Biology subjects

Fernandes, H.

Publications and source records attributed to Fernandes, H..

9 recordsLinked to original sources

bioRxiv2025

Physical exercise and brain network dynamics: reduction of frontoparietal-striatal connectivity following 1 hour of aerobic cycling

Physical exercise is beneficial for metabolic health and cognitive performance. In addition, exercise can be highly pleasurable and and serves as an effective stress reliever. Extant studies have highlighted frontal, parietal, and subcortical brain changes following acute bouts of exercise. However, slower, slightly delayed brain correlates after exercise at the network level have not been studied. Therefore, this studys objective was to investigate the changes in dynamic functional connectivity after 60 minutes of exercise in healthy males. Here we measured a 6-minute resting state fMRI in 24 young males at baseline and after a 60-minute cycling exercise challenge. Apart from routine preprocessing, the data were denoised with FSL-FIX and modeled with i) leading eigenvector dynamics analysis (LEiDA) to probe whole brain network dynamics and ii) with group independent component analysis (ICA) and dual regression to quantify static brain connectivity. The within subject statistical tests compared baseline to post-exercise conditions. We found that a striato-fronto-parietal network is destabilized after exercise, as indicated by a lower probability of occurrence in dynamic analysis through LEiDA. The brain areas in the network include the bilateral caudate, putamen and pallidum as well as middle orbitofrontal, frontal operculum, frontal trigonum and inferior parietal cortices. No differences between baseline and post exercise conditions were found in the dual regression of the group ICA components. We conclude that 60 minutes of cycling causes a prolonged effect in brain network dynamics, reducing synchronization between the striatum and frontoparietal networks with respect to baseline. This provides insights into the network-level neural correlates of aerobic exercise, which may be directly linked with the stress relieving effects of physical exercise.

neuroscience↗

bioRxiv2023

Longitudinal conditional probability of symmetric DNA methylation in Arabidopsis plants

DNA replication in high eukaryotes requires the faithful transmission of both the sequence and its methylation status. DNA methyltransferases are not consistently reliable enzymes for accurately restoring methylation in newly synthesised DNA strands when working in isolation. In this study, we evaluated some of the factors that enhance the fidelity of DNA methyltransferases and measure their local and distant impacts on the neighbouring methylation status. A clear understanding of DNA methylation fidelity during replication is important for advances in epigenetic knowledge in general and the potential development of new diagnostics and therapies for epigenetic diseases. We used the Arabidopsis model system because it is moderately methylated, which is an important advantage over animal models since it reduces the chance of a fully-methylated symmetric methylation to virtually nil while providing sufficient occupancy to ensure reliable interpretations. In this study, we employed hairpin bisulfite and nanopore sequencing (1D and 1D2) to test the inter- and intra-strand relationships among the neighbouring 5-methylcytosines (5mC) and evaluate the distribution of hemimethylated sites, as well as the correlations to other cues such as DNA methylation and histone marks. We observed that the presence of a CpG methylation site can predict the occurrence of neighbouring CpG methylation sites, but not necessarily CWG sites, whereas CWG methylation can predict both neighbouring CWG and CpG methylation locations. These predictabilities extend far beyond the size of a nucleosome, and sites 4 kb away still show higher probabilities of methylation compared to the global average. Graphic abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=64 SRC="FIGDIR/small/573516v1_ufig1.gif" ALT="Figure 1"> View larger version (6K): org.highwire.dtl.DTLVardef@13b52fcorg.highwire.dtl.DTLVardef@1c544faorg.highwire.dtl.DTLVardef@338b6eorg.highwire.dtl.DTLVardef@71a41_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphic abstractC_FLOATNO Fidelity and longitudinal conditional methylation probability of CpG and CWG DNA methylation in Arabidopsis plants C_FIG

plant biology↗

bioRxiv2022

A potential marker for problematic mother-infant bonding revealed by magnetoencephalography study of first-time mothers listening to infant cries

