Scanning ultrasound-mediated memory and functional improvements do not require amyloid-ß reduction.

A prevalent view in treating age-dependent disorders including Alzheimer's disease (AD) is that the underlying amyloid plaque pathology must be targeted for cognitive improvements. In contrast, we report here that repeated scanning ultrasound (SUS) treatment at 1 MHz frequency can ameliorate memory deficits in the APP23 mouse model of AD without reducing amyloid-ß (Aß) burden. Different from previous studies that had shown Aß clearance as a consequence of blood-brain barrier (BBB) opening, here, the BBB was not opened as no microbubbles were used. Quantitative SWATH proteomics and functional magnetic resonance imaging revealed that ultrasound induced long-lasting functional changes that correlate with the improvement in memory. Intriguingly, the treatment was more effective at a higher frequency (1 MHz) than at a frequency within the range currently explored in clinical trials in AD patients (286 kHz). Together, our data suggest frequency-dependent bio-effects of ultrasound and a dissociation of cognitive improvement and Aß clearance, with important implications for the design of trials for AD therapies.

Cascaded Multi-Modal Mixing Transformers for Alzheimer's Disease Classification with Incomplete Data.

Accurate medical classification requires a large number of multi-modal data, and in many cases, different feature types. Previous studies have shown promising results when using multi-modal data, outperforming single-modality models when classifying diseases such as Alzheimer's Disease (AD). However, those models are usually not flexible enough to handle missing modalities. Currently, the most common workaround is discarding samples with missing modalities which leads to considerable data under-utilisation. Adding to the fact that labelled medical images are already scarce, the performance of data-driven methods like deep learning can be severely hampered. Therefore, a multi-modal method that can handle missing data in various clinical settings is highly desirable. In this paper, we present Multi-Modal Mixing Transformer (3MT), a disease classification transformer that not only leverages multi-modal data but also handles missing data scenarios. In this work, we test 3MT for AD and Cognitively normal (CN) classification and mild cognitive impairment (MCI) conversion prediction to progressive MCI (pMCI) or stable MCI (sMCI) using clinical and neuroimaging data. The model uses a novel Cascaded Modality Transformers architecture with cross-attention to incorporate multi-modal information for more informed predictions. We propose a novel modality dropout mechanism to ensure an unprecedented level of modality independence and robustness to handle missing data scenarios. The result is a versatile network that enables the mixing of arbitrary numbers of modalities with different feature types and also ensures full data utilization in missing data scenarios. The model is trained and evaluated on the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset with the state-of-the-art performance and further evaluated with The Australian Imaging Biomarker & Lifestyle Flagship Study of Ageing (AIBL) dataset with missing data.

Instant tissue field and magnetic susceptibility mapping from MRI raw phase using Laplacian enhanced deep neural networks.

Quantitative susceptibility mapping (QSM) is an MRI post-processing technique that produces spatially resolved magnetic susceptibility maps from phase data. However, the traditional QSM reconstruction pipeline involves multiple non-trivial steps, including phase unwrapping, background field removal, and dipole inversion. These intermediate steps not only increase the reconstruction time but accumulates errors. This study aims to overcome existing limitations by developing a Laplacian-of-Trigonometric-functions (LoT) enhanced deep neural network for near-instant quantitative field and susceptibility mapping (i.e., iQFM and iQSM) from raw MRI phase data. The proposed iQFM and iQSM methods were compared with established reconstruction pipelines on simulated and in vivo datasets. In addition, experiments on patients with intracranial hemorrhage and multiple sclerosis were also performed to test the generalization of the proposed neural networks. The proposed iQFM and iQSM methods in healthy subjects yielded comparable results to those involving the intermediate steps while dramatically improving reconstruction accuracies on intracranial hemorrhages with large susceptibilities. High susceptibility contrast between multiple sclerosis lesions and healthy tissue was also achieved using the proposed methods. Comparative studies indicated that the most significant contributor to iQFM and iQSM over conventional multi-step methods was the elimination of traditional Laplacian unwrapping. The reconstruction time on the order of minutes for traditional approaches was shortened to around 0.1 s using the trained iQFM and iQSM neural networks.

