ICe - Artigos publicados em periódicos

URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/6192

Repositório da produção científica do Instituto do Cérebro - ICe, da UFRN, Unidade Acadêmica Especializada em neurociências.

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A importância do sistema nervoso para as políticas judiciárias do país
(12-12-10) Pereira, Antonio
Segundo pesquisa divulgada recentemente pelo Senado Federal, a opinião de quase 90% dos entrevistados é de que a maioridade penal deve ser reduzida no Brasil. Um resultado parecido com esse é provável de ser alcançado em qualquer roda de conversa informal quando o assunto vem à tona. Afinal, as pessoas estão perplexas e frustradas com o fato de que cada vez mais pessoas aparentemente adultas cometem crimes e, no final das contas, não têm a retribuição adequada para o crime que cometeram, sendo tratadas de maneira "privilegiada" pela justiça.
Minocycline treatment reduces white matter damage after excitotoxic striatal injury
(2010) Guimarães, Joanilson S.; Freire, Marco Aurelio M.; Lima, Rafael R.; Picanço-Diniz, Cristovam W.; Pereira, Antonio; Gomes-Leal, Walace
We investigated the protective effects of minocycline following white matter damage (WMD) in the rat striatum. Excitotoxic lesions were induced by N-Methyl-D-Aspartate (NMDA) microinjections and caused striatal damage, concomitant with microglial/ macrophage activation. The excitotoxic lesion both damaged oligodendrocytes (Tau-1+ cells) and caused a decrease in tissue reactivity for myelin basic protein (MBP) after postlesional day 3 (PLD). Treatment with the semi-synthetic tetracycline antibiotic minocycline, however, led to oligodendrocyte preservation and decreased myelin impairment. Taken together, these results suggest that white matter damage (WMD) is an important component of the physiopathology of acute striatal damage and that microglial/ macrophage activation contributes to this pathological phenomenon.
Electrophysiological effects of guanosine and MK-801 in a quinolinic acid-induced seizure model
(2010) Torres, Felipe V.; Silva Filho, Manoel da; Antunes, Catiele; Kalinine, Eduardo; Antoniolli, Eduardo; Portela, Luis V.C.; Souza, Diogo O.; Tort, Adriano Bretanha Lopes
Neuronal Assembly Detection and Cell Membership Specification by Principal Component Analysis
(2011) Lopes-dos-Santos, Vítor; Conde-Ocazionez, Sergio; Nicolelis, Miguel A. L.; Ribeiro, Sidarta Tollendal Gomes; Tort, Adriano Bretanha Lopes
Comprehensive Analysis of Tissue Preservation and Recording Quality from Chronic Multielectrode Implants
(2011) Freire, Marco Aurelio M.; Morya, Edgard; Santos, Jose Ronaldo; Guimaraes, Joanilson S.; Lemos, Nelson A. M.; Sameshima, Koichi; Pereira, Antonio; Ribeiro, Sidarta Tollendal Gomes; Nicolelis, Miguel A. L.
Multielectrodes have been used with great success to simultaneously record the activity of neuronal populations in awake, behaving animals. In particular, there is great promise in the use of this technique to allow the control of neuroprosthetic devices by human patients. However, it is crucial to fully characterize the tissue response to the chronic implants in animal models ahead of the initiation of human clinical trials. Here we evaluated the effects of unilateral multielectrode implants on the motor cortex of rats weekly recorded for 1–6 months using several histological methods to assess metabolic markers, inflammatory response, immediate-early gene (IEG) expression, cytoskeletal integrity and apoptotic profiles. We also investigated the correlations between each of these features and firing rates, to estimate the impact of post-implant time on neuronal recordings. Overall, limited neuronal loss and glial activation were observed on the implanted sites. Reactivity to enzymatic metabolic markers and IEG expression were not significantly different between implanted and non-implanted hemispheres. Multielectrode recordings remained viable for up to 6 months after implantation, and firing rates correlated well to the histochemical and immunohistochemical markers. Altogether, our results indicate that chronic tungsten multielectrode implants do not substantially alter the histological and functional integrity of target sites in the cerebral cortex.
