Introdução: A anemia aguda tem sido associada com distúrbios neurofisiológicos e cognitivos em pacientes saudáveis. Evidências experimentais sugerem que a hemodiluição pode aumentar lesões cerebrais, limitando o suprimento de oxigênio ao tecido cerebral. No entanto, o mecanismo exato pelo qual as lesões cerebrais ocorrem em pacientes anêmicos ainda não está claramente definido. O objetivo desse estudo foi avaliar os precursores da apoptose neuronal Bax, Bcl-x no córtex frontal, atividade das caspases 3 e 9 na fração citosólica do hipocampo e na fração mitocondrial do córtex frontal, assim como a fragmentação do DNA na fração nuclear e mitocondrial do córtex frontal, após hemodiluição normovolêmica aguda. Métodos: Vinte e quatro porcos foram anestesiados e randomizados em 4 grupos de 6 animais: Controle, hemodiluição normovolêmica aguda (HNA) com hematócrito alvo de 15% (Ht 15%), HNA com hematócrito alvo de 10% (Ht 10%) e hipóxia-hipóxica (HH). A HNA foi realizada com 1ml de hidroxetil amido (130/0,4) por ml de sangue retirado, até o hematócrito alvo desejado (10 ou 15%). O HH consistiu de ventilação com baixa fração expirada de O2 (FiO2), sendo de 6% por 60 minutos, servindo como grupo controle positivo. Os animais do grupo controle não sofreram nenhuma dessas intervenções. As proteínas pró-apoptótica Bax e anti-apoptótica Bcl-x foram avaliadas por Western blotting nas frações nucleares e mitocondriais do córtex frontal. A atividade das caspases 3 e 9 foi avaliada nas frações mitocondrial e citosólica do hipocampo por espectrofluorometria. A fragmentação do DNA foi avaliada por eletroforese nas frações nuclear e mitocondrial do córtex frontal. Os dados foram comparados por análise de variância (ANOVA) seguida por teste de Tukey (p<0,05). Resultados: Não foi observada diferença significativa entre os grupos controle, Ht 15% e Ht 10% em relação à proteína pró-apoptótica Bax nas frações nuclear e mitocondrial. Entretanto, o grupo HH foi significativamente diferente dos grupos controle e Ht 15% na fração nuclear e de todos os grupos na fração mitocondrial. Não foi encontrada diferença significativa em relação à Bcl-x. A atividade das caspases 3 e 9 nas frações mitocondrial e nuclear foi diferente no grupo HH quando comparado com os demais grupos. Não foi observada diferença significativa em relação à fragmentação do DNA entre os grupos controle, Ht 15% e Ht 10%. Conclusão: A avaliação dos precursores da apoptose demonstrou que a hemodiluição normovolêmica aguda com hematócrito alvo de 15% e 10% não induziu apoptose, sugerindo que a oxigenação cerebral foi preservada / Background: Acute anemia has been associated with neurophysiologic and cognitive dysfunctions in healthy patients. Experimental evidences suggest that hemodilution may increase cerebral lesions, limiting oxygen supply to the brain tissue. Nevertheless, the exact mechanisms through which cerebral lesions occur in anemic patients havent been clearly defined. Therefore, the objective of the present study was to evaluate neuronal apoptosis precursors Bax, Bcl-x in the frontal cortex, caspase 3 and 9 activity in the mitochondrial and cytosolic fractions of the hippocampus, even as DNA fragmentation in the mitochondrial and nuclear fractions of the frontal cortex after acute normovolemic hemodilution. Methods: Twenty four pigs were anesthetized and randomized into 4 groups of 6 animals: sham, acute normovolemic hemodilution (ANH) to reach a hematocrit of 15% (Ht 15%), ANH to reach a hematocrit of 10% (Ht 10%) and hypoxic-hipoxia (HH). ANH was performed with 1ml hydroxyethyl starch 130/0.4 (HES) per ml of blood withdrawn to the desired target hematocrit (10 or 15%). HH consisted of ventilation with low fraction of inspired oxygen (FiO2) of 6% for 60 minutes, serving as a positive control group. Sham animals were not involved in any of these interventions. Pro-apoptotic Bax and anti-apoptotic Bcl-x proteins were evaluated by Western blotting in nuclear and mitochondrial fractions of the frontal cortex and activities of caspases-3 and-9 were evaluated in the mitochondrial and cytosolic fractions of the hippocampus by