PRISM :: Browsing by Author "Bray, Signe"

Browsing by Author "Bray, Signe"

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Open Access
Advancing the Study of Functional Connectome Development
(2023-08) Graff, Kirk; Bray, Signe; Goodyear, Brad; Lebel, Catherine
A better understanding of functional changes in the brain across childhood offers the potential to better support neurodevelopmental and learning challenges. However, neuroimaging tools such as functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are vulnerable to head motion and other artifacts, and studies have had limited reproducibility. To accomplish research goals, we need to understand the reliability and validity of data collection, processing, and analysis strategies. Neuroimaging datasets contain individually unique information, but identifiability is reduced by noise or lack of signal, suggesting it can be a measure of validity. The goal of this thesis was to use identifiability to benchmark different methodologies, and describe how identifiability associates with age across early childhood. I first compared several different fMRI preprocessing pipelines for data collected from young children. Preprocessing techniques are often controversial due to specific drawbacks and have typically been assessed with adult datasets, which have much less head motion. I found benefits to the use of global signal regression and temporal censoring, but overly strict censoring can impact identifiability, suggesting noise removed must be balanced against signal retained. I also compared several different EEG measures of functional connectivity (FC). EEG can be vulnerable to volume conduction artifacts that can be mitigated by only considering shared information with a time delay between signals. However, I found that mitigation strategies result in lower identifiability, suggesting that while removing confounding noise they also discard substantial signal of interest. Individual experiences may shape development in an individually unique way, which is supported by evidence that adults have more individually identifiable patterns of FC than children. I found that across 4 to 8 years of age, identifiability increased via increased self-stability, but without changes in similarity-to-others. In the absence of ground truth, it is difficult to argue for or against analysis decisions based solely on a theoretical framework and need to also be validated. My work highlights the importance of not thinking about techniques in a valid-invalid dichotomy; certain methods may be sub-optimal while still being preferable to alternatives if they better manage the trade off between noise removed and signal retained.
Open Access
Age and Task Related Changes in Neural Complexity
(2016) Hart, Jessie Marie; Protzner, Andrea; Sears, Christopher; Bray, Signe
Recent work suggests brain signal variability tracks maturational changes in information processing capacity. Evidence also suggests variability changes with task demands. Here, we investigate whether there is an interaction between age and task related changes in brain signal variability measured with electroencephalography (EEG). We looked at brain signal variability changes during different epochs within trial (i.e., before to after stimulus onset, and after response) and with task difficulty, in children (age 8-14) and adults (age 18-33). In the epochs within trial analysis, we found similar changes pre- to post-stimulus onset in both age groups, but a later return to baseline in children then adults. In the task difficulty analysis, variability changed with difficulty conditions only in children. Our data suggest that age-related differences in variability changes with task reflect differences in the cognitive processing performed by children and adults during task performance.
Open Access
Alteration in, and recovery of, cerebral activation during a working memory task following pediatric mild traumatic brain injury
(2018-01-12) Khetani, Aneesh; Barlow, Karen; Bray, Signe; Yeates, Keith; Lebel, Catherine
Introduction: Mild traumatic brain injuries (mTBIs) are most common in children and adolescents. For some, symptoms can persist for an extended duration, especially in the cognitive and working memory domains. The neurological changes that underlie these differences in children with persistent symptoms, and their recovery over time, have not been characterized at distinct time points. Objectives: To determine how cortical activation during a working memory task is different in children with persistent symptoms, relative to control and asymptomatic children, and to observe how that changes with time. Methods: This was a prospective, controlled cohort study of pediatric mTBI at approximately one- and two- months post-injury. Symptom status was determined by the post-concussion symptom inventory (PCSI). A visuospatial n-back working memory task was designed for use with functional magnetic resonance imaging (fMRI). The primary outcome measures were the blood oxygen level dependent (BOLD) signal and n-back working memory task performance. Results: 107 participants (60 symptomatic mTBI, 30 asymptomatic mTBI and 17 controls) were compared approximately one month following mTBI. Mean age was 14.2 years (SD 2.5) and 44% were male. During the n-back task, at approximately one month post-injury, symptomatic mTBI children had decreased activation in the posterior cingulate and precuneus regions compared to asymptomatic children, with no difference in performance. By approximately two months post-injury, we found that symptomatic children had less working memory related cortical activation compared to their own one month post-injury scan, and an improvement in task performance (n=45). Conclusions: Symptomatic mTBI children have cortical activation differences compared to asymptomatic children. Over time, there is a decrease in working memory functional activation within that symptomatic group. Our findings highlight the neurobiological consequences of pediatric mTBI on working memory cortical activation and recovery.