A new look at gamma? High- (>60 Hz) g-band activity in cortical networks: Function, mechanisms and impairment
(2011) Uhlhaas, Peter J.; Pipa, Gordon; Maciel, Sergio Tulio Neuenschwander; Wibral, Michael; Singer, Wolf
g-band oscillations are thought to play a crucial role in information processing in cortical networks. In addition to oscillatory activity between 30 and 60 Hz, current evidence from electro- and magnetoencephalography (EEG/MEG) and local-field potentials (LFPs) has consistently shown oscillations >60 Hz (high g-band) whose function and generating mechanisms are unclear. In the present paper, we summarize data that highlights the importance of high g-band activity for cortical computations through establishing correlations between the modulation of oscillations in the 60e200 Hz frequency and specific cognitive functions. Moreover, we will suggest that high g-band activity is impaired in neuropsychiatric disorders, such as schizophrenia and epilepsy. In the final part of the paper, we will review physiological mechanisms underlying the generation of high g-band oscillations and discuss the functional implications of low vs. high g-band activity patterns in cortical networks.
Pattern motion representation in primary visual cortex is mediated by transcortical feedback
(2011) Schmidt, Kerstin Erika; Lomber, S.G.; Payne, B.R.; Galuske, R.A.W.
A highly important question in visual neuroscience is to identify where in the visual system information from different processing channels is integrated to form the complex scenery we perceive. A common view to this question is that information is processed hierarchically because small and selective receptive fields in lower visual areas melt into larger receptive fields in specialized higher visual areas. However, a higher order area in which all incoming signals ultimately converge has not yet been identified. Rather, modulation of subthreshold influences from outside the classical receptive field related to contextual integration occurs already in early visual areas. So far it is unclear how these influences are mediated (Gilbert, 1998; Angelucci and Bullier, 2003; Gilbert and Sigman, 2007). In the present study, we show that feedback connections from a higher motion processing area critically influence the integration of subthreshold global motion cues in early visual areas. Global motion cues are theoretically not discernible for a local motion detector in V1, however, imprints of pattern motion have been observed in this area (Guo et al., 2004; Schmidt et al., 2006). By combining reversible thermal deactivation and optical imaging of intrinsic signals we demonstrate that feedback signals from the posteromedial suprasylvian sulcus are critical for the discrimination between global and local motions already in early visual areas. These results suggest that global features of the visual scenery are fed back to lower visual processing units in order to facilitate the integration of local cues into a global construct.
Antecedent descriptions change brain reactivity to emotional stimuli: a Functional Magnetic Resonance imaging study of an extrinsic and incidental reappraisal strategy
(2011) MOCAIBER, I.; SANCHEZ, T. A.; PEREIRA, M. G.; ERTHAL, F. S.; JOFFILY, M.; Araújo, Dráulio Barros de; VOLCHAN, E.; OLIVEIRA, L. DE
In the present study we investigated whether individuals would take advantage of an extrinsic and incidental reappraisal strategy by giving them precedent descriptions to attenuate the emotional impact of unpleasant pictures. In fact, precedent descriptions have successfully promoted down-regulation of electrocortical activity and physiological responses to unpleasant pictures. However, the neuronal substrate underlying this effect remains unclear. Particularly, we investigated whether amygdala and insula responses, brain regions consistently implicated in emotional processing, would be modulated by this strategy. To achieve this, highly unpleasant pictures were shown in two contexts in which a prior description presented them as taken from movie scenes (fictitious) or real scenes. Results showed that the fictitious condition was characterized by down-regulation of amygdala and insula responses. Thus, the present study provides new evidence on reappraisal strategies to downregulate emotional reactions and suggest that amygdala and insula responses to emotional stimuli are adaptive and highly flexible.
A Mismatch-Based Model for Memory Reconsolidation and Extinction in Attractor Networks
(Gennady Cymbalyuk, Georgia State University, United States of America, 2011) Osan, Remus; Tort, Adriano Bretanha Lopes; Olavo B., Amaral
Selective Coupling between Theta Phase and Neocortical Fast Gamma Oscillations during REM-Sleep in Mice
(2011) Scheffzu¨ k, Claudia; Kukushka, Valeriy I.; Vyssotski, Alexei L.; Draguhn, Andreas; Tort, Adriano Bretanha Lopes; Brankacˇk, Jurij
Arterial Spin Labeling Measurements of Cerebral Perfusion Territories in Experimental Ischemic Stroke
(2011) Leoni, Renata F.; Paiva, Fernando F.; Kang, Byeong-Teck; Henning, Erica C.; Nascimento, George Carlos; Tannús, Alberto; Araújo, Dráulio Barros de; Silva, Afonso C.
