Aberrant Neuromagnetic Activation in the Motor Cortex in Children with Acute Migraine: A Magnetoencephalography Study

Migraine attacks have been shown to interfere with normal function in the brain such as motor or sensory function. However, to date, there has been no clinical neurophysiology study focusing on the motor function in children with migraine during headache attacks. To investigate the motor function in children with migraine, twenty-six children with acute migraine, meeting International Classification of Headache Disorders criteria and age- and gender-matched healthy children were studied using a 275-channel magnetoencephalography system. A finger-tapping paradigm was designed to elicit neuromagnetic activation in the motor cortex. Children with migraine showed significantly prolonged latency of movement-evoked magnetic fields (MEF) during finger movement compared with the controls. The correlation coefficient of MEF latency and age in children with migraine was significantly different from that in healthy controls. The spectral power of high gamma (65–150 Hz) oscillations during finger movement in the primary motor cortex is also significantly higher in children with migraine than in controls. The alteration of responding latency and aberrant high gamma oscillations suggest that the developmental trajectory of motor function in children with migraine is impaired during migraine attacks and/or developmentally delayed. This finding indicates that childhood migraine may affect the development of brain function and result in long-term problems

The correlation between white-matter microstructure and the complexity of spontaneous brain activity: A difussion tensor imaging-MEG study

The advent of new signal processing methods, such as non-linear analysis techniques, represents a new perspective which adds further value to brain signals' analysis. Particularly, Lempel–Ziv's Complexity (LZC) has proven to be useful in exploring the complexity of the brain electromagnetic activity. However, an important problem is the lack of knowledge about the physiological determinants of these measures. Although acorrelation between complexity and connectivity has been proposed, this hypothesis was never tested in vivo. Thus, the correlation between the microstructure of the anatomic connectivity and the functional complexity of the brain needs to be inspected. In this study we analyzed the correlation between LZC and fractional anisotropy (FA), a scalar quantity derived from diffusion tensors that is particularly useful as an estimate of the functional integrity of myelinated axonal fibers, in a group of sixteen healthy adults (all female, mean age 65.56 ± 6.06 years, intervals 58–82). Our results showed a positive correlation between FA and LZC scores in regions including clusters in the splenium of the corpus callosum, cingulum, parahipocampal regions and the sagittal stratum. This study supports the notion of a positive correlation between the functional complexity of the brain and the microstructure of its anatomical connectivity. Our investigation proved that a combination of neuroanatomical and neurophysiological techniques may shed some light on the underlying physiological determinants of brain's oscillation

Cognitive Impairments in Schizophrenia as Assessed Through Activation and Connectivity Measures of Magnetoencephalography (MEG) Data

The cognitive dysfunction present in patients with schizophrenia is thought to be driven in part by disorganized connections between higher-order cortical fields. Although studies utilizing electroencephalography (EEG), PET and fMRI have contributed significantly to our understanding of these mechanisms, magnetoencephalography (MEG) possesses great potential to answer long-standing questions linking brain interactions to cognitive operations in the disorder. Many experimental paradigms employed in EEG and fMRI are readily extendible to MEG and have expanded our understanding of the neurophysiological architecture present in schizophrenia. Source reconstruction techniques, such as adaptive spatial filtering, take advantage of the spatial localization abilities of MEG, allowing us to evaluate which specific structures contribute to atypical cognition in schizophrenia. Finally, both bivariate and multivariate functional connectivity metrics of MEG data are useful for understanding how these interactions in the brain are impaired in schizophrenia, and how cognitive and clinical outcomes are affected as a result. We also present here data from our own laboratory that illustrates how some of these novel functional connectivity measures, specifically imaginary coherence (IC), are quite powerful in relating disconnectivity in the brain to characteristic behavioral findings in the disorder

