Cortical Changes Research Articles

Stronger tilt aftereffects in individuals diagnosed with schizophrenia spectrum disorders but not bipolar disorder

An altered use of context and experience to interpret incoming information has been posited to explain schizophrenia symptoms. The visual system can serve as a model system for examining how context and experience guide perception and the neural mechanisms underlying putative alterations. The influence of prior experience on current perception is evident in visual aftereffects, the perception of the “opposite” of a previously viewed stimulus. Aftereffects are associated with neural adaptation and concomitant change in strength of lateral inhibitory connections in visually responsive neurons. In a previous study, we observed stronger aftereffects related to orientation (tilt aftereffects) but not luminance (negative afterimages) in individuals diagnosed with schizophrenia, which we interpreted as potentially suggesting altered cortical (but not subcortical) adaptability and local changes in excitatory-inhibitory interactions. Here, we tested whether stronger tilt aftereffects were specific to individuals with schizophrenia or extended to individuals with bipolar disorder. We measured tilt aftereffects and negative afterimages in 32 individuals with bipolar disorder, and compared aftereffect strength to a previously reported group of 36 individuals with schizophrenia and 22 healthy controls. We observed stronger tilt aftereffects, but not negative afterimages, in individuals with schizophrenia as compared to both controls and individuals with bipolar disorder, who did not differ from each other. These results mitigate concerns that stronger tilt aftereffects in schizophrenia are a consequence of medication or of the psychosocial consequences of a severe mental illness.

Changes in cerebral cortex activity during a simple motor task after MRgFUS treatment in patients affected by essential tremor and Parkinson's disease: a pilot study using functional NIRS

Objective. Magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS) is a non-invasive thermal ablation method that involves high-intensity focused ultrasound surgery (FUS) and Magnetic Resonance Imaging for anatomical imaging and real-time thermal mapping. This technique is widely employed for the treatment of patients affected by essential tremor (ET) and Parkinson’s disease (PD). In the current study, functional near-infrared spectroscopy (fNIRS) was used to highlight hemodynamics changes in cerebral cortex activity, during a simple hand motor task, i.e. unimanual left and right finger-tapping, in ET and PD patients. Approach. All patients were evaluated before, one week and one month after MRgFUS treatment. Main results. fNIRS revealed cerebral hemodynamic changes one week and one month after MRgFUS treatment, especially in the ET group, that showed a significant clinical improvement in tremor clinical scores. Significance. To our knowledge, our study is the first that showed the use of fNIRS system to measure the cortical activity changes following unilateral ventral intermediate nucleus thalamotomy after MRgFUS treatment. Our findings showed that therapeutic MRgFUS promoted the remodeling of neuronal networks and changes in cortical activity in association with symptomatic improvements.

Women's neuroplasticity during gestation, childbirth and postpartum.

Pregnancy is a unique neuroplastic period in adult life. This longitudinal study tracked brain cortical changes during the peripartum period and explored how the type of childbirth affects these changes. We collected neuroanatomic, obstetric and neuropsychological data from 110 first-time mothers during late pregnancy and early postpartum, as well as from 34 nulliparous women evaluated at similar time points. During late pregnancy, mothers showed lower cortical volume than controls across all functional networks. These cortical differences attenuated in the early postpartum session. Default mode and frontoparietal networks showed below-expected volume increases during peripartum, suggesting that their reductions may persist longer. Results also pointed to different cortical trajectories in mothers who delivered by scheduled C-section. The main findings were replicated in an independent sample of 29 mothers and 24 nulliparous women. These data suggest a dynamic trajectory of cortical decreases during pregnancy that attenuates in the postpartum period, at a different rate depending on the brain network and childbirth type.

Vanadium administration ameliorates cortical structural and functional changes in juvenile hydrocephalic mice.