Collateral circulation, defined as the supplementary vascular network that maintains cerebral blood flow (CBF) when the main vessels fail, constitutes one important defense mechanism of the brain against ischemic stroke. In the present study, continuous arterial spin labeling (CASL) was used to quantify CBF and obtain perfusion territory maps of the major cerebral arteries in spontaneously hypertensive rats (SHRs) and their normotensive Wistar-Kyoto (WKY) controls. Results show that both WKY and SHR have complementary, yet significantly asymmetric perfusion territories. Right or left dominances were observed in territories of the anterior (ACA), middle and posterior cerebral arteries, and the thalamic artery. Magnetic resonance angiography showed that some of the asymmetries were correlated with variations of the ACA. The leptomeningeal circulation perfusing the outer layers of the cortex was observed as well. Significant and permanent changes in perfusion territories were obtained after temporary occlusion of the right middle cerebral artery in both SHR and WKY, regardless of their particular dominance. However, animals with right dominance presented a larger volume change of the left perfusion territory (23±9%) than animals with left dominance (7±5%, P<0.002). The data suggest that animals with contralesional dominance primarily safeguard local CBF values with small changes in contralesional perfusion territory, while animals with ipsilesional dominance show a reversal of dominance and a substantial increase in contralesional perfusion territory. These findings show the usefulness of CASL to probe the collateral circulation.
A mechanism for the formation of hippocampal neuronal firing patterns that represent what happens where
(2011) Tort, Adriano Bretanha Lopes; Komorowski, Robert; Kopell, Nancy; Eichenbaum, Howard
The association of specific events with the context in which they occur is a fundamental feature of episodic memory. However, the underlying network mechanisms generating what–where associations are poorly understood. Recently we reported that some hippocampal principal neurons develop representations of specific events occurring in particular locations (item-position cells). Here, we investigate the emergence of item-position selectivity as rats learn new associations for reward and find that before the animal’s performance rises above chance in the task, neurons that will later become itemposition cells have a strong selective bias toward one of two behavioral responses, which the animal will subsequently make to that stimulus. This response bias results in an asymmetry of neural activity on correct and error trials that could drive the emergence of particular item specificities based on a simple reward-driven synaptic plasticity mechanism.
Continuous live imaging of adult neural stem cell division and lineage progression in vitro
(2011) Costa, Marcos Romualdo; Ortega, Felipe; Brill, Monika S.; Beckervordersandforth, Ruth; Petrone, Ciro; Schroeder, Timm; Götz, Magdalena; Berninger, Benedikt
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.
Persistent pusher behavior after a stroke
(2011) Santos-Pontelli, Taiza Elaine Grespan; Pontes-Neto, Octavio Marques; Araújo, Dráulio Barros de; Santos, Antonio Carlos dos; Leite, João Pereira
Pusher behavior (PB) is a postural control disorder characterized by actively pushing away from the nonparetic side and resisting passive correction with a tendency to fall toward the paralyzed side.1 These patients have no awareness that their active pushing is counterproductive, which precludes the patients from standing without assistance. Several studies have already demonstrated that PB can occur in patients with lesions in both hemispheres, and PB is distinct from neglect and anosognosia.2-8 The high frequency of the association between PB and neurophysiological deficits might reflect an increased vulnerability of certain regions to stroke-induced injury rather than any direct involvement with the occurrence of PB.9,10 Traditionally, PB has only been reported in stroke patients; however, it has also been described under nonstroke conditions.8 Previous imaging studies have suggested the posterolateral thalamus as the brain structure that is typically damaged in pusher patients.4,11 Nevertheless, other cortical and subcortical areas, such as the insular cortex and post-central gyrus, have also been highlighted as structures that are potentially involved in the pathophysiology of PB.2,12-16
Seeing With the Eyes Shut: Neural Basis of Enhanced Imagery Following Ayahuasca Ingestion
(2011) Araújo, Dráulio Barros de; Ribeiro, Sidarta Tollendal Gomes; Cecchi, Guillermo A.; Carvalho, Fabiana M.; Sanchez, Tiago A.; Pinto, Joel P.; Martinis, Bruno S. de; Crippa, Jose A.; Hallak, Jaime E.C.; Antonio C. Santos, Antonio C.
