Biology subjects

Karolis, V.

Publications and source records attributed to Karolis, V..

8 recordsLinked to original sources

bioRxiv2026

Simultaneous EEG-fMRI investigation of sound sequence processing in human neonates

The ability to detect sensory regularities and their violations (i.e. deviance) is fundamental for learning and the orientation of attention across the lifespan. This starts from the prenatal period, where the environment is rich in regular patterns and deviations of auditory stimulation which likely provides the basis for the emergence of early learning capacities. Following birth, EEG recordings of brain activity have demonstrated that neonates detect violations of regularity and show a robust mismatch response to deviant auditory stimuli. However, it is unknown how this processing is integrated across wider regions within emergent brain networks. To gain comprehensive insight into both the temporal and spatial properties of the processing underlying sensory deviance detection in the neonatal brain, we acquired simultaneous EEG and fMRI data in sleeping neonates during an auditory oddball paradigm. A mismatch response was identified with EEG when a deviant sound appeared after a sequence of identical sounds but not when a sound was omitted, suggesting encoding of deviances that violated local sequence regularity, but not global sequence structure. Simultaneous fMRI demonstrated engagement of distributed cortical networks during sound sequence processing, encompassing temporal, sensori-motor, and inferior frontal cortices, as well as subcortical regions including the thalamus and hippocampus. Deviance detection was associated with activity in the superior and ventromedial (hippocampus and parahippocampus) parts of the temporal lobe, and the precentral gyrus. Together, these findings suggest that neonatal brain detects deviance in sound sequences through the encoding of local regularities, supported by distinct processing pathways within sensory and limbic systems. These insights help advance our understanding of early auditory learning mechanisms, with implications for understanding how atypical developmental trajectories may emerge in these substrates.

neuroscience↗

bioRxiv2023

Dynamic changes in subplate and cortical plate microstructure precede the onset of cortical folding in vivo

Cortical gyrification takes place predominantly during the second to third trimester, alongside other fundamental developmental processes, such as the development of white matter connections, lamination of the cortex and formation of neural circuits. The mechanistic biology that drives the formation cortical folding patterns remains an open question in neuroscience. In our previous work, we modelled the in utero diffusion signal to quantify the maturation of microstructure in transient fetal compartments, identifying patterns of change in diffusion metrics that reflect critical neurobiological transitions occurring in the second to third trimester. In this work, we apply the same modelling approach to explore whether microstructural maturation of these compartments is correlated with the process of gyrification. We quantify the relationship between sulcal depth and tissue anisotropy within the cortical plate (CP) and underlying subplate (SP), key transient fetal compartments often implicated in mechanistic hypotheses about the onset of gyrification. Using in utero high angular resolution multi-shell diffusion-weighted imaging (HARDI) from the Developing Human Connectome Project (dHCP), our analysis reveals that the anisotropic, tissue component of the diffusion signal in the SP and CP decreases immediately prior to the formation of sulcal pits in the fetal brain. By back-projecting a map of folded brain regions onto the unfolded brain, we find evidence for cytoarchitectural differences between gyral and sulcal areas in the late second trimester, suggesting that regional variation in the microstructure of transient fetal compartments precedes, and thus may have a mechanistic function, in the onset of cortical folding in the developing human brain.

neuroscience↗

bioRxiv2019

ADHD symptoms and their neurodevelopmental correlates in children born very preterm

