Query: limbic system

title: Dissociating Bottom Up and Top Down Mechanisms in the Cortico Limbic System during Emotion Processing.
abstract: The cortico limbic system is critically involved in emotional responses and resulting adaptive behaviors. Within this circuit, complementary regions are believed to be involved in either the appraisal or the regulation of affective state. However, the respective contribution of these bottom up and top down mechanisms during emotion processing remains to be clarified. We used a new functional magnetic resonance imaging (fMRI) paradigm varying 3 parameters: emotional valence, emotional congruency, and allocation of attention, to distinguish the functional variation in activity and connectivity between amygdala, anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (DLPFC) Bottom up appraisal of negative compared with positive stimuli led to a greater amygdala response and stronger functional interaction between amygdala and both dorsal ACC and DLPFC. Top down resolution of emotional conflict was associated with increased activity within ACC and higher functional connectivity between this structure, and both the amygdala and DLPFC. Finally, increased top down attentional control caused greater engagement of the DLPFC, accompanied by increased connectivity between DLPFC and dorsal ACC. This novel task provides an efficient tool for exploring bottom up and top down processes underlying emotion and may be particularly helpful for investigating the neurofunctional underpinnings of psychiatric disorders.

title: The limbic system
abstract: What is the limbic system; what are the key brain areas involved, and what do they do? This encylopedia entry gives the reader a brief overview of this key neural system and of several clinical conditions marked by limbic disorder.

title: Limbic systems for emotion and for memory, but no single limbic system
abstract: The concept of a (single) limbic system is shown to be outmoded. Instead, anatomical, neurophysiological, functional neuroimaging, and neuropsychological evidence is described that anterior limbic and related structures including the orbitofrontal cortex and amygdala are involved in emotion, reward valuation, and reward related decision making (but not memory) with the value representations transmitted to the anterior cingulate cortex for action outcome learning. In this 'emotion limbic system' a computational principle is that feedforward pattern association networks learn associations from visual, olfactory and auditory stimuli, to primary reinforcers such as taste, touch, and pain. In primates including humans this learning can be very rapid and rule based, with the orbitofrontal cortex overshadowing the amygdala in this learning important for social and emotional behaviour. Complementary evidence is described showing that the hippocampus and limbic structures to which it is connected including the posterior cingulate cortex and the fornix mammillary body anterior thalamus posterior cingulate circuit are involved in episodic or event memory, but not emotion. This 'hippocampal system' receives information from neocortical areas about spatial location, and objects, and can rapidly associate this information together by the different computational principle of autoassociation in the CA3 region of the hippocampus involving feedback. The system can later recall the whole of this information in the CA3 region from any component, a feedback process, and can recall the information back to neocortical areas, again a feedback (to neocortex) recall process. Emotion can enter this memory system from the orbitofrontal cortex etc. and be recalled back to the orbitofrontal cortex etc. during memory recall, but the emotional and hippocampal networks or 'limbic systems' operate by different computational principles, and operate independently of each other except insofar as an emotional state or reward value attribute may be part of an episodic memory.

title: Architectural Representation of Valence in the Limbic System
abstract: In order to thrive, animals must be able to recognize aversive and appetitive stimuli within the environment and subsequently initiate appropriate behavioral responses. This assignment of positive or negative valence to a stimulus is a key feature of emotional processing, the neural substrates of which have been a topic of study for several decades. Until recently, the result of this work has been the identification of specific brain regions, such as the basolateral amygdala (BLA) and nucleus accumbens (NAc) as important to valence encoding. The advent of modern tools in neuroscience has allowed further dissection of these regions to identify specific populations of neurons signaling the valence of environmental stimuli. In this review, we focus upon recent work examining the mechanisms of valence encoding, and provide a model for the systematic investigation of valence within anatomically genetically and functionally defined populations of neurons.

title: CORRIGENDUM: Resting state functional reorganization of the rat limbic system following neuropathic injury
abstract: Resting state functional reorganization of the rat limbic system following neuropathic injury

title: A revised limbic system model for memory, emotion and behaviour
abstract: Emotion, memories and behaviour emerge from the coordinated activities of regions connected by the limbic system. Here, we propose an update of the limbic model based on the seminal work of Papez, Yakovlev and MacLean. In the revised model we identify three distinct but partially overlapping networks: (i) the Hippocampal diencephalic and parahippocampal retrosplenial network dedicated to memory and spatial orientation; (ii) The temporo amygdala orbitofrontal network for the integration of visceral sensation and emotion with semantic memory and behaviour; (iii) the default mode network involved in autobiographical memories and introspective self directed thinking. The three networks share cortical nodes that are emerging as principal hubs in connectomic analysis. This revised network model of the limbic system reconciles recent functional imaging findings with anatomical accounts of clinical disorders commonly associated with limbic pathology.

