Set Of Brain Structures Research Articles

Modulation of the Rat Intergeniculate Leaflet of the Thalamus Network by Norepinephrine

Circadian rhythms are regulated by a set of brain structures, one of which is the Intergeniculate Leaflet of the Thalamus (IGL). The most recognised role of the IGL is the integration of a variety of stimuli affecting rhythmicity, such as lighting conditions, received by the eye, or light-independent (non-photic) cues, the information about which is delivered via the activation of the non-specific projections. One of them is the norepinephrinergic system originating in the brainstem Locus Coeruleus (LC). In order to investigate the effect of norepinephrine (NE) on the IGL neurons we have performed ex vivo recordings using the extracellular multi-electrode array technique as well as the intracellular whole-cell patch clamp. Using both agonists and antagonists of specific NE receptor subtypes, we confirmed the presence of functional α1-, α2- and β-adrenergic receptors within the investigated structure, allowing NE to exert multiple types of effects on different IGL neurons, mainly depolarisation of the neurons projecting to the Suprachiasmatic Nuclei – the master circadian pacemaker, and various responses exhibited by the cells creating the connection with the contralateral IGL. Moreover, NE was shown to affect IGL cells both directly and via modulation of the synaptic network, in particular the miniature inhibitory postsynaptic currents. To the best of our knowledge, these are the first studies to confirm the effects of NE on the activity of the IGL network.

Emotional system in complex cognitive activities of working memory: A literature review of its role.

Cognitive processing is needed to elicit emotional responses. At the same time, emotional responses modulate and guide cognition to enable adaptive responses to the environment. However, most empirical studies and theoretical models of cognitive functions have been investigated without taking into account emotion, which is considered interference that is counterproductive to the correct functioning of the cognitive system. To understand how complex behaviors are carried out in the brain, an understanding of the interactions between emotion and cognition may be indispensable. Given the enormous scope of this topic for both cognition and emotion, these concepts will not be further defined here; instead, this review will be relatively narrow in scope and will emphasize several brain systems involved in the interactions between emotion and working memory because an important dimension of cognition involves working memory function. In attempting to understand the relationship between emotion and working memory, we will describe the projections of a set of brain structures that support our emotional life and the neuromodulator dopamine (which is also involved in emotion processing and incentive motivational behavior) in the prefrontal cortex. According to the literature, working memory engages the cortical regions. Thus, the prefrontal cortex, particularly the dorsolateral prefrontal cortex (DLPFC), although commonly viewed as a purely cognitive area, provides a test for the hypothesis that working memory and emotion are strongly integrated in the brain. In this review, we provide an overview of neuropsychological, neuroanatomical and molecular evidence, with the aim of establishing the extent to which working memory and emotion are related.

A Review Essay onSocial Neuroscience: Can Research on the Social Brain and Economics Inform Each Other?

Social neuroscience studies the “social brain,” conceived as the set of brain structures and functions supporting the perception and evaluation of the social environment. This article provides an overview of the field, using the book Social Neuroscience: Brain, Mind, and Society (Russell K. Schutt, Larry J. Seidman, and Matcheri S. Keshavan, editors) as a starting point. Topics include the evolution of the social brain, the concept of “theory of mind,” the relevant brain networks, and documented failures of the social brain. I argue that social neuroscience and economics can greatly benefit from each other because the social brain underlies interpersonal decision making, as studied in economics. (JEL D11, D71, D87, Z13)

Leptin receptor-positive and leptin receptor-negative proopiomelanocortin neurons innervate an identical set of brain structures

Neurons that express the prohormone proopiomelanocortin (POMC) in the arcuate hypothalamic nucleus (Arc) are engaged in the regulation of energy balance and glucose homeostasis. Additionally, POMC neurons are considered key first-order cells regulated by leptin. Interestingly, in the Arc, POMC cells that express the leptin receptor (POMC/LepR+ cells) are found side by side with POMC cells not directly responsive to leptin (POMC/LepR− cells). However, it remains unknown whether these distinct populations innervate different target regions. Therefore, the objective of the present study was to compare the projections of POMC/LepR+ and POMC/LepR− neurons. Using genetically modified LepR-reporter mice to identify leptin receptor-expressing cells and immunohistochemistry to stain POMC-derived peptides (α-MSH or β-endorphin) we confirmed that approximately 80% of Arc β-endorphin-positive neurons co-expressed leptin receptors. POMC/LepR+ and POMC/LepR− axons were intermingled in all of their target regions. As revealed by confocal microscopy, we found an elevated degree of co-localization between α-MSH+ axons and the reporter protein (tdTomato) in all brain regions analyzed, with co-localization coefficients ranging from 0.889 to 0.701. Thus, these two populations of POMC neurons seem to project to the same set of brain structures, although one of the two subtypes of POMC axons was sometimes found to be more abundant than the other in distinct subregions of the same nucleus. Therefore, POMC/LepR+ and POMC/LepR− cells may target separate neuronal populations and consequently activate distinct neuronal circuits within some target nuclei. These findings contribute to unravel the neuronal circuits involved in the regulation of energy balance and glucose homeostasis.

