Search results for "Metaplast"
showing 10 items of 16 documents
Intrinsic volatility of synaptic connections — a challenge to the synaptic trace theory of memory
2017
According to the synaptic trace theory of memory, activity-induced changes in the pattern of synaptic connections underlie the storage of information for long periods. In this framework, the stability of memory critically depends on the stability of the underlying synaptic connections. Surprisingly however, synaptic connections in the living brain are highly volatile, which poses a fundamental challenge to the synaptic trace theory. Here we review recent experimental evidence that link the initial formation of a memory with changes in the pattern of connectivity, but also evidence that synaptic connections are considerably volatile even in the absence of learning. Then we consider different…
The stressed cytoskeleton: How actin dynamics can shape stress-related consequences on synaptic plasticity and complex behavior
2015
Stress alters synaptic plasticity but the molecular and cellular mechanisms through which environmental stimuli modulate synaptic function remain to be elucidated. Actin filaments are the major structural component of synapses and their rearrangements by actin-binding proteins (ABPs) are critical for fine-tuning synaptic plasticity. Accumulating evidence suggests that some ABPs are specifically regulated by stress and stress-related effectors such as glucocorticoids and corticotropin releasing hormone. ABPs may thus be central in stress-induced perturbations at the level of synaptic plasticity, leading to impairments in behavioral domains including cognitive performance and social behavior.…
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…
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…
Ossified spinal meningiomas: Clinical and surgical features
2016
Abstract Object Meningiomas constitute 25% of primary spinal tumors and predominantly involve the thoracic spinal cord. Although calcifications are commonly seen in intracranial meningiomas, gross calcifications are observed in only 1–5% of all spinal meningiomas. We report the clinical findings, surgical strategy and histological features of 9 patients with ossified spinal meningiomas (OSMs). Patients and methods Clinical and surgical features of 9 patients with ossified spinal meningiomas were retrospectively reviewed. Results There were 8 women and 1 man with a mean age of 59 years. In 7 patients, the lesions were localized in the thoracic segment of the spine while in 2 patients in the …
Plasticity of mouse enteric synapses mediated through endocannabinoid and purinergic signaling
2012
The myenteric and submucosal plexuses of the enteric nervous system (ENS) exist as interconnected integrative nerve networks within the wall of the gastrointestinal (GI) tract. Activity of the ENS is responsible for the control of the digestive and protective functions of the gut.1 Synaptic transmission between enteric neurons propagates information from intrinsic afferent neurons to interneurons, and then from interneurons to motor neurons that control final effectors such as smooth muscle and the secretory epithelium. Acetylcholine (ACh) is the major excitatory neurotransmitter in the myenteric plexus, acting on nicotinic receptors at synapses between neurons and on muscarinic receptors a…
Membrane-Derived Phospholipids Control Synaptic Neurotransmission and Plasticity
2015
Synaptic communication is a dynamic process that is key to the regulation of neuronal excitability and information processing in the brain. To date, however, the molecular signals controlling synaptic dynamics have been poorly understood. Membrane-derived bioactive phospholipids are potential candidates to control short-term tuning of synaptic signaling, a plastic event essential for information processing at both the cellular and neuronal network levels in the brain. Here, we showed that phospholipids affect excitatory and inhibitory neurotransmission by different degrees, loci, and mechanisms of action. Signaling triggered by lysophosphatidic acid (LPA) evoked rapid and reversible depress…
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…
A common thread for pain and memory synapses? Brain-derived neurotrophic factor and trkB receptors.
2003
Recent evidence indicates that trophic factors can exert fast effects on neurones and so alter synaptic plasticity. Here, we focus on brain-derived neurotrophic factor (BDNF), which exerts a modulatory action at hippocampal synapses that are involved in learning and memory, and at the first pain synapse between primary sensory neurones and dorsal horn neurones. Hippocampal and sensory neurones share some properties for the release of endogenous BDNF. In the Schaffer collateral pathway of the hippocampus, binding of BDNF to high-affinity trkB receptors is essential for the induction of long-term potentiation, a specific type of synaptic plasticity. However, the consequences of BDNF binding t…