Subacute cytokine changes after a traumatic brain injury predict chronic brain microstructural alterations on advanced diffusion imaging in the male rat.

INTRODUCTION: The process of neuroinflammation occurring after traumatic brain injury (TBI) has received significant attention as a potential prognostic indicator and interventional target to improve patients' outcomes. Indeed, many of the secondary consequences of TBI have been attributed to neuroinflammation and peripheral inflammatory changes. However, inflammatory biomarkers in blood have not yet emerged as a clinical tool for diagnosis of TBI and predicting outcome. The controlled cortical impact model of TBI in the rodent gives reliable readouts of the dynamics of post-TBI neuroinflammation. We now extend this model to include a panel of plasma cytokine biomarkers measured at different time points post-injury, to test the hypothesis that these markers can predict brain microstructural outcome as quantified by advanced diffusion-weighted magnetic resonance imaging (MRI). METHODS: Fourteen 8-10-week-old male rats were randomly assigned to sham surgery (n = 6) and TBI (n = 8) treatment with a single moderate-severe controlled cortical impact. We collected blood samples for cytokine analysis at days 1, 3, 7, and 60 post-surgery, and carried out standard structural and advanced diffusion-weighted MRI at day 60. We then utilized principal component regression to build an equation predicting different aspects of microstructural changes from the plasma inflammatory marker concentrations measured at different time points. RESULTS: The TBI group had elevated plasma levels of IL-1ß and several neuroprotective cytokines and chemokines (IL-7, CCL3, and GM-CSF) compared to the sham group from days 3 to 60 post-injury. The plasma marker panels obtained at day 7 were significantly associated with the outcome at day 60 of the trans-hemispheric cortical map transfer process that is a frequent finding in unilateral TBI models. DISCUSSION: These results confirm and extend prior studies showing that day 7 post-injury is a critical temporal window for the reorganisation process following TBI. High plasma level of IL-1ß and low plasma levels of the neuroprotective IL-7, CCL3, and GM-CSF of TBI animals at day 60 were associated with greater TBI pathology.

Diagnostic Sensitivity of Plasma Endothelin-1 for Cerebral Vasospasm After Subarachnoid Hemorrhage, a Multicentre Double-Blind Study.

The purpose of this study is to establish the diagnostic sensitivity of Endothelin-1 for risk stratification and screening of clinical vasospasm after subarachnoid hemorrhage.This is a multicentre, observational study, correlating daily blood Endothelin-1 with clinical variables. Binary logistic regression used to examine if Endothelin-1 levels could be used to predict clinical vasospasm. Bivariate modelling used to explore associations between patient characteristics and vasospasm. A Receiver Operating Curve used to explore cut-off values for Endothelin-1. Sensitivity and specificity was used to validate the cut-point found in the pilot study. A total of 96 patients were enrolled over two years. Median Endothelin-1 was higher for patients who experienced clinical vasospasm except for day-5, where median endothelin for patients without vasospasm was higher (3.6 IQR = 5.3), compared to patients with vasospasm (3.3 IQR = 8.5) although differences were not significant. The Receiver Operating Curve analysis confirmed that day-5 Endothelin-1 was not a good indicator of vasospasm, with an area under the curve of 0.506 (95% CI: 0.350-0.663, p = 0.938). The levels of Endothelin-1 in blood do not discriminate patients who may develop symptomatic vasospasm. The high variability in Endothelin-1 levels, aligns with the pathophysiological variability of most biomarkers, decreasing their ability to predict a clinical event.

Functional connectivity of brain associated with passive range of motion exercise: Proprioceptive input promoting motor activation?