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.
Modulation of dendritic synaptic processing in the lateral superior olive by hyperpolarization-activated currents
(2011-01-10) Leão, Emelie Katarina Svahn; Leão, Richardson Naves; Walmsley, Bruce
We have previously shown that mice lateral superior olive (LSO) neurons exhibit a large hyperpolarization-activated current (Ih), and that hyperpolarization-activated cyclic-nucleotide-gated type 1 channels are present in both the soma and dendrites of these cells. Here we show that the dendritic Ih in LSO neurons modulates the integration of multiple synaptic inputs. We tested the LSO neuron’s ability to integrate synaptic inputs by evoking excitatory post-synaptic potentials (EPSPs) in conjunction with brief depolarizing current pulses (to simulate a second excitatory input) at different time delays. We compared LSO neurons with the native Ih present in both the soma and dendrites (control) with LSO neurons without Ih (blocked with ZD7288) and with LSO neurons with Ih only present perisomatically (ZD7288+ computer-simulated Ih using a dynamic clamp). LSO neurons without Ih had a wider time window for firing in response to inputs with short time separations. Simulated somatic Ih (dynamic clamp) could not reverse this effect. Blocking Ih also increased the summation of EPSPs elicited at both proximal and distal dendritic regions, and dramatically altered the integration of EPSPs and inhibitory post-synaptic potentials. The addition of simulated peri-somatic Ih could not abolish a ZD7288-induced increase of responsiveness to widely separated excitatory inputs. Using a compartmental LSO model, we show that dendritic Ih can reduce EPSP integration by locally decreasing the input resistance. Our results suggest a significant role for dendritic Ih in LSO neurons, where the activation ⁄ deactivation of Ih can alter the LSO response to synaptic inputs.
Lateral superior olive function in congenital deafness
(2011-01-27) Couchman, Kiri; Garrett, Andrew; Deardorff, Adam S.; Rattay, Frank; Resatz, Susanne; Fyffe, Robert; Walmsley, Bruce; Leão, Richardson Naves
The development of cochlear ilmplants for the treatment of patients with profound hearing loss has advanced considerably in the last few decades, particularly in the field of speech comprehension. However, attempts to provide not only sound decoding but also spatial hearing are limited by our understanding of circuit adaptations in the absence of auditory input. Here we investigate the lateral superior olive (LSO), a nucleus involved in interaural level difference (ILD) processing in the auditory brainstem using a mouse model of congenital deafness (the dn/dn mouse). An electrophysiological investigation of principal neurons of the LSO from the dn/dn mouse reveals a higher than normal proportion of single spiking (SS) neurons, and an increase in the hyperpolarisation-activated Ih current. However, inhibitory glycinergic input to the LSO appears to develop normally both pre and postsynaptically in dn/dn mice despite the absence of auditory nerve activity. In combination with previous electrophysiological findings from the dn/ dn mouse, we also compile a simple Hodgkin and Huxley circuit model in order to investigate possible computational deficits in ILD processing resulting from congenital hearing loss. We find that the predominance of SS neurons in the dn/dn LSO may compensate for upstream modifications and help to maintain a functioning ILD circuit in the dn/dn mouse. This could have clinical repercussions on the development of stimulation paradigms for spatial hearing with cochlear implants.
Extraction of network topology from multi-electrode recordings: is there a small-world effect?
(2011-02-07) Gerhard, Felipe; Pipa, Gordon; Lima, Bruss; Maciel, Sergio Tulio Neuenschwander; Gerstner, Wulfram
The simultaneous recording of the activity of many neurons poses challenges for multivariate data analysis. Here, we propose a general scheme of reconstruction of the functional network from spike train recordings. Effective, causal interactions are estimated by fitting generalized linear models on the neural responses, incorporating effects of the neurons’ self-history, of input from other neurons in the recorded network and of modulation by an external stimulus. The coupling terms arising from synaptic input can be transformed by thresholding into a binary connectivity matrix which is directed. Each link between two neurons represents a causal influence from one neuron to the other, given the observation of all other neurons from the population. The resulting graph is analyzed with respect to small-world and scale-free properties using quantitative measures for directed networks. Such graph-theoretic analyses have been performed on many complex dynamic networks, including the connectivity structure between different brain areas. Only few studies have attempted to look at the structure of cortical neural networks on the level of individual neurons. Here, using multi-electrode recordings from the visual system of the awake monkey, we find that cortical networks lack scale-free behavior, but show a small, but significant small-world structure. Assuming a simple distance-dependent probabilistic wiring between neurons, we find that this connectivity structure can account for all of the networks’ observed small-world‑ness. Moreover, for multi-electrode recordings the sampling of neurons is not uniform across the population. We show that the small-world-ness obtained by such a localized sub-sampling overestimates the strength of the true small-world structure of the network. This bias is likely to be present in all previous experiments based on multi-electrode recordings.
