Cortical Activity Research Articles

Biomarkers for cognitive impairment in alpha-synucleinopathies: an overview of systematic reviews and meta-analyses

Cognitive impairment (CI) is common in α-synucleinopathies, i.e., Parkinson’s disease, Lewy bodies dementia, and multiple system atrophy. We summarize data from systematic reviews/meta-analyses on neuroimaging, neurophysiology, biofluid and genetic diagnostic/prognostic biomarkers of CI in α-synucleinopathies. Diagnostic biomarkers include atrophy/functional neuroimaging brain changes, abnormal cortical amyloid and tau deposition, and cerebrospinal fluid (CSF) Alzheimer’s disease (AD) biomarkers, cortical rhythm slowing, reduced cortical cholinergic and glutamatergic and increased cortical GABAergic activity, delayed P300 latency, increased plasma homocysteine and cystatin C and decreased vitamin B12 and folate, increased CSF/serum albumin quotient, and serum neurofilament light chain. Prognostic biomarkers include brain regional atrophy, cortical rhythm slowing, CSF amyloid biomarkers, Val66Met polymorphism, and apolipoprotein-E ε2 and ε4 alleles. Some AD/amyloid/tau biomarkers may diagnose/predict CI in α-synucleinopathies, but single, validated diagnostic/prognostic biomarkers lack. Future studies should include large consortia, biobanks, multi-omics approach, artificial intelligence, and machine learning to better reflect the complexity of CI in α-synucleinopathies.

Monitoring Cortical and Neuromuscular Activity: Six-month Insights into Knee Joint Position Sense Following ACL Reconstruction

Monitoring Cortical and Neuromuscular Activity: Six-month Insights into Knee Joint Position Sense Following ACL Reconstruction

Postoperative reorganization of the supplementary motor area complex: a possible latent bihemispheric network

Brain plasticity after multistep surgery in low-grade glioma is highly variable; the neurosurgical approach must be individualised and functional imaging can be used for this purpose. In supplementary motor area complex (SMAC) tumors, the early and adequate functional recovery of patients raises the possibility of a latent bihemispheric or "mirror" cortico-subcortical network, which would develop depending on the needs of each patient. Functional and DTI-MR data from 4 right-handed patients with left frontal low grade gliomas near the SMAC, who were operated at least in two occasions were collected. The time of the reintervention was variable (18 months- 8 years), related to the tumor growth. All patients were evaluated by a neuropsychologist and imaged before each surgery, in a 3 T MR, with a 24 multichanel head coil Motor and expressive language task-fMRI and DTI sequences were obtained to evidence the main cortico-subcortical components of the SMAC. Data were processed with Brainwave (GE Medical Systems) and with an Iplan Fiber Tracking tool (MEDTRONIC), respectively RESULTS: None of our patients presented permanent neurological deficits after the first or second functional surgery. Three patients with partial or complete resection of the left middle and / or inferior frontal gyrus, and the left frontal aslant tract evidenced new right hemispherical cortical activity. This right shift were not observed in the patient without left middle gyrus resection, indeed with partial absent of the left frontal aslant tract. SMAC is a latent cortico-subcortical bihemispheric network that allows it to reorganize itself in response to specific neurological deficits. We highlight the importance in the cortical reorganization of the left middle frontal gyrus in the SMAC, closely connected with the essential language areas of this region, but also we focused in the potential cortioco-subcortical changes to compensate the functionality of the FAT.

Aesthetic evaluation of body movements shaped by embodied and arts experience: Insights from behaviour and fNIRS

Aesthetic appreciation of full-body movements is likely shaped by our cumulative bodily experiences, yet most of the extant literature in this domain has focused on expertise and familiarity. We ran two experiments exploring individual differences in embodied experience and experience with the arts: In Study 1, we explored how participants’ (n = 41) abilities to learn a choreography shaped their aesthetic perceptions while viewing learned vs. unknown movements, using functional near-infrared spectroscopy (fNIRS) to measure cortical activation over the Action Observation Network (i.e., inferior frontal gyrus [IFG], inferior parietal lobule, middle temporal gyrus [MTG]). Study 1 demonstrated that embodied experience enhanced ratings of enjoyment, familiarity, and reproducibility of movements, and that individual differences in participants’ performance of the learned choreography were not associated with aesthetic ratings, but rather cortical activation in IFG and right MTG while viewing learned choreography. In Study 2, we combined the behavioural data from Study 1 with data from additional participants (total n = 141) to examine the relationship between arts experience and aesthetic perceptions of movements robustly. Study 2 revealed that previous arts and sports experience correlated with aesthetic judgements of familiarity and reproducibility of movements. Our findings highlight the relevance of examining individual experiences to fill theoretical gaps in our understanding of action aesthetics.