Soft robotics have come to the forefront of devices available for rehabilitation following stroke; however, objective evaluation of the specific brain changes following rehabilitation with these devices is lacking. In this study, we utilized functional Magnetic Resonance Imaging (fMRI) and dynamic causal modeling (DCM) to characterize the activation of brain areas with a MRI compatible glove actuator compared to the conventional manual therapy. Thirteen healthy volunteers engaged in a motor-visual fMRI task under four different conditions namely active movement, manual passive movement, passive movement using a glove actuator, and crude tactile stimulation. Brain activity following each task clearly identified the somatosensory motor area (SMA) as a major hub orchestrating activity between the primary motor (M1) and sensory (S1) cortex. During the glove-induced passive movement, activity in the motor-somatosensory areas was reduced, but there were significant increases in motor cortical activity compared to manual passive movement. We estimated the modulatory signaling from within a defined sensorimotor network (SMA, M1, and S1), through DCM and highlighted a dual-gating of sensorimotor inputs to the SMA. Proprioceptive signaling from S1 to the SMA reflected positive coupling for the manually assisted condition, while M1 activity was positively coupled to the SMA during the glove condition. Importantly, both the S1 and M1 were shown to influence each other's connections with the SMA, with inhibitory nonlinear modulation by the M1 on the S1-SMA connection, and similarly S1 gated the M1-SMA connection. The work is one of the first to have applied effective connectivity to examine sensorimotor activity ensued by manual or robotic passive range of motion exercise, crude tactile stimulation, and voluntary movements to provide a basis for the mechanism by which soft actuators can alter brain activity.

Evaluation of nuisance removal for functional MRI of rodent brain.

Functional MRI (fMRI) has become an important translational tool for studying brain activity and connectivity in animal models and humans. For accurate and reliable measurement of functional connectivity, nuisance removal strategies developed for human brain, such as regressing motion parameters, cerebrospinal fluid (CSF)/white matter-derived signals and the global signal, have been applied to rodent. However, due to the very different anatomy, with the majority of the rodent brain being gray matter, and experimental conditions, in which animals are anesthetized and head-fixed, these methods may not be suitable for rodent fMRI. In this study, we assessed various nuisance regression methods and the effects of motion correction on a large dataset of both task and resting fMRI of anesthetized rat brain. Sensitivity and specificity were assessed in the somatosensory pathway under forepaw stimulation and resting state. Reproducibility at various sample sizes was simulated by randomly subsampling the dataset. To overcome the difficulty in extracting nuisance from the brain, a method using principal components estimated from tissues outside the brain was evaluated. Our results showed that neither detrend, motion correction, motion regression nor CSF signal regression could improve specificity despite increasing temporal signal-to-noise ratios. Although global signal regression increased the specificity of task activation and functional connectivity, the sensitivity and connectivity strength was drastically reduced, likely due to its strong correlation with the cortical signal. Motion parameters also correlated with task activation and the global signal, indicating that motion correction detected intensity variations in the brain. The nuisance estimated from tissues outside the brain produced a moderate improvement in specificity. In conclusion, nuisance removal suitable for human fMRI may not be optimal for rodents. While further development is needed, estimating nuisance from tissues outside the brain may be an alternative.

Tauopathy in veterans with long-term posttraumatic stress disorder and traumatic brain injury.

PURPOSE: Traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) have emerged as independent risk factors for an earlier onset of Alzheimer's disease (AD), although the pathophysiology underlying this risk is unclear. Postmortem studies have revealed extensive cerebral accumulation of tau following multiple and single TBI incidents. We hypothesized that a history of TBI and/or PTSD may induce an AD-like pattern of tau accumulation in the brain of nondemented war veterans. METHODS: Vietnam War veterans (mean age 71.4 years) with a history of war-related TBI and/or PTSD underwent [18F]AV145 PET as part of the US Department of Defense Alzheimer's Disease Neuroimaging Initiative. Subjects were classified into the following four groups: healthy controls (n = 21), TBI (n = 10), PTSD (n = 32), and TBI+PTSD (n = 17). [18F]AV1451 reference tissue-normalized standardized uptake value (SUVr) maps, scaled to the cerebellar grey matter, were tested for differences in tau accumulation between groups using voxel-wise and region of interest approaches, and the SUVr results were correlated with neuropsychological test scores. RESULTS: Compared to healthy controls, all groups showed widespread tau accumulation in neocortical regions overlapping with typical and atypical patterns of AD-like tau distribution. The TBI group showed higher tau accumulation than the other clinical groups. The extent of tauopathy was positively correlated with the neuropsychological deficit scores in the TBI+PTSD and PTSD groups. CONCLUSION: A history of TBI and/or PTSD may manifest in neurocognitive deficits in association with increased tau deposition in the brain of nondemented war veterans decades after their trauma. Further investigation is required to establish the burden of increased risk of dementia imparted by earlier TBI and/or PTSD.

