Neuroscience
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The ability to recognize a tool's affordances (how a spoon should be appropriately grasped and used), is vital for daily life. Prior research has identified parietofrontal circuits, including mirror neurons, to be critical in understanding affordances. However, parietofrontal action-encoding regions receive extensive visual input and are adjacent to parietofrontal attention control networks. ⋯ Particularly, only overt gaze toward the hand-tool interaction engaged mirror neurons (frontal N400) when discerning grasps that manipulate but not functionally use a tool - (grasp bowl rather than stem of spoon). Results here detail the first human electrophysiological evidence on how attention selectively modulates multiple parietofrontal grasp-perception circuits, especially the mirror neuron system, while unaffecting parietofrontal encoding of tool-use contexts. These results are pertinent to neurophysiological models of affordances that typically neglect the role of attention in action perception.
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Age- and menopause-related deficits in working memory can be partially restored with estradiol replacement in women and female nonhuman primates. Working memory is a cognitive function reliant on persistent firing of dorsolateral prefrontal cortex (dlPFC) neurons that requires the activation of GluN2B-containing glutamate NMDA receptors. We tested the hypothesis that the distribution of phospho-Tyr1472-GluN2B (pGluN2B), a predominant form of GluN2B seen at the synapse, is sensitive to aging or estradiol treatment and coupled to working memory performance. ⋯ On the other hand, the percentage of pGluN2B gold particles in the spine cytoplasm was decreased with E treatment in young, but increased with E in aged monkeys. In aged monkeys, DR average accuracy inversely correlated with the percentage of synaptic pGluN2B, while it positively correlated with the percentage of cytoplasmic pGluN2B. Together, E replacement may promote cognitive health in aged monkeys, in part, by decreasing the relative representation of synaptic pGluN2B and potentially protecting the dlPFC from calcium toxicity.
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Transient receptor potential vanilloid type 4 (TRPV4) channels are involved in astrocyte volume regulation; however, only limited data exist about its mechanism in astrocytes in situ. We performed middle cerebral artery occlusion in adult mice, where we found twice larger edema 1 day after the insult in trpv4-/- mice compared to the controls, which was quantified using magnetic resonance imaging. This result suggests disrupted volume regulation in the brain cells in trpv4-/- mice leading to increased edema formation. ⋯ In contrast to in vitro experiments, we found little evidence of the contribution of TRPV4 channels to volume regulation in astrocytes in situ in adult mice. Moreover, we only found a rare expression of TRPV4 channels in adult mouse astrocytes. Our data suggest that TRPV4 channels are not involved in astrocyte volume regulation in situ; however, they play a protective role during the ischemia-induced brain edema formation.
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Being able to inhibit an impending movement in response to a contextual change is a distinctive feature of action control. Such inhibitory control relies on a complex cortical-subcortical network, including posterior prefrontal regions such as caudal inferior frontal gyrus and pre-supplementary motor area. According to hierarchical models of action control, both areas represent the intermediate level between prefronto-dependent and motor-related cortices. ⋯ Effective TMS on SMA-proper produced no effect on STOP trials' performance (p = 0.31) nor in the GO trial performance (p = 0.56). Our data show that there is at least a portion of PMCd playing a distinctive role in the control of mouth-related M1 during instructed visuomotor inhibitory behavior. This region could therefore represent a low-level hierarchical node for externally cued action inhibition.
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Deficits in dopaminergic function are thought to underlie attention-deficit/hyperactivity disorder (ADHD). Dopaminergic neurons are the main source of dopamine (DA), a neurotransmitter that acts as a neuromodulator of cognitive function in the prefrontal cortex, including the anterior cingulate cortex (ACC), which receives dopaminergic inputs from the ventral tegmental area. The spontaneously hypertensive rat (SHR) has been widely studied as an animal model of ADHD. ⋯ Furthermore, DA activity enhanced the amplitude of evoked and unitary IPSCs from fast-spiking interneurons; the amplitude was also larger in control WKY than in SHRs. Notably, the amplitude of evoked IPSCs was enhanced by the activation of D1-like receptor-mediated pathways. These results suggest that hypofunction of D1-like receptor-mediated regulation of GABAergic inhibitory synaptic transmission onto layer V pyramidal cells of the ACC may contribute to the pathophysiology of ADHD.