synaptic scaling of mouse dentate granule cells as a model system. This form of plasticity is of considerable interest in the context of neurological diseases that are associated with the loss of neurons and subsequent denervation of connected brain regions. In entorhino-hippocampal slice cultures prepared from SP-de…
Brain stimulation in migraine
2013
Migraine is a very prevalent disease with great individual disability and socioeconomic burden. Despite intensive research effort in recent years, the etiopathogenesis of the disease remains to be elucidated. Recently, much importance has been given to mechanisms underlying the cortical excitability that has been suggested to be dysfunctional in migraine. In recent years, noninvasive brain stimulation techniques based on magnetic fields (transcranial magnetic stimulation, TMS) and on direct electrical currents (transcranial direct current stimulation, tDCS) have been shown to be safe and effective tools to explore the issue of cortical excitability, activation, and plasticity in migraine. M…
From different neurophysiological methods to conflicting pathophysiological views in migraine: a critical review of literature.
2014
Abnormal increased cortical responsivity to various types of stimuli plays a major role in migraine pathogenesis. Neurophysiological studies, however, have provided ambiguous findings of either hypo or hyper cortical excitability. This is why the term "dysexcitability" has been recently proposed to indicate a more general dysregulation of cortical excitability. The aims of this review are: (1) to provide existing knowledge and research advances in migraine pathophysiology; (2) to propose a unitary interpretation of apparently conflicting neurophysiological findings. Data of studies conducted in migraine through various evoked potentials techniques and non-invasive brain stimulation methods …