Functional networks and network perturbations in rodents.

Synchronous low-frequency oscillation in the resting human brain has been found to form networks of functionally associated areas and hence has been widely used to map the functional connectivity of the brain using techniques such as resting-state functional MRI (rsfMRI). Interestingly, similar resting-state networks can also be detected in the anesthetized rodent brain, including the default mode-like network. This opens up opportunities for understanding the neurophysiological basis of the rsfMRI signal, the behavioral relevance of the network characteristics, connectomic deficits in diseases and treatment effects on brain connectivity using rodents, particularly transgenic mouse models. In this review, we will provide an overview on the resting-state networks in the rat and mouse brains, the effects of pharmacological agents, brain stimulation, structural connectivity, genetics on these networks, neuroplasticity after behavioral training and applications in models of neurological disease and psychiatric disorders. The influence of anesthesia, strain difference, and physiological variation on the rsfMRI-based connectivity measure will be discussed.

GABAergic effect on resting-state functional connectivity: Dynamics under pharmacological antagonism.

Resting state functional connectivity MRI measures synchronous activity among brain regions although the mechanisms governing the temporally coherent BOLD signals remain unclear. Recent studies suggest that γ-amino butyric acid (GABA) levels are correlated with functional connectivity. To understand whether changes in GABA transmission alter functional connectivity, we modulated the GABAergic activity by a GABAA receptor antagonist, bicuculline. Resting and evoked electrophysiology and BOLD signals were measured in isoflurane-anesthetized rats under infusion of low-dose bicuculline or vehicle individually. Both somatosensory BOLD activations and evoked potentials induced by forepaw stimulation were increased significantly under bicuculline compared to vehicle, indicating increased excitability. Gradually elevated resting BOLD correlation within and between the somatosensory and visual cortices, as well as between somatosensory and caudate putamen but not within subcortical areas were found with the infusion of bicuculline. Increased cerebral blood flow was observed throughout the cortical and subcortical areas where the receptor density is high, but it didn't correlate with BOLD connectivity except in the primary somatosensory cortex. Furthermore, resting EEG coherence in the alpha and beta bands exhibited consistent change with the BOLD correlation. The increased cortico-cortical and cortico-striatal connectivity without dependence on the receptor distribution indicate that the functional connectivity may be mediated by long-range projection via the cortical and striatal GABAergic inter-neurons. Our results indicate an important role of the GABAergic system on neural and hemodynamic oscillations, which further supports the neuronal basis of functional connectivity MRI and its correlation with neurotransmission.

Functional connectivity MRI tracks memory networks after maze learning in rodents.

Learning and memory employs a series of cognitive processes which require the coordination of multiple areas across the brain. However in vivo imaging of cognitive function has been challenging in rodents. Since these processes involve synchronous firing among different brain loci we explored functional connectivity imaging with resting-state fMRI. After 5-day training on a hidden platform watermaze task, notable signal correlations were seen between the hippocampal CA3 and other structures, including thalamus, septum and cingulate cortex, compared to swim control or naïve animals. The connectivity sustained 7 days after training and was reorganized toward the cortex, consistent with views of memory trace distribution leading to memory consolidation. These data demonstrates that, after a cognitive task, altered functional connectivity can be detected in the subsequently sedated rodent using in vivo imaging. This approach paves the way to understand dynamics of area-dependent distribution processes in animal models of cognition.