Correction: Comparing the effects of Swiss-ball training and virtual reality training on balance, mobility, and cortical activation in individuals with chronic stroke: study protocol for a multi-center randomized controlled trial

Correction: Comparing the effects of Swiss-ball training and virtual reality training on balance, mobility, and cortical activation in individuals with chronic stroke: study protocol for a multi-center randomized controlled trial

Time dependent changes in protein expression induced by intermittent theta burst stimulation in a cell line

BackgroundIntermittent Theta Burst Stimulation (iTBS), a non-invasive brain stimulation technique, is recognized for its ability to modulate cortical neuronal activity. However, its effects over time and the dynamics following stimulation are less well understood. Understanding the temporal dynamics of iTBS effects is essential for optimizing the timing and frequency of stimulation in therapeutic applications.ObjectiveThis study investigated the temporal changes in protein expression induced by iTBS in Neuro-2a cells.MethodsWe analyzed protein expression in retinoic acid-differentiated Neuro-2a cells at multiple time points — 0.5, 3, 6, 12, and 24 hours post-iTBS — using Western blot and immunocytochemistry techniques.ResultsOur findings reveal a significant early increase in neurotransmitter receptor subunits, neurotrophic factors, and cytoskeletal proteins within the first 0.5 hour following iTBS. Notably, proteins such as mGLuR1, NMDAR1, GABBR2, and β-tubulin III showed substantial increase in expression. However, the effects of iTBS on protein expression was not sustained at later timepoints.ConclusionOur results suggest that iTBS can transiently alter the expression of specific proteins in Neuro-2a cells. Future research should investigate the potential benefits of repeated stimulations within the early time window to refine iTBS interventions, potentially expanding their research and clinical applications.

GABAergic neurons in the central amygdala promote emergence from isoflurane anesthesia in mice.

Recent evidence indicates that general anesthesia and sleep-wake behavior share some overlapping neural substrates. GABAergic neurons in the central amygdala (CeA) have a high firing rate during wakefulness and play a role in regulating arousal-related behaviors. The objective of this study is to investigate whether CeA GABAergic neurons participate in the regulation of isoflurane general anesthesia and uncover the underlying neural circuitry. Fiber photometry recording was used to determine the changes in calcium signals of CeA GABAergic neurons during isoflurane anesthesia in Vgat-Cre mice. Chemogenetic and optogenetic approaches were used to manipulate the activity of CeA GABAergic neurons, and a righting reflex test was used to determine the induction and emergence from isoflurane anesthesia. Cortical electroencephalogram (EEG) recording was used to assess the changes in EEG spectral power and burst-suppression ratio during 0.8% and 1.4% isoflurane anesthesia, respectively. Both male and female mice were used in this study. The calcium signals of CeA GABAergic neurons decreased during the induction of isoflurane anesthesia and was restored during the emergence. Chemogenetic activation of CeA GABAergic neurons delayed induction time (mean ± SD, vehicle vs. clozapine-N-oxide: 58.75±5.42 s vs. 67.63±5.01 s; n=8, P=0.0017) and shortened emergence time (385.50±66.26 s vs. 214.60±40.21 s; n=8, P=0.0017) from isoflurane anesthesia. Optogenetic activation of CeA GABAergic neurons produced a similar effect. Furthermore, optogenetic activation decreased EEG delta power (Pre-stim vs. Stim: 46.63%±4.40% vs. 34.16%±6.47%; n=8, P=0.0195) and burst-suppression ratio (83.39%±5.15% vs. 52.60%±12.98%; n=8, P=0.0002). Moreover, optogenetic stimulation of terminals of CeA GABAergic neurons in the basal forebrain (BF) also promoted cortical activation and accelerated behavioral emergence from isoflurane anesthesia. Our results suggest that CeA GABAergic neurons play a role in general anesthesia regulation, which facilitates behavioral and cortical emergence from isoflurane anesthesia through the GABAergic CeA-BF pathway.