spectrofluorometry. DNA fragmentation was evaluated by electrophoresis in the mitochondrial and nuclear fraction. Data were compared by analysis of variance (ANOVA) followed by Tukeys test (p<0.05). Results: No statistical significance was found among sham, Ht 15% or Ht 10% groups regarding pro-apoptotic protein Bax, in nuclear or mitochondrial fractions. However, group HH presented significant difference from sham and Ht 15% groups in the nuclear fraction and from all groups in the mitochondrial fraction. No statistical significance was found with Bcl-x. The activities of caspases-3 and-9 in cytosolic and mitochondrial fractions were statisticaly different in group HH when compared with all other groups. No statistical significance was found in relation to DNA fragmentation among sham, Ht 15% or Ht 10%. Conclusion: The evaluation of apoptosis precursors demonstrated that ANH with target hematocrit 15% and 10% did not induce neuronal lesion, suggesting that cerebral oxygenation was preserved

O estudo ocorreu durante o verão e inverno do Canal de São Sebastião e Baía do Araçá, com o objetivo de analisar a influência da massa de Água Central do Atlântico Sul (ACAS), marés e passagens de sistemas frontais na estrutura de tamanho fitoplanctônico, representada pela concentração de clorofila-a nas classes de tamanho do micro, nano e picofitoplâncton. Para tanto foram realizadas coletas semanais, para a obtenção de dados físico-químicos e concentração de clorofila-a. O Canal de São Sebastião foi considerado um sistema em três estratos de profundidade no verão, aonde os eventos episódicos de entrada de ACAS se apresentou de forma variada, trazendo concentrações de nutrientes de baixas a moderadas. No verão, a ACAS foi responsável pela maior quantidade de nitrato, possibilitando um pequeno acúmulo de biomassa da classe do microfitoplâncton, igualando-a a aquela do nanofitoplâncton. No inverno, o silicato, provindo da baía do Araçá, permaneceu com concentrações altas sugerindo o rápido consumo dos outros compostos. As baixas concentrações de nutrientes na baia indicam um alto consumo local. No inverno, com a coluna de água homogênea, devido à mistura, e a entrada de uma menor concentração de nutrientes, porém constante pela Água Costeira, o nanofitoplâncton se sobressaiu em relação às outras classes de tamanho e promoveu a maior concentração de clorofila-a. Os pontos mais rasos amostrados apresentaram maior variabilidade na concentração de clorofila-a em relação aos pontos mais profundos. Isso sugere que tanto a produção como a retirada da clorofila-a ocorram em uma escala temporal menor quanto menor a profundidade. / This study was conducted in São Sebastião Channel and Araçá Bay during summer and winter months in 2012 to analyze the influence of the South Atlantic Central Water (SACW), tides and passage of cold fronts in the phytoplankton size structure, represented by size classes chlorophyll-a concentration of micro, nano and picophytoplankton. Physical and chemical data, as well as chlorophyll-a concentration samples were collected weekly. The São Sebastião Channel was considered a three depth layer system in the Summer, when episodic and variable events of SACW intrusions brought low to moderate nutrients contents. In the Summer, SACW was responsible of the larger nitrate concentration observed, providing a small accumulation of microphytoplankton class biomass, that was equivalent to that of nanophytoplankton. In the Winter, the high silicate concentration was observed in Araçá Bay, suggesting a quickly consumption of other compounds. The overall low nutrient concentration in the Araçá bay suggests a high local consumption. With a homogeneous water column due to mixing, and a probably lower but constant input of nutrients by the Coastal Water mass, the nanophytoplankton predominated over the other size classes and drove the observed higher chlorophyll-a concentration in the Winter. The shallower stations showed a bigger chlorophyll-a concentration variability than the deeper stations, suggesting that both production and removal of chlorophyll-a happen in a smaller temporal scale near shore.