Toluene inhalation in adolescent rats reduces flexible behaviour in adulthood and alters glutamatergic and GABAergic signalling.

Toluene is a commonly abused inhalant that is easily accessible to adolescents. Despite the increasing incidence of use, our understanding of its long-term impact remains limited. Here, we used a range of techniques to examine the acute and chronic effects of toluene exposure on glutameteric and GABAergic function, and on indices of psychological function in adult rats after adolescent exposure. Metabolomics conducted on cortical tissue established that acute exposure to toluene produces alterations in cellular metabolism indicative of a glutamatergic and GABAergic profile. Similarly, in vitro electrophysiology in Xenopus oocytes found that acute toluene exposure reduced NMDA receptor signalling. Finally, in an adolescent rodent model of chronic intermittent exposure to toluene (10 000 ppm), we found that, while toluene exposure did not affect initial learning, it induced a deficit in updating that learning when response-outcome relationships were reversed or degraded in an instrumental conditioning paradigm. There were also group differences when more effort was required to obtain the reward; toluene-exposed animals were less sensitive to progressive ratio schedules and to delayed discounting. These behavioural deficits were accompanied by changes in subunit expression of both NMDA and GABA receptors in adulthood, up to 10 weeks after the final exposure to toluene in the hippocampus, prefrontal cortex and ventromedial striatum; regions with recognized roles in behavioural flexibility and decision-making. Collectively, our data suggest that exposure to toluene is sufficient to induce adaptive changes in glutamatergic and GABAergic systems and in adaptive behaviour that may underlie the deficits observed following adolescent inhalant abuse, including susceptibility to further drug-use.

Dependence of BOLD signal fluctuation on arterial blood CO2 and O2: Implication for resting-state functional connectivity.

Blood oxygenation level dependent (BOLD) functional MRI signal is known to be modulated by the CO2 level. Typically only end-tidal CO2, rather than the arterial partial pressure of CO2 (paCO2), was measured while the arterial partial pressure of O2 (paO2) level was not controlled due to free breathing, making their contribution not separable. Especially, the influences of paO2 and paCO2 on resting-state functional connectivity are not well studied. In this study, we investigated the relationship between paCO2 and resting as well as stimulus-evoked BOLD signals under hyperoxic and hypercapnic manipulation with tight control of arterial paO2. Rats under isoflurane anesthesia were subjected to six inspired gas conditions: 47% O2 in air (Normal), adding 1%, 2% or 5% CO2, carbogen (95% O2/5% CO2), and 100% O2. Somatosensory BOLD activation was significantly increased under 100% O2, while reduced with increased paCO2 levels. However, while resting BOLD connectivity pattern expanded and bilateral correlation increased under 100% O2, the correlation coefficient between the left and right somatosensory cortex was generally not dependent on paCO2 or paO2. Interestingly, the correlation in 0.04-0.07Hz range significantly increased with CO2 levels. Intracortical electrophysiological recordings showed a similar trend as the BOLD but the neurovascular coupling varied. The results suggest that paO2 and paCO2 together rather than paCO2 alone alter the BOLD signal. The response is not purely vascular in nature but has strong neuronal origins. This should be taken into consideration when designing calibrated BOLD experiment and interpreting functional connectivity data especially in aging, under drug, or neurological disorders.

Detection of functional connectivity in the resting mouse brain.