Open Access
An Investigation of Sleep and Physical Activity in Young Adults with Autism Spectrum Disorder and the Effects of a Physical Activity Intervention
(2017) Benson, Sarah; Werthner, Penny; Clarke, Margaret; Millet, Guillaume; Bray, Signe; Charles, Samuels
Background: Physical inactivity, motor coordination difficulties, and sleep problems are often present in autism spectrum disorder (ASD). Sleep problems seem to persist into young adulthood. Physical activity (PA) may positively impact both sleep and daytime behaviour. Objectives: The first part of the study investigated sleep, sleepiness, and PA in 15 young adults (age 18-35 years old) with ASD compared to typically developing controls (TDC). The second part of the study investigated the effects of a 15-week PA intervention on PA levels, gross motor proficiency, daytime functioning, and sleep in 12 of the young adults with ASD. Methods: Young adults with an autism diagnosis (inclusive of all levels of functioning) and TDC wore a wrist-worn actigraph to gather objective PA and sleep data. Questionnaires on sleep, sleepiness, and PA were completed through participant or parent-report. Further, the ASD sample completed a daytime functioning measure, gross motor proficiency, and autism symptom severity assessment. Results: The ASD group had more sleep duration but took longer to fall asleep than TDC. Objective PA levels were lower in the ASD sample, but those with more PA had increased sleepiness and earlier bedtimes and wake times. Fewer wake minutes during the sleep period in the ASD group were associated with more PA the following day. Results included an autism symptom severity by time interaction effect for objective PA, an improvement in subjective sleep quality, a reduction in behaviour problems - specifically Attention Deficit/Hyperactivity (AD/H) problems - and an improvement in physical strength. Correlations were found between objective PA and bilateral coordination, AD/H, and antisocial personality problems. Conclusion: Our findings support previous research that demonstrates differences in sleep parameters and PA between ASD and TDC. Interventions aimed at increasing PA in ASD may be beneficial for sleep and more PA the following day. These findings indicate the potential benefit of group-based PA interventions on PA level, gross motor proficiency, daytime functioning, and sleep in young adults with ASD.
Open Access
Brain connectomes in youth at risk for serious mental illness: an exploratory analysis
(2022-09-15) Metzak, Paul D.; Shakeel, Mohammed K.; Long, Xiangyu; Lasby, Mike; Souza, Roberto; Bray, Signe; Goldstein, Benjamin I.; MacQueen, Glenda; Wang, JianLi; Kennedy, Sidney H.; Addington, Jean; Lebel, Catherine
Abstract Background Identifying early biomarkers of serious mental illness (SMI)—such as changes in brain structure and function—can aid in early diagnosis and treatment. Whole brain structural and functional connectomes were investigated in youth at risk for SMI. Methods Participants were classified as healthy controls (HC; n = 33), familial risk for serious mental illness (stage 0; n = 31), mild symptoms (stage 1a; n = 37), attenuated syndromes (stage 1b; n = 61), or discrete disorder (transition; n = 9) based on clinical assessments. Imaging data was collected from two sites. Graph-theory based analysis was performed on the connectivity matrix constructed from whole-brain white matter fibers derived from constrained spherical deconvolution of the diffusion tensor imaging (DTI) scans, and from the correlations between brain regions measured with resting state functional magnetic resonance imaging (fMRI) data. Results Linear mixed effects analysis and analysis of covariance revealed no significant differences between groups in global or nodal metrics after correction for multiple comparisons. A follow up machine learning analysis broadly supported the findings. Several non-overlapping frontal and temporal network differences were identified in the structural and functional connectomes before corrections. Conclusions Results suggest significant brain connectome changes in youth at transdiagnostic risk may not be evident before illness onset.