Vanadium is a prevalent neurotoxic transition metal with therapeutic potentials in some neurological conditions. Hydrocephalus poses a major clinical burden in neurological practice in Africa. Its primary treatment (shunting) has complications, including infection and blockage; alternative drug-based therapies are therefore necessary. This study investigates the function and cytoarchitecture of motor and cerebellar cortices in juvenile hydrocephalic mice following treatment with varying doses of vanadium. Fifty juvenile mice were allocated into five groups (n=10 each): controls, hydrocephalus-only, low- (0.15mg/kg), moderate- (0.3mg/kg), and high- (3.0mg/kg) dose vanadium groups. Hydrocephalus was induced by the intracisternal injection of kaolin and sodium metavanadate administered by intraperitoneal injection 72hourly for 28 days. Neurobehavioral tests: open field, hanging wire, and pole tests, were carried out to assess locomotion, muscular strength, and motor coordination, respectively. The cerebral motor and the cerebellar cortices were processed for cresyl violet staining and immunohistochemistry for neurons (NeuN) and astrocytes (glial fibrillary acidic protein). Hydrocephalic mice exhibited body weight loss and behavioral deficits. Horizontal and vertical movements and latency to fall from hanging wire were significantly reduced, while latency to turn and descend the pole were prolonged in hydrocephalic mice, suggesting impaired motor ability; this was improved in vanadium-treated mice. Increased neuronal count, pyknotic cells, neurodegeneration and reactive astrogliosis were observed in the hydrocephalic mice. These were mostly mitigated in the vanadium-treated mice, except in the high-dose group where astrogliosis persisted. These results demonstrate a neuroprotective potential of vanadium administration in hydrocephalus. The molecular basis of these effects needs further exploration.

Asymmetries and hemispheric interaction in the auditory system of elderly people.

Age-related changes of asymmetries in the auditory system and decreasing efficiency of hemispheric interaction have been discussed for some time. This mini-review discusses recent neuroimaging studies on alterations in lateralization of cortical processing and structural changes concerning the division of labor and interaction between hemispheres during auditory processing in elderly people with the focus on people without severe hearing loss. Several changes of asymmetries in anatomy, function and neurotransmitter concentration were observed in auditory cortical areas of older compared to younger adults. It was shown that connections between left and right auditory cortex are reduced during aging. Functionally, aging seems to lead to a reduction in asymmetry of auditory processing. However, the results do not always point into the same direction. Furthermore, correlations between function, anatomy and behavior in the left and right hemisphere appear to differ between younger and older adults. The changes in auditory cortex asymmetries with aging might be due to compensation of declining processing capacities, but at the same time these mechanisms could impair the balanced division of labor between the two hemispheres that is required for the processing of complex auditory stimuli such as speech. Neuroimaging studies are essential to follow the slow changes with aging as in the beginning no behavioral effects might be visible due to compensation. Future studies should control well for peripheral hearing loss and cognitive decline. Furthermore, for the interpretability of results it is necessary to use specific tasks with well-controlled task difficulty.

Altered brain function and structure in carpal tunnel syndrome: a systematic review and meta-analysis of structural and functional brain imaging.

This systematic review with a meta-analysis aimed to identify the altered brain structure and function in carpal tunnel syndrome (CTS) by summarizing the literature about magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG) outcomes compared to healthy controls (HC). CTS is the most common nerve entrapment in the arm associated with altered peripheral and central nociceptive system. PRISMA guidelines were used to report the outcomes. Six databases were searched for relevant literature (Web of Science, Scopus, PubMed, Sage, EBSCO host, and Cochrane). Eligible studies comparing MRI, fMRI, and MEG findings in people with CTS (present for at least 2months) and HC through the following parameters: (1) interdigit cortical separation distance, (2) white and grey matter changes, (3) peak latency of M20 wave and recovery function of N20 from the somatosensory cortex (SI), and (4) surface area of activated digit cortical representation. The results from different studies were pooled and a meta-analysis was done. From 17 included, there was a significant reduction of interdigit cortical separation distance of index-middle and index-little fingers in the CTS (SMD = -0.869, 95% CI (-1.325, -0.413), p-value = 0.000) and (SMD = -0.79, 95% CI (-1.217, -0.364), p-value = 0.000), respectively. Middle-little fingers interdigit separation showed no difference (SMD = -0.2, 95% CI (-0.903, 1.309), p-value = 0.718). There is evidence supporting the altered brain structure and function in CTS as evidenced by reduction of interdigit cortical separation distance, and excessive blurring and disinhibition of SI, with low resting state functional connectivity. Thus, centrally directed therapeutic approaches might complement peripheral treatments.

