Academic literature on the topic 'HEMISPHERIC ASYMMETRY ANALYSES'

The extent to which pattern reversal evoked potential amplitudes are distributed symmetrically over the scalp was investigated as a function of stimulus spatial frequency. Nine right-handed male subjects viewed sinusoidal grating stimuli of 4.0 and 0.5 c/deg phase reversed every 900 msec. A visual half-field configuration enabled selective stimulation of the right- or left-hemisphere visual cortex. Evoked responses were recorded from the 2 cm above the inion (Oz) and at 7 and 13 cm lateral to Oz. Analyses of normalized evoked response amplitudes showed a significant asymmetry for the 4.0 c/deg stimulus; right-hemisphere amplitudes declined as a function of distance from the midline, while left-hemisphere amplitudes were greatest at the 7 cm recording site. No hemispheric differences were observed for the 0.5 c/deg stimulus; amplitudes for both hemispheres declined as a function of distance from the midline. The data are discussed in terms of hemispheric differences in morphology and functional asymmetries at early levels of sensory processing.

Despite many studies reporting hemispheric asymmetry in the representation and processing of emotions, the essence of the asymmetry remains controversial. Brain network analysis based on electroencephalography (EEG) is a useful biological method to study brain function. Here, EEG data were recorded while participants watched different emotional videos. According to the videos’ emotional categories, the data were divided into four categories: high arousal high valence (HAHV), low arousal high valence (LAHV), low arousal low valence (LALV) and high arousal low valence (HALV). The phase lag index as a connectivity index was calculated in theta (4–7 Hz), alpha (8–13 Hz), beta (14–30 Hz) and gamma (31–45 Hz) bands. Hemispheric networks were constructed for each trial, and graph theory was applied to quantify the hemispheric networks’ topological properties. Statistical analyses showed significant topological differences in the gamma band. The left hemispheric network showed significantly higher clustering coefficient (Cp), global efficiency (Eg) and local efficiency (Eloc) and lower characteristic path length (Lp) under HAHV emotion. The right hemispheric network showed significantly higher Cp and Eloc and lower Lp under HALV emotion. The results showed that the left hemisphere was dominant for HAHV emotion, while the right hemisphere was dominant for HALV emotion. The research revealed the relationship between emotion and hemispheric asymmetry from the perspective of brain networks.

Aims. Hemispheric irregularities of solar magnetic activity is a well-observed phenomenon, the origin of which has been studied through numerical simulations and data analysis techniques. In this work we explore possible causes generating north-south asymmetry in the reversal timing and amplitude of the polar field during cycle minimum. Additionally, we investigate how hemispheric asymmetry is translated from cycle to cycle. Methods. We pursued a three-step approach. Firstly, we explored the asymmetry present in the observed polar flux and sunspot area by analysing observational data of the last 110 years. Secondly, we investigated the contribution from various factors involved in the Babcock–Leighton mechanism to the evolution and generation of polar flux by performing numerical simulations with a surface flux transport model and synthetic sunspot input profiles. Thirdly, translation of hemispheric asymmetry in the following cycle was estimated by assimilating simulation-generated surface magnetic field maps at cycle minimum in a dynamo simulation. Finally, we assessed our understanding of hemispheric asymmetry in the context of observations by performing additional observational data-driven simulations. Results. Analysis of observational data shows a profound connection between the hemispheric asymmetry in the polar flux at cycle minimum and the total hemispheric activity during the following cycle. We find that the randomness associated with the tilt angle of sunspots is the most crucial element among diverse components of the Babcock–Leighton mechanism in resulting hemispheric irregularities in the evolution of polar field. Our analyses with dynamo simulations indicate that an asymmetric poloidal field at the solar minimum can introduce significant north-south asymmetry in the amplitude and timing of peak activity during the following cycle. While observational data-driven simulations reproduce salient features of the observed asymmetry in the solar cycles during the last 100 years, we speculate that fluctuations in the mean-field α-effect and meridional circulation can have finite contributions in this regard.

