Limited axon regeneration following peripheral nerve injury may be related to activation of the lysosomal protease, asparaginyl endopeptidase (AEP, δ-secretase), and its degradation of the microtubule associated protein, Tau. Activity of AEP was increased at the site of sciatic nerve transection and repair but blocked in mice treated systemically with a specific AEP inhibitor, compound 11 (CP11). Treatments with CP11 enhanced axon regeneration in vivo. Amplitudes of compound muscle action potentials recorded four weeks after nerve transection and repair and two weeks after daily treatments with CP11 were double those of vehicle-treated mice. At that time after injury, axons of significantly more motor and sensory neurons had regenerated successfully and reinnervated the tibialis anterior and gastrocnemius muscles in CP11-treated mice than vehicle-treated controls. In cultured adult dorsal root ganglion neurons derived from wild type mice that were treated in vitro for 24 hours with CP11, neurites were nearly 50% longer than in vehicle-treated controls, and similar to neurite lengths in cultures treated with the TrkB agonist, 7,8-dihydroxyflavone (7,8-DHF). Combined treatment with CP11 and 7,8-DHF did not enhance outgrowth more than treatments with either one alone. Enhanced neurite outgrowth produced by CP11 was found also in the presence of the TrkB inhibitor, ANA-12, indicating that the enhancement was independent of TrkB signaling. Longer neurites were found after CP11 treatment in both TrkB+ and TrkB- neurons. Delta secretase inhibition by CP11 is a treatment for peripheral nerve injury with great potential.

Parkinson’s disease is a neurodegenerative disorder characterized by the progressive dysfunction and loss of dopamine (DA) neurons of the substantia nigra pars compacta (SNc). Several pathways of programmed cell death are likely to play a role in DA neuron death, such as apoptosis, necrosis, pyroptosis, ferroptosis as well as cell death associated with proteasomal and mitochondrial dysfunction. A better understanding of the molecular mechanisms underlying DA neuron death could inform the design of drugs that promote neuron survival. Necroptosis is a recently characterized regulated cell death mechanism that exhibits morphological features common to both apoptosis and necrosis. It requires activation of an intracellular pathway involving receptor-interacting protein 1 (RIP1) and its kinase (RIP1 kinase, RIPK1), receptor-interacting protein 3 (RIP3) and its kinase (RIP3 kinase, RIPK3), and mixed lineage kinase domain like pseudokinase (MLKL). The potential involvement of this programmed cell death pathway in the pathogenesis of PD has been studied by analyzing the biomarkers for necroptosis, such as the levels and oligomerization of pRIPK3 and pMLKL, in several PD preclinical models and in PD human tissue. While there is evidence that other types of cell death also have a role in DA neuron death, most studies support the hypothesis that this cell death mechanism is activated in PD tissues. Thus drugs that prevent or reduce necroptosis may provide neuroprotection for PD. In this review, we summarize the findings from these studies. We also discuss how manipulating necroptosis might open a novel therapeutic approach to reduce neuronal degeneration in PD.

It is generally accepted that Cyclooxygenase-2 (COX-2) is activated to cause inflammation. However, COX-2 is also constitutively expressed at the postsynaptic dendrites and excitatory terminals of the cortical and spinal cord neurons. Although some evidence suggests that COX-2 release during neuronal signaling may be pivotal for regulating the function of memory, the significance of constitutively expressed COX-2 in neuron is still unclear. This research aims to discover the role of COX-2 in memory beyond neuroinflammation and to determine whether the inhibition of COX-2 can cause cognitive dysfunction by influencing dendritic plasticity and its underlying mechanism. The cognitive ability was assessed by novel object recognition task (NORT) and Morris water maze (MWM) test. Immunofluorescence, Golgi-cox staining were used to observe dendritic synaptic. Gamma oscillation in hippocampus CA1 was performed by Tetrode in-vivo recording. Prostaglandins were measured by HPLC/mass spectrometry. We observed the expressions of cyclic adenosine monophosphate (cAMP)/ brain-derived neurotrophic factor (BDNF) pathway proteins in hippocampus and N2a cells by Elisa and western blot. We found COX-2 gene knockout (KO) could significantly impact the learning and memory ability; reduce the expression of postsynaptic density protein 95 (PSD95) in the neuron; cause synaptic disorder; influence gamma oscillation and reduce the expression prostaglandin (PG) E2, cAMP, phosphorylated protein kinase A (p-PKA), phosphorylated cAMP response element binding protein (p-CREB) and BDNF in the hippocampus. It suggested COX-2 might play a critical role in learning, regulating synaptic plasticity and gamma oscillation in the hippocampus CA1 by regulating COX-2/BDNF signaling pathway.

