Neuroscience
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Synaptic plasticity, specifically long-term potentiation and long-term depression, is thought to be the underlying cellular mechanism for learning and memory processes in the brain. About two decades ago a new concept was introduced, namely metaplasticity, which comprises changes that modify the properties of synaptic plasticity due to a priming or preconditioning event. ⋯ We consider here whether it is helpful to conceptualize these latter effects as "behavioral metaplasticity", and in which sense this view fits into the original concept of metaplasticity. By integrating the literature on environmental effects on plasticity, especially stress, plus developmental aspects as well as genetic and epigenetic modifications, we shape the framework in which the term "behavioral metaplasticity" should be considered and discuss research directions that can help to unravel the mechanisms involved in both synaptic and behavioral metaplasticity.
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In both perceptual and motor learning, numerous studies have shown specificity of learning to the trained eye or hand and to the physical features of the task. However, generalization of learning is possible in both perceptual and motor domains. Here, I review evidence for perceptual and motor learning generalization, suggesting that generalization patterns are affected by the way in which the original memory is encoded and consolidated. ⋯ Such generalization may be supported by sleep, involving functional interactions between low and higher-order brain areas. Repeated exposure to the task may alter generalization patterns of learning and overall offline learning. Development of unifying frameworks across learning modalities and better understanding of the conditions under which learning can generalize may enable to gain insight regarding the neural mechanisms underlying procedural learning and have useful clinical implications.
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The human brain can dynamically adapt to the changing surroundings. To explore this issue, we adopted graph theoretical tools to examine changes in electroencephalography (EEG) functional networks while listening to music. Three different excerpts of Chinese Guqin music were played to 16 non-musician subjects. ⋯ Moreover, differences in network measures were not observed between musical excerpts. These experimental results demonstrate an increase of functional connectivity as well as a more random network structure in the alpha2 band during music perception. The present study offers support for the effects of music on human brain functional networks with a trend toward a more efficient but less economical architecture.
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This review evaluates and contextualizes the behavioral studies undertaken on cetaceans in terms of the relationship of these behaviors to special levels of intelligence associated with these marine mammals and the evolution of their relatively and absolutely large brain size. Many believe that the large size of the cetacean brain and reported behaviors indicate the need to create a special status for these animals in terms of their intellect, positing that they are second to humans in terms of general intelligence. Cetacean brains became relatively large approximately 32millionyearsago, at the Archaeocete-Neocete faunal transition, and have since remained stable in relative size. ⋯ This contextualization indicates that cetacean intelligence is qualitatively no different to other vertebrates. In addition, the inability of cetaceans to surpass Piaget stage 4/5 on object permanence tests and to solve an "if and only if, then" abstract task indicates the possibility that their levels of general intelligence may be less than that seen in other vertebrates. Sophisticated cognitive abilities appear to play no role in the evolution of large brain size in cetaceans, indicating that alternative theories of large brain size evolution in cetaceans should be considered in more detail.
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Experiments were done to investigate whether hypothalamic hypocretin-1 (hcrt-1; orexin-A) neurons that sent axonal projections to cardiovascular responsive sites in the nucleus of the solitary tract (NTS) co-expressed leucine-enkephalin (L-Enk), and to determine the effects of co-administration of hcrt-1 and D-Ala2,D-Leu5-Enkephalin (DADL) into NTS on mean arterial pressure (MAP) and heart rate. In the first series, in the Wistar rat the retrograde tract-tracer fluorogold (FG) was microinjected (50nl) into caudal NTS sites at which L-glutamate (0.25 M; 10 nl) elicited decreases in MAP and where fibers hcrt-1 immunoreactive fibers were observed that also contained L-Enk immunoreactivity. Of the number of hypothalamic hcrt-1 immunoreactive neurons identified ipsilateral to the NTS injection site (1207 ± 78), 32.3 ± 2.3% co-expressed L-Enk immunoreactivity and of these, 2.6 ± 1.1% were retrogradely labeled with FG. ⋯ An hcrt-1 injection immediately after the DADL injection elicited an almost twofold increase in the magnitude of the depressor and bradycardia responses compared to those elicited by hcrt-1 alone. Prior injections of the non-specific opioid receptor antagonist naloxone or the specific opioid δ-receptor antagonist ICI 154,129 significantly attenuated the cardiovascular responses to the combined hcrt-1-DADL injections. Taken together, these data suggest that activation of hypothalamic-opioidergic neuronal systems contribute to the NTS hcrt-1 induced cardiovascular responses, and that this descending hypothalamo-medullary pathway may represent the anatomical substrate by which hcrt-1/L-Enk neurons function in the coordination of autonomic-cardiovascular responses during different behavioral states.