Sleep electroencephalographic (EEG) slow-wave activity is increased after wakefulness and decreases during sleep. Regional sleep EEG differences are thought to be a consequence of activation of specific cortical neuronal circuits during waking. We investigated the relationship between handedness and interhemispheric brain asymmetry. Bilateral EEG recordings were obtained from the frontal and occipital cortex in rats with a clear paw preference in a food-reaching task (right, n = 5; left, n = 5). While still naïve to the task, no waking or sleep EEG asymmetry was present. During the food-reaching task, the waking EEG showed significant, substantial power increases in the frontal hemisphere contralateral to the dominant paw in the low theta range (4.5–6.0 Hz). Moreover, the non-REM sleep EEG following feeding bouts was markedly asymmetric, with significantly higher power in the hemisphere contralateral to the preferred paw in frequencies >1.5 Hz. No asymmetry was evident in the occipital EEG. Correlation analyses revealed a positive association between the hemispheric asymmetry during sleep and the degree of preferred use of the contralateral paw during waking in frequencies <9.0 Hz. Our findings show that handedness is reflected in specific, regional EEG asymmetry during sleep. Neuronal activity induced by preferential use of a particular forelimb led to a local enhancement of EEG power in frequencies within the delta and sigma ranges, supporting the hypothesis of use-dependent local sleep regulation. We conclude that inherent laterality is manifested when animals are exposed to complex behavioral tasks, and sleep plays a role in consolidating the hemispheric dominance of the brain.

Context. The hemispheric asymmetry of sunspot activity observed possesses a regular component varying on a timescale of several solar cycles whose origin and properties are currently debated. Aims This paper addresses the question of whether the long-term hemispheric asymmetry can result from random variations of solar dynamo parameters in time and latitude. Methods. Scatter in the observed tilt angles of sunspot groups was estimated to infer constraints on fluctuations in the dynamo mechanism for poloidal field regeneration. A dynamo model with fluctuations in the Babcock-Leighton type α-effect was designed in accordance with these constraints and then used to compute a large number of magnetic cycles for statistical analyses of their hemispheric asymmetry. Results Hemispheric asymmetry in the simulated dynamo results from the presence of an equator-symmetric part in the oscillating magnetic field. The sub-dominant quadrupolar oscillations are stochastically forced by dominant dipolar oscillations via the equator-symmetric part of the fluctuating α-effect. The amplitude and sense of the asymmetry of individual cycles varies on a timescale of the order of four dynamo-cycle periods. The variations are irregular and not periodic. The model suggests that asymmetry in the polar magnetic fields in the solar minima can be used as a precursor for asymmetry of sunspot activity in the following solar cycle.

A hemispheric asymmetry for the processing of global versus local visual information is known. In this study, we investigated the existence of a hemispheric asymmetry for the visual processing of low versus high spatial frequency gratings. The event-related potentials were recorded in a group of healthy right-handed volunteers from 30 scalp sites. Six types of stimuli (1.5, 3 and 6 c/deg gratings) were randomly flashed 180 times in the left and right upper hemifields. The stimulus duration was 80 ms, and the interstimulus interval (ISI) ranged between 850 and 1000 ms. Participants paid attention and responded to targets based on their spatial frequency and location. The C1 and P1 visual responses, as well as a later selection negativity and a P300 component of event-related potentials (ERPs), were quantified and subjected to repeated-measure analyses of variance (ANOVAs). Overall, the performance was faster for the right visual field (RVF), thus suggesting a left hemispheric advantage for the attentional selection of local elements. Similarly, the analysis of the mean area amplitude of the C1 (60–110 ms) sensory response showed a stronger attentional effect (F+L+ vs. F−L+) at the left occipital areas, thus suggesting the sensory nature of this hemispheric asymmetry.