Alcohol abuse is not only responsible for 5.3% of the total deaths in the world, but also has a substantial impact on neurological and memory disabilities throughout the population. One extensively studied brain area involved in cognitive functions is the hippocampus. Evidence in several rodent models has shown that ethanol produces cognitive impairment in hippocampal-dependent tasks and that the damage is varied according to the stage of development at which the rodent was exposed to ethanol and the dose. To the authors’ knowledge, there is a biomarker for cognitive processes in the hippocampus that has not been evaluated in association with memory impairment by alcohol administration. This biomarker is called Sharp Wave Ripples which are synchronous neuronal population events that are well known to be involved in memory consolidation. Methodologies for facilitation or automatic identification of ripples and their analysis have been reported for a wider bandwidth than Sharp Wave Ripples. This review is focused on communicating the state-of-the art about the relationship between alcohol, memory consolidation and ripple activity as well as the use of the main methodologies to identify SWRs automatically.

Combining magnetic resonance imaging (MRI) data from multi-site studies is a popular approach for constructing larger datasets to greatly enhance the reliability and reproducibility of neuroscience research. However, the scanner/site variability is a significant confound that complicates the interpretation of the results, so effective and complete removal of the scanner/site variability is necessary to realize the full advantages of pooling multi-site datasets. Independent component analysis (ICA) and general linear model (GLM) based harmonization methods are the two primary methods used to eliminate scanner/site-related effects. Unfortunately, there are challenges with both ICA-based and GLM-based harmonization methods to remove site effects completely when the signals of interest and scanner/site-related variables are correlated, which may occur in neuroscience studies. In this study, we propose an effective and powerful harmonization strategy that implements dual-projection (DP) theory based on ICA to remove the scanner/site-related effects more completely. This method can separate the signal effects correlated with site variables from the identified site-related effects for removal without losing signals of interest. Both simulations and vivo structural MRI datasets, including a dataset from Autism Brain Imaging Data Exchange II and a traveling subject dataset from the Strategic Research Program for Brain Sciences, were used to test the performance of DP-based ICA harmonization method. Results show that DP-based ICA harmonization has superior performance for removing site effects and enhancing the sensitivity to detect signal of interest as compared with GLM-based and conventional ICA harmonization methods.

The aim of this study was to clarify the effects of transcutaneous vagus nerve stimulation (tVNS) to the left cymba concha on the pain perception using nociceptive withdrawal reflex (NWR), which is known to be associated with chronic pain, and to investigate whether tVNS-induced suppression of the NWR and parasympathetic activation is correlated. We applied either 3.0 mA, 100 Hz tVNS for 120 s in the left cymba concha (tVNS condition) or the left earlobe (Sham condition) for twenty healthy adults. NWR threshold was measured before (Baseline), immediately after (Post 0), 10 min (Post 10) and 30 min after (Post 30) stimulation. The NWR threshold was obtained from biceps femoris muscle by applying electrical stimulation to the sural nerve. During tVNS, electrocardiograph was recorded, and changes in autonomic nervous activity were analyzed. We found that the NWR thresholds at Post 10 and Post 30 increased compared to baseline in the tVNS group (10 min after: p = 0.048 30 min after: p = 0.037). In addition, increased parasympathetic activity by tVNS correlated with a greater increase in NWR threshold at Post 10 and Post 30 (Post 10: p = 0.01; Post 30: p = 0.005). The present results demonstrate the pain-suppressing effect of tVNS as assessed with NWR threshold and suggest that the degree of parasympathetic activation during tVNS may predict the effect of tVNS after its application.