Cortical Gray Matter Thickness and Volume Changes and Their Association with Memory Functions in Hyperthyroid Patients

Introduction: Hyperthyroidism, characterized by excessive thyroid hormone production, is a common endocrine disorder that affects various physiological processes, including brain function. Recent advancements in neuroimaging techniques have enabled researchers to investigate structural alterations in the brain associated with hyperthyroidism. This study aimed to examine regional cortical thickness and cortical volume differences across the brain between hyperthyroid patients and control subjects. Methods: We examined localized cortical thicknesses and volumes in 34 hyperthyroid patients and 35 control subjects with high-resolution T1-weighted images using FreeSurfer software and assessed group differences with analysis of covariance (covariates: age, sex, education, and total intracranial volume). Spearman and partial correlations were performed between clinical variables and cortical thicknesses/volumes and between neuropsychological scores and cortical thicknesses/volumes, respectively. Results: Hyperthyroid patients exhibited significantly increased cortical thickness in bilateral superior temporal and superior frontal gyri, along with higher cortical volumes in various regions, including the right superior temporal gyrus, right superior parietal gyrus, right rostral and caudal middle frontal gyrus, and left superior frontal gyrus. Notably, thyroid hormones (fT3, fT4) correlated positively with cortical thicknesses and volumes in the superior temporal gyrus and superior frontal gyrus. Additionally, recognition memory scores negatively correlated with the right superior temporal gyrus and right superior frontal gyrus cortical thickness. Conclusion: The observed cortical thickening and increased cortical volume in specific brain areas provide new insights into the pathophysiological mechanism associated with brain impairment in hyperthyroidism.

Unveiling MRI markers for Parkinson’s Disease: GABAergic dysfunction and cortical changes

ObjectiveThe study aimed to investigate changes in basal levels of the inhibitory γ-aminobutyric acid (GABA) neurotransmitter in the sensorimotor cortex (SMC) and cortical gyrification in patients with Parkinson’s disease (PD), which could further identify potential imaging biomarkers for PD, particularly in patients with early-onset Parkinson’s disease (EOPD). MethodFifty patients with PD (EOPD: 10, late-onset Parkinson’s disease [LOPD]: 40) and fifty-two age- and gender-matched healthy controls (HC) underwent GABA-edited 1H MRS of the SMC and high-resolution 3D T1-weighted brain imaging. GABA levels and local gyrification index (LGI) were calculated to assess GABAergic and cortical gyrification deficits in PD. ResultThe Pearson correlation coefficients revealed significant negative associations between eight indicators, including GABA/Cr level and local gyrification index (LGI) of specific cortical regions (precentral, postcentral, entorhinal, superiortemporal, posteriorcingulate, cuneus, and transversetemporal cortex), and the likelihood of Parkinson’s disease (r < -0.4, p < 0.001). Additionally, GABA levels were significantly lower in the SMC region of both EOPD and LOPD patients compared to healthy controls (mean ± SD [u.i.]: EOPD=0.081 ± 0.022 vs. Young-HC=0.112 ± 0.021, p = 0.003; LOPD=0.054 ± 0.024 vs. Old-HC=0.099 ± 0.021, p < 0.001). The logistic regression model was established by using multivariate analysis, identifying two statistically significant indicators: GABA/Cr and LGI of the transversetemporal. The combined model exhibited the highest AUC values in both younger and older populations. ConclusionGABAergic dysfunction may play an important role in the pathogenesis of PD patients. Changes in neurotransmitter and morphological may serve as potential markers for the preclinical diagnosis and progression of PD, including EOPD.

Morphological changes of cerebral gray matter in spinocerebellar ataxia type 3 using fractal dimension analysis.

