Ribeiro T.L.,Federal University of Pernambuco |
Copelli M.,Federal University of Pernambuco |
Copelli M.,Federal University of Rio Grande do Norte |
Caixeta F.,Federal University of Rio Grande do Norte |
And 9 more authors.
PLoS ONE | Year: 2010
Background: Scale-invariant neuronal avalanches have been observed in cell cultures and slices as well as anesthetized and awake brains, suggesting that the brain operates near criticality, i.e. within a narrow margin between avalanche propagation and extinction. In theory, criticality provides many desirable features for the behaving brain, optimizing computational capabilities, information transmission, sensitivity to sensory stimuli and size of memory repertoires. However, a thorough characterization of neuronal avalanches in freely-behaving (FB) animals is still missing, thus raising doubts about their relevance for brain function. Methodology/Principal Findings: To address this issue, we employed chronically implanted multielectrode arrays (MEA) to record avalanches of action potentials (spikes) from the cerebral cortex and hippocampus of 14 rats, as they spontaneously traversed the wake-sleep cycle, explored novel objects or were subjected to anesthesia (AN). We then modeled spike avalanches to evaluate the impact of sparse MEA sampling on their statistics. We found that the size distribution of spike avalanches are well fit by lognormal distributions in FB animals, and by truncated power laws in the AN group. FB data surrogation markedly decreases the tail of the distribution, i.e. spike shuffling destroys the largest avalanches. The FB data are also characterized by multiple key features compatible with criticality in the temporal domain, such as 1/f spectra and long-term correlations as measured by detrended fluctuation analysis. These signatures are very stable across waking, slowwave sleep and rapid-eye-movement sleep, but collapse during anesthesia. Likewise, waiting time distributions obey a single scaling function during all natural behavioral states, but not during anesthesia. Results are equivalent for neuronal ensembles recorded from visual and tactile areas of the cerebral cortex, as well as the hippocampus. Conclusions/Significance: Altogether, the data provide a comprehensive link between behavior and brain criticality, revealing a unique scale-invariant regime of spike avalanches across all major behaviors. © 2010 Ribeiro et al.
De Araujo D.B.,Federal University of Rio Grande do Norte |
De Araujo D.B.,Onofre Lopes University Hospital |
De Araujo D.B.,University of Sao Paulo |
Ribeiro S.,Federal University of Rio Grande do Norte |
And 9 more authors.
Human Brain Mapping | Year: 2012
The hallucinogenic brew Ayahuasca, a rich source of serotonergic agonists and reuptake inhibitors, has been used for ages by Amazonian populations during religious ceremonies. Among all perceptual changes induced by Ayahuasca, the most remarkable are vivid "seeings." During such seeings, users report potent imagery. Using functional magnetic resonance imaging during a closed-eyes imagery task, we found that Ayahuasca produces a robust increase in the activation of several occipital, temporal, and frontal areas. In the primary visual area, the effect was comparable in magnitude to the activation levels of natural image with the eyes open. Importantly, this effect was specifically correlated with the occurrence of individual perceptual changes measured by psychiatric scales. The activity of cortical areas BA30 and BA37, known to be involved with episodic memory and the processing of contextual associations, was also potentiated by Ayahuasca intake during imagery. Finally, we detected a positive modulation by Ayahuasca of BA 10, a frontal area involved with intentional prospective imagination, working memory and the processing of information from internal sources. Therefore, our results indicate that Ayahuasca seeings stem from the activation of an extensive network generally involved with vision, memory, and intention. By boosting the intensity of recalled images to the same level of natural image, Ayahuasca lends a status of reality to inner experiences. It is therefore understandable why Ayahuasca was culturally selected over many centuries by rain forest shamans to facilitate mystical revelations of visual nature. © 2011 Wiley Periodicals, Inc.
PubMed | Grande Rio University, Federal University of Säo João del Rei, Edmond and Lily Safra International Institute of Neuroscience of Natal ELS IINN and Federal University of Rio Grande do Norte
Type: Journal Article | Journal: PLoS computational biology | Year: 2015
Sleep is critical for hippocampus-dependent memory consolidation. However, the underlying mechanisms of synaptic plasticity are poorly understood. The central controversy is on whether long-term potentiation (LTP) takes a role during sleep and which would be its specific effect on memory. To address this question, we used immunohistochemistry to measure phosphorylation of Ca2+/calmodulin-dependent protein kinase II (pCaMKII) in the rat hippocampus immediately after specific sleep-wake states were interrupted. Control animals not exposed to novel objects during waking (WK) showed stable pCaMKII levels across the sleep-wake cycle, but animals exposed to novel objects showed a decrease during subsequent slow-wave sleep (SWS) followed by a rebound during rapid-eye-movement sleep (REM). The levels of pCaMKII during REM were proportional to cortical spindles near SWS/REM transitions. Based on these results, we modeled sleep-dependent LTP on a network of fully connected excitatory neurons fed with spikes recorded from the rat hippocampus across WK, SWS and REM. Sleep without LTP orderly rescaled synaptic weights to a narrow range of intermediate values. In contrast, LTP triggered near the SWS/REM transition led to marked swaps in synaptic weight ranking. To better understand the interaction between rescaling and restructuring during sleep, we implemented synaptic homeostasis and embossing in a detailed hippocampal-cortical model with both excitatory and inhibitory neurons. Synaptic homeostasis was implemented by weakening potentiation and strengthening depression, while synaptic embossing was simulated by evoking LTP on selected synapses. We observed that synaptic homeostasis facilitates controlled synaptic restructuring. The results imply a mechanism for a cognitive synergy between SWS and REM, and suggest that LTP at the SWS/REM transition critically influences the effect of sleep: Its lack determines synaptic homeostasis, its presence causes synaptic restructuring.