Correlation Between the Cortical Activation Studied by Functional Near Infrared Spectroscopy Neuroimaging (fNIRS) With Performance of 3rd Grade Students

The cortical activation and performance of 3rd grade students were investigated using Functional near infrared spectroscopy (fNIRS) during reading Arabic language. The main cortical activation parameter tested was hemoglobin difference (HbDiff), while the performance was evaluated according to the number of committed errors and latency. The recorded HbDiff concentrations for the typically developed (TD) were significantly higher (0.05) than that of students with dyslexia (Dys), confirming higher brain activities for TD students. TD students committed less errors and need less time to finish the task. Moreover, Pearson correlation analysis performed showed that there was a negative correlation between cortical activation parameters and performance. Limited studies explored the use of fNIRS to investigate the cortical activation of Arabic students' brains or correlated between the cortical activation and performance variables. Therefore, this current research is novel and showed the potential utilization of the fNIRS in the field of educational neuroscience.

Early visual modulation and selection predict saccadic timing during visual search: An ERP study.

Saccadic eye movements, a critical aspect of real-world visual behavior, are preceded by an initial accumulation of visual information followed by the selection of a single location to move one's eyes. However, it is currently unclear how each of these stages uniquely affects saccadic timing. In this study, participants searched for a contour integration target while EEG was used to measure posterior cortical activity between search display onset and first saccade initiation. The goal was to determine whether saccade timing could be attributed to differences in early ERP amplitudes, with the P1 reflecting the magnitude of early perceptual information accumulation and the N1 reflecting the strength of selection leading to the saccadic decision. EOG was used to measure saccade timing, and trials were divided into fast, middle, and slow bins. The N1 response was smallest in the slow saccade tertile, relative to both the fast and middle tertiles, suggesting weak selection. In contrast, the P1 response was largest for this same slow saccadic tertile relative to the middle saccadic tertile, suggesting vigorous information accumulation. Therefore, delays in saccadic behavior may occur when the visual system is overwhelmed with visual input, thus increasing the time to reach a saccadic decision. These findings reconcile models of eye movement behavior which often prioritize either the impact of information accrual or selection, rather than regarding both as an integrated whole.

Cross-modal representation of chewing food in posterior parietal and visual cortex.

Even though the oral cavity is not visible, food chewing can be performed without damaging the tongue, oral mucosa, or other intraoral parts, with cross-modal perception of chewing possibly critical for appropriate recognition of its performance. This study was conducted to clarify the relationship of chewing food cross-modal perception with cortex activities based on examinations of the posterior parietal cortex (PPC) and visual cortex during chewing in comparison with sham chewing without food, imaginary chewing, and rest using functional near-infrared spectroscopy. Additionally, the effects of a deafferent tongue dorsum on PPC/visual cortex activities during chewing performance were examined. The results showed that chewing food increased activity in the PPC/visual cortex as compared with imaginary chewing, sham chewing without food, and rest. Nevertheless, those activities were not significantly different during imaginary chewing or sham chewing without food as compared with rest. Moreover, subjects with a deafferent tongue dorsum showed reduced PPC/visual cortex activities during chewing food performance. These findings suggest that chewing of food involves cross-modal recognition, while an oral somatosensory deficit may modulate such cross-modal activities.

Neural mechanisms of fear responses to emotional stimuli: a preliminary study combining early posterior negativity and electroencephalogram source network analysis

Fear emotion is a typical negative emotion that is commonly present in daily life and significantly influences human behavior. A deeper understanding of the mechanisms underlying negative emotions contributes to the improvement of diagnosing and treating disorders related to negative emotions. However, the neural mechanisms of the brain when faced with fearful emotional stimuli remain unclear. To this end, this study further combined electroencephalogram (EEG) source analysis and cortical brain network construction based on early posterior negativity (EPN) analysis to explore the differences in brain information processing mechanisms under fearful and neutral emotional picture stimuli from a spatiotemporal perspective. The results revealed that neutral emotional stimuli could elicit higher EPN amplitudes compared to fearful stimuli. Further source analysis of EEG data containing EPN components revealed significant differences in brain cortical activation areas between fearful and neutral emotional stimuli. Subsequently, more functional connections were observed in the brain network in the alpha frequency band for fearful emotions compared to neutral emotions. By quantifying brain network properties, we found that the average node degree and average clustering coefficient under fearful emotional stimuli were significantly larger compared to neutral emotions. These results indicate that combining EPN analysis with EEG source component and brain network analysis helps to explore brain functional modulation in the processing of fearful emotions with higher spatiotemporal resolution, providing a new perspective on the neural mechanisms of negative emotions.