Spinocerebellar ataxia type 3 (SCA3), or Machado-Joseph disease, presents as a cerebellar cognitive affective syndrome (CCAS) and represents the predominant SCA genotype in Taiwan. Beyond cerebellar involvement, SCA3 patients exhibit cerebral atrophy. While prior neurodegenerative disease studies relied on voxel-based morphometry (VBM) for brain atrophy assessment, its qualitative nature limits individual and region-specific evaluations. To address this, we employed fractal dimension (FD) analysis to quantify cortical complexity changes in SCA3 patients. We examined 50 SCA3 patients and 50 age- and sex-matched healthy controls (HC), dividing MRI cerebral gray matter (GM) into 68 auto-anatomical subregions. Using three-dimensional FD analysis, we identified GM atrophy manifestations in SCA3 patients. Results revealed lateral atrophy symptoms in the left frontal, parietal, and occipital lobes, and fewer symptoms in the right hemisphere's parietal and occipital lobes. Focal areas of atrophy included regions previously identified in SCA3 studies, alongside additional regions with decreased FD values. Bilateral postcentral gyrus and inferior parietal gyrus exhibited pronounced atrophy, correlating with Scale for the Assessment and Rating of Ataxia (SARA) scores and disease duration. Notably, the most notable focal areas were the bilateral postcentral gyrus and the left superior temporal gyrus, serving as imaging biomarkers for SCA3. Our study enhances understanding of regional brain atrophy in SCA3, corroborating known clinical features while offering new insights into disease progression.

A systematic review of the impact of type 2 diabetes on brain cortical thickness.

Type 2 diabetes (T2D) has been linked to cognitive impairment and dementia, but its impact on brain cortical structures in individuals prior to or without cognitive impairment remains unclear. We conducted a systematic review of 2,331 entries investigating cerebral cortical thickness changes in T2D individuals without cognitive impairment, 55 of which met our inclusion criteria. Most studies (45/55) reported cortical brain atrophy and reduced thickness in the anterior cingulate, temporal, and frontal lobes between T2D and otherwise cognitively healthy controls. However, the balance of studies (10/55) reported no significant differences in either cortical or total brain volumes. A few reports also noticed changes in the occipital cortex and its gyri. As part of the reports, less than half of studies (18/55) described a correlation between T2D and hippocampal atrophy. Variability in sample characteristics, imaging methods, and software could affect findings on T2D and cortical atrophy. In conclusion, T2D appears linked to reduced cortical thickness, possibly impacting cognition and dementia risk. Microvascular disease and inflammation in T2D may also contribute to this risk. Further research is needed to understand the underlying mechanisms and brain health implications.

Association between seated trunk control and cortical sensorimotor white matter brain changes in patients with chronic low back pain.

Trunk control involves integration of sensorimotor information in the brain. Individuals with chronic low back pain (cLBP) have impaired trunk control and show differences in brain structure and function in sensorimotor areas compared with healthy controls (HC). However, the relationship between brain structure and trunk control in this group is not well understood. This cross-sectional study aimed to compare seated trunk control and sensorimotor white matter (WM) structure in people with cLBP and HC and explore relationships between WM properties and trunk control in each group. Thirty-two people with cLBP and 35 HC were tested sitting on an unstable chair to isolate trunk control; performance was measured using the 95% confidence ellipse area (CEA95) of center-of-pressure tracing. A WM network between cortical sensorimotor regions of interest was derived using probabilistic tractography. WM microstructure and anatomical connectivity between cortical sensorimotor regions were assessed. A mixed-model ANOVA showed that people with cLBP had worse trunk control than HC (F = 12.96; p < .001; ηp2 = .091). There were no differences in WM microstructure or anatomical connectivity between groups (p = 0.564 to 0.940). In the cLBP group, WM microstructure was moderately correlated (|r| = .456 to .565; p ≤ .009) with trunk control. Additionally, the cLBP group demonstrated stronger relationships between anatomical connectivity and trunk control (|r| = .377 to .618 p < .034) compared to the HC group. Unique to the cLBP group, WM connectivity between right somatosensory and left motor areas highlights the importance of interhemispheric information exchange for trunk control. Parietal areas associated with attention and spatial reference frames were also relevant to trunk control. These findings suggest that people with cLBP adopt a more cortically driven sensorimotor integration strategy for trunk control. Future research should replicate these findings and identify interventions to effectively modulate this strategy.