White Matter Information Flow Mapping from Diffusion MRI and EEG

International audienceThe human brain can be described as a network of specialized and spatially distributed regions. The activity of individual regions can be estimated using electroencephalography and the structure of the network can be measured using diffusion magnetic resonance imaging. However, the communication between the different cortical regions occurring through the white matter, coined information flow, cannot be observed by either modalities independently. Here, we present a new method to infer information flow in the white matter of the brain from joint diffusion MRI and EEG measurements. This is made possible by the millisecond resolution of EEG which makes the transfer of information from one region to another observable. A subject specific Bayesian network is built which captures the possible interactions between brain regions at different times. This network encodes the connections between brain regions detected using diffusion MRI tractography derived white matter bundles and their associated delays. By injecting the EEG measurements as evidence into this model, we are able to estimate the directed dynamical functional connectivity whose delays are supported by the diffusion MRI derived structural connectivity. We present our results in the form of information flow diagrams that trace transient communication between cortical regions over a functional data window. The performance of our algorithm under different noise levels is assessed using receiver operating characteristic curves on simulated data. In addition, using the well-characterized visual motor network as grounds to test our model, we present the information flow obtained during a reaching task following left or right visual stimuli. These promising results present the transfer of information from the eyes to the primary motor cortex. The information flow obtained using our technique can also be projected back to the anatomy and animated to produce videos of the information path through the white matter, opening a new window into multi-modal dynamic brain connectivity

The neurophysiological changes associated with motor learning in adults and adolescents

One main purpose of this dissertation was to explore how sensorimotor cortical oscillations changed after practicing a novel ankle plantarflexion target matching task. We behaviorally quantified the speed, accuracy, reaction time, velocity, and variability of the participant’s performance of the task, while collecting their neurophysiological responses with magnetoencephalography (MEG). With these data, we assessed how the motor planning and execution stages of movement during a goal directed target matching task changed after practicing a task in typically developing young adults with their non-dominant ankle. We found that the cortical oscillations in the beta frequency range that were sourced from the sensorimotor and occipital cortices were weaker after practice. These individuals also improved behaviorally, with faster speed, greater accuracy, higher velocity, and less variability. The decreased strength likely reflects a more refined motor plan, a reduction in neural resources needed to perform the task, and/or an enhancement of the processes that are involved in the visuomotor transformations that occur prior to the onset of the motor action. The second purpose was to explore how the changes of the sensorimotor cortical oscillations after practicing a novel ankle plantarflexion target matching task differ between adults and adolescents. We assessed these behavioral and neurophysiological changes in a cohort of typically developed adults and adolescents. After practice, all of the participants matched more targets, matched the targets faster, had improved accuracy, faster reaction times, and faster force production. However, the motor performance of the adults exceeded what was seen in the adolescents regardless of practice. In conjunction with the behavioral results, the strength of the beta ERD across the motor planning and execution stages was reduced after practice in the sensorimotor cortices of the adolescents, but was stronger in the adults. These outcomes suggest that there are age-dependent changes in the sensorimotor cortical oscillations after practice, which might be related to familiarity with the motor task. The third purpose was to explore how movement attenuates the somatosensory cortical oscillations and how this attenuation differs in adults and adolescents. We used MEG to address this knowledge gap by applying an electrical stimulation to the tibial nerve as adolescents and adults produced an isometric ankle plantarflexion force, or sat quietly with no motor activity. We found movement-related attenuation of the somatosensory oscillations. Attenuation of the alpha-beta ERS while producing the isometric force was greater in adolescents when compared with adults, while the adults had a greater attenuation of the beta ERD. These results imply that alterations of frequency specific somatosensory cortical oscillations may partly underlie the altered motor performance characteristics seen in adolescents

SPATIOTEMPORAL BRAIN DYNAMICS OF INHIBITORY CONTROL IN ADOLESCENTS AND YOUNG ADULTS

Inhibitory control, the ability to inhibit impulsive responses in favor of voluntary responses, remains immature during adolescence. Although this behavior has been well documented, the cognitive and neural processes associated with immature inhibitory control during adolescence are still not well understood. To address this question, we collected Magnetoencephalography (MEG) data from 17 adolescents (age 14-16) and 20 adult participants (age 20-30), where participants performed the antisaccade (AS) and control prosaccade (PS) tasks. Leveraging MEG’s high temporal resolution, our goal was to delineate developmental changes in local neural oscillations and inter-regional neural synchronization associated with preparatory inhibitory control. Participants were shown a preparatory cue (a red “x” for AS or a green “x” for PS) for 1500 ms, followed by a peripheral target where participants were instructed to make a saccade toward (PS) or away (AS) from the target. Neural activity estimates from a priori brain regions were then extracted for oscillatory power and phase synchrony analyses. We found that compared to adults, adolescents showed decreased alpha-band power in the oculomotor regions in preparation to inhibit an upcoming reflexive saccade, suggesting immaturities in functional inhibition of task-inappropriate activity. Furthermore, adolescents showed weaker beta-band power in prefrontal cognitive control regions, which could reflect less robust top-down biasing of sensory and motor processes. Lastly, we found that adolescents showed decreased levels of phase synchrony between frontal and parietal regions, possibly reflecting immaturities in iv coordinating distributed cortical activities. Our results suggest that immaturities in functional inhibition, top-down control, and inter-regional synchrony collectively contribute to immature inhibitory control during adolescence