Open Access
Contributions of Affective States and Traits to Autistic Features
(2024-04) Godfrey, Kate J.; Bray, Signe; Harris, Ashley D.; McMorris, Carly; Protzner, Andrea
This thesis considered the role of affect and reward in autistic features, based on the important role affective brain systems play in emotion and motivated behaviors known to be impacted in autistic individuals. I directly tested multiple affect-based hypotheses in children with and without an autism diagnosis and aimed to inform future clinical work by exploring several methodologies for examining both inter-individual (trait) and intra-individual (state) variation in measures of affect and reward. I first examined multiple behavioral domains (reward sensitivity, anxiety symptoms, and executive function) for associations with interest intensity in early childhood autism. I report that the executive functioning domain of attention shifting associated with interest intensity in early childhood, while there was no relation with general sensitivity to reward and anxiety symptoms. I then considered how to better characterize inter-individuality in reward sensitivity during early childhood, specifically regarding social rewards. I therefore developed and validated the Social Reward Questionnaire–Early Childhood (SRQ-EC) to quantify wanting and liking of distinctly rewarding social situations in young children. I found that autistic-like traits in a community sample associated with reduced wanting and liking of social rewards, particularly for large group interactions, suggesting potential utility of the SRQ-EC for future autism research. I additionally considered a protocol for investigating brain functional connectivity for associations with intra-individual affect variation in a community sample of adults, with relevance for designing future studies to examine neurobiological mechanisms of affective disorders that commonly co-occur in autism. My work replicates recent findings that variance in functional connectivity is largely attributable to individual identity, and that variance attributable to intra-individual affect variation is 7–100x smaller than what can be attributed to viewing condition. This thesis advances methodologies for measuring and modeling both inter- and intra-individual variation in autism, specifically in relation to affective processes which are difficult to measure in a laboratory setting. The methods presented and refined here could be used in future work to better understand state- and trait-like features in autism.
Open Access
Decreasing Brain Functional Network Segregation with Healthy Aging
(2023-03-20) Singh Sidhu, Abhijot; Frayne, Richard; Goodyear, Bradley; Bray, Signe; McCreary, Cheryl
The functional architecture of the human brain consists of distinct sensory and associative functional networks that interact as needed. Resting-state functional magnetic resonance imaging (rs-fMRI) has shown that functional connections (connectivity) between networks strengthen with age, suggesting that networks reconfigure in healthy aging by becoming less segregated. Few studies, however, have replicated these findings or investigated sex differences in network organization, and no studies have thoroughly investigated if age-related differences involve certain networks more than others. It is crucial to better understand healthy age-related brain changes as it provides a foundation to better address and investigate age-related diseases like dementia or Alzheimer’s disease. In this thesis, cross-sectional functional and structural MR data from 231 presumed healthy adult participants (~59% self-reported as female, aged 18-91 y) from the Calgary Normative Study were examined to investigate the hypotheses that (1) whole-brain and network segregation decreases with age due to decreasing within-network and increasing between-network connectivity, and (2) age-associated increases in between-network functional connectivity occur in associative network connections. Structural and functional MR data were parcellated into seven known functional networks, and average within- and between-network connectivity were computed as the z-transformed Pearson cross-correlation coefficients (zw and zb, respectively). Whole-brain and network segregation were then computed using the segregation index, SI = (|zw|-|zb|)/(|zw|). All networks exhibited decreasing segregation with age, because of increasing between-network connectivity; however, within-network connectivity did not change with age. Further, between-network connectivity increased with age in sensory-to-associative and associative-to-associative network connections, as hypothesized. Increased connectivity between associative networks was also observed in males, regardless of age. This thesis demonstrates that functional networks reconfigure with age because of increased connectivity in sensory-to-associative and associative-to-associative network connections. This may constitute compensatory and/or de-differentiation processes as humans age. The findings of this thesis also provide a foundation for better interpretation of changes in brain function that occur in age-related diseases.