Beyond the Buzz: Cortical and subcortical brain changes in patients with pulsatile tinnitus

Pulsatile tinnitus (PT) can be a debilitating condition characterized by rhythmic, heartbeat-synchronous sounds, which can severely impact patients’ quality of life. Understanding the neuroanatomical changes in PT patients may provide critical insights into the impacts of this condition. This study aimed to investigate potential differences in cortical and subcortical brain volume between adults with PT and age-matched controls (60 to 70 years of age). A retrospective, cross-sectional analysis of imaging and medical records was conducted, with data collected from January 2015 to December 2021. The study was conducted in a tertiary referral center with a specialized tinnitus clinic. A total of 135 adults diagnosed with PT and 135 age-matched controls were included. All participants were screened for PT and relevant medical history, with consecutive sampling used for selection. Cortical and subcortical brain volume differences between PT patients and controls were measured using Freesurfer. PT patients (n = 79, after exclusion of patients with inadequate imaging data) exhibited significant decreases in cortical thickness in the anterior cingulate and entorhinal cortex, and decreased volume in the left putamen, compared to age-matched controls (n = 135). PT patients also demonstrated significant increased volume in frontal and occipital lobe structures, the cerebellum, hippocampi, and ventral pallidum. In conclusion, our findings suggest that individuals with PT may have structural differences in brain regions related to auditory processing, and depression, which provides additional evidence of the psychiatric sequalae of PT. These findings demonstrate that there are neuroanatomical alterations in patients with PT, emphasizing the value in evaluating and treating this disease to prevent these neuroanatomical differences from developing.

Brain structural network modular and connectivity alterations in subtypes of patients with migraine and medication overuse headache.

Migraine, one of the most prevalent and debilitating neurological disorders, can be classified based on attack frequency into episodic migraine (EM) and chronic migraine (CM). Medication overuse headache (MOH), a type of chronic headache, arises when painkillers are overused by individuals with untreated or inadequately treated headaches. This study compares regional cortical morphological alterations and brain structural network changes among these headache subgroups. Sixty participants, including 20 in each of the following patient groups (EM, CM, MOH), and healthy controls (HC) completed the study. Our results show that the EM group exhibited cortical thickness (CTs) thinning predominantly in the left limbic, whereas CM patients exhibited CTs thinning across both left and right hemispheres. The MOH group demonstrated the most widespread CTs thinning. Both CM and MOH exhibited comparable patterns of CTs thinning within lobes, leading to reduced intra-lobe connectivity. While there were no significant differences in total inter-lobe connectivity between migraine groups and HC, both CM and MOH groups exhibited significantly decreased inter-limbic connectivity compared to HC and EM groups. In addition, they showed increased inter-frontal and inter-parietal connectivity, suggesting possible compensatory mechanisms to offset the loss of inter-lobe connectivity between the limbic and other lobes. Both CM and MOH groups exhibited a significant loss of global efficiency and a decrease in betweenness centrality in their brain networks, with MOH showing the most pronounced decrease and CM showing the second largest decrease. Our results suggest that aberrant structural brain networks in CM and MOH are less efficient, less centralization, and abnormally segregated.

The effect of inflammation markers on cortical thinning in major depressive disorder: A possible mediator of depression and cortical changes

BackgroundMajor depressive disorder (MDD) is a prevalent mental health condition with significant societal impact. Owing to the intricate biological diversity of MDD, treatment efficacy remains limited. Immune biomarkers have emerged as potential predictors of treatment response, underscoring the interaction between the immune system and the brain. This study investigated the relationship between cytokine levels and cortical thickness in patients with MDD, focusing on the corticolimbic circuit, to elucidate the influence of neuroinflammation on structural brain changes and contribute to a deeper understanding of the pathophysiology of MDD. MethodA total of 114 patients with MDD and 101 healthy controls (HC) matched for age, sex, and body mass index (BMI) were recruited. All participants were assessed for depression severity using the Hamilton Depression Rating Scale (HDRS), and 3.0 T T1 weighted brain MRI data were acquired. Additionally, cytokine levels were measured using a highly sensitive bead-based multiplex immunosorbent assay. ResultsPatients diagnosed with MDD exhibited notably elevated levels of interleukin-6 (p = 0.005) and interleukin-8 (p = 0.005), alongside significant cortical thinning in the left anterior cingulate gyrus and left superior frontal gyrus, with these findings maintaining significance even after applying Bonferroni correction. Furthermore, increased interleukin-6 and interleukin-8 levels in patients with MDD are associated with alterations in the left frontomarginal gyrus and right anterior cingulate cortex (ACC). ConclusionsThis suggests a potential influence of neuroinflammation on right ACC function in MDD patients, warranting longitudinal research to explore interleukin-6 and interleukin-8 mediated neurotoxicity in MDD vulnerability and brain morphology changes.