O córtex pré-frontal medial ventral (CPFMv) é uma estrutura límbica que está envolvida em respostas autonômicas associadas a reações aversivas. O CPFMv é dividido em córtex pré- límbico (PL), córtex infralímbico (IL) e córtex dorsopeduncular (DP). A estimulação elétrica ou química destas regiões causa respostas defensivas e alterações autonômicas tais como respostas cardiovasculares, dependendo da sub-região estimulada. O estresse de restrição (ER) causa alterações hormonais e respostas autonômicas, tais como aumento de pressão arterial (PA) e frequência cardíaca (FC). A ativação de neurônios presentes no CPFMv durante essa situação aversiva, assim como os resultados da inibição farmacológica das sinapses presentes no PL e IL sugerem o envolvimento destas estruturas na modulação das respostas cardiovasculares causadas pelo ER. Entretanto, os possíveis neurotransmissores presentes no vCPFM, envolvidos nesta modulação, ainda não foram elucidados. O sistema opioidérgico central modula o sistema cardiovascular inclusive durante situações aversivas, sendo que tanto receptores quanto peptídeos opióides estão presentes no CPFMv. Considerando o exposto acima, a hipótese a ser testada no presente trabalho foi que a neurotransmissão opioidérgica do PL e IL está envolvida na modulação das respostas cardiovasculares de aumento da PA e FC desencadeadas pelo ER. Assim, a administração de naloxona (antagonista não-seletivo de receptores opióides) no PL ou IL reduziu a resposta pressora e taquicardíaca induzida pelo ER, sendo o perfil da curva dose-inibição em forma de U-invertido. A administração de CTAP (antagonista dos receptores opióides µ) ou nor-BNI (antagonista dos receptores opióides ?) no PL também reduziu a resposta pressora e taquicardíaca induzida pelo ER, de forma semelhante à naloxona, sugerindo o envolvimento desses receptores na modulação das respostas cardiovasculares desencadeadas pelo ER, enquanto que no IL, apenas a administração de nor-BNI reduziu a resposta cardiovascular induzida pelo ER. O tratamento com naltrindole (antagonista ?-seletivo) em ambas as estruturas não alterou a resposta pressora e taquicardíaca gerada pelo ER. A administração de UPF-101 (antagonista ORL-1) no PL potencializou a resposta taquicardíaca, sem alterar a resposta pressora enquanto a administração no IL não gerou efeito. Em resumo, os resultados indicam que o sistema opioidérgico, presente no PL e IL, desempenha papel facilitatório sobre as respostas cardiovasculares induzidas pelo ER, enquanto o sistema nociceptina/orfanina FQ apresentaria papel inibitório. / The ventral medial prefrontal cortex (vMPFC) is a limbic structure involved in the mediation of autonomic responses associated to aversive situations. The vMPFC is divided into prelimbic cortex (PL), infralimbic cortex (IL) and dorsal peduncular cortex (DP). The electrical or chemical stimulation of these regions cause defensive responses and autonomic changes, such as cardiovascular responses, depending on the subregion stimulated. The restraint stress (RS) evokes hormonal and autonomic responses, as well as arterial pressure and heart rate increases. Neuronal activation in the vMPFM was reported during this aversive situation, and the pharmacological inhibition of synapses in the PL and IL has suggested the involvement of these structures in the modulation of cardiovascular responses caused by RS. However, the possible neurotransmitters present in vCPFM that are involved in this modulation have not yet been identified. Opioid peptides and their receptors are present in the CPFMv. Furthermore, the central opioid system is known to modulate the cardiovascular system, even during aversive situations. Therefore, the hypothesis of this study was that PL and IL opioid neurotransmission is involved in the modulation of cardiovascular responses caused by RS. Naloxone (opioid nonselective antagonist) administration in PL or IL reduced the pressure and tachycardiac response evoked by RS, with the dose-inhibition curve having an U-inverset shape. Similar to naloxone, the selective µ-opioid antagonist CTAP and the selective ?-opioid antagonist nor-BNI when administered into the PL also reduced the pressor and tachycardiac response induced by RS, thus suggesting an involvement of these receptors in the modulation of cardiovascular responses evoked by RS, while in the IL, only administration of nor- BNI reduced the cardiovascular response induced by RS. In both structures, the treatment with the selective ?-opioid antagonist naltrindole did not affect the pressor and tachycardic response caused by RS. The pretreatment of the PL with the selective ORL-1 antagonist UPF-101 increased the tachycardic response, without affecting the RSevoked pressor, while the administration of UPF-101 into the IL did not affect the RS-evoked cardiovascular response. In summary, the opioid system in PL and IL appear to play a facilitatory role on the cardiovascular responses induced by RS, while the system nociceptin / orphanin FQ would have an inhibitory role on these responses.