Open Access
Effect of Scrabble© Expertise on Brain Ageing as Measured with Brain Signal Variability and Event-Related Potentials
(2016) Wang, Hongye; Protzner, Andrea; Bray, Signe; Pexman, Penny
We examined the effect of Scrabble expertise on brain ageing using brain signal variability as measured with multiscale entropy (MSE) and brain signal mean as measured with event-related potentials (ERP). We collected ERP data while age-matched Scrabble experts and controls (age range: 24 to 83) performed an expertise-related task (lexical decision task; LDT) and a non-expertise-related task (symbol decision task; SDT). During both tasks, fine-scale MSE increased with age for both groups, suggesting that short-range neural communication increases with age. Midscale MSE increased with age for experts but decreased for controls, suggesting that longer-range neural communication is maintained through older age for experts but not for controls. In addition, experts did not show the typical age-related decrease in frontal P300 amplitude. However, all age-related effects, regardless of direction, were associated with worse performance in both groups. This study provides a better understanding of how expertise affects brain ageing.
Open Access
Efficacy of Connectivity-Based Targeting in TMS for Adolescents with Treatment-Resistant Depression
(2021-04-29) Tapia Palacio, Clara; MacMaster, Frank; Bray, Signe; Rittenbach, Katherine; Kopala-Sibley, Daniel
Background. Thirteen percent of 12- to 17-year-old adolescents suffer from depression, but only half respond to antidepressants and psychotherapy. Recent studies have successfully employed repetitive Transcranial Magnetic Stimulation (rTMS) to treat depression. However, there is a need to precisely determine the rTMS site of stimulation. A recent study in adults with depression (Fox et al., 2012) proposes that using the connectivity between the dorsolateral prefrontal cortex (DLPFC) and subgenual cingulate to define the site of stimulation for rTMS results in increased clinical efficacy. To date, no studies have investigated this phenomenon in the pediatric population. Methodology. Functional magnetic resonance imaging (fMRI) scans of 37 adolescents with treatment-resistant depression (TRD) and 18 controls were analysed. TRD individuals underwent 15 consecutive rTMS sessions and were assessed for depression before and after treatment by the Hamilton Depression Rating Scale (Ham-D). We calculated the DLPFC-Subgenual connectivity for the seven different rTMS targeting approaches described in Fox et al. (2012). Then, we measured the DLPFC-Subgenual connectivity from the individual stimulation sites and explored any correlation with clinical efficacy. Results. Contrary to Fox et al. (2012), four and three targeting approaches presented a positive correlation for the TRD and control groups respectively. Moreover, more positive values of DLPFC-Subgenual connectivity were significantly associated with a higher decrease in Ham-D scores (p = 0.025, one-tailed). Limitations. We used coordinates for the targeting approaches and subgenual cingulate that had been originally defined in adults. Furthermore, small changes in the noise reduction procedure causes great divergence in the outcomes. Conclusions. Since adolescents showed a distinctive and stronger functional connectivity between DLPFC and the subgenual cingulate, depression treatments have to be directly adjusted to pediatric population. Additionally, higher DLPFC-Subgenual positive connectivity predicted a higher clinical efficacy. This suggests that future work should consider defining the stimulation site at the DLPFC location with the strongest positive connectivity with the subgenual cingulate. However, the novelty of this research and the differences in outcomes with the literature in adult population indicates that reanalysing this association is necessary.
Open Access
Electrophysiological Correlates of Naturally Occurring Thought Patterns
(2024-01-24) Park, YeEun; Kam, Julia; Bray, Signe; Iaria, Giuseppe; Protzner, Andrea
Humans engage in a continuous flow of thoughts throughout the day. These thoughts change depending on the context in which they occur and correspond with unique patterns of connectivity within and between neural networks. Notably, less is known about the electrophysiological signatures of these thought patterns. To address this question, this study examined the interplay between thought patterns and electrophysiological activity in internally and externally oriented contexts. Forty-one participants were asked to attend internally to their own thoughts (thought focus condition) and externally to a set of videos (video focus condition), during which they were asked to report various dimensions of their ongoing thoughts. We implemented principal component analysis on the ratings of these multiple thought dimensions and identified three thought patterns (representing co-occurring thought dimensions): present external thought, goal-oriented future thoughts, and freely moving external positive thoughts. We found that these three thought patterns differentially associated with the experimental conditions and EEG measures. Present external thought was more closely associated with the video focus condition and showed increased frontal alpha and posterior alpha. Goal-oriented future thoughts increased during the thought versus video focus condition but was not significantly linked to any EEG measures. Freely moving external positive thoughts were more strongly associated with the video focus condition and showed decreased frontal alpha activity. Taken together, our results highlight the complex relationship between thought patterns and electrophysiological activity in different contexts.