IntroductionThe functional interplay between brain hemispheres is fundamental for behavioral, cognitive and emotional control. Several pathophysiological aspects of eating disorders (EDs) have been investigated by the use of functional Magnetic Resonance Imaging (fMRI).ObjectivesThe objective of the study was to investigate functional brain asymmetry of resting-state fMRI correlations in symptomatic patients with anorexia nervosa (AN) and bulimia nervosa (BN).AimsWe aimed at revealing whether brain regions implicated in reward, cognitive control, starvation and emotion regulation show altered inter-hemispheric functional connectivity in patients with AN and BN.MethodsUsing resting-state fMRI, voxel-mirrored homotopic connectivity (VMHC) and regional inter-hemispheric spectral coherence (IHSC) analyses in two canonical slow frequency bands (“Slow-5”, “Slow-4”) were studied in 15AN and 13BN patients and 16 healthy controls (HC). Using T1-weighted and diffusion tensor imaging MRI scans, regional VMHC values were correlated with the left-right asymmetry of corresponding homotopic gray matter volumes and with the white matter callosal fractional anisotropy (FA).ResultsCompared to HC, AN patients exhibited reduced VMHC in cerebellum, insula and precuneus, while BN patients showed reduced VMHC in dorso-lateral prefrontal and orbito-frontal cortices. The regional IHSC analysis highlighted that the inter-hemispheric functional connectivity was higher in the ‘Slow-5′Band in all regions except the insula. No group differences in left-right structural asymmetries and in VMHC vs callosal FA correlations were found.ConclusionsThese anomalies indicate that AN and BN, at least in their acute phase, are associated with a loss of inter-hemispheric connectivity in regions implicated in self-referential, cognitive control and reward processing.Disclosure of interestThe authors have not supplied their declaration of competing interest.

The ability to suppress irrelevant information while executing a task, also known as interference resistance ability, is a function of pFC that is critical for successful goal-directed human behavior. In the study of interference resistance and, more generally, executive functions, two key questions are still open: Does pFC contribute to cognitive control abilities through lateralized but domain-general mechanisms or through hemispheric specialization of domain-specific processes? And what are the underlying causes of interindividual differences in executive control performance? To shed light on these issues, here we employed an interindividual difference approach to investigate whether participants' hemispheric asymmetry in resting-state electrophysiological brain dynamics may reflect their variability in domain-general interference resistance. We recorded participants' resting-state electroencephalographic activity and performed spectral power analyses on the estimated cortical source activity. To measure participants' lateralized brain dynamics at rest, we computed the right–left hemispheric asymmetry score for the β/α power ratio. To measure their domain-general interference resistance ability, verbal and spatial Stroop tasks were used. Robust correlations followed by intersection analyses showed that participants with stronger resting-state-related left-lateralized activity in different pFC regions, namely the mid-posterior superior frontal gyrus, middle and posterior middle frontal gyrus, and inferior frontal junction, were more able to inhibit irrelevant information in both domains. The present results confirm and extend previous findings showing that neurophysiological difference factors may explain interindividual differences in executive functioning. They also provide support for the hypothesis of a left pFC hemispheric specialization for domain-independent phasic cognitive control processes mediating Stroop performance.

AbstractPrevious studies have documented the serotonin transporter linked polymorphic region (5-HTTLPR) as a genetic susceptibility variant that contributes to variability in outcomes related to affective psychopathology, with the short allele associated with negative affectivity and the long allele associated with positive affectivity. In a separate but related line of research, extensive evidence suggests that frontal electroencephalography (EEG) hemispheric asymmetry in the alpha band is also associated with risk for affective psychopathologies, with leftward asymmetry associated with approach-related behavior patterns and rightward frontal EEG asymmetry associated with withdrawn behavioral tendencies. We examined frontal EEG hemispheric asymmetries in relation to 5-HTTLPR genotyping in 70 children between 4 and 6 years of age. Analyses revealed that frontal EEG lateralization interacted with genotype such that children homozygous for the short allele exhibited rightward frontal EEG asymmetries, children who were homozygous for the long allele consistently exhibited a positive pattern of leftward asymmetry, and heterozygotes exhibited equivalent left and right frontal activity. These findings suggest that the 5-HTTLPR short allele may provide a degree of susceptibility for later affective psychopathology in adolescence and adulthood, through mediation of frontal brain activity that is associated with cognitive–behavioral withdrawal tendencies and negative affectivity.