Multimodal studies evaluating associations between specific for Parkinson’s disease (PD) neuroimaging and neurophysiological biomarkers in revealing executive dysfunction mechanisms are scarce and needed to be validated. Hence, our study aimed to evaluate associations between electroencephalographic power spectral density (PSD-EEG), striatal [18F]Fluorodopa uptake and neuropsychological testing parameters in PD. Additional aim was to estimate PD diagnostic accuracy of the PSD-EEG parameters. We compared resting PSD-EEG, striatal [18F]Fluorodopa uptake ratio with positron emission computed tomography ([18F]FDOPA PET/CT), and neuropsychological test outcomes between PD patients and healthy controls, and then calculated correlations among these outcomes. Additionally we estimated PD diagnostic sensitivity and specificity (with the receiver operating characteristic curves) of the PSD-EEG parameters in reference to the gold diagnostic standard of the striatal [18F]FDOPA PET/CT uptake ratio.PD patients exhibited (i) increased power of the EEG theta and lower-alpha bands in the frontal lobe areas, (ii) decreased putaminal and caudate nuclei [18F]FDOPA PET/CT uptake ratios and (iii) longer performance times of part A and B of the Trail Making Test (TMT-A and TMT-B). Most of the PSD-EEG parameters negatively correlated with striatal [18F]FDOPA PET/CT uptake ratios and positively correlated with TMT-A and TMT-B. Furthermore, [18F]FDOPA PET/CT uptake ratios positively correlated with TMT-A and TMT-B. Theta and lower-alpha bands PSD-EEG were found to have high diagnostic accuracy. Our findings showed that slowing of EEG waves in the frontal lobe was correlated with striatal dopaminergic deficiency and executive dysfunction in mild PD patients, and appears to be a promising biomarker of PD-related executive dysfunction.

The dopaminergic system is implicated in the pathophysiology of migraine. However, the underlying mechanisms remain unclear. We explored the effects and mechanisms of dopaminergic system modulation in the in-vivo and in-vitro rat models of migraine. Dopaminergic agonist apomorphine, D2 receptor antagonists metoclopramide and haloperidol, and 5-HT3 receptor antagonist ondansetron alone and together were tested in nitroglycerin-induced migraine model, in vivo. Likewise, the combinations of drugs were also tested on basal CGRP release in-vitro hemiskull preparations. Mechanical allodynia was tested by von-Frey filaments. CGRP concentrations in trigeminovascular structures and in-vitro superfusates, and c-Fos levels in brainstem were determined by ELISA. Meningeal-mast cells were evaluated with toluidine-blue staining. Apomorphine further enhanced nitroglycerin-induced mechanical allodynia, brainstem c-fos expression, trigeminal ganglion and brainstem CGRP concentrations, and meningeal mast cell degranulation, in vivo. Haloperidol completely antagonised all apomorphine-induced effects and also alleviated changes induced by nitroglycerin without apomorphine. Metoclopramide and ondansetron partially attenuated apomorphine- or nitroglycerin-induced effects. A combination of haloperidol and ondansetron decreased basal CGRP release, in-vitro, while the other administrations were ineffective. Apomorphine-mediated dopaminergic activation exacerbated nitroglycerin-stimulated migraine pain by further enchancing c-fos expression, CGRP release and mast cell degranulation in strategical structures associated with migraine pain. Metoclopramide partially attenuated the effects of apomorphine, most likely because it is also a 5-HT3 receptor antagonist. Haloperidol with pure D2 receptor antagonism feature appears to be more effective than metoclopramide in reducing migraine-related parameters in dopaminergic activation- and/or NTG-induced migrane like conditions.

