Neuroscience
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Successful response inhibition relies on the suppression of motor cortex activity. The striatum has previously been linked to motor cortex suppression during the act of inhibition (reactive), but activation was also seen during anticipation of stop signals (proactive). More specifically, striatal activation increased with a higher stop probability. ⋯ We found that striatal activity during reactive inhibition was higher when subjects expected stop signals. These results help explain conflicting findings of previous studies on the association between striatal activation and inhibition, since we demonstrate a crucial role of the subjects' expectation of a stop signal and thus their ability to prepare for a stop in advance. In conclusion, the current results show for the first time that striatal contributions to reactive response inhibition are, in part, related to subjective anticipation.
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Tardive dyskinesia (TD) is a potentially disabling condition encompassing all delayed, persistent, and often irreversible abnormal involuntary movements arising in a fraction of subjects during long-term exposure to centrally acting dopamine receptor-blocking agents such as antipsychotic drugs and metoclopramide. However, the pathogenesis of TD has proved complex and remains elusive. To investigate the mechanism underlying the development of TD, we have chronically exposed 17 Cebus apella monkeys to typical (11) or atypical (6) antipsychotic drugs. ⋯ Haloperidol treatment significantly upregulated the levels of serotonin 5-HT2A receptor, NR2A-containing NMDA receptors, and tyrosine hydroxylase contents in the monkey putamen, whereas clozapine regulated putamen NMDA receptor levels and tyrosine hydroxylase contents, and 5-HT2A and dopamine transporter outside the putamen. Comparisons of neurochemical alterations between dyskinetic and non dyskinetic animals within the haloperidol-treated group indicate that modulations of 5-HT2A, metabotropic glutamate type 5, NR2A- and NR2B-containing NMDA receptors, and vesicular monoamine transporter type 2 levels were restricted to the non dyskinetic group. The foregoing results suggest that TD is associated with complex deficient adaptation in aminergic and glutamatergic neurotransmission in the striatum of non-human primates chronically exposed to antipsychotic drugs.
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Because of their difficulties with figurative language in conversation, it is commonly thought that individuals with autism spectrum disorder (ASD) do not understand figurative meaning. However, recent research indicates that individuals with and without ASD are similar in the first two stages of metaphor comprehension, up to and including successful generation of the figurative meaning. In the current study, we used a sentence decision task to evaluate the subsequent stage of metaphor comprehension, the selection stage, which requires suppression/inhibition of the unintended meaning as part of selecting the intended meaning. fMRI activation and functional connectivity were used to compare the selection stage of metaphor comprehension between high-functioning individuals with ASD and carefully matched controls. ⋯ There was a novel finding of maintenance of subcortical-subcortical connectivity in the ASD group, specific to the selection condition, despite differences in cortically involved connections. Reduced cortical-subcortical connectivity in the ASD group compared to controls may reflect a more global impairment in cognitive control pathways, while consistent subcortical-subcortical connectivity may reflect systemic inflexibility or preserved subcortical function and dissociation between subcortical and cortical systems. Further investigation is required.
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Sites and mechanisms by which trigeminal nerve stimulation (TNS) exerts beneficial effects on symptoms of drug-resistant epilepsy and depression are still unknown. Effects of short-term TNS on brain regions involved in the physiopathology of these disorders were investigated in this study. Forty male rats were assigned to three groups: TNS (undergoing electrical stimulation of the left infraorbitary nerve via surgically implanted cuff electrodes); Sham (undergoing surgical procedure but without a stimulation); Naïve rats. ⋯ In the TNS group the number of BrdU-positive cells in the dentate gyrus was significantly greater with respect to both Naïve and Sham groups. Data show that acute TNS effectively counteracted PTZ-induced seizures and boosted hippocampal cell proliferation in rats. TNS increased c-Fos-like immunoreactivity in brainstem and forebrain structures which play a pivotal role in the physiopathology of epilepsy and depression.
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In the neocortex, interaction and cooperation between different areas are important for information processing, which also applies to different areas within one sensory modality. In the temporal cortex of rodents and cats, both the primary auditory cortex (A1) and the anterior auditory field (AAF) have tonotopicity but with a mirrored frequency gradient. ⋯ We found that activation of A1 axon terminals in AAF did not change AAF responses, but activating A1 neuronal cell bodies could increase the sound-evoked responses in AAF, as well as decrease the intensity threshold and broaden the frequency bandwidth, while suppressing A1 could cause the opposite effects. Our results suggested that A1 could modulate the general excitability of AAF through indirect pathways, which provides a potential relationship between these two parallel auditory ascending pathways.