Resting-state functional connectivity, manifested as spontaneous synchronous activity in the brain, has been detected by functional MRI (fMRI) across species such as humans, monkeys, and rats. Yet, most networks, especially the classical bilateral connectivity between hemispheres, have not been reliably found in the mouse brain. This could be due to anesthetic effects on neural activity and difficulty in maintaining proper physiology and neurovascular coupling in anesthetized mouse. For example, α2 adrenoceptor agonist, medetomidine, is a sedative for longitudinal mouse fMRI. However, the higher dosage needed compared to rats may suppress the functional synchrony and lead to unilateral connectivity. In this study, we investigated the influence of medetomidine dosage on neural activation and resting-state networks in mouse brain. We show that mouse can be stabilized with dosage as low as 0.1mg/kg/h. The stimulation-induced somatosensory activation was unchanged when medetomidine was increased from 0.1 to 6 and 10 folds. Especially, robust bilateral connectivity can be observed in the primary, secondary somatosensory and visual cortices, as well as the hippocampus, caudate putamen, and thalamus at low dose of medetomidine. Significant suppression of inter-hemispheric correlation was seen in the thalamus, where the receptor density is high, under 0.6mg/kg/h, and in all regions except the caudate, where the receptor density is low, under 1.0mg/kg/h. Furthermore, in mice whose activation was weaker or took longer time to detect, the bilateral connectivity was lower. This demonstrates that, with proper sedation and conservation of neurovascular coupling, similar bilateral networks like other species can be detected in the mouse brain.

Neural correlate of resting-state functional connectivity under α2 adrenergic receptor agonist, medetomidine.

Correlative fluctuations in functional MRI (fMRI) signals across the brain at rest have been taken as a measure of functional connectivity, but the neural basis of this resting-state MRI (rsMRI) signal is not clear. Previously, we found that the α2 adrenergic agonist, medetomidine, suppressed the rsMRI correlation dose-dependently but not the stimulus evoked activation. To understand the underlying electrophysiology and neurovascular coupling, which might be altered due to the vasoconstrictive nature of medetomidine, somatosensory evoked potential (SEP) and resting electroencephalography (EEG) were measured and correlated with corresponding BOLD signals in rat brains under three dosages of medetomidine. The SEP elicited by electrical stimulation to both forepaws was unchanged regardless of medetomidine dosage, which was consistent with the BOLD activation. Identical relationship between the SEP and BOLD signal under different medetomidine dosages indicates that the neurovascular coupling was not affected. Under resting state, EEG power was the same but a depression of inter-hemispheric EEG coherence in the gamma band was observed at higher medetomidine dosage. Different from medetomidine, both resting EEG power and BOLD power and coherence were significantly suppressed with increased isoflurane level. Such reduction was likely due to suppressed neural activity as shown by diminished SEP and BOLD activation under isoflurane, suggesting different mechanisms of losing synchrony at resting-state. Even though, similarity between electrophysiology and BOLD under stimulation and resting-state implicates a tight neurovascular coupling in both medetomidine and isoflurane. Our results confirm that medetomidine does not suppress neural activity but dissociates connectivity in the somatosensory cortex. The differential effect of medetomidine and its receptor specific action supports the neuronal origin of functional connectivity and implicates the mechanism of its sedative effect.

Pharmacological insight into neurotransmission origins of resting-state functional connectivity: α2-adrenergic agonist vs antagonist.

Resting-state functional connectivity MRI has emerged as a powerful tool for mapping large-scale neural networks based on synchronous BOLD signal; however, the neurobiological mechanisms are still unknown. To understand its neural substrates, especially the underlying neurotransmission, we applied pharmacological modulation with a receptor specific agonist and antagonist. Resting and evoked electrophysiology and BOLD signals in rat brains were measured under infusion of α2-adrenergic receptor agonist, medetomidine, the antagonist, atipamezole, and the vehicle individually. Both somatosensory BOLD activation and evoked potential were increased significantly under medetomidine compared to the vehicle while atipamezole slightly decreased both. The interhemispheric correlation at the resting state, in contrast, was suppressed by medetomidine but increased by atipamezole in regions with high receptor densities including the somatosensory cortex and thalamus. No change was seen in the caudate putamen, where receptor occupancy is low. The regional difference in connectivity was not related to cerebral blood flow, indicating that BOLD signal correlation is unlikely due to the vascular effects of the drugs. Resting intracortical recording exhibited agonist/antagonist dependent changes in beta and gamma bands that correlated with the BOLD functional connectivity measure. Our results confirm an important role of the adrenergic system on functional connectivity and suggest a neurotransmission basis of the phenomenon.