Mismatch negativity (MMN) and P3b are well known for their clinical utility. There exists no gold standard, however, to acquire these markers. This may explain why the within-individual sensitivity of MMN/P3b is often quite poor and why seemingly identical markers can behave differently across studies. Here we compare two traditional paradigms for MMN or P3b assessment with the recently more popular local-global paradigm which promises to assess MMN and P3b orthogonally within one oddball sequence. All three paradigms were administered to healthy participants (N=15) with concurrent EEG. A clear MMN and local effect were found for 15/15 participants. The P3b and global effect were found for 14/15 and 13/15 participants, respectively. There were no systematic differences between the global effect and P3b. Indeed, P3b amplitude was highly correlated across paradigms. The local effect differed clearly from the MMN, however. It occurred earlier compared to MMN and was followed by a much more prominent P3a effect. The two sets of peak latencies and amplitudes were also not correlated across paradigms. We conclude that the local-global paradigm is effective in evoking the traditional P3b component, but it does not capture the MMN. Caution should therefore be exercised when comparing the local effect and MMN across studies. Nevertheless, the within-individual sensitivity of both MMN and the local effect was satisfactory. The within-individual sensitivity of P3b was lower than expected in a healthy control group, which may explain the often-low sensitivity of P3b in patients with disorders of consciousness.

I comment on the article JN-2022-11-29991.R1 by quickly summarizing the findings and going further by putting it in the context of current knowledge and elaborate on open questions that this article raises

Post-stroke depression (PSD), a common complication after stroke, severely affects the recovery and quality of life of patients with stroke. Owing to its complex mechanisms, PSD treatment remains highly challenging. Hippocampal synaptic plasticity is one of the key factors leading to PSD; however, the precise molecular mechanisms remain unclear. Numerous studies have found that neurotrophic factors, protein kinases, and neurotransmitters influence depressive behavior by modulating hippocampal synaptic plasticity. This review further elaborates on the role of hippocampal synaptic plasticity in PSD by summarizing recent research and analyzing possible molecular mechanisms. Evidence for the correlation between hippocampal mechanisms and PSD helps to better understand the pathological process of PSD and improve its treatment.

The rise of deepfakes and AI-generated images has raised concerns regarding their potential misuse in society. However, this commentary highlights the valuable opportunities these technologies offer for neuroscience research. Deepfakes provide accessible, realistic, and customisable dynamic face stimuli, while generative adversarial networks (GANs) can generate and modify diverse and high-quality static content. These advancements enhance the variability and ecological validity of research methods, and enable the creation of previously unattainable stimuli. When AI-generated images are informed by brain responses, they provide unique insights into the structure and function of visual systems. The authors encourage experimental psychologists and cognitive neuroscientists to stay informed about these emerging tools and embrace their potential to advance visual neuroscience.

Conventional transcranial direct-current stimulation (tDCS) delivered to the primary motor cortex (M1) has been shown to enhance implicit motor sequence learning (IMSL). Conventional tDCS targets M1 but also the motor association cortices (MAC), making the precise contribution of M1 to IMSL presently unclear. We aimed to address the roles of these areas by comparing conventional tDCS of M1 and MAC to High-Definition (HD) tDCS, which more focally targets M1. In this sham-controlled, crossover study in 89 healthy adults, we used mixed-effects models to analyze sequence-specific and general learning effects in the acquisition, short- and long-term consolidation phases of IMSL, as measured by the serial reaction time task. Conventional tDCS did not influence general learning, improved sequence-specific learning during acquisition (anodal: M=42.64 ms, sham: M=32.87 ms, p=.041) and deteriorated it at long-term consolidation (anodal: M=75.37 ms, sham: M=86.63 ms, p=.019). HD tDCS did not influence general learning, slowed performance specifically in sequential blocks across all learning phases (all p’s<.050), and consequently deteriorated sequence-specific learning during acquisition (anodal: M=24.13 ms, sham: M=35.67 ms, p=.014) and long-term consolidation (anodal: M=60.03 ms, sham: M=75.01 ms, p=.002). Our findings indicate that generalized stimulation of M1 and MAC enhanced acquisition, but hindered consolidation of IMSL. In contrast, focal M1 stimulation by HD tDCS worsened overall performance, likely due to cathodal inhibition of MAC as induced by the return electrodes. Consequently, this disruption of performance supports the notion that these areas fundamentally contribute to IMSL as an integral part in the cortico-basal ganglia-thalamo-cortical network.