A administração sistêmica de canabidiol (CBD), o principal constituinte não psicomimético da Cannabis sativa, induz efeito antidepressivo em modelos préclínicos. O mecanismo de ação do canabidiol, no entanto, permanece pouco conhecido, podendo envolver a ativação de receptores serotoninérgicos do tipo 1A (5-HT1A). Ademais, as estruturas encefálicas envolvidas nesses efeitos permanecem desconhecidas. O córtex pré-frontal medial ventral (CPFmv), dividido em infra-límbico (IL) e pré-límbico (PL), recebe densa inervação serotoninérgica e desempenha importante papel na modulação da resposta emocional ao estresse e na neurobiologia da depressão. Dessa forma, o objetivo do presente trabalho foi avaliar a hipótese de que a administração de canabidiol no CPFmv, diferenciado em PL e IL, produz efeito tipo-antidepressivo por meio da ativação de receptores 5- HT1A. Para tanto, ratos Wistar canulados bilateralmente no CPFmv, receberam CBD (10, 30, 60 nmol/0,2?l) ou veículo intra-PL e CBD (30, 45 e 60nmol/0,2?l) ou veículo intra-IL e foram submetidos ao teste do nado forçado ou ao teste do campo aberto. Outro grupo de animais recebeu microinjeção (intra PL ou IL) do agonista de receptores 5-HT1A, 8-OH-DPAT (5, 10nmol/0,2?l) e foram submetidos aos mesmos testes. Um grupo adicional recebeu um antagonista 5-HT1A, WAY1006365 (10, 30nmol/0,2?l), seguido pela administração de 8-OH-DPAT (10nmol0,2?l) ou CBD (10 nmol0,2?l) intra-PL, ou 8-OH-DPAT (10nmol0,2?l) ou CBD (45 nmol0,2?l) intra-IL, e avaliados no teste do nado forçado. Os resultados demonstraram que a administração de CBD e de 8-OH-DPAT, intra-PL e intra-IL, reduziu significativamente o tempo de imobilidade no teste do nado forçado, um efeito tipoantidepressivo, sem alterar a atividade locomotora dos animais no teste do campo aberto. Além disso, a administração de WAY100635 intra-PL e intra-IL não alterou o tempo de imobilidade per se, mas foi capaz de bloquear os efeitos da administração do CBD e do 8-OH-DPAT. Esses resultados sugerem que a administração local do CBD no CPFmv induz efeito tipo-antidepressivo por meio da ativação de receptores 5-HT1A. Portanto, é possível que o CPFmv esteja envolvido no efeito tipoantidepressivo induzido pelo CBD. / Systemic administration of cannabidiol (CBD), the main non-psychotomimetic constituent of Cannabis sativa, induces antidepressant-like effects in pre-clinical models. The mechanism of action of Cannabidiol, which remains poorly understood, may involve serotonergic type 1A receptors activation (5-HT1A). Furthermore, the brain structures involved in these effects are still unknown. The ventral medial prefrontal cortex (vmPFC), divided in infra-limbic (IL) and pre-limbic (PL) subregions, receives dense serotonergic innervation and plays an important role in the modulation of emotional responses to stress and in the neurobiology of depression. Thus, the aim of this study was evaluate the hypothesis that the administration of cannabidiol into the vmPFC, differentiated into IL and PL, would induce antidepressant-like effect by activating 5-HT1A receptors. Therefore, male Wistar rats with cannulae bilaterally implanted into the Il and PL were given CBD (10, 30, 45, 60 nmol/0,2?l) or vehicle and were submitted to the forced swimming test or to the open field test. Another group of animals received microinjections (intra PL or IL) of the 5- HT1A agonist 8-OH-DPAT (5, 10nmol/0,2?l) and was submitted to the same tests. An additional group received an 5-HT1A antagonist, WAY100635 (10, 30 nmol/0,2?l.), followed by the administration of 8-OH-DPAT (10 nmol/0,2?l) or CBD (10 nmol0,2?l) intra-PL, or 8-OH-DPAT (10nmol0,2?l) or CBD (45 nmol0,2?l) intra- IL, and avaluated in the forced swimming test. The results showed that CBD and 8- OH-DPAT administration, intra-PL and intra-IL, significantly reduced the immobility time in the forced swimming test, an antidepressant-like effect, without changing the locomotor activity of the animals in the open field test. Moreover, the administration of WAY100635, intra-PL and intra-IL, did not change the immobility time per se, but blocked the CBD- and 8-OH-DPAT-induced effects. These results suggest that the local administration of CBD into the vmPFC induces antidepressant-like effects through the activation of 5-HT1A receptors. Therefore, it is possible that the vmPFC is involved in CBD-induced antidepressant-like effect.

