Neuroscience
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Neural populations produce complex oscillatory patterns thought to implement brain function. The dominant rhythm in the healthy adult human brain is formed by alpha oscillations with a typical power peak most commonly found between 8 and 12Hz. This alpha peak frequency has been repeatedly discussed as a highly heritable and stable neurophysiological "trait" marker reflecting anatomical properties of the brain, and individuals' general cognitive capacity. ⋯ Based on the converging experimental and theoretical results from numerous recent studies, here we propose that alpha frequency variability forms the basis of an adaptive mechanism mirroring the activation level of neural populations which has important functional implications. We here integrate experimental and computational perspectives to shed new light on the potential role played by shifts in alpha peak frequency and discuss resulting implications. We further propose a potential mechanism by which alpha oscillations are regulated in a noisy network of spiking neurons in presence of delayed feedback.
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Cholinergic interneurons provide rich local innervation of the striatum and play an important role in controlling behavior, as evidenced by the variety of movement and psychiatric disorders linked to disrupted striatal cholinergic transmission. Much progress has been made in recent years regarding our understanding of how these interneurons contribute to the processing of information in the striatum. In particular, investigation of the activity of presumed striatal cholinergic interneurons, identified as tonically active neurons or TANs in behaving animals, has pointed to their role in the signaling and learning of the motivational relevance of environmental stimuli. ⋯ Consequently, our current understanding of the function of cholinergic transmission in the striatum is challenged by the rapidly growing, but often confusing literature on the relationship between TAN activity and specific behaviors. As regards the precise nature of the information conveyed by the cholinergic TANs, a recent influential view emphasized that these local circuit neurons may play a special role in the processing of contextual information that is important for reinforcement learning and selection of appropriate actions. This review provides a summary of recent progress in TAN physiology from which it is proposed that striatal cholinergic interneurons are crucial elements for flexible switching of behaviors under changing environmental conditions.
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The vast majority of functional studies investigating mirror neurons (MNs) explored their properties in relation to hand actions, and very few investigated how MNs respond to mouth actions or communicative gestures. Since hand and mouth MNs were recorded in two partially overlapping sectors of the ventral precentral cortex of the macaque monkey, there is a general assumption that they share a same neuroanatomical network, with the parietal cortex as a main source of visual information. In the current review, we challenge this perspective and describe the connectivity pattern of mouth MN sector. ⋯ Further strong connections derive from limbic structures involved in encoding emotional facial expressions and motivational/reward processing. These brain structures include the anterior cingulate cortex, the anterior and mid-dorsal insula, orbitofrontal cortex and the basolateral amygdala. The mirror mechanism is therefore composed and supported by at least two different anatomical pathways: one is concerned with sensorimotor transformation in relation to reaching and hand grasping within the traditional parietal-premotor circuits; the second one is linked to the mouth/face motor control and is connected with limbic structures, involved in communication/emotions and reward processing.
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Epilepsy is one of the most common chronic neurological conditions worldwide. The current poor understanding and lack of reliable biomarkers of the epileptogenic process are the major limitations in the development of anti-epileptic drugs that are able to prevent or modify the underlying disease. ⋯ Here we review the advances of different in vivo imaging techniques, including magnetic resonance-based and nuclear imaging-based modalities, in animal models of epilepsy. Together these techniques can be applied to visualize and quantify structural, metabolic, functional and molecular changes in longitudinal study designs to provide unique information about early pathophysiological changes and their interplay involved in epileptogenesis, monitoring the disease progression, assessing the effectiveness of possible therapies, and potentially identify translatable biomarkers for clinical use.
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An intriguing feature of nervous system development in most animal species is that the initial number of generated neurons is higher than the number of neurons incorporated into mature circuits. A substantial portion of neurons is indeed eliminated via apoptosis during a short time window - in rodents the first two postnatal weeks. ⋯ In postnatal rodent neocortex, the peak of apoptosis coincides with the occurrence of spontaneous, synchronous activity patterns. In this article, we review recent results that demonstrate the important role of electrical activity for neuronal survival in the neocortex, describe the role of Ca2+ and neurotrophic factors in translating electrical activity into pro-survival signals, and finally discuss the clinical impact of the tight relation between electrical activity and neuronal survival versus apoptosis.