Calais J.B.,University of Sao Paulo |
Valvassori S.S.,National University of Santa |
Resende W.R.,National University of Santa |
Feier G.,National University of Santa |
And 6 more authors.
Journal of Neural Transmission | Year: 2013
Electroconvulsive therapy (ECT) is a well-established psychiatric treatment for severe depression. Despite its clinical utility, post-ECT memory deficits are a common side effect. Neuronal plasticity and memory consolidation are intimately related to the expression of immediate early genes (IEG), such as Egr1, Fos and Arc. Changes in IEG activation have been postulated to underlie long-term neuronal adaptations following electroconvulsive seizures (ECS), an animal model of ECT. To test this hypothesis, we used real-time PCR to examine the effect of acute and chronic ECS (8 sessions, one every other day) on the long-term (>24 h) expression of IEG Egr1, Fos and Arc in the hippocampus, a brain region implicated both in the pathophysiology of depression as well as in memory function. We observed a transient increase in Egr1 and Fos expression immediately after ECS, followed by a long-term decrease of IEG levels after both acute and chronic ECS. A separate group of animals, submitted to the same chronic ECS protocol and then subjected to open field or passive avoidance tasks, confirmed robust memory deficits 2 weeks after the last chronic ECS. The possible role of IEG downregulation on long-term learning deficits observed following ECS are discussed. © 2012 Springer-Verlag.
Del-Ben C.M.,University of Sao Paulo |
Ferreira C.A.Q.,University of Sao Paulo |
Sanchez T.A.,University of Sao Paulo |
Alves-Neto W.C.,University of Sao Paulo |
And 5 more authors.
Journal of Psychopharmacology | Year: 2012
This study aimed to measure, using fMRI, the effect of diazepam on the haemodynamic response to emotional faces. Twelve healthy male volunteers (mean age = 24.83 ± 3.16 years), were evaluated in a randomized, balanced-order, double-blind, placebo-controlled crossover design. Diazepam (10 mg) or placebo was given 1 h before the neuroimaging acquisition. In a blocked design covert face emotional task, subjects were presented with neutral (A) and aversive (B) (angry or fearful) faces. Participants were also submitted to an explicit emotional face recognition task, and subjective anxiety was evaluated throughout the procedures. Diazepam attenuated the activation of right amygdala and right orbitofrontal cortex and enhanced the activation of right anterior cingulate cortex (ACC) to fearful faces. In contrast, diazepam enhanced the activation of posterior left insula and attenuated the activation of bilateral ACC to angry faces. In the behavioural task, diazepam impaired the recognition of fear in female faces. Under the action of diazepam, volunteers were less anxious at the end of the experimental session. These results suggest that benzodiazepines can differentially modulate brain activation to aversive stimuli, depending on the stimulus features and indicate a role of amygdala and insula in the anxiolytic action of benzodiazepines. © The Author(s) 2012.
PubMed | Edmond and Lily Safra International Institute of Neuroscience of Natal ELS IINN and University of Sao Paulo
Type: Journal Article | Journal: Neurosurgical review | Year: 2016
Axial symptoms are a late-developing phenomenon in the course of Parkinsons disease (PD) and represent a therapeutic challenge given their poor response to levodopa therapy and deep brain stimulation. Spinal cord stimulation (SCS) may be a new therapeutic approach for the alleviation of levodopa-resistant motor symptoms of PD. Our purpose was to systematically review the effectiveness of SCS for the treatment of motor symptoms of PD and to evaluate the technical and pathophysiological mechanisms that may influence the outcome efficacy of SCS. A comprehensive literature search was conducted using electronic databases for the period from January 1966 through April 2014. The methodology utilized in this work follows a review process derived from evidence-based systematic review and meta-analysis of randomized trials described in the PRISMA statement. Reports examining SCS for the treatment of PD are limited. Eight studies with a total of 24 patients were included in this review. The overall motor score of the Unified Parkinsons Disease Rating Scale in the on/off-stimulation condition remained unchanged in 6 patients and improved in 18 patients after SCS. SCS appears to yield positive results for PD symptoms, especially for impairments in gait function and postural stability. However, evidence is limited and long-term prospective studies will be required to identify the optimal candidates for SCS and the best parameters of stimulation and to fully characterize the effects of stimulation on motor and nonmotor symptoms of PD.