The topological architecture of the cerebral anatomical network reflects the structural organization of the human brain. Recently, topological measures based on graph theory have provided new approaches for quantifying large-scale anatomical networks. However, few studies have investigated the hemispheric asymmetries of the human brain from the perspective of the network model, and little is known about the asymmetries of the connection patterns of brain regions, which may reflect the functional integration and interaction between different regions. Here, we utilized diffusion tensor imaging to construct binary anatomical networks for 72 right-handed healthy adult subjects. We established the existence of structural connections between any pair of the 90 cortical and subcortical regions using deterministic tractography. To investigate the hemispheric asymmetries of the brain, statistical analyses were performed to reveal the brain regions with significant differences between bilateral topological properties, such as degree of connectivity, characteristic path length, and betweenness centrality. Furthermore, local structural connections were also investigated to examine the local asymmetries of some specific white matter tracts. From the perspective of both the global and local connection patterns, we identified the brain regions with hemispheric asymmetries. Combined with the previous studies, we suggested that the topological asymmetries in the anatomical network may reflect the functional lateralization of the human brain.

INTRODUCTION A mood characterised by alternating mania and depression have been matter of curiosity and attention since ancient times. According to T.J. Crow’s theory on psychosis, Schizophrenia is strictly linked to the development of the faculty of language (begun in hominids from 6 to 4.2 million years ago) which depends by (anatomical and functional) asymmetry observable between the two cerebral hemispheres (Crow 2004). Several data in the recent (and older) (Griesinger 1845) scientific literature support the hypothesis that schizophrenia and bipolar disorder are similar due to a large number of partially common features: symptomatology, genetics, cognitive features, neurobiology, connectivity alteration, etc.. A brief historical account about how often the classification of this disease changed across the last two centuries may suggest how the knowledge underling this diagnostic category is still fragile. AIM OF THE RESEARCH The goal of this paper is to study Functional Connectivity (FC) among bipolar patients and to test the compatibility of Crow’s paradigm with Bipolar Disorder, verifying the potential presence of hemispheric asymmetry alteration (left dominance deficit) through fMRI analysis. MATERIALS AND METHODS 18 outpatients of the Mood Disorders Unit at the Psychiatric Clinic of the University of Padua have been recruited. All subjects had a diagnosis of Bipolar Disorder type I or type II, according to the criteria of the DSM-IV-TR). 16 healthy individuals were chosen matched for age, sex and education. Clinical and psychological conditions at the time of the experiment were investigated through some psychometric scales widely used for the evaluation of mood, anxiety and other psychopathologic aspects. All subjects underwent a MRI scan both in resting state and while they were attending two tasks: a phonemic (verbal fluency) exercise and a visuo-spatial test (mental rotations). RESULTS From the neuropsychological point of view the phonemic task revealed no significant (p<0.05) differences between groups; on the contrary patients group showed decreased performance at the visuo-spatial task. MRI FC was analysed using two different techniques. Independent Component Analysis (ICA) showed mainly a volume within the Dorsal Attention Network located in left Precuneus (Brodmann Area 7) where patient group presented a reduction of FC compared to controls. Graph analysis brought to light a number of inter-hemispheric and left intra-hemispheric connections revealed to be significantly less active in patients compared to controls, on the contrary substantial conservation of indices at the Network Level was observed.