Open Access
Evoked Responses to Affective Stimuli as a Marker for Reward System Dysfunction in Adolescents with Autism Spectrum Disorder (ASD)
(2017) Rivard, Keelin; Bray, Signe; Protzner, Andrea; Curtin, Suzanne; Graham, Susan; Monchi, Oury
The core symptoms of autism spectrum disorder (ASD) may be related to atypical engagement of the brain’s reward system. We investigated whether visual reinforcers, images depicting restricted interests, are processed abnormally in ASD, as a marker for reward system dysfunction. We collected electroencephalography (EEG) while 20 ASD and 20 typically developing (TD) control participants, aged 14-20, performed a visual target detection task. We evaluated differences in the late positive potential (LPP), a marker for emotional processing, as well as trial-to-trial variability in the visual P1 response, which may indicate ‘noisier’ processing of visual reinforcers. We found greater LPP amplitude for high- and low-interest images, relative to neutral, with no significant group difference. In contrast, for the P1, we found overall greater amplitude and amplitude-variability in the ASD group that did not differentiate between conditions. This study provides new insight into processing of visual reinforcers in ASD.
Open Access
Exploring Region-Specific Changes in Brain Glutamate and Gamma-Aminobutyric Acid (GABA) Across the Migraine Cycle in Children and Adolescents
(2023-06) Cho, Lydia Youngju; Harris, Ashley; Orr, Serena; Bray, Signe; Jacobs-Levan, Julia
Migraine is a neurological disorder with multiple phases (i.e., migraine cycle). There is evidence that migraine is associated with excitation-inhibition imbalances and dysregulation of glutamate and gamma-aminobutyric acid (GABA), the primary excitatory and inhibitory neurochemicals, respectively. Magnetic resonance spectroscopy (MRS) is a non-invasive imaging method to quantify brain levels of glutamate and GABA. It has been proposed progressing through the migraine cycle is also related to changes in excitation and inhibition. Few studies have measured glutamate and GABA in adults with migraine, and migraine studies in the pediatric population specifically focusing on glutamate and GABA are very scarce. In this study, children and adolescents with migraine were recruited to have four MRS scans over two weeks to quantify levels of glutamate and GABA in the sensorimotor cortex, thalamus, and occipital cortex. Two approaches were used to determine glutamate and GABA changes across the migraine cycle: (1) binning by migraine cycle phases and (2) time as a continuous metric leading up to or following headache. Analysis of migraine cycle phases showed occipital cortex glutamate was higher in the headache phase and thalamic glutamate was higher in the postdrome phase, both compared to the interictal phase. When using a continuous time metric, glutamate significantly decreased following the onset of the headache phase in the occipital cortex and thalamus, and sensorimotor GABA significantly increased leading up to the headache. I propose that these changes reflect increased excitation in the occipital cortex and thalamus and increased inhibition in the sensorimotor cortex during the migraine attack which may be evidence of thalamocortical dysrhythmia underlying migraine pathophysiology. This study provides insight into the underlying biology of migraine in children and adolescents, and if replicated, may help inform development of future treatments and interventions.
Open Access
Limited somatosensory functional connectivity differences in youth with ASD, at rest
(2017) Cechmanek, Brian; Bray, Signe; Lebel, Catherine; Dunn, Jeff; McCrimmon, Adam; Barlow, Karen; Curtin, Suzanne
Children and adolescents with autism spectrum disorder typically experience sensory sensitivities, involving over- and/or under-reactions to sensory stimuli. Tactile hyper-reactivity, in particular, is implicated in negative outcomes such as aversion to oral hygiene, dietary issues, and self-harm. Presently, there is no established overarching neurological basis for these sensitivities in autism. Understanding the underlying causes of these sensitivities may help guide pharmacological and behavioural interventions. Motivated by suggested linkages between over-connectivity measures and negative outcomes in ASD, this thesis used resting-state functional-MRI to examine somatosensory functional connectivity differences in youth with autism. Connectivity differences, arising in the somatosensory region, may represent a good marker of sensory sensitivities in ASD. Our findings show limited functional connectivity differences in ASD, and scarce changes in age by diagnosis interaction or autism symptom severity. This suggests that functional connectivity of the somatosensory network in youth with autism is not disrupted, at rest, compared to neurotypical controls.