Diffusion weighted magnetic resonance spectroscopy revealed neuronal specific microstructural alterations in Alzheimer's disease.

In Alzheimer's disease, reconfiguration and deterioration of tissue microstructure occur before substantial degeneration become evident. We explored the diffusion properties of both water, a ubiquitous marker measured by diffusion MRI, and N-acetyl-aspartate, a neuronal metabolite probed by diffusion-weighted magnetic resonance spectroscopy, for investigating cortical microstructural changes downstream of Alzheimer's disease pathology. To this aim, 50 participants from the Swedish BioFINDER-2 study were scanned on both 7 and 3 T MRI systems. We found that in cognitively impaired participants with evidence of both abnormal amyloid-beta (CSF amyloid-beta42/40) and tau accumulation (tau-PET), the N-acetyl-aspartate diffusion rate was significantly lower than in cognitively unimpaired participants (P < 0.05). This supports the hypothesis that intraneuronal tau accumulation hinders diffusion in the neuronal cytosol. Conversely, water diffusivity was higher in cognitively impaired participants (P < 0.001) and was positively associated with the concentration of myo-inositol, a preferentially astrocytic metabolite (P < 0.001), suggesting that water diffusion is sensitive to alterations in the extracellular space and in glia. In conclusion, measuring the diffusion properties of both water and N-acetyl-aspartate provides rich information on the cortical microstructure in Alzheimer's disease, and can be used to develop new sensitive and specific markers to microstructural changes occurring during the disease course.

Diffusion MRI tracks cortical microstructural changes during the early stages of Alzheimer's disease.

There is increased interest in developing markers reflecting microstructural changes that could serve as outcome measures in clinical trials. This is especially important after unexpected results in trials evaluating disease-modifying therapies targeting amyloid-β (Aβ), where morphological metrics from MRI showed increased volume loss despite promising clinical treatment effects. In this study, changes over time in cortical mean diffusivity, derived using diffusion tensor imaging, were investigated in a large cohort (n = 424) of non-demented participants from the Swedish BioFINDER study. Participants were stratified following the Aβ/tau (AT) framework. The results revealed a widespread increase in mean diffusivity over time, including both temporal and parietal cortical regions, in Aβ-positive but still tau-negative individuals. These increases were steeper in Aβ-positive and tau-positive individuals and robust to the inclusion of cortical thickness in the model. A steeper increase in mean diffusivity was also associated with both changes over time in fluid markers reflecting astrocytic activity (i.e. plasma level of glial fibrillary acidic protein and CSF levels of YKL-40) and worsening of cognitive performance (all P < 0.01). By tracking cortical microstructural changes over time and possibly reflecting variations related to the astrocytic response, cortical mean diffusivity emerges as a promising marker for tracking treatments-induced microstructural changes in clinical trials.

Effect of Nano-curcumin versus Black Seed Oil on Renal Cortical Changes Induced by Aspartame in Adult Male Albino Rat. Histological and Immunohistochemical Study

Effect of Nano-curcumin versus Black Seed Oil on Renal Cortical Changes Induced by Aspartame in Adult Male Albino Rat. Histological and Immunohistochemical Study

Distinct age-related brain activity patterns in the prefrontal cortex when increasing cognitive load: A functional near-infrared spectroscopy study

Researchers have long observed distinct brain activity patterns in older adults compared with younger adults that correlate with cognitive performance. Mainly, older adults tend to show over-recruitment of bilateral brain regions during lower task loads and improved performance interpreted as compensation, but not observed at higher loads. However, there are discrepancies about whether increases in activity are compensatory and whether older adults can show compensation at higher loads. Our aim was to examine age-related differences in prefrontal cortex (PFC) activity and cognitive performance using functional near-infrared spectroscopy (fNIRS) during single and dual N-back tasks. Twenty-seven young adults (18–27 years) and 31 older adults (64–84 yrs) took part in the study. We used a robust fNIRS data methodology consisting of channel and region of interest analyses. Results showed differences in performance between task load conditions and age-related differences in reaction times but no age-group effects for accuracy. Older adults exhibited more bilateral PFC activation compared with young adults across all tasks and showed increases in brain activity in high compared to low load conditions. Our findings further support previous reports showing that older adults use compensatory recruitment of additional brain regions in PFC to maintain cognitive performance but go against the notion that such compensation is not present at higher cognitive loads. Additionally, our results indicate that fNIRS is a sensitive tool that can characterize adaptive cortical changes in healthy aging.