Examining the relationship between sensory processing and attention in individuals with autism spectrum disorders

2017 Fall.Includes bibliographical references.Attention is a crucial element of our goal-directed, purposeful response to sensory information in our social and physical environments. Individuals with autism spectrum disorders (ASD) have significant deficits in sensory processing and attention. However, there is limited research examining the relationship between attention and sensory processing in individuals with autism spectrum disorders (ASD). The purpose of this dissertation was to examine the relationship between attention and sensory processing in individuals with autism spectrum disorders (ASD) and neurotypical individuals. Specifically, the objective was to examine if consciously directing attention to incoming information would result in more typical neural processing in individuals with ASD. To answer this question, study 1 was designed to understand how attention and distraction impacted sensory processing in neurotypical individuals. Studies 2 and 3 examined neural measures of sensory processing in individuals with ASD as compared to age-matched neurotypical controls during passive and active attentional states. In Study 1, electroencephalography (EEG) data were recorded while 60 adults (18-35 years) heard random presentations of 4 auditory stimuli at 2 frequencies (1 and 3 kHz) each at 2 intensities (50 and 70 dB). Participants were randomly divided into 2 viewing conditions; one group watched a silent movie and the other viewed a fixation point during the recording. All participants completed 2 attention conditions, the passive condition involved only listening to the stimuli, followed by the active condition, wherein participants were instructed to press a button to the 1 kHz 50 dB tone. Amplitude and latency measures were obtained for the N1, P2, N2, and P3 components for each of the auditory stimuli. The ANOVAs revealed a significant main effect of attention condition for the N1, P2, N2, and P3 amplitudes. There were also significant attention-by-viewing condition interaction effects at the P3 component. Results indicated that actively directing attention to the tones impacts auditory processing at all components. Additionally, manipulation of attention by changing the viewing environment significantly interacted with sensory processing, such that movie viewing resulted in larger P3 amplitudes compared with fixation viewing. Thus, viewing environment or distraction impacts sensory processing. In study 2, we examined the effect of attention on auditory filtering using the sensory gating paradigm in individuals with ASD. EEG data were recorded during 2 attention conditions from 24 adults with ASD and 24 neurotypical individuals during the sensory gating paradigm. During the passive condition, participants were presented with single and paired clicks. For the active condition, participants made a motor response following the single click but not the paired click. Attending to the clicks resulted in larger P50 and N1 amplitudes, and reduced gating for all participants. Although, the ASD group had P50 and N1 gating during both attention conditions, they had significantly longer N1 latencies to the Click 1 during both the attention conditions, suggesting a delayed orienting response. However, click 2 latencies were delayed only in the passive condition and not the active condition for the ASD group compared to the neurotypical group. This finding suggests of attention-based amelioration of processing speed in individuals with ASD. Individuals with ASD also had significantly more deficits on behavioral measures of social responsivity, attention, sensory and perceptual processing. Additionally, neural measures of gating were associated with several behavioral measures of sensory processing as measured by self-report questionnaires and a performance-based measure of attention, such that efficient neural processing was associated with more typical sensory processing and attention. In study 3, we examined the effect of attention on auditory discrimination in individuals with ASD. EEG data were recorded from 24 individuals with ASD and 24 neurotypical individuals, while they heard random presentations of 4 auditory stimuli at 2 different frequencies (1 and 3 kHz) each at 2 different intensities (50 and 70 dB). All participants completed two attention conditions; the passive condition involved only listening to the stimuli, followed by the active condition, wherein participants were instructed to press a button to the 1 kHz 50 dB tone. Attention impacted N2, and P3 amplitudes, and P2 and N2 latencies. The ASD group had significantly longer N1, N2, and P3 latencies, suggesting delayed processing. N2 and P3 latency delays in the ASD group were present during the passive but not active condition, implying an attention-based amelioration of processing delay. Behavioral measures of sensory processing and attention correlated with neural measures of auditory processing. Thus, through the series of studies, we found that actively directing attention to the tones impacts auditory processing, and may result in more typical processing in ASD. The study findings also suggest that sensory processing deficits observed in ASD may be associated with underlying deficits of attention. Study findings have significant implications related to understanding auditory discrimination in individuals with ASD and examining the impact of attention on sensory processing. Additionally, these results can help practitioners understand the neural basis of behavioral manifestations of ASD, especially those atypical behaviors that occur in response to sensory experiences in everyday activities