title: The role of the medial temporal limbic system in processing emotions in voice and music
abstract: Subcortical brain structures of the limbic system, such as the amygdala, are thought to decode the emotional value of sensory information. Recent neuroimaging studies, as well as lesion studies in patients, have shown that the amygdala is sensitive to emotions in voice and music. Similarly, the hippocampus, another part of the temporal limbic system (TLS) is responsive to vocal and musical emotions, but its specific roles in emotional processing from music and especially from voices have been largely neglected. Here we review recent research on vocal and musical emotions, and outline commonalities and differences in the neural processing of emotions in the TLS in terms of emotional valence, emotional intensity and arousal, as well as in terms of acoustic and structural features of voices and music. We summarize the findings in a neural framework including several subcortical and cortical functional pathways between the auditory system and the TLS. This framework proposes that some vocal expressions might already receive a fast emotional evaluation via a subcortical pathway to the amygdala, whereas cortical pathways to the TLS are thought to be equally used for vocal and musical emotions. While the amygdala might be specifically involved in a coarse decoding of the emotional value of voices and music, the hippocampus might process more complex vocal and musical emotions, and might have an important role especially for the decoding of musical emotions by providing memory based and contextual associations.

title: The Limbic System
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title: Revealing the ventral amygdalofugal pathway of the human limbic system using high spatial resolution diffusion tensor tractography
abstract: The amygdala is known to have a role in core processes regulated by the limbic system such as motivation, memory, emotion, social behavior, self awareness as well as certain primitive instincts. Several functional studies have investigated some of these brain tasks of the human limbic system. However, the underlying neuronal fiber connectivity of the amygdalo diencephalon, as part of the limbic system, has not been delineated separately by prior diffusion weighted imaging studies. The ability to trace the underlying fiber connections individually will be helpful in understanding the neurophysiology of these tracts in different functions. To date, few diffusion weighted studies have focused on the amygdala, yet the fine connections of the amygdala, hypothalamus, septum or other adjacent limbic structures have yet to be elucidated by diffusion weighted tractography studies. We therefore aimed to further investigate these fine neuronal connections using fiber tractography and high spatial resolution diffusion tensor imaging on 3T on 15 healthy right handed male human subjects (age range 24 37 years) The ventral amygdalofugal pathway, anterior commissure and stria terminalis are the three main efferent pathways of the amygdala. We delineated the detailed trajectories of the ventral amygdalofugal tract, anterior commissure and their connections bilaterally in 15 normal adult human brains. Using a high resolution diffusion tensor tractography technique, for the first time, we were able to demonstrate the trajectory of amygdalofugal tract and its connections to the hypothalamic and septal nuclei. We further revealed, for the first time, the close relationship of the amygdalofugal tract and anterior commissure with the fornix, stria terminalis and uncinate fasciculus bilaterally in 15 healthy adult human brains.

title: Resting sate functional reorganization of the rat limbic system following neuropathic injury
abstract: Human brain imaging studies from various clinical cohorts show that chronic pain is associated with large scale brain functional and morphological reorganization. However, how the rat whole brain network is topologically reorganized to support persistent pain like behavior following neuropathic injury remains unknown. Here we compare resting state fMRI functional connectivity based whole brain network properties between rats receiving spared nerve injury (SNI) vs. sham injury, at 5 days (n 11 SNI; n 12 sham) and 28 days (n 11 SNI; n 12 sham) post injury. Similar to the human, the rat brain topological properties exhibited small world features and did not differ between SNI and sham. Local neural networks in SNI animals showed minimal disruption at day 5, and more extensive reorganization at day 28 post injury. Twenty eight days after SNI, functional connection changes were localized mainly to within the limbic system, as well as between the limbic and nociceptive systems. No connectivity changes were observed within the nociceptive network. Furthermore, these changes were lateralized and in proportion to the tactile allodynia exhibited by SNI animals. The findings establish that SNI is primarily associated with altered information transfer of limbic regions and provides a novel translational framework for understanding brain functional reorganization in response to a persistent neuropathic injury.