Costa M.R.,Federal University of Rio Grande do Norte |
Costa M.R.,Edmond and Lily Safra International Institute of Neuroscience of Natal ELS IINN |
Ortega F.,Ludwig Maximilians University of Munich |
Brill M.S.,Ludwig Maximilians University of Munich |
And 8 more authors.
Development | Year: 2011
Little is known about the intrinsic specification of adult neural stem cells (NSCs) and to what extent they depend on their local niche. To observe adult NSC division and lineage progression independent of their niche, we isolated cells from the adult mouse subependymal zone (SEZ) and cultured them at low density without growth factors. We demonstrate here that SEZ cells in this culture system are primarily neurogenic and that adult NSCs progress through stereotypic lineage trees consisting of asymmetric stem cell divisions, symmetric transit-amplifying divisions and final symmetric neurogenic divisions. Stem cells, identified by their astro/radial glial identity and their slow-dividing nature, were observed to generate asymmetrically and fast-dividing cells that maintained an astro/radial glia identity. These, in turn, gave rise to symmetrically and fast-dividing cells that lost glial hallmarks, but had not yet acquired neuronal features. The number of amplifying divisions was limited to a maximum of five in this system. Moreover, we found that cell growth correlated with the number of subsequent divisions of SEZ cells, with slow-dividing astro/radial glia exhibiting the most substantial growth prior to division. The fact that in the absence both of exogenously supplied growth factors and of signals provided by the local niche neurogenic lineage progression takes place in such stereotypic fashion, suggests that lineage progression is, to a significant degree, cell intrinsic or pre-programmed at the beginning of the lineage. © 2011. Published by The Company of Biologists Ltd.
Franca A.S.C.,Federal University of Rio Grande do Norte |
Lobao-Soares B.,Federal University of Rio Grande do Norte |
Muratori L.,Federal University of Rio Grande do Norte |
Nascimento G.,Federal University of Rio Grande do Norte |
And 5 more authors.
European Neuropsychopharmacology | Year: 2015
Dopamine and sleep have been independently linked with hippocampus-dependent learning. Since D2 dopaminergic transmission is required for the occurrence of rapid-eye-movement (REM) sleep, it is possible that dopamine affects learning by way of changes in post-acquisition REM sleep. To investigate this hypothesis, we first assessed whether D2 dopaminergic modulation in mice affects novel object preference, a hippocampus-dependent task. Animals trained in the dark period, when sleep is reduced, did not improve significantly in performance when tested 24h after training. In contrast, animals trained in the sleep-rich light period showed significant learning after 24h. When injected with the D2 inverse agonist haloperidol immediately after the exploration of novel objects, animals trained in the light period showed reduced novelty preference upon retesting 24h later. Next we investigated whether haloperidol affected the protein levels of plasticity factors shown to be up-regulated in an experience-dependent manner during REM sleep. Haloperidol decreased post-exploration hippocampal protein levels at 3h, 6h and 12h for phosphorylated Ca2+/calmodulin-dependent protein kinase II, at 6h for Zif-268; and at 12h for the brain-derived neurotrophic factor. Electrophysiological and kinematic recordings showed a significant decrease in the amount of REM sleep following haloperidol injection, while slow-wave sleep remained unaltered. Importantly, REM sleep decrease across animals was strongly correlated with deficits in novelty preference (Rho=0.56, p=0.012). Altogether, the results suggest that the dopaminergic regulation of REM sleep affects learning by modulating post-training levels of calcium-dependent plasticity factors. © 2015 Elsevier B.V. and ECNP.
Nunes A.C.L.,Federal University of Rio Grande do Norte |
Duarte R.B.,Federal University of Rio Grande do Norte |
Sousa T.B.,Federal University of Rio Grande do Norte |
Dos Santos J.R.,Edmond and Lily Safra International Institute of Neuroscience of Natal ELS IINN |
And 2 more authors.
Brain Research | Year: 2010
The immediate-early gene egr-1 has been shown to have an increased expression during long-term potentiation (LTP). High frequency electrical stimulation induces an increase in such expression in the dorsal horn of the spinal cord. However, evidence demonstrating the activation of this gene in the spinal cord and its relationship with LTP is still scarce. The substance P (SP) has also been associated with LTP in the dorsal horn of the spinal cord following high frequency stimulation. Here we evaluated the expression of both Egr-1 and SP in the sacrolumbar area of the spinal cord after locomotor training in adult rats. Increased neuronal Egr-1 expression was found in the spinal cord sections in rats that underwent locomotor training, especially in laminae IV and X across L3-S4 levels (p < 0.05). Conversely, SP expression in synaptic terminals was not altered in the abovementioned regions. Our results suggest that locomotor training activates mechanisms in a similar way to LTP, and is involved in the synaptic plasticity in the spinal cord. The results also indicate that variations in the training protocol influence Egr-1 expression. Such events appear not to be directly influenced by SP, which suggests a plastic process that differs from those triggered by nociceptive stimuli. © 2010 Elsevier B.V.