Advances from probabilistic tractography in connections of the limbic system with the cerebellum

The limbic system is a complex set of brain structures located on both sides of the thalamus, right under the cerebrum. It is not a separate system but a collection of structures from the telencephalon, diencephalon, and mesencephalon, including the hippocampus, amygdala, anterior thalamic nuclei, fornix, columns of fornix, mammillary body, septum pellucidum, habenular commissure, cingulate gyrus, parahippocampal gyrus, limbic cortex, pars of olfactory system and limbic midbrain areas. Nevertheless, recent studies showed that the definition of anatomical structures considered part of the limbic system is a controversial subject. Although the role of the cerebellum was traditionally considered mainly associated to motion control, it has been recently suggested a cerebellar involvement in emotions control, cognitive processes and social behavior. In this regard, we have previously demonstrated that the cerebellum is interconnected with the hippocampus [1]. In this work, a wider sample of normal subjects was examined by using probabilistic Constrained Spherical Deconvolution (CSD) tractography, which represents a method able to overcome many limitations of other Diffusion Tensor Imaging (DTI) techniques, providing more accurate data [2]. We found evidences in the human brain that the cerebellum is widely linked with limbic-related structures and provided a more reliable demonstration of direct cerebello-limbic pathways. In addition, we further extendend our analysis to the other limbic connections including uncinated fasciculus, cingulate fasciculus, inferior longitudinal fasciculus, anterior thalamic connections and fornix. Although these pathways have been already described in the tractographic literature we provided reconstruction and quantitative analysis, which could be potentially useful to explore pathological conditions damaging this system. Finally, the demonstration of the existence of cerebello-limbic connections could constitute an important step in the knowledge of the anatomic substrate of non-motor cerebellar functions.

43. Delineating the role of medial and MEDIO-lateral temporal networks in déjá vu using structural covariance mapping

Objective In a previous study (Brazdil et al., 2012), we revealed that the frequency of non-pathological deja vu (DV) experience is related inversely to grey-matter (GM) volume throughout a diffuse set of cortical and subcortical brain structures. In this study, we set out to develop this finding by examining if patterns of GM decline occur in a co-ordinated fashion among these brain structures, and how patterns of GM co-variance relate to DV frequency. Method We compared GM covariance among 16 regions of interest emerging from our previous analyses, between three groups defined according to self-reported DV experience. To do so we employed partial least-squares (PLS). In contrast to voxel-based morphometry, this is a multivariate technique for structural co-variance mapping. To assess whether the emerging patterns of structural co-variance indexed functional networks, we compared our results to functional connectivity data supplied under the Human Connectome Project (HCP) database ( http://www.humanconnectomeproject.org ). Results Our PLS analyses revealed two patterns of GM co-variance associated with non-pathological DV frequency. The first revealed that grey-matter alterations co-varied increasingly with higher DV frequency among limbic structures and the caudate; the second identified decreasing co-variance in GM alterations with higher DV frequency among medial and lateral temporal structures. Assessing functional connectivity among the same set of brain structures comprising each structural covariance pattern indicated that they reflect two distinct brain networks. Conclusions We suggest non-pathological DV emerges as a result of specific alterations in patterns of neural connectivity within and between medial and lateral temporal cortical networks, leading to these distinct patterns of coordinated structural alterations. This goes some way towards reconciling the discrepant findings concerning the role of lateral temporal cortex in pathological DV. Acknowledgements This work was supported by the project “CEITEC – Central European Institute of Technology” (CZ.1.05/1.1.00/02.0068) from European Regional Development Fund. Resting-state functional MRI data were provided by the Human Connectome Project, WU-Minn Consortium (Principal Investigators: David Van Essen and Kamil Ugurbil; 1U54MH091657) funded by the 16 NIH Institutes and Centers that support the NIH Blueprint for Neuroscience Research; and by the McDonnell Center for Systems Neuroscience at Washington University. Collectively, the HCP is the result of efforts of co-investigators from the University of California, Los Angeles, Martinos Center for Biomedical Imaging at Massachusetts General Hospital (MGH), Washington University, and the University of Minnesota.