Module hierarchy and centralisation in the anatomy and dynamics of human cortex

Systems neuroscience has recently unveiled numerous fundamental features of the macroscopic architecture of the human brain, the connectome, and we are beginning to understand how characteristics of brain dynamics emerge from the underlying anatomical connectivity. The current work utilises complex network analysis on a high-resolution structural connectivity of the human cortex to identify generic organisation principles, such as centralised, modular and hierarchical properties, as well as specific areas that are pivotal in shaping cortical dynamics and function. After confirming its small-world and modular architecture, we characterise the cortex’ multilevel modular hierarchy, which appears to be reasonably centralised towards the brain’s strong global structural core. The potential functional importance of the core and hub regions is assessed by various complex network metrics, such as integration measures, network vulnerability and motif spectrum analysis. Dynamics facilitated by the large-scale cortical topology is explored by simulating coupled oscillators on the anatomical connectivity. The results indicate that cortical connectivity appears to favour high dynamical complexity over high synchronizability. Taking the ability to entrain other brain regions as a proxy for the threat posed by a potential epileptic focus in a given region, we also show that epileptic foci in topologically more central areas should pose a higher epileptic threat than foci in more peripheral areas. To assess the influence of macroscopic brain anatomy in shaping global resting state dynamics on slower time scales, we compare empirically obtained functional connectivity data with data from simulating dynamics on the structural connectivity. Despite considerable micro-scale variability between the two functional connectivities, our simulations are able to approximate the profile of the empirical functional connectivity. Our results outline the combined characteristics a hierarchically modular and reasonably centralised macroscopic architecture of the human cerebral cortex, which, through these topological attributes, appears to facilitate highly complex dynamics and fundamentally shape brain function

Structural and functional integrity of neural circuits

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, September 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections."September, 2011." Cataloged from student submitted PDF version of thesis.Includes bibliographical references.This dissertation documents how healthy aging and Parkinson's disease (PD) affect brain anatomy and physiology and how these neural changes relate to measures of cognition and perception. While healthy aging and PD are both accompanied by a wide-range of cognitive impairments, the neural underpinnings of cognitive decline in each is likely mediated by deterioration of different systems. The four chapters of this dissertation address specific aspects of how healthy aging and PD affect the neural circuits that support sensory processes and high-level cognition. The experiments in Chapters 2 and 3 examine the effects of healthy aging on the integrity of neural circuits that modulate cognitive control processes. In Chapter 2, we test the hypothesis that the patterns of age-related change differ between white matter and gray matter regions, and that changes in the integrity of anterior regions correlate most strongly with performance on cognitive control tasks. In Chapter 3, we build upon the structural findings by examining the hypothesis that age-related changes in white matter integrity are associated with disrupted oscillatory dynamics observed during a visual search task. Chapter 4 investigates healthy age-related changes in somatosensory mu rhythms and evoked responses and uses a computational model of primary somatosensory cortex to predict the underlying cellular and neurophysiolgical bases of these alterations. In contrast to the widespread cortical changes seen in healthy OA, the cardinal motor symptoms of PD are largely explained by degeneration of the dopaminergic substantia nigra, pars compacta (SNc). Cognitive sequelae of PD, however, likely result from disruptions in multiple neurotransmitter systems, including nondopaminergic nuclei, but research on these aspects of the disease has been hindered by a lack of sensitive MRI biomarkers for the affected structures. Chapter 5 presents new multispectral MRI tools that visualize the SNc and the cholinergic basal forebrain (BF). We applied these methods to test the hypothesis that degenerative processes in PD affect the SNc before the BF. This experiment lays important groundwork for future studies that will examine the relative contribution of the SNc and BF to cognitive impairments in PD.by David A. Ziegler.Ph.D