Studies using magnetoencephalography (MEG) have identified the orbitofrontal cortex (OFC) to be an important early hub for a parental instinct in the brain. This complements the finding from functional magnetic resonance imaging (fMRI) studies linking reward, emotion regulation, empathy and mentalisation networks to the parental brain. Here, we used MEG in 43 first-time mothers listening to infant and adult cry vocalisations to investigate the link with mother-infant postpartum bonding scores and their level of sleep deprivation (assessed using both actigraphy and sleep logs). We found significant differences 800-1000ms after onset of infant compared to adult cries in source-reconstructed brain activity in areas previously linked to the parental brain. Importantly, mothers with weaker bonding scores showed decreased brain responses to infant cries in the auditory cortex, middle and superior temporal gyrus, OFC, hippocampal areas, supramarginal gyrus and inferior frontal gyrus at around 100-200ms after stimulus onset. In contrast, we did not find correlations with sleep deprivation scores. The significant changes in brain processing of an infants distress signals could be a novel marker of weaker infant bonding in new mothers and should be investigated in vulnerable populations.

neuroscience↗

bioRxiv2020

Deep brain stimulation modulates the dynamics of resting-state networks in patients with Parkinson's Disease

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is increasingly used for the treatment of Parkinsons Disease (PD), but despite its success, the neural mechanisms behind this surgical procedure remain partly unclear. As one working hypothesis, it was proposed that DBS works by restoring the balance of the brains resting-state networks (RSNs), which is reported to be disrupted in people with PD. Hence, to elucidate the effects that STN-DBS induces on disseminated networks, we analyzed an fMRI dataset of 20 PD patients at rest under DBS ON and OFF conditions. Moving beyond static functional connectivity studies, we employ a recently developed fMRI analysis tool, the Leading Eigenvector Dynamic Analysis (LEiDA), to characterize the recurrence of brain-wide phase-locking patterns overlapping with known RSNs. Here, STN-DBS seems to increase the Default Mode Network (DMN) occurrence in individuals with PD. Since the DMN is usually disturbed in PD patients presenting deficits in cognition, our observation might be suggestive that STN-DBS contributes to a normalization of the PD-induced cognitive impairment. Moreover, we addressed the effects of DBS lead placement on RSNs balance, considering the overlap between the DBS-induced electric field and 3 STN subsections. We found that the Visual Network (VN) probability of occurrence increased proportionally to the electric field-limbic STN overlap. Our finding might be indicative that stimulation of the limbic STN is related to the stabilization of visual symptoms sometimes presented by PD patients, which are usually accompanied by VN disruption. Overall, this study offers new insights into the fine-grained temporal dynamics of brain states portraying the effects of STN-DBS in patients with PD, while at the same time trying to pave the way to improved planning strategies for this surgical procedure.

neuroscience↗

bioRxiv2020

Beauty and the brain: Investigating the neural and musical attributes of beauty during a naturalistic music listening experience

Evaluative beauty judgments are very common, but in spite of this commonality, are rarely studied in cognitive neuroscience. Here we investigated the neural and musical attributes of musical beauty using a naturalistic free-listening paradigm applied to behavioral and neuroimaging recordings and validated by experts judgments. In Study 1, 30 Western healthy adult participants rated continuously the perceived beauty of three musical pieces using a motion sensor. This allowed us to identify the passages in the three musical pieces that were inter-subjectively judged as beautiful or ugly. This informed the analysis for Study 2, where additional 36 participants were recorded with functional magnetic resonance imaging (fMRI) while they listened attentively to the same musical pieces as in Study 1. In Study 3, in order to identify the musicological features characterizing the passages that were consistently rated as beautiful or ugly in Study 1, we collected post-hoc questionnaires from 12 music-composition experts. Results from Study 2 evidenced focal regional activity in the orbitofrontal brain structure when listening to beautiful passages of music, irrespectively of the subjective reactions and individual listening biographies. In turn, the moments in the music that were consistently rated as ugly were associated with bilateral supratemporal activity. Effective connectivity analysis also discovered inhibition of auditory activation and neural communication with orbitofrontal cortex, especially in the right hemisphere, during listening to beautiful musical passages as opposed to intrinsic activation of auditory cortices and decreased coupling to orbitofrontal cortex during listening to ugly musical passages. Experts questionnaires indicated that the beautiful passages were more melodic, calm, sad, slow, tonal, traditional and simple than the ones negatively valenced. In sum, we identified a neural mechanism for inter-subjective beauty judgments of music in the supratemporal-orbitofrontal circuit, irrespectively of individual taste and listening biography. Furthermore, some invariance in objective musical attributes of beautiful and ugly passages was evidenced. Future studies might address the generalizability of the findings to non-Western listeners.

neuroscience↗

bioRxiv2019

A map of transcriptional heterogeneity and regulatory variation in human microglia