Open Access
Mapping developmental motor plasticity in children with perinatal stroke using functional magnetic resonance imaging
(2017) Baker, Kayla; Kirton, Adam; Pike, Bruce; Bray, Signe; Monchi, Oury
Perinatal stroke results in lifelong unilateral motor impairment. Periventricular venous infarct (PVI) is a subcortical injury sustained in utero whereas arterial ischemic stroke (AIS) occurs near term birth and often damages the primary motor cortex (M1). Both disease-states result in the maladaptive emergence of aberrant ipsilateral (M1’) connections. Task-based functional magnetic resonance imaging defined patterns of motor cortex activity during unilateral tapping of the paretic and non-paretic hand. Peak bilateral coordinates of M1 and M1’ were compared to controls. AIS cases displayed the greatest extent of M1 displacement in the lesioned hemisphere, but M1 displacement in PVI cases approximated controls. For stroke cases with bilateral control of their paretic hand, M1’ responses in the intact hemisphere were displaced from the canonical hand knob. We conclude that extensive motor reorganization occurs bilaterally following perinatal stroke. Targeting individualized M1 and M1’ displacements may facilitate opportunities for precision medicine in pediatric neurorehabilitation.
Open Access
Modular Development of Gray Matter in Childhood and Adolescence
(2015-07-13) Krongold, Mark; Bray, Signe
The brain is becoming increasingly understood by its networks rather than regional architecture. Understanding the development of networks in the healthy human brain during childhood and adolescence is an important foundational step in determining what may go wrong in neurodevelopmental disorders. Moreover, it has been hypothesized that networks of functionally coupled regions may develop in parallel. In this thesis regions of the cerebral cortex undergoing synchronized development in anatomical structure were found and described. The findings indicated that cortical thickness, surface area, and volume underwent different developmental trajectories and showed differential synchronized developmental patterns. Cortical thickness based modules were distributed while surface area and volume based modules showed anterior to posterior organization. Additionally, comparisons between developmental modules and well-established functional networks in the brain found only partial overlap. This suggests that neuronal networks do not singularly arise from similar development of cortical regions.
Open Access
Pre-reading language abilities and the brain's functional reading network in young children
(Elsevier, 2020-08-15) Benischek, Alina; Long, Xiangyu; Rohr, Christiane S; Bray, Signe; Dewey, Deborah; Lebel, Catherine
Early childhood is an important period for language development that lays the foundation for future reading abilities. However, little research has focused on the functional brain systems supporting pre-reading language abilities in typically developing children. Here, we investigated functional connectivity using passive viewing functional magnetic resonance imaging (fMRI) in 50 healthy children aged 2.85-5.07 years (3.84 ± 0.60 years, 22 female/28 male). Children completed the NEPSY-II Phonological Processing and Speeded Naming subtests and underwent fMRI while watching a movie of their choice. Functional connectivity was measured between key brain reading areas (bilateral angular gyrus, superior temporal gyrus, and inferior frontal gyrus) and the rest of the brain. Age-adjusted pre-reading scores positively correlated with functional connectivity between (1) the right angular gyrus and superior temporal gyrus, (2) the bilateral angular gyri and right pars triangularis and motor areas, (3) the left superior temporal gyrus and bilateral medial frontal gyrus and right cerebellum, (4) the left pars triangularis and middle occipital gyrus and insula, and (5) the right pars triangularis and the bilateral thalamus. Higher pre-reading scores were associated with stronger negative functional connectivity between (1) the left angular gyrus and auditory cortex, (2) the left superior temporal gyrus and occipital vision areas, (3) the right pars triangularis and medial frontal region, and (4) the right superior temporal gyrus and the posterior cingulate/precuneus. These results suggest better integration of the reading network, as well as its connections with other brain areas that support language or reading, and more dissociation between reading areas and the default mode network, in young children with better pre-reading skills. Our findings show that relationships between functional connectivity and pre-reading language skills are evident in young children even before formal reading instruction.