This study investigated the association between attention-deficit/hyperactivity disorder (ADHD) symptomatology in preschool-aged children who were born very preterm (<32 weeks) and cognitive outcomes, clinical risk and socio-demographic characteristics. 119 very preterm children who participated in the Evaluation of Preterm Imaging Study at term-equivalent age were assessed at a mean age of 4.5 years. Parents completed the ADHD Rating Scale IV, a norm-referenced checklist that evaluates ADHD symptomatology according to diagnostic criteria, and the Behavior Rating Inventory of Executive Function-Preschool version. Children completed the Wechsler Preschool and Primary Scales of Intelligence and the Forward Digit Span task. Longitudinal data including perinatal clinical, qualitative MRI classification, socio-demographic variables and neurodevelopmental disabilities were investigated in relation to ADHD symptomatology. All results were corrected for multiple comparisons using false discovery rate. Results showed that although the proportion of very preterm children with clinically significant ADHD did not differ from normative data after excluding those with neurodevelopmental disabilities, 32.7% met criteria for subthreshold ADHD inattentive type and 33.6% for combined type, which was higher than the expected 20% in normative samples. Higher ADHD symptom scores (all) were associated with greater executive dysfunction (inhibitory self-control, flexibility, and emergent metacognition, corrected p<0.001 for all tests). Higher inattentive ADHD symptom scores were associated with lower IQ ({rho}=-0.241, p=0.036) and higher perinatal clinical risk (more days on mechanical ventilation ({rho}=0.206, p=0.025) and more days on parenteral nutrition ({rho}=0.223, p=0.015)). Higher hyperactive ADHD symptom scores instead were associated with lower socio-economic status ({rho}=0.278, p=0.002). These results highlight the importance of monitoring and supporting the development of very preterm children throughout the school years, as subthreshold ADHD symptoms represent risk factors for psychosocial problems and for receiving a future clinical diagnosis of ADHD.

neuroscience↗

bioRxiv2019

The developing Human Connectome Project (dHCP) automated resting-state functional processing framework for newborn infants.

The developing Human Connectome Project (dHCP) aims to create a detailed 4-dimensional connectome of early life spanning 20 to 45 weeks post-menstrual age. This is being achieved through the acquisition of multi-modal MRI data from over 1000 in- and ex-utero subjects combined with the development of optimised pre-processing pipelines. In this paper we present an automated and robust pipeline to minimally pre-process highly confounded neonatal resting-state fMRI data, robustly, with low failure rates and high quality-assurance. The pipeline has been designed to specifically address the challenges that neonatal data presents including low and variable contrast and high levels of head motion. We provide a detailed description and evaluation of the pipeline which includes integrated slice-to-volume motion correction and dynamic susceptibility distortion correction, a robust multimodal registration approach, bespoke ICA-based denoising, and an automated QC framework. We assess these components on a large cohort of dHCP subjects and demonstrate that processing refinements integrated into the pipeline provide substantial reduction in movement related distortions, resulting in significant improvements in SNR, and detection of high quality RSNs from neonates. HighlightsO_LIAn automated and robust pipeline to minimally pre-process highly confounded neonatal fMRI data C_LIO_LIIncludes integrated dynamic distortion and slice-to-volume motion correction C_LIO_LIA robust multimodal registration approach which includes custom neonatal templates C_LIO_LIIncorporates an automated and self-reporting QC framework to quantify data quality and identify issues for further inspection C_LIO_LIData analysis of 538 infants imaged at 26-45 weeks post-menstrual age C_LI

neuroscience↗

bioRxiv2019

Subcortical Anatomy of the Default Mode Network: a functional and structural connectivity study

Most existing research into the default-mode network (DMN) has taken a corticocentric approach. Despite the resemblance of the DMN with the unitary model of the limbic system, the anatomy and contribution of subcortical structures to the network may be underappreciated due to methods limitation. Here, we propose a new and more comprehensive neuroanatomical model of the DMN including the basal forebrain and anterior and mediodorsal thalamic nuclei and cholinergic nuclei. This has been achieved by considering functional territories during interindividual brain alignment. Additionally, tractography of diffusion-weighted imaging was employed to explore the structural connectivity of the DMN and revealed that the thalamus and basal forebrain had high importance in term of values of node degree and centrality in the network. The contribution of these neurochemically diverse brain nuclei reconciles previous neuroimaging with neuropathological findings in diseased brain and offers the potential for identifying a conserved homologue of the DMN in other mammalian species.

