Neuroscience
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Motor variability prior to learning does not facilitate the ability to adopt new movement solutions.
Many contexts in motor learning require a learner to change from an existing movement solution to a novel movement solution to perform the same task. Recent evidence has pointed to motor variability prior to learning as a potential marker for predicting individual differences in motor learning. However, it is not known if this variability is predictive of the ability to adopt a new movement solution for the same task. ⋯ Results showed that participants were able to learn the new solution, and this change was associated with changes in both the amount and structure of variability. However, increased baseline motor variability did not facilitate initial or final task performance when using the new solution - in fact, greater variability was associated with higher errors. These results suggest that motor variability is not necessarily indicative of flexibility and highlight the role of the task context in determining the relation between motor variability and learning.
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Motor memories undergo a period of consolidation before they become resistant to the practice of another task. Although movement variability is important in motor memory consolidation, its role is not fully understood in redundant tasks where variability can exist along two orthogonal subspaces (the 'task space' and the 'null space') that have different effects on task performance. Here, we used haptic perturbations to augment variability in these different spaces and examined their effect on motor memory consolidation. ⋯ We found that regardless of the amplitude, augmenting variability in the task space resulted in significantly better consolidation relative to augmenting variability in the null space, but was not different from a control group that practiced with no variability. This benefit of increasing task space variability relative to increasing null space variability was likely due to the fact that it did not disrupt the pre-existing coordination strategy. These results suggest that the effects of variability on motor memory consolidation depend on the interplay between the induced variability and the pre-existing coordination strategy.
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Review
The potential role of AMPA receptor trafficking in autism and other neurodevelopmental conditions.
Autism Spectrum Disorder (ASD) is a multifaceted condition associated with difficulties in social interaction and communication. It also shares several comorbidities with other neurodevelopmental conditions. Intensive research examining the molecular basis and characteristics of ASD has revealed an association with a large number and variety of low-penetrance genes. ⋯ Despite the high genetic heterogeneity in ASD, surface trafficking of the α-amino-3-hydroxy-5-Methyl-4-isoxazolepropionate (AMPA) receptor is a vulnerable pathway in ASD. In this review, we discuss autism-related alterations in the trafficking of AMPA receptors, whose surface density and composition at the post-synapse determine the strength of the excitatory connection between neurons. We highlight genes associated with neurodevelopmental conditions that share the autism comorbidity, including Fragile X syndrome, Rett Syndrome, and Tuberous Sclerosis, as well as the autism-risk genes NLGNs, IQSEC2, DOCK4, and STXBP5, all of which are involved in regulating AMPAR trafficking to the post-synaptic surface.
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In recent decades, our understanding of the molecular changes involved in neurodegenerative diseases has been transformed. Single-cell RNA sequencing and single-nucleus RNA sequencing technologies have been applied to provide cellular and molecular details of the brain at the single-cell level. This has expanded our knowledge of the central nervous system and provided insights into the molecular vulnerability of brain cell types and underlying mechanisms in neurodegenerative diseases. In this review, we highlight the recent advances and findings related to neurodegenerative diseases using these cutting-edge technologies.
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The spinal trigeminal nucleus caudalis (SpVc) in the mammalian brainstem serves a pivotal function in pain processing. As the main relay center for nociceptive signals, SpVc conducts pain-related signals from various regions of the head toward higher levels of central processing such as the thalamus. SpVc also receives modulatory signals from other brain areas, which can alleviate the perception of headache. ⋯ We found that the floral odorants phenylethyl alcohol (PEA) and lavender oil mitigated the aversive response to AITC. Consistent with this finding, a newly developed, automated quantification of c-Fos expression in SpVc revealed that co-stimulation with PEA or lavender profoundly reduced network activity in the presence of AITC. These results demonstrated a substantial analgesic potential of odor stimulation in the trigeminal system and provide an explanation for the palliative effect of odors in the treatment of headache.