Open Access
Studying Network Variants With Electroencephalography
(2024-02-15) McCarthy, Michael; Protzner, Andrea; Bray, Signe; Goodyear, Bradley; Pexman, Penny
Functional MRI (fMRI) studies have shown that the human functional connectome exhibits reliable and substantial variability in organization across individuals, so-called network variants. However, it is unclear whether neuroimaging modalities that measure different aspects of brain function show similar evidence of such individual differences. Here we explored the feasibility of using electroencephalography (EEG) to study network variants using repeated measures eyes-closed and eyes-open resting state data from 14 participants taken across three sessions over the course of three months—estimating how much and in which ways band-limited phase coupling and amplitude coupling functional connectomes differed in similarity within and between individuals across contexts. For each coupling mode and frequency band, we hypothesized that if functional connectome organization was influenced by stable individual- dependent factors in our sample, then functional connectomes would be more similar within than between individuals across all contexts, on average, with smaller variations in similarity related to session or state. Overall, our results were inconclusive. Although we generally found consistently positive differences in functional connectome similarity across coupling modes, frequency bands, and contexts on average—depending on the comparison, these differences were either negligible or at most small, and were inconsistent across participants. We discuss several factors that may explain the differences between our results and the larger, more consistent effects reported in fMRI network variant studies, such as the spatial and temporal resolution of EEG and fMRI, and the methods used to estimate functional connectivity. We then offer suggestions for future EEG research that might address some shortcomings of our study.
Open Access
Tactile cortical responses and association with tactile reactivity in young children on the autism spectrum
(2021-04-01) Espenhahn, Svenja; Godfrey, Kate J; Kaur, Sakshi; Ross, Maia; Nath, Niloy; Dmitrieva, Olesya; McMorris, Carly; Cortese, Filomeno; Wright, Charlene; Murias, Kara; Dewey, Deborah; Protzner, Andrea B; McCrimmon, Adam; Bray, Signe; Harris, Ashley D
Abstract Background Unusual behavioral reactions to sensory stimuli are frequently reported in individuals on the autism spectrum (AS). Despite the early emergence of sensory features (< age 3) and their potential impact on development and quality of life, little is known about the neural mechanisms underlying sensory reactivity in early childhood autism. Methods Here, we used electroencephalography (EEG) to investigate tactile cortical processing in young children aged 3–6 years with autism and in neurotypical (NT) children. Scalp EEG was recorded from 33 children with autism, including those with low cognitive and/or verbal abilities, and 45 age- and sex-matched NT children during passive tactile fingertip stimulation. We compared properties of early and later somatosensory-evoked potentials (SEPs) and their adaptation with repetitive stimulation between autistic and NT children and assessed whether these neural measures are linked to “real-world” parent-reported tactile reactivity. Results As expected, we found elevated tactile reactivity in children on the autism spectrum. Our findings indicated no differences in amplitude or latency of early and mid-latency somatosensory-evoked potentials (P50, N80, P100), nor adaptation between autistic and NT children. However, latency of later processing of tactile information (N140) was shorter in young children with autism compared to NT children, suggesting faster processing speed in young autistic children. Further, correlational analyses and exploratory analyses using tactile reactivity as a grouping variable found that enhanced early neural responses were associated with greater tactile reactivity in autism. Limitations The relatively small sample size and the inclusion of a broad range of autistic children (e.g., with low cognitive and/or verbal abilities) may have limited our power to detect subtle group differences and associations. Hence, replications are needed to verify these results. Conclusions Our findings suggest that electrophysiological somatosensory cortex processing measures may be indices of “real-world” tactile reactivity in early childhood autism. Together, these findings advance our understanding of the neurophysiological mechanisms underlying tactile reactivity in early childhood autism and, in the clinical context, may have therapeutic implications.