Laminar fMRI in the locked-in stage of amyotrophic lateral sclerosis shows preserved activity in layer Vb of primary motor cortex

Amyotrophic lateral sclerosis (ALS) affects the cerebral cortex layer-dependently, most notably by the foremost targeting of upper motor neurons (UMNs) sited in layer Vb. Previous studies have shown a retained ability of paralysed patients to activate cortical motor networks, even in late-stage ALS. However, it is currently unknown whether such activation reflects a retained capacity to process sensorimotor inputs or if it is a result of actual motor output. Given the distinct function of individual cortical layers, layer-specific functional measurements may provide insight to this question. In this study, using submillimetre resolution laminar fMRI, we assessed the layer-dependent activation associated with attempted (motor) and passive (somatosensory) movements in a locked-in stage ALS patient. We found robust activation in both superficial and deep layers of primary motor cortex (M1). The peak activation in deep layers was localised to layer Vb. These findings demonstrate preserved activity in deep output layers of M1, possibly reflecting a retained ability to engage surviving UMNs despite years of paralysis. Our study underscores the capacity of laminar fMRI to discern subtle cortical activity and elucidates a promising pathway for probing in vivo human ALS pathology with unprecedented resolution.

Off-axis freeform optical design for large curved field of view imaging

Recording neuron activities is pivotal for elucidating the functionality of the nervous system. However, the curved cortex surface of experimental mice presents a significant challenge for optical systems, particularly when a larger field of view (FOV) is required. To address this challenge, we have designed an off-axis three-mirror system that incorporates freeform surfaces on both the primary and secondary mirrors. This system achieves a large imaging FOV of 18°×9°, delivering near-diffraction-limit imaging quality across a curvature spectrum of −14.7 to −15.3mm. A manufacturability analysis indicates that the freeform surfaces are straightforward to produce, and the overall system demonstrates low sensitivity to tolerance and measurement errors. This study introduces a novel, to the best of our knowledge, solution to the field curvature constraints in optical imaging of cortical activity, providing substantial technical support for in vivo neuronal imaging endeavors.

Latent dynamics of primary sensory cortical population activity structured by fluctuations in the local field potential

IntroductionAs emerging technologies enable measurement of precise details of the activity within microcircuits at ever-increasing scales, there is a growing need to identify the salient features and patterns within the neural populations that represent physiologically and behaviorally relevant aspects of the network. Accumulating evidence from recordings of large neural populations suggests that neural population activity frequently exhibits relatively low-dimensional structure, with a small number of variables explaining a substantial fraction of the structure of the activity. While such structure has been observed across the brain, it is not known how reduced-dimension representations of neural population activity relate to classical metrics of “brain state,” typically described in terms of fluctuations in the local field potential (LFP), single-cell activity, and behavioral metrics.MethodsHidden state models were fit to spontaneous spiking activity of populations of neurons, recorded in the whisker area of primary somatosensory cortex of awake mice. Classic measures of cortical state in S1, including the LFP and whisking activity, were compared to the dynamics of states inferred from spiking activity.ResultsA hidden Markov model fit the population spiking data well with a relatively small number of states, and putative inhibitory neurons played an outsize role in determining the latent state dynamics. Spiking states inferred from the model were more informative of the cortical state than a direct readout of the spiking activity of single neurons or of the population. Further, the spiking states predicted both the trial-by-trial variability in sensory responses and one aspect of behavior, whisking activity.DiscussionOur results show how classical measurements of brain state relate to neural population spiking dynamics at the scale of the microcircuit and provide an approach for quantitative mapping of brain state dynamics across brain areas.