Microglia, the tissue resident macrophages of the CNS, are implicated in a broad range of neurological pathologies, from acute brain injury to dementia. Here, we profiled gene expression variation in primary human microglia isolated from 141 patients undergoing neurosurgery. Using single cell and bulk RNA sequencing, we defined distinct cellular populations of acutely in vivo-activated microglia, and characterised a dramatic switch in microglial population composition in patients suffering from acute brain injury. We mapped expression quantitative trait loci (eQTLs) in human microglia and show that many disease-associated eQTLs in microglia replicate well in a human induced pluripotent stem cell (hIPSC) derived macrophage model system. Using ATAC-seq from 95 individuals in this hIPSC model we fine-map candidate causal variants at risk loci for Alzheimers disease, the most prevalent neurodegenerative condition in acute brain injury patients. Our study provides the first population-scale transcriptional map of a critically important cell for neurodegenerative disorders.

genomics↗

bioRxiv2019

Hue tuning curves in V4 change with visual context

Neurons are often probed by presenting a set of stimuli that vary along one dimension (e.g. color) and quantifying how this stimulus property affect neural activity. An open question, in particular where higher-level areas are involved, is how much tuning measured with one stimulus set reveals about tuning to a new set. Here we ask this question by estimating tuning to hue in macaque V4 from a set of natural scenes and a set of simple color stimuli. We found that hue tuning was strong in each dataset but was not correlated across the datasets, a finding expected if neurons have strong mixed selectivity. We also show how such mixed selectivity may be useful for transmitting information about multiple dimensions of the world. Our finding suggest that tuning in higher visual areas measured with simple stimuli may thus not generalize to naturalistic stimuli. New & NoteworthyVisual cortex is often investigated by mapping neural tuning to variables selected by the researcher such as color. How much does this approach tell us a neurons general role in vision? Here we show that for strongly hue-tuned neurons in V4, estimating hue tuning from artificial stimuli does not reveal the hue tuning in the context of natural scenes. We show how models of optimal information processing suggest that such mixed selectivity maximizes information transmission.

neuroscience↗

bioRxiv2019

Reduced structural connectivity in Insomnia Disorder

Insomnia Disorder is the most prevalent sleep disorder and it involves both sleep difficulties and daytime complaints. The neural underpinnings of Insomnia Disorder are poorly understood. Existing neuroimaging studies are limited by their focus on local measures and specific regions of interests. To address this shortcoming, we applied a data-driven approach to assess differences in whole-brain structural connectivity between adults with Insomnia Disorder and matched controls without sleep complaints. We used diffusion tensor imaging and probabilistic tractography to assess whole-brain structural connectivity and examined group differences using Network-Based Statistics. The results revealed a significant difference in the structural connectivity of the two groups. Participants with Insomnia Disorder showed reduced connectivity in a subnetwork that was largely left lateralized, including mainly fronto-subcortical connections with the insula as a key region. By taking a whole-brain network perspective, our study succeeds at integrating previous inconsistent findings, and our results reveal that reduced structural connectivity of the left insula and the connections between frontal and subcortical regions are central neurobiological features of Insomnia Disorder. The importance of these areas for interoception, emotional processing, stress responses and the generation of slow wave sleep may help guide the development of neurobiology-based models of the highly prevalent condition of Insomnia Disorder.

neuroscience↗

bioRxiv2017

Policies or Knowledge: Priors differ between perceptual and sensorimotor tasks

If the brain abstractly represents probability distributions as knowledge, then the modality of a decision, e.g. movement vs perception, should not matter. If on the other hand, learned representations are policies, they may be specific to the task where learning takes place. Here, we test this by asking if a learned spatial prior generalizes from a sensorimotor estimation task to a two-alternative-forced choice (2-Afc) perceptual comparison task. A model and simulation-based analysis revealed that while participants learn the experimentally-imposed prior distribution in the sensorimotor estimation task, measured priors are consistently broader than expected in the 2-Afc task. That the prior does not fully generalize suggests that sensorimotor priors strongly resemble policies. In disagreement with standard Bayesian thought, the modality of the decision has a strong influence on the implied prior distribution.\n\nNEW AND NOTEWORTHYWe do not know if the brain represents abstract and generalizable knowledge or task-specific policies that map internal states to actions. We find that learning in a sensorimotor task does not generalize strongly to a perceptual task, suggesting that humans learned policies and did not truly acquire knowledge. Priors differ across tasks, thus casting doubt on the central tenet of may Bayesian models, that the brains representation of the world is built on generalizable knowledge.

neuroscience↗