Neuroscience
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Patients with Parkinson's disease (PD) often present with bimanual coordination deficits whose exact origins remain unclear. One aspect of bimanual coordination is inter-limb coupling. This is characterized by the harmonization of movement parameters between limbs. ⋯ However, PD patients did not exhibit spatial inter-limb coupling. Again, this was not altered by medication or stimulation. Collectively, the results suggest that structures independent of the dopaminergic system and basal ganglia may mediate temporal and spatial inter-limb coupling.
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Investigation of the neural basis of self-generated thought is moving beyond a simple identification with default network activation toward a more comprehensive view recognizing the role of the frontoparietal control network and other areas. A major task ahead is to unravel the functional roles and temporal dynamics of the widely distributed brain regions recruited during self-generated thought. We argue that various other neuroscientific methods - including lesion studies, human intracranial electrophysiology, and manipulation of neurochemistry - have much to contribute to this project. ⋯ Human intracranial electrophysiology illuminates how and where in the brain thought is generated and where this activity subsequently spreads. Finally, measurement and manipulation of neurotransmitter and hormone levels can clarify what kind of neurochemical milieu drives or facilitates self-generated cognition. Integrating evidence from multiple complementary modalities will be a critical step on the way to improving our understanding of the neurobiology of functional and dysfunctional forms of self-generated thought.
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Microinjection of morphine into the periaqueductal gray (PAG) produces antinociception. In vitro slice recordings indicate that all PAG neurons are sensitive to morphine either by direct inhibition or indirect disinhibition. We tested the hypothesis that all PAG neurons respond to opioids in vivo by examining the extracellular activity of PAG neurons recorded in lightly anesthetized and awake rats. ⋯ Changes in activity caused by morphine were surprisingly modest (a median increase from 0.7 to 1.3Hz). The small inconsistent effects of morphine are in stark contrast to the large changes produced by morphine on the activity of rostral ventromedial medulla (RVM) neurons or the widespread inhibition and excitation of PAG neurons treated with opioids in in vitro slice experiments. The relatively modest effects of morphine in the present study suggest that morphine produces antinociception by causing small changes in the activity of many PAG neurons.
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There is a strong need to better understand the neurobiology of juvenile sociability (tendency to seek social interaction), a phenotype of central relevance to autism spectrum disorders (ASD). Although numerous genetic mouse models of ASD showing reduced sociability have been reported, and certain brain regions, such as the amygdala, have been implicated in sociability, there has been little emphasis on delineating brain structures and circuits activated during social interactions in the critical juvenile period of the mouse strain that serves as the most common genetic background for these models-the highly sociable C57BL/6J (B6) strain. ⋯ The basolateral amygdala (BLA) was activated by social exposure in highly sociable, 4-week-old B6 mice. In light of these data, and the many lines of evidence indicating alteration of amygdala circuits in human ASD, future studies are warranted to assess structural and functional alterations in the BLA, particularly at BLA synapses, in various mouse models of ASD.