Brain-movement relationship during upper-limb functional movements in chronic post-stroke patients

BackgroundFollowing a stroke, brain activation reorganisation, movement compensatory strategies, motor performance and their evolution through rehabilitation are matters of importance for clinicians. Two non-invasive neuroimaging methods allow for recording task-related brain activation: functional near-infrared spectroscopy (fNIRS) and electroencephalography (fEEG), respectively based on hemodynamic response and neuronal electrical activity. Their simultaneous measurement during movements could allow a better spatiotemporal mapping of brain activation, and when associated to kinematic parameters could unveil underlying mechanisms of functional upper limb (UL) recovery. This study aims to depict the motor cortical activity patterns using combined fNIRS-fEEG and their relationship to motor performance and strategies during UL functional tasks in chronic post-stroke patients.MethodsTwenty-one healthy old adults and 21 chronic post-stroke patients were recruited and completed two standardised functional tasks of the UL: a paced-reaching task where they had to reach a target in front of them and a circular steering task where they had to displace a target using a hand-held stylus, as fast as possible inside a circular track projected on a computer screen. The activity of the bilateral motor cortices and motor performance were recorded simultaneously utilizing a fNIRS-fEEG and kinematics platform.Results and conclusionsKinematic analysis revealed that post-stroke patients performed worse in the circular steering task and used more trunk compensation in both tasks. Brain analysis of bilateral motor cortices revealed that stroke individuals over-activated during the paretic UL reaching task, which was associated with more trunk usage and a higher level of impairment (clinical scores). This work opens up avenues for using such combined methods to better track and understand brain-movement evolution through stroke rehabilitation.

Cortical activity in body balance tasks as a function of motor and cognitive demands: A systematic review.

Technological tools, like electroencephalography and functional near-infrared spectroscopy, have deepened our understanding of cortical regions involved in balance control. In this systematic literature review, we aimed to identify the prevalent cortical areas activated during balance tasks with specific motor or cognitive demands. Our search strategy encompassed terms related to balance control and cortical activity, yielding 2250 results across five databases. After screening, 67 relevant articles were included in the review. Results indicated that manipulations of visual and/or somatosensory information led to prevalent activity in the parietal, frontal and temporal regions; manipulations of the support base led to prevalent activity of the parietal and frontal regions; both balance-cognitive dual-tasking and reactive responses to extrinsic perturbations led to prevalent activity in the frontal and central regions. These findings deepen our comprehension of the cortical regions activated to manage the complex demands of maintaining body balance in the performance of tasks posing specific requirements. By understanding these cortical activation patterns, researchers and clinicians can develop targeted interventions for balance-related disorders.

Investigating the impact of mental rehearsal on prefrontal and motor cortical haemodynamic responses in surgeons using optical neuroimaging

IntroductionInadequate exposure to real-life operating can impede timely acquisition of technical competence among surgical residents, and is a major challenge faced in the current training climate. Mental rehearsal (MR)—the cognitive rehearsal of a motor task without overt physical movement—has been shown to accelerate surgical skills learning. However, the neuroplastic effect of MR of a complex bimanual surgical task is unknown. The aim of this study is to use functional near-infrared spectroscopy (fNIRS) to assess the impact of MR on prefrontal and motor cortical activation during a laparoscopic knot tying task.MethodsTwelve surgical residents performed a laparoscopic knot tying task before and after either mental rehearsal (MR, intervention group) or textbook reading (TR, control group). In both groups, fNIRS was used to measure changes in oxygenated hemoglobin concentration (HbO2) in the prefrontal (24 channels) and motor cortices (22 channels). Technical performance was measured using leak volume, objective performance score and task progression score.ResultsMR led to a decrease in HbO2 (reduced activation) in the bilateral prefrontal cortex (PFC), and an increase in HbO2 (increased activation) in the left middle frontal gyrus, left precentral gyrus, and left postcentral gyrus. No discernible changes in activation were observed after TR in either the PFC or motor cortex. Moreover, smaller ΔHbO2 responses in the right PFC and greater ΔHbO2 responses in the left motor cortex were observed in the MR group compared with the TR group. Leak volume was significantly less following MR (p = 0.019), but not after TR (p = 0.347). Mean objective performance score was significantly higher following MR compared with TR (p = 0.043).ConclusionMental rehearsal may enhance surgical skill acquisition and technical proficiency by reducing utilization of attentional resources in the prefrontal cortex and improving neural efficiency in motor areas during a laparoscopic surgical task.