Open Access
The Critical Brain Hypothesis in Different Physiological Settings
(2024-01) Curic, Davor; Davidsen, Joern; Beggs, John; Bray, Signe; Orlandi, Javier; Nicola, Wilten
Observations of neural activity across scales and species have often been found to display diverging correlations and scale-free collective dynamics in the form of information cascades, also called ‘neuronal avalanches’. These findings have motivated the critical brain hypothesis which posits that brain dynamics are self-tuned (e.g., perhaps via excitation-inhibition balance) to a second-order phase transition (or critical point), that separates exponentially-growing dynamics from quiescent states, to achieve optimality. At criticality, the physics of phase transitions predict various scale-free quantities and macroscopic observables that depend only on a few properties, such as network symmetries and neurons dynamics, but not on the exact connectivity between neurons. The ubiquity of signatures of criticality suggest this critical state could be related to ‘normal’ brain function. However, this relationship is not yet fully understood, and most of what is known is only in the context of spontaneous or resting-state brain dynamics. This thesis explores how different physiological states of the subject affect signatures of criticality. It is shown that measures of criticality are susceptible to the natural heterogeneity between neurons in the response to a stimulus. This can skew observed statistics and could potentially explain current difficulties in establishing criticality in behaviour. It is also found that signatures of cortical desynchronization associated with the rapid eye movement state of sleep, spread across the cortical surface in a scale-free manner. This feature is absent if spatial information is excluded, emphasizing the importance of considering spatial connectivity when addressing questions of criticality. Finally, it is shown that while low-dose anesthetics do not significantly alter the critical state, surgical-plane anesthesia is non-universal, reflecting the mechanisms of said anesthetic. This fills a crucial knowledge gap as it was not know prior to this if deviations from criticality observed across previous experiments indeed reflected the anesthetic or trivially reflected differences in experimental setups. These results show how physiological state changes may result in deviations away from criticality, and further our understanding of the relationship between criticality and normal brain function. It is also found that signatures of cortical desynchronization associated with the rapid eye movement state of sleep, spread across the cortical surface in a scale-free manner. This feature is absent if spatial information is excluded, emphasizing the importance of considering spatial connectivity when addressing questions of criticality. Finally, it is shown that while low-dose anesthetics do not significantly alter the critical state, surgical-plane anesthesia is non-universal, reflecting the mechanisms of said anesthetic. This fills a crucial knowledge gap as it was not know prior to this if deviations from criticality observed across previous experiments indeed reflected the anesthetic or trivially reflected differences in experimental setups. These results show how physiological state changes may result in deviations away from criticality, and further our understanding of the relationship between criticality and normal brain function.
Open Access
The effect of movie-watching on electroencephalographic responses to tactile stimulation
(Elsevier BV, 2020-10-01) Espenhahn, Svenja; Yan, Tingting; Beltrano, Winnica; Kaur, Sakshi; Godfrey, Kate; Cortese, Filomeno; Bray, Signe; Harris, Ashley D.
Movie-watching is becoming a popular acquisition method to increase compliance and enable neuroimaging data collection in challenging populations such as children, with potential to facilitate studying the somatosensory system. However, relatively little is known about the possible crossmodal (audiovisual) influence of movies on cortical somatosensory processing. In this study, we examined the impact of dynamic audiovisual movies on concurrent cortical somatosensory processing using electroencephalography (EEG). Forty healthy young adults (18–25 years) received passive tactile fingertip stimulation while watching an “entertaining” movie and a novel “low-demand” movie called ‘Inscapes’ compared to eyes-open rest. Watching a movie did not modulate properties of early or late somatosensory-evoked potentials (SEPs). Similarly, no crossmodal influence on somatosensory adaptation, denoted by a reduction in SEP amplitude with repetitive tactile stimulation, was found. The prominent oscillatory responses in the alpha and beta frequency bands following tactile stimulation differed as a function of viewing condition, with stronger alpha/beta event-related desynchronization (ERD) during movie-watching compared to rest. These findings highlight that movie-watching is a valid acquisition method during which SEPs can be measured in basic research and clinical studies, but that the attentional demands of movies need to be taken into account when performing oscillatory analyses.