INTRODUZIONE Un tono timico caratterizzato da un’alternanza di mania e depressione è stato oggetto di interesse e attenzione fin dai tempi antichi. Secondo La teoria di T.J. Crow sulla psicosi, la schizofrenia è strettamente legata allo sviluppo della facoltà del linguaggio (che ha avuto origine negli ominidi da 6 a 4,2 milioni di anni fa) che dipende dall'asimmetria (anatomica e funzionale) osservabile tra i due emisferi cerebrali (Crow 2004). Diversi dati nella letteratura scientifica recente (e più antica – Griesinger 1845) supportano l'ipotesi che la schizofrenia e il disturbo bipolare siano simili per un gran numero di caratteristiche parzialmente comuni: sintomatologia, genetica, cognitività, neurobiologia, alterazione della connettività, ecc. Un breve resoconto storico di quanto spesso la classificazione di questa malattia sia cambiata negli ultimi due secoli può suggerire come la conoscenza sottesa a questa categoria diagnostica sia ancora fragile. SCOPO DELLA RICERCA L'obiettivo di questo studio è quello di studiare la connettività funzionale (FC) tra i pazienti bipolari e testare la compatibilità del paradigma di Crow con il disturbo bipolare, verificando la potenziale presenza di alterazioni dell'asimmetria emisferica (deficit di dominanza sinistra) attraverso l'analisi fMRI (risonanza magnetica funzionale). MATERIALI E METODI Sono stati reclutati 18 pazienti ambulatoriali dell'Unità di Disturbi dell'Umore presso la Clinica Psichiatrica dell'Università di Padova. Tutti i soggetti avevano una diagnosi di disturbo bipolare di tipo I o di tipo II, secondo i criteri del DSM-IV-TR). Sono stati scelti 16 individui sani abbinati per età, sesso e istruzione. Le condizioni cliniche e psicologiche al momento dell'esperimento sono state studiate attraverso alcune scale psicometriche ampiamente utilizzate per la valutazione dell'umore, dell'ansia e di altri aspetti psicopatologici. Tutti i soggetti sono stati sottoposti a una risonanza magnetica sia in stato di riposo che durante l’esecuzione di due compiti: un esercizio fonemico (fluenza verbale) e un test visuo-spaziale (rotazioni mentali). RISULTATI Dal punto di vista neuropsicologico, il compito fonemico non ha rivelato differenze significative (p<0.05) tra i gruppi; al contrario, il gruppo di pazienti ha mostrato una riduzione delle prestazioni nel compito visuo-spaziale. I dati fMRI sono stati analizzati utilizzando due tecniche diverse. L'Independent Component Analysis (ICA) ha mostrato principalmente un volume all'interno della Dorsal Attention Network situato nel precuneo sinistro (area 7 di Brodmann) dove il gruppo di pazienti presentava una riduzione significativa della FC rispetto ai controlli. L'analisi dei grafi ha portato alla luce un numero di connessioni intra-emisferiche e intra-emisferiche di sinistra rivelate significativamente meno attive nei pazienti rispetto ai controlli, al contrario è stata osservata una sostanziale conservazione degli indici a livello di rete.