Ethanol, not detectably metabolized in brain, significantly reduces brain metabolism, probably via action at specific GABA(A) receptors and has measureable metabolic effects at very low concentrations.

Ethanol is a known neuromodulatory agent with reported actions at a range of neurotransmitter receptors. Here, we measured the effect of alcohol on metabolism of [3-¹³C]pyruvate in the adult Guinea pig brain cortical tissue slice and compared the outcomes to those from a library of ligands active in the GABAergic system as well as studying the metabolic fate of [1,2-¹³C]ethanol. Analyses of metabolic profile clusters suggest that the significant reductions in metabolism induced by ethanol (10, 30 and 60 mM) are via action at neurotransmitter receptors, particularly α4ß3δ receptors, whereas very low concentrations of ethanol may produce metabolic responses owing to release of GABA via GABA transporter 1 (GAT1) and the subsequent interaction of this GABA with local α5- or α1-containing GABA(A)R. There was no measureable metabolism of [1,2-¹³C]ethanol with no significant incorporation of ¹³C from [1,2-¹³C]ethanol into any measured metabolite above natural abundance, although there were measurable effects on total metabolite sizes similar to those seen with unlabelled ethanol.

From impact to recovery: tracking mild traumatic brain injury with MRI-a pilot study and case series.

Background: Diagnosis and recovery tracking of mild traumatic brain injury (mTBI) is often challenging due to the lack of clear findings on routine imaging techniques. This also complicates defining safe points for returning to activities. Hypothesis/purpose: Quantitative susceptibility mapping (QSM) can provide information about cerebral venous oxygen saturation (CSvO2) in the context of brain injury. We tested the prediction that these imaging modalities would enable the detection of changes and recovery patterns in the brains of patients with mTBI. Study design: In a case-control study, we recruited a cohort of 24 contact sport athletes for baseline QSM and resting-state functional MRI (rs-fMRI) scanning. Two of those who subsequently experienced head impact with significant post-injury symptoms underwent scans at 3, 7, 14 and 28 days post-injury; one had a boxing match without classical mTBI symptoms were also followed-up on. Results: The cohort baseline QSM measurements of the straight sinus were established. The two injured athletes with post-impact symptoms consistent with mTBI had susceptibility results at days 3 and 7 post-impact that fell below the 25th percentile of the baseline values. The per cent amplitude fluctuation quantified from rs-fMRI agreed with the susceptibility trends in the straight sinus. Conclusion: QSM holds promise as a diagnostic tool for tracking mTBI progression or recovery in contact sport head injury.

High Neural Efficiency in Unconscious Perceptual Processing among Table Tennis Athletes: An Event-Related Potential Study.

BACKGROUND: Neural efficiency refers to the brain's ability to function with reduced resource expenditure while maintaining high performance levels. Previous research has demonstrated that table tennis athletes have greater neural efficiency at the conscious level. However, it is unknown whether they exhibit greater neural efficiency at the unconscious level. Therefore, this study aims to investigate unconscious perceptual processing and neural efficiency in elite table tennis athletes through tasks involving the judgment of spin serves. METHODS: Fifty healthy, right-handed individuals participated in this study, including 25 elite table tennis athletes and 25 control participants without professional training experience. To evaluate the unconscious perceptual characteristics of both groups, we used a combination of masked priming paradigm and event-related potential techniques. RESULTS: The behavioral results reveal that, compared to the control group, the table tennis athletes displayed reduced reaction times (p < 0.001) and increased priming effects (p < 0.001) under unconscious conditions. The electrophysiological findings indicated that both groups elicited N1, N2, and P2 components. Notably, compared to the control group, the table tennis athletes exhibited significantly lower amplitude responses at the occipital lobe electrodes PO3, POz, PO4, O1, Oz, and O2 (p < 0.001). CONCLUSIONS: These results further support the neural efficiency hypothesis, indicating that prolonged professional training enhances athletes' capacities for specialized unconscious cognitive processing.