Inside the gamer's mind: How violent video games and emotional dysregulation affect EEG interbrain synchronization

BackgroundExposure to violent video games influences players’ cortical activations. In addition, intra-individual variables like emotional regulation play an important role in the consequences of such exposures. However, most research has studied these relationships at the intra-individual level. Therefore, the present study investigated the effects of violent video games on the interbrain synchronization (IBS) of dyads in which one member played video games, and evaluated IBS differences between high and low-emotionally dysregulated groups. MethodsEighteen participants (M = 24.1 ± 2.1) were enrolled in this study. Participants gazed into another person's eyes before playing (“First Direct Gaze”), after playing a violent video game (“Post-VV”), and after playing a nonviolent video game (“Post-NVV”) during an electroencephalographic hyperscanning acquisition. Afterward, each participant completed a socio-demographic questionnaire and the Difficulties in Emotion Regulation Scale. ResultsA cluster-based analysis revealed an increased theta IBS Post-VV compared to Post-NVV. A median split was used to define the high emotionally dysregulated (“HED”) and low emotionally dysregulated (“LED”) groups. Results showed a decreased alpha IBS in the First Direct Gaze, Post-VV, and Post-NVV in the HED group compared to the LED group. ConclusionsExposure to violent video games was associated with higher theta IBS, suggesting a greater social attunement, potentially due to a higher perceived dominance and control or due to an effort of managing the emotional activations elicited. In addition, difficulties in emotional regulation could elicit specific alpha activities regardless of exposure to a video game, leading to a lower tendency to attune with another person on this band.Results from this study should not be generalized to infer that playing any type of video game causes harm to people's brains.

Long-term administration of paroxetine increases cortical EEG beta and gamma band activities in healthy awake rats

Understanding the electrophysiological properties of antidepressant medications is important to resolve the response heterogeneity of these drugs in clinical practice. Administration of paroxetine, a selective serotonin reuptake inhibitor, has been shown to increase serotonin levels that affect cortical activities in healthy subjects. However, the extent to which cortical oscillations can be altered by ongoing administration of paroxetine is not known. Here, we develop EEG biomarkers showing long-term effects of paroxetine. EEG changes were analyzed using Neuroscan in healthy wakeful rats administered paroxetine (4 mg/kg/day) for six weeks. Subsequent EEG recordings taken at 3 and 6 weeks after treatment showed differences in cortical oscillations obtained from both hemispheres and frontal-central-parietal regions. Chronic paroxetine administration resulted in an increase in gamma band activity. Comparison of EEG frequency bands of paroxetine and saline groups showed an enhancement in higher frequency activities at third weeks after the treatment. Higher activity of alpha oscillations in the temporal cortex was persistent at sixth week of the administration. Overall, our results suggest that chronic paroxetine administration affects cortical oscillations across an expansive network.

Effects of Motor and Cognitive Dual-Task Demands on Ankle Dorsiflexor and Plantarflexor Force Control in Older Adults

ABSTRACT Background Force steadiness can be impaired under dual-task conditions in older adults. Since this impairment is attributed to their limited attentional resources, we hypothesized that the degree of cortical activity involved in muscle contraction would affect force steadiness under dual-task conditions. To test this hypothesis, based on the premise that dorsiflexion requires more cortical resources than plantarflexion, we compared the effects of additional motor and cognitive task demands on force steadiness between dorsiflexion and plantarflexion contractions in young and older adults. Method Eighteen young and eighteen older adults performed a force tracking task by applying either isometric dorsiflexion or plantarflexion force concurrently with and without (control) secondary upper-limb motor or cognitive task. Results Force steadiness was impaired by both secondary upper-limb motor and cognitive tasks for the dorsiflexors and plantarflexors in older adults. While force steadiness was impaired similarly by additional task demands regardless of the secondary task type for the dorsiflexors, the impairment effect was larger in the secondary cognitive than motor task for the plantarflexors. Conclusion The effects of dual-task demand on force steadiness could depend on the degree of cortical activity involved in muscle contraction in older adults.