In this work I present several studies, which might appear rather heterogeneous for both experimental questions and methodological approaches, and yet are linked by a common leitmotiv: spatial attention. I will address issues related to the assessment of attentional asymmetries, in the healthy individual as in patients with neurological disorders, their role in various aspects of human cognition, and their neural underpinning, driven by the deep belief that spatial attention plays an important role in various mental processes that are not necessarily confined to perception. What follows is organized into two distinct sections. In the first I will focus on the evaluation of visuospatial asymmetries, starting from the description of a new paradigm particularly suitable for this purpose. In the first chapter I will describe the effects of multitasking in a spatial monitoring test; the main result shows a striking decreasing in detection performance as a function of the introduced memory load. In the second chapter I will apply the same paradigm to a clinical population characterized by a brain lesion affecting the left hemisphere. Despite a standard neuropsychological battery failed to highlight any lateralized attentional deficit, I will show that exploiting concurrent demands might lead to enhanced sensitivity of diagnostic tests and consequently positive effects on patients’ diagnostic and therapeutic management. Finally, in the third chapter I will suggest, in light of preliminary data, that attentional asymmetries also occur along the sagittal axis; I will argue, in particular, that more attentional resources appear to be allocated around peripersonal space, the resulting benefits extending to various tasks (i.e., discrimination tasks). Then, in the second section, I will follow a complementary approach: I will seek to induce attentional shifts in order to evaluate their role in different cognitive tasks. In the fourth and fifth chapters this will be pursued exploiting sensory stimulations: visual optokinetic stimulation and galvanic vestibular stimulation, respectively. In the fourth chapter I will show that spatial attention is highly involved in numerical cognition, this relationship being bidirectional. Specifically, I will show that optokinetic stimulation modulates the occurrence of procedural errors during mental arithmetics, and that calculation itself affects oculomotor behaviour in turn. In the fifth chapter I will examine the effects of galvanic vestibular stimulation, a particularly promising technique for the rehabilitation of lateralized attention disorders, on spatial representations. I will discuss critically a recent account for unilateral spatial neglect, suggesting that vestibular stimulations or disorders might indeed affect the metric representation of space, but not necessarily resulting in spatial unawareness. Finally, in the sixth chapter I will describe an attentional capture phenomenon by intrinsically rewarding distracters. I will seek, in particular, to predict the degree of attentional capture from resting-state functional magnetic resonance imaging data and the related brain connectivity pattern; I will report preliminary data focused on the importance of the cingulate-opercular network, and discuss the results through a parallel with clinical populations characterized by behavioural addictions.
In questo lavoro presenterò una serie di ricerche che possono sembrare piuttosto eterogenee per quesiti sperimentali e approcci metodologici, ma sono tuttavia legate da un filo conduttore comune: i costrutti di ragionamento e attenzione spaziale. Affronterò in particolare aspetti legati alla valutazione delle asimmetrie attenzionali, nell'individuo sano come nel paziente con disturbi neurologici, il loro ruolo in vari aspetti della cognizione umana, e i loro substrati neurali, guidato dalla convinzione che l’attenzione spaziale giochi un ruolo importante in svariati processi mentali non necessariamente limitati alla percezione. Quanto segue è stato dunque organizzato in due sezioni distinte. Nella prima mi soffermerò sulla valutazione delle asimmetrie visuospaziali, iniziando dalla descrizione di un nuovo paradigma particolarmente adatto a questo scopo. Nel primo capitolo descriverò gli effetti del doppio compito e del carico attenzionale su un test di monitoraggio spaziale; il risultato principale mostra un netto peggioramento nella prestazione al compito di detezione spaziale in funzione del carico di memoria introdotto. Nel secondo capitolo applicherò lo stesso paradigma ad una popolazione clinica contraddistinta da lesione cerebrale dell’emisfero sinistro. Nonostante una valutazione neuropsicologica standard non evidenziasse alcun deficit lateralizzato dell’attenzione, mostrerò che sfruttare un compito accessorio può portare ad una spiccata maggiore sensibilità dei test diagnostici, con evidenti ricadute benefiche sull'iter clinico e terapeutico dei pazienti. Infine, nel terzo capitolo suggerirò, tramite