As we speak, corollary discharge mechanisms suppress the auditory conscious perception of the self-generated voice in healthy subjects. This suppression has been associated with the attenuation of the auditory N1 component. To analyze this corollary discharge phenomenon (agency and ownership), we registered the Event-Related Potentials of forty-two healthy subjects. The N1 and P2 components were elicited by spoken vowels (talk condition; agency), by played-back vowels recorded with their own voice (listen-self condition; ownership), and by played-back vowels recorded with an external voice (listen-other condition). The N1 amplitude elicited by the talk condition was smaller compared to the listen-self and listen-other conditions. There were no amplitude differences in N1 between listen-self and listen-other conditions. The P2 component did not show differences between conditions. Additionally, a peak latency analysis of N1 and P2 components between the three conditions showed no differences. These findings corroborate previous results showing that the corollary discharge mechanisms dampen sensory responses to self-generated speech (agency experience), and provide new neurophysiological evidence about the similarities in the processing of played-back vowels with our own voice (ownership experience) and with an external voice.

Working memory (WM) is one of the fundamental cognitive functions associated with the dorsolateral prefrontal cortex (DLPFC). However, we still know little about the neurochemical mechanisms of WM in the DLPFC. Here, we investigated WM-related dynamic neurometabolite and hemodynamic responses in the DLPFC. We measured Glx (glutamate+glutamine) and GABA alterations as well as blood-oxygen-level-dependent (BOLD) signal changes during a WM task combining functional magnetic resonance spectroscopy and functional magnetic resonance imaging (fMRI). In the DLPFC, we found that a 2-back task increased Glx concentrations and larger BOLD signal changes, and that these task-modulated Glx increases were positively correlated with task-induced regional activity. Importantly, task induced Glx changes in the DLPFC were associated with individual WM performance. Higher Glx increases were associated with increased DLPFC activation and lower WM task performance in the individuals. There were no changes in DLPFC GABA levels during WM processing. Our findings suggest that glutamatergic modulation in the DLPFC may play a critical role in WM processing and its performance.

A document by Jinfeng Huang. Click on the document to view its contents.

Listening effort can be defined as a measure of cognitive resources used by listeners to perform a listening task. Several methods have been proposed to assess listening effort, but the reliability of these methods has not yet been thoroughly established, which is necessary before using them in research or clinical settings. This study included 32 participants who performed speech-in-noise tasks in two sessions (separated approx. 1 week apart) by listening to Sentences and Word lists presented at different signal-to-noise ratios (-9, -6, -3, and 0 dB). We assessed the test-retest reliability of the self-reported measure of listening effort and frontal midline theta (Fmθ) power, which has been proposed as a neural correlate of listening effort. The reliability of the percentage of correct words was also examined. Relative and absolute reliability was evaluated using intraclass correlation coefficients (ICC) and Bland-Altman analysis, respectively. The standard error of measurement (SEM) and the smallest detectable change (SDC) were also assessed. Overall, the reliability analysis revealed an acceptable between-session variability for the correct words and effort rating. However, Fmθ power showed high variability, which brings into question its use as a reliable correlate of listening effort.

Auditory processing and the complexity of neural activity can both indicate residual conscious-ness levels and differentiate between states of arousal. However, how measures of neural signal diversity, or complexity, manifest in evoked activity, and, more generally, how the electrophys-iological characteristics of auditory responses change in states of reduced consciousness, re-main under-explored. Here, we tested the hypothesis that measures of neural complexity and the spectral slope would discriminate stages of sleep not only in spontaneous EEG, but also in auditory-evoked responses. High-density EEG was recorded in 21 participants to determine the spatial relationship between these measures, and between spontaneous and auditory-evoked signals. Results showed that the complexity and the spectral slope in the 2-20 Hz range dis-criminated between sleep stages and had a high correlation in sleep. In wakefulness, complexity was strongly correlated to the 20-40 Hz spectral slope. Auditory stimulation resulted in reduced complexity in sleep compared to spontaneous activity and modulated the spectral slope in wake-fulness. These findings demonstrate the persistence of electrophysiological markers of arousal during both spontaneous and evoked EEG activity and have direct applications to studies using auditory stimulation to probe neural functions in states of reduced consciousness.