Feasibility of using fNIRS to explore motor-related regional haemodynamic signal changes in patients with sensorimotor impairment and healthy controls: A pilot study.

While functional near-infrared spectroscopy (fNIRS) can provide insight into cortical brain activity during motor tasks in healthy and diseased populations, the feasibility of using fNIRS to assess haemoglobin-evoked responses to reanimated upper limb motor function in patients with tetraplegia remains unknown. The primary objective of this pilot study is to determine the feasibility of using fNIRS to assess cortical signal intensity changes during upper limb motor tasks in individuals with surgically restored grip functions. The secondary objectives are: 1) to collect pilot data on individuals with tetraplegia to determine any trends in the cortical signal intensity changes as measured by fNIRS and 2) to compare cortical signal intensity changes in affected individuals versus age-appropriate healthy volunteers. Specifically, patients presented with tetraplegia, a type of paralysis resulting from a cervical spinal cord injury causing loss of movement and sensation in both lower and upper limbs. All patients have their grip functions restored by surgical tendon transfer, a procedure which constitutes a unique, focused stimulus for brain plasticity. fNIRS is used to assess changes in cortical signal intensity during the performance of two motor tasks (isometric elbow and thumb flexion). Six individuals with tetraplegia and six healthy controls participate in the study. A block paradigm is utilized to assess contralateral and ipsilateral haemodynamic responses in the premotor cortex (PMC) and primary motor cortex (M1). We assess the amplitude of the optical signal and spatial features during the paradigms. The accuracy of channel locations is maximized through 3D digitizations of channel locations and co-registering these locations to template atlas brains. A general linear model approach, with short-separation regression, is used to extract haemodynamic response functions at the individual and group levels. Peak oxyhaemoglobin (oxy-Hb) changes in PMC appear to be particularly bilateral in nature in the tetraplegia group during both pinch and elbow trials whereas for controls, a bilateral PMC response is not especially evident. In M1 / primary sensory cortex (S1), the oxy-Hb responses to the pinch task are mainly contralateral in both groups, while for the elbow flexion task, lateralization is not particularly clear. This pilot study shows that the experimental setup is feasible for assessing brain activation using fNIRS during volitional upper limb motor tasks in individuals with surgically restored grip functions. Cortical signal changes in brain regions associated with upper extremity sensorimotor processing appear to be larger and more bilateral in nature in the tetraplegia group than in the control group. The bilateral hemispheric response in the tetraplegia group may reflect a signature of adaptive brain plasticity mechanisms. Larger studies than this one are needed to confirm these findings and draw reliable conclusions.

Periodontitis causally affects the brain cortical structure: A Mendelian randomization study.

To estimate whether genetically proxied periodontitis causally impacts the brain cortical structure using Mendelian randomization (MR). Periodontitis is one of the most prevalent inflammatory conditions globally, and emerging evidence has indicated its influences on distal organs, including the brain, whose disorders are always accompanied by magnetic resonance imaging (MRI)-identified brain cortical changes. However, to date, no available evidence has revealed the association between periodontitis and brain cortical structures. The instrumental variables (IVs) were adopted from previous genome-wide association study (GWAS) studies and meta-analyses of GWAS studies of periodontitis from 1844 to 5266 cases and 8255 to 12 515 controls. IVs were linked to GWAS summary data of 51 665 patients from the ENIGMA Consortium, assessing the impacts of genetically proxied periodontitis on the surficial area (SA) or the cortical thickness (TH) of the global and 34 MRI-identified functional regions of the brain. Inverse-variance weighted was used as the primary estimate; the MR pleiotropy residual sum and outlier (MR-PRESSO), the MR-Egger intercept test, and leave-one-out analyses were used to examine the potential horizontal pleiotropy. Genetically proxied periodontitis affects the SA of the medial orbitofrontal cortex, the lateral orbitofrontal cortex, the inferior temporal cortex, the entorhinal cortex, and the temporal pole, as well as the TH of the entorhinal. No pleiotropy was detected. Periodontitis causally influences the brain cortical structures, implying the existence of a periodontal tissue-brain axis.