dati preliminari, che asimmetrie attenzionali possono essere individuate, nell'individuo sano, anche lungo l’asse sagittale; argomenterò, in particolare, che attorno allo spazio peripersonale sembrano essere generalmente concentrate più risorse attentive, e che i benefici conseguenti si estendono a compiti di varia natura (ad esempio compiti di discriminazione). Passerò dunque alla seconda sezione, in cui, seguendo una logica inversa, indurrò degli spostamenti nel focus attentivo in modo da valutarne il ruolo in compiti di varia natura. Nei capitoli quarto e quinto sfrutterò delle stimolazioni sensoriali: la stimolazione visiva optocinetica e la stimolazione galvanico vestibolare, rispettivamente. Nel quarto capitolo mostrerò che l’attenzione spaziale è coinvolta nella cognizione numerica, con cui intrattiene rapporti bidirezionali. Nello specifico mostrerò da un lato che la stimolazione optocinetica può modulare l’occorrenza di errori procedurali nel calcolo mentale, dall'altro che il calcolo stesso ha degli effetti sull'attenzione spaziale e in particolare sul comportamento oculomotorio. Nel quinto capitolo esaminerò gli effetti della stimolazione galvanica vestibolare, una tecnica particolarmente promettente per la riabilitazione dei disturbi attentivi lateralizzati, sulle rappresentazioni mentali dello spazio. Discuterò in modo critico un recente modello della negligenza spaziale unilaterale, suggerendo che stimolazioni e disturbi vestibolari possano sì avere ripercussioni sulle rappresentazioni metriche dello spazio, ma senza comportare necessariamente inattenzione per lo spazio stesso. Infine, nel sesto capitolo descriverò gli effetti di cattura dell’attenzione visuospaziale che stimoli distrattori intrinsecamente motivanti possono esercitare nell'adulto sano. Cercherò, in particolare, di predire l’entità di questa cattura attenzionale partendo da immagini di risonanza magnetica funzionale a riposo: riporterò dati preliminari focalizzati sull'importanza del circuito cingolo-opercolare, effettuando un parallelismo con popolazioni cliniche caratterizzate da comportamenti di dipendenza.

Over twenty years of research have examined the cognitive consequences of positive affect states, and suggested that positive affect leads to a broadening of cognition. However, this research has primarily examined positive affect that is low in approach motivational intensity (e.g. contentment). In my program of research, I have systematically examined positive affect that varies in approach motivational intensity, and found that positive affect high in approach motivation (e.g. desire) narrow cognition, whereas positive affect low in approach motivation broaden cognition. In this dissertation, I will review past models and present a motivational dimension model of affect that expands understanding of how affective states influence attentional and cognitive breadth. I then review a body of research that has varied the motivational intensity of positive and negative affect and found that affect of low motivational intensity broadens cognitive processes, whereas affect of high motivational intensity narrows cognitive processes. Furthermore, a bi-directional link exists between attentional narrowing and approach motivation, such that a narrowed attentional focus to appetitive stimuli causes greater approach motivation than a broadened attentional focus.

It is often assumed that there is a direct correlation between the knowledge an individual possesses and that individual's actions. However, many hidden processes influence decisionmaking processes. Asymmetric processing of affective, cognitive, and sensory information has long been one of the fascinating properties of human brain function. Thus, understanding hemispheric asymmetry as one of those hidden processes can bridge the gap between what a person knows and what one decides to do. One widely used technique for analysis of brain asymmetry is Electroencephalography (EEG), whose simplicity, portability, and high temporal resolution enable its usage in a relatively wide-range of real-world environments. Howbeit, it also poses a drawback of less spatial resolution as the localization of an active site is limited to several centimeters. The hemispheric difference between EEG alpha activity over the frontal regions has been termed as frontal EEG asymmetry. This phenomenon was first linked to patterns of emotion processing decades ago. functional Magnetic Resonance Imaging (fMRI) is another technique that provides a unique view of the human brain by detecting changes in blood oxygenation. It poses an advantage of high spatial resolution; however, it possesses a low temporal resolution. The hemispheric dominance in fMRI has been called the laterality index. The laterality index enables one value per subject per contrast as a descriptor for activation pattern based hemispheric dominance. Also, vii simultaneous recordings and analysis of EEG-fMRI techniques, which can counteract the limitations