neuroscience↗

bioRxiv2018

Architecture of functional lateralisation in the human brain

Functional lateralisation is a fundamental principle of the human brain. However, a comprehensive taxonomy of functional lateralisation and its organisation in the brain is missing. We report the first complete map of functional hemispheric asymmetries in the human brain, reveal its low dimensional structure, and its relationship with structural inter-hemispheric connectivity. Our results suggest that the lateralisation of brain functions is distributed along four functional axes: symbolic communication, perception/action, emotion, and decision-making, and that cortical regions showing asymmetries in task-evoked activity have reduced connections with the opposite hemisphere.

neuroscience↗

bioRxiv2017

A Dimensional Approach To Assessing Psychiatric Risk In Adults Born Very Preterm

BackgroundIndividuals who were born very preterm have higher rates of psychiatric diagnoses compared to term-born controls; however, it remains unclear whether they also display increased sub-clinical psychiatric symptomatology. Hence our objective is to utilise a dimensional approach to assess psychiatric symptomatology in adults who were born very preterm.\n\nMethods152 adults who were born very preterm (before 33 weeks gestation; gestational range 24-32 weeks) and 96 term-born controls. We examined participants clinical profile using the Comprehensive Assessment of At-Risk Mental States (CAARMS), a measure of sub-clinical symptomatology that yields seven subscales including general psychopathology, positive, negative, cognitive, behavioural, motor and emotional symptoms, in addition to a total psychopathology score. Intellectual abilities were examined using the Wechsler Abbreviated Scale of Intelligence.\n\nResultsBetween-group differences on the CAARMS showed elevated symptomatology in very preterm participants compared to controls in positive, negative, cognitive and behavioural symptoms. Total psychopathology scores were significantly correlated with IQ in the very preterm group only. In order to examine the characteristics of participants clinical profile a principal component analysis was conducted. This revealed two components, one reflecting a non-specific psychopathology dimension, and the other indicating a variance in symptomatology along a positive-to-negative symptom axis. K-means (k=4) were used to further separate the study sample into clusters. Very preterm adults were more likely to belong to the high non-specific psychopathology cluster compared to controls.\n\nConclusion and RelevanceVery preterm individuals demonstrated elevated psychopathology compared to full-term controls. Psychiatric risk was characterised by a non-specific clinical profile and was associated with lower IQ.

developmental biology↗

bioRxiv2017

The Effect Of Perinatal Brain Injury On Dopaminergic Function And Hippocampal Volume In Adult Life

BackgroundVery preterm birth (<32 weeks of gestation) is associated with long-lasting brain alterations and an increased risk of psychiatric disorders associated with dopaminergic abnormalities. Preclinical studies have shown perinatal brain injuries, including hippocampal lesions, cause lasting changes in dopamine function, but it is not known if this occurs in humans. The purpose of this study was to determine whether very preterm birth and perinatal brain injury were associated with altered dopamine synthesis and reduced hippocampal volume in humans in adulthood.\n\nMethodsWe compared adults who were born very preterm with associated perinatal brain injury to adults born very preterm without perinatal brain injury, and age-matched controls born at full term using [18F]-DOPA PET and structural MRI imaging.\n\nResultsDopamine synthesis capacity was significantly reduced in the perinatal brain injury group relative to both the group born very preterm without brain injury (Cohens d=1.36, p=0.02) and the control group (Cohens d=1.07, p=0.01). Hippocampal volume was reduced in the perinatal brain injury group relative to controls (Cohens d = 1.17, p = 0.01). There was a significant correlation between hippocampal volume and striatal dopamine synthesis capacity (r = 0.344, p= 0.03).\n\nConclusionsPerinatal brain injury, but not very preterm birth without macroscopic brain injury, is associated with persistent alterations in dopaminergic function and reductions in hippocampal volume. This is the first evidence in humans linking neonatal hippocampal injury to adult dopamine dysfunction, and has implications for understanding the mechanism underlying cognitive impairments and neuropsychiatric disorders following very preterm birth.

neuroscience↗