A participação do córtex pré-frontal na memória episódica verbal e seu envolvimento na estratégia organizacional semântica têm sido demonstrados em vários estudos de neuroimagem funcional. Entretanto nenhum estudo anterior investigou os efeitos do treino cognitivo com uso de estratégia semântica sobre a cirtuitaria neural. No presente estudo Investigou-se a codificação da memória episódica verbal, por meio de ressonância magnética funcional (RMf). Quinze voluntários viram listas de palavras apresentadas em três condições de organização semântica: 1) RE relacionada estruturada, 2) RNE relacionada não estruturada e 3) NR não relacionada, antes e após trinta minutos de treino com uso de estratégia organizacional semântica. O principal objetivo foi verificar os efeitos do treino no padrão de ativação neural. Observou-se a participação de uma ampla rede de estruturas cerebrais. O giro frontal inferior e o córtex frontal ventrolateral foram mais ativados após o treino. O córtex pré-frontal dorsolateral e o órbito-frontal foram ativados nas condições RNE e RE antes do treino, as quais permitiram a manipulação e o uso organizacional da estratégia semântica. Os resultados sugerem que: 1) a ativação do giro frontal inferior BA 45 e do córtex pré-frontal ventrolateral BA 47 após o treino pode estar associada ao melhor desempenho da memória episódica verbal. 2) o córtex órbito-frontal BA 11 esteja possivelmente envolvido na mobilização de estratégias e o córtex pré-frontal dorsolateral BA 46 e 9 na manutenção e uso da estratégia mais eficiente / The participation of prefrontal cortex in episodic verbal memory and its involvement in organizational semantic strategy has been demonstrated in several studies of functional neuroimage. However any previous study investigated the effects of cognitive training with semantic organizational strategy use under neural circuitry. At the present study verbal episodic memory encoding were investigated, through functional magnetic resonance (fMRI). Words lists were visually presented to fifteen volunteers in three organizational semantic conditions: 1) RS related structured, 2) RNS related unstructured e 3) UR unrelated, before and after thirty minutes in organizational semantic strategy training. The main objective was to verify the effects of training on neural activation circuitry. The participation of an active broad structure cerebral network was observed. After training the inferior frontal gyrus and the ventrolateral prefrontal cortex were mainly activated. The dorsolateral prefrontal cortex and o orbitofrontal cortex were activated in RNS and RS conditions before training; witch enabled the application and manipulation of semantic organizational strategy. This result suggest: 1) better performance on retrieval and strategy uses after training might be associated to modification of neural activation pattern, and 2) orbitofrontal cortex BA 11 possibly is involved in strategies mobilization, and dorsolateral prefrontal cortex BA 46 e 9 in the uses and maintenance the most efficient strategy

A hallmark of human behaviour is that we can either couple or decouple our thoughts, decision and motor plans from actions. Previous studies have reported evidence of gating of information between intention and action that can happen at different levels in the central nervous system (CNS) involving the motor cortex, subcortical structures such as the basal ganglia and even in the spinal cord. In my research I examine the extent of this gating and its modulation by task context. I will present results obtained by data collected from (a) neck muscles and neural recording from frontal eye field (FEF) in macaque monkeys and (b) putative motor units (MUs) from high density electrode arrays using surface EMG signals in human to delineate the type of information that leaks into muscles in the periphery when subjects are involved in preparing eye and hand movements, respectively, and its modulation by task context Overall, my results reveal that we can assess some aspects of central planning in the activity of motor units Further, the recruitment of these motor units depend on task context.