Neural correlates of the motivational and somatic components of naloxone‐precipitated morphine withdrawal

In morphine-dependent rats, low naloxone doses have been shown to induce conditioned place aversion, which reflects the negative motivational component of opiate withdrawal. In contrast, higher naloxone doses are able to induce a 'full' withdrawal syndrome, including overt somatic signs. The c-fos gene is commonly used as a marker of neuronal reactivity to map the neural substrates that are recruited by various stimuli. Using in situ hybridization, we have analysed in the brain of morphine-dependent rats the effects of acute withdrawal syndrome precipitated by increasing naloxone doses on c-fos mRNA expression. Morphine dependence was induced by subcutaneous implantation of slow-release morphine pellets for 6 days and withdrawal was precipitated by increasing naloxone doses inducing the motivational (7.5 and 15 micro g/kg) and somatic (30 and 120 micro g/kg) components of withdrawal. Our mapping study revealed a dissociation between a set of brain structures (extended amygdala, lateral septal nucleus, basolateral amygdala and field CA1 of the hippocampus) which exhibited c-fos mRNA dose-dependent variations from the lowest naloxone doses, and many other structures (dopaminergic and noradrenergic nuclei, motor striatal areas, hypothalamic nuclei and periaqueductal grey) which were less sensitive and recruited only by the higher doses. In addition, we found opposite dose-dependent variations of c-fos gene expression within the central (increase) and the basolateral (decrease) amygdala after acute morphine withdrawal. Altogether, these results emphasize that limbic structures of the extended amygdala along with the lateral septal nucleus, the basolateral amygdala and CA1 could specifically mediate the negative motivational component of opiate withdrawal.

Differential expression of Fos protein in the rat brain induced by performance of avoidance or escape in the elevated T-maze

Analysis of Fos protein expression was used to map brain areas activated by exposure of male Wistar rats to the elevated T-maze, an animal model of anxiety where tasks of inhibitory avoidance or one-way escape can be separately performed. The apparatus consists of three elevated arms — one enclosed and two open. In the inhibitory avoidance task — considered to represent learned fear — the time taken by rats to leave from the enclosed arm in three consecutive trials is measured. One-way escape task is measured by recording the time taken by animals to withdraw from the open arm and is thought to reflect innate fear. Control animals were placed three times at the end of the transversal arm of a T-maze composed of three enclosed arms and withdrawal latencies from this arm was similarly measured. Performance of avoidance task increased Fos-like immunoreactivity in the medial amygdaloid nucleus, in the anterior hypothalamic nucleus and in the median raphe nucleus. In contrast, performance of escape task enhanced Fos-like immunoreactivity in the basolateral amygdaloid nucleus and in the dorsal periaqueductal gray matter of the mesencephalon. Both behavioural tasks promoted an increase in Fos-like immunoreactivity in the paraventricular nucleus of the thalamus and in the dorsomedial hypothalamic nucleus. Therefore, the obtained results indicate that different sets of brain structures were, respectively, activated by inhibitory avoidance and one-way escape. This evidence supports the original hypothesis that two types of fear/anxiety are generated in the elevated T-maze.

Multiphasic Consequences of the Acute Administration of Ethanol on Cerebral Glucose Metabolism in the Rat

The present study investigated the role of the postinjection interval in determining the functional consequences of acute ethanol administration in the CNS. Local cerebral metabolic rates for glucose (LCMRglc) were determined by the 2[ 14C]deoxyglucose method in 48 brain structures of ethanol-naive Sprague–Dawley rats. Tracer was injected 1 or 45 min after a 0.8 g/kg intragastric dose of ethanol or water. At the early time point, LCMRglc was increased in a highly restricted portion of the basal ganglia that included the dorsal striatum, globus pallidus, and core of the nucleus accumbens, compared to water controls. No significant decreases were found at this early time point. At the later time point, by contrast, LCMRglc was decreased in a different set of brain structures. These sites were limbic in nature and included the infralimbic and anterior cingulate cortices, dentate gyrus, lateral septum, and the bed nucleus of the stria terminalis. These data indicate that there are multiple phases that can be detected during the time course of an acute dose of ethanol. They further demonstrate the involvement of different neural systems at the two time points. Increased activity in basal ganglia is consistent with stimulated motor activity, whereas diminished activity in limbic sites may correspond to changes in mood and motivation.