Magnetic resonance imaging quantification of regional cerebral blood flow and cerebrovascular reactivity to carbon dioxide in normotensive and hypertensive rats
(2011-06-25) Leoni, Renata F.; Paiva, Fernando F.; Henning, Erica C.; Nascimento, George Carlos do; Tannús, Alberto; Araújo, Dráulio Barros de; Silva, Afonso C.
Hypertension afflicts 25% of the general population and over 50% of the elderly. In the presentwork, arterial spin labeling MRI was used to non-invasively quantify regional cerebral blood flow (CBF), cerebrovascular resistance and CO2 reactivity in spontaneously hypertensive rats (SHR) and in normotensive Wistar Kyoto rats (WKY), at two different ages (3 months and 10months) and under the effects of two anesthetics, α-chloralose and 2% isoflurane (1.5 MAC). Repeated CBF measurements were highly consistent, differing by less than 10% and 18% within and across animals, respectively. Under α-chloralose, whole brain CBF at normocapnia did not differ between groups (young WKY: 61±3 ml/100 g/min; adult WKY: 62±4 ml/100 g/min; young SHR: 70± 9 ml/100 g/min; adult SHR: 69±8 ml/100 g/min), indicating normal cerebral autoregulation in SHR. At hypercapnia, CBF values increased significantly, and a linear relationship between CBF and PaCO2 levels was observed. In contrast, 2% isoflurane impaired cerebral autoregulation. Whole brain CBF in SHR was significantly higher than inWKYrats at normocapnia (young SHR: 139±25 ml/100 g/min; adult SHR: 104±23 ml/100 g/min; young WKY: 55±9ml/100 g/min; adult WKY: 71±19 ml/100 g/min). CBF values increased significantly with increasing CO2; however, there was a clear saturation of CBF at PaCO2 levels greater than 70 mm Hg in both young and adult rats, regardless of absolute CBF values, suggesting that isoflurane interferes with the vasodilatory mechanisms of CO2. This behavior was observed for both cortical and subcortical structures. Under either anesthetic, CO2 reactivity values in adult SHRwere decreased, confirming that hypertension, when combined with age, increases cerebrovascular resistance and reduces cerebrovascular compliance.
Diferenças cognitivas entre homens e mulheres na produção de associações livres de palavras
(2011-07) Pegado, J.F; Mota-Rolim, S.A.; Ribeiro, Sidarta Tollendal Gomes; Alchieri, J.C.
Introdução: Embora diversos estudos demonstrem diferenças no desempenho cognitivo, entre homens e mulheres, ainda não se sabe se essas diferenças ocorrem em tarefas que envolvam associação livre de palavras (AP). Objetivo: Avaliar as distâncias semânticas de palavras produzidas por AP entre homens e mulheres. Método: Aplicamos uma tarefa de AP em 68 voluntários adultos (52 mulheres e 16 homens). A tarefa de AP consistiu em listar por escrito a primeira palavra pensada após visualizar outra palavra oferecida como estímulo. Na ausência de um corpus em português adequado para à mensuração de distancias semânticas, as palavras coletadas foram traduzidas para o idioma inglês, e semanticamente quantifi cadas em um corpus representativo e sistemático desse idioma (Wordnet). Esse procedimento retirou as polissemias típicas do português, mas preservou a macro-estrutura semântica comum às duas línguas. Resultados: Na vigília, verifi camos que as distâncias semânticas são signifi cativamente menores nas AP produzidas por homens, em comparação com as distâncias semânticas verifi cadas em AP realizadas por mulheres. Conclusão: Os resultados são compatíveis com a noção de que as mulheres possuem um raciocínio mais abstrato do que homens.

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