Magíster en Ciencias, Mención Geología / El segmento Chileno de los Andes ubicado al este de la ciudad de Vallenar, entre los 28°30' y los 29°S, presenta dos contrastantes estilos estructurales. Por el este, la Cordillera Frontal consiste en bloques de basamento limitados por fallas que alternan con franjas N-S de sucesiones mesozoicas con distintos grados de deformación. Por el oeste, en la Provincia Costera, solo afloran sucesiones del Mesozoico superior con una deformación de suaves pliegues de longitud de onda kilométrica. Paralelamente, las sucesiones mesozoicas también presentan una variación en sentido E-O caracterizada por cambios en su espesor y en litología. Estudios estructurales y estratigráficos realizados en este trabajo indican que las variaciones laterales en la estratigrafía mesozoica están ligadas al desarrollo de una serie de hemi-grabenes abiertos hacia el oeste que acomodan sucesiones continentales y sedimentarias entre el Triásico y el Cretácico Inferior. Las arquitecturas estratigráficas de los rellenos de estas cuencas responden a las geometrías producidas por el arreglo espacial y evolución estructural de las fallas normales de borde. Los principales sistemas de fallas de borde de estas cuencas se ubican a lo largo de heterogeneidades del el basamento paleozoico. El Cretácico Superior marca una etapa de tectónica compresiva evidenciada por la inversión tectónica de estas cuencas extensionales por medio de la reactivación inversa de las fallas de borde. Esta deformación produce un acortamiento del 5,7 % (3,6 km) y un transporte tectónico hacia el oeste que induce el alzamiento relativo de la Cordillera Frontal por sobre el Dominio Costero. Sincrónico a esta deformación se acumulan potentes secuencias volcánicas en el Dominio Costero que, consecuentemente, se acuñan hacia el este contra el margen occidental de la Cordillera Frontal, aquí referido como Frente Cordillerano. A partir del Eoceno se identifica un nuevo período de deformación compresiva marcado por la progresiva inversión tectónica de las cuencas extensionales mesozoicas por medio de la generación de fallas de "short-cut" y de "bypass" que cortan a las fallas normales mesozoicas. Los menores manteos de estas fallas producen un acortamiento que alcanza el 8,6% (5,2 km), acumulándose un acortamiento total mínimo de 13,7% (8,9 km) para el área de estudio. Estas fallas también tienen una vergencia oeste y se ubican en el Frente Cordillerano, cuya ubicación corresponde a un cambio litológico mayor en el basamento paleozoico. Estos resultados muestran que las discontinuidades en el basamento controlan la localización de los principales sistemas de fallas mesozoicos y cenozoicos, así como la arquitectura extensional mesozoica controla la imposición de un estilo estructural de inversión tectónica para esta parte de los Andes.

Bear Seamount (39° 55’ N; 67° 30’ W) is the westernmost peak of extinct undersea volcanoes in the New England Seamount Chain (Moore et al., 2003). It is located on the continental slope off Georges Bank, and is governed by unique environmental factors and currents that may be unlike those of the other seamounts (Moore et al., 2003). Previous cruises to this seamount have been successful in capturing abundant fishes, cephalopods and invertebrates (Moore et al., 2003; Moore et al., 2004; Moore et al., 2008), but only the distribution patterns of the fishes and cephalopods have been examined, leaving a lack of information on the deep-sea crustaceans. The diversity, catch per unit effort (CPUE) and biogeography of trawl-vulnerable micronekton in the vicinity of Bear Seamount were investigated, with primary focus on baseline data collection. Sixty-six species of pelagic Crustacea (Decapoda, Lophogastrida, and Euphausiacea) were collected at 35 trawl stations in the spring of 2003 and 2004 and fall of 2014 with the International Young Gadoid Pelagic Trawl (IYGPT) and a Polytron Midwater Rope Trawl (PMRT). Depths sampled ranged from the surface to 1700 m, with most trawls sampling primarily below 1000 m. When comparing relative biogeography of the nekton in IYGPT samples, the assemblage on the south side of the seamount was the most diverse, while the summit assemblage was the most abundant and species rich. In the PMRT samples, the summit assemblage was the most diverse and species rich while the assemblage on the west side had the greatest abundance. Overall CPUE was dominated by cold temperate species, typical of mid- to higher latitudes in the North Atlantic. Eusergestes arcticus and Meganyctiphanes norvegica were particularly dominant in both the IYGPT and PMRT samples. At least two species were new records for Northwest Atlantic waters and may have traveled by means of currents and/or from nearby seamounts.

Les aires cérébrales frontales et pariétales sont impliquées dans différents processus cognitifs importants pour la performance visuelle, tels que l'attention ou la conscience. Malgré les preuves existantes en faveur d'une implication de ces régions dans la cognition visuelle, leurs contributions dans le traitement de stimuli non masqués de faible contraste ainsi que l'activité spatio-temporelle sous-tendant ces contributions restent largement inexplorées, tout particulièrement en termes de causalité. Nous avons mené une exploration approfondie de ces contributions chez l'humain, en mettant l'accent sur la dynamique de l'activité neurale et les améliorations perceptives potentielles qui peuvent résulter de la manipulation non invasive de l'activité cérébrale. À cette fin, nous avons testé chez des sujets sains les effets d'impulsions simples ou de rafales courtes de stimulation magnétique transcrânienne (SMT) réelle versus fausse, délivrée sur le champ oculomoteur frontal ou le sillon intrapariétal avant la présentation d'un filtre de Gabor de faible contraste, sur la discrimination et la détection consciente de ce filtre de Gabor. Nos résultats montrent que chez l'humain, la distribution spatio-temporelle de l'activité frontale et pariétale joue un rôle causal dans la performance visuelle. Nos recherches contribuent à mieux comprendre les bases oscillatoires de la cognition visuelle et les comportements associés et à préparer le terrain pour le développement de nouvelles thérapies basées sur la manipulation non-invasive de l'activité cérébrale oscillatoire avec, pour objectif ultime, l'amélioration des pathologies neuropsychiatriques. / Frontal and parietal areas have been shown to subtend different cognitive processes such as attentional orienting, decision making and access to consciousness, with bearing on visual performance. In spite of prior evidence supporting an implication of those regions in visual cognition, their contributions to the processing of low-contrast unmasked stimuli and the characteristic spatiotemporal activity patterns underlying them remain to be fully explored and causation is lacking. We here addressed a thorough exploration of such contributions in humans, with an emphasis on the dynamics of neural activity and visual performance enhancements as probed by patterns of noninvasive manipulation of local brain oscillatory activity. To this end, we tested in healthy participants the effects of either single pulses or short bursts of active vs. sham transcranial magnetic stimulation (TMS), delivered to the frontal eye field (FEF) and the intraparietal sulcus (IPS) prior to the presentation of a lateralized low-contrast near-threshold Gabor stimulus, on the visual discrimination and conscious detection of such stimulus. Our findings contribute to better substantiate the oscillatory basis of visual cognition and its associated behaviors and to set the stage for the development of novel therapies based on noninvasive manipulation of dysfunctional brain oscillatory activity.

The development of cholinergic neurons in mouse frontal cortex was studied both in vivo and in vitro by immunocytochemistry with an antibody to choline acetyltransferase (ChAT), the enzyme responsible for acetylcholine synthesis. While cortical cholinergic neurons have previously been characterized in rat cortex, up until very recently, intrinsic cortical cholinergic neurons were considered to be absent in mouse, and little is known about their development or phenotypic characteristics. The present study found no ChAT-positive neurons in mouse frontal cortex on postnatal day 0 (P0, the day of birth). On P7 there were few, faintly stained, ChAT-positive neurons. The numerical density of ChAT-positive neurons increased substantially with age, from none on P0, to 9.2 + 1.4 on P7, to 14.8 + 0.9 on P16, and 41.6 + 3.9 in adulthood. Considering that the numerical density of total neurons decreases during this postnatal period, the data represent a marked developmental increase in the percentage of cholinergic neurons. The development of cholinergic neurons showed very similar timelines in rat and mouse frontal cortex. Cultures prepared from mouse frontal cortex on embryonic day 16 were maintained for 25, 76, or 100 days in vitro (div). The percentage of ChAT-positive neurons was considerably higher than in vivo, ranging from a mean 28% to 31% across the three age (div) groups. With increasing age of the cultures, the numerical density of total neurons and ChAT-positive neurons decreased while the percentage of ChAT-positive neurons did not change significantly. These observations suggest some temporal stability in the cultures. Using dual immunofluorescence, ChAT-positive neurons were tested for colocalization with GAD or TH. The majority of ChAT-positive neurons colocalized with GAD, both in vitro and in vivo. However, ChAT did not colocalize with TH, either in vitro or in vivo. Our comparison of intact frontal cortex and cultures suggest that while the percentage of cholinergic neurons was greater in the cultures, the cholinergic neurons developed phenotypic similarities in vitro and in vivo.