posed by EEG-FMRI, have recently gained attention and can be gauged for effectiveness in the hemispheric asymmetry research. The current thesis aims to corroborate the hemispheric asymmetry research by exploring the resting-state EEG/fMRI hemispheric asymmetry models after simultaneous EEG-fMRI data acquisition. These resting-state models of hemispheric asymmetry in the brain may serve as potential parameters for comprehending the human actions when engaged in any exogenously directed task. Thus, the standard resting frontal alpha EEG hemispheric asymmetry model was first examined before engagement in a Situational awareness (SA) task to vindicate the relationship between pre-task resting asymmetry and SA-task performance. SA is the knowledge of the environment, and maintenance of SA is crucial for optimal performance in the aviation and military domain. Thus, understanding the linkage of the neural mechanisms underlying the pre-task resting frontal alpha asymmetry model with subsequently performed SA-task can improve SA. For this purpose, initially, an SA-task with influence from the Stroop effect was designed and developed, and pre-task resting EEG absolute alpha power and its frontal alpha hemispheric asymmetry were assessed. This study revealed a strong association of SA-task performance measures with resting frontal alpha hemispheric asymmetry. Further, the neural mechanisms underlying pre-SA task resting absolute alpha power and its frontal asymmetry, as assessed through the EEG-informed fMRI approach, significantly influenced the SA-task's neural mechanisms. After examining the relationship between the pre-task resting alpha EEG asymmetry model with subsequently performed SA-task, the association of this standard asymmetry model with affect and approach/withdrawal measures of an individual was gauged. The purpose of this viii study was to understand the significance of real-time standalone recordings of pre-task resting alpha EEG asymmetry in terms of its connectedness with measures of positive/negative affect and approach/withdrawal behavior. Further, to strengthen the findings, the mapping between pretask resting alpha EEG asymmetry model and fMRI through EEG-informed fMRI analysis was explored. For this purpose, initially, the robust correlation of standard resting frontal alpha asymmetry with affect and approach/withdrawal measures was carried out. Next, the neural underpinnings and Hemodynamic Lateralization Index, HLI (based on these neural underpinnings) for standard resting frontal alpha asymmetry were assessed. The results yielded no significant relationship between the standard resting frontal asymmetry and its HLI with any psychological measures. This ambivalence on the validity of standard resting frontal alpha asymmetry in terms of its association with affect and approach/withdrawal psychological measures motivated us towards the estimation of a novel microstate-based frontal alpha asymmetry model and assessment of this model’s linkage with positive/negative affect and approach/withdrawal measures. The microstates represent global electrical brain activity on the scalp that remains semi-stable for brief transient periods. The utilization of microstates was based on the evidence that supported the importance of stable EEG patterns in bringing forth the interrelation of affect and approach/withdrawal measures with resting frontal alpha asymmetry. The results revealed that the microstate-based resting frontal alpha asymmetry model correlated significantly with negative affect, and its neural underpinning’s HLI significantly correlated with positive/Negative affect and approach/withdrawal measures. Thus, the novel microstate-based microstate-based resting frontal alpha asymmetry model proved efficacious in bringing forth the association with affect and approach/withdrawal measures. ix In addition, to understand the role of subcortical regions, and their interaction with cortical regions in bringing forth the hemispheric asymmetries of affect and approach/withdrawal behavior, a study based on the hemispheric asymmetry model of resting fMRI graph theory functional connectivity metrics was carried out, as the viability to detect subcortical signals through EEG is still debatable. In this analysis, we report the neuroimaging finding based on Region of Interest (ROI) based analysis and graph-theory measures for global networks and subnetworks. The study revealed the involvement of emotion and memory-related subcorticalcortical interactions in positive and negative affect and basal ganglia structures in approachwithdrawal dichotomy. Further, lateralization of the strength of degree-measures of the corticalregions vital for subcortical-cortical interaction revealed higher connectivity within the lefthemisphere for affective measures. Thus, the current thesis demonstrates the benefit of assessing the standard resting hemispheric asymmetry model before a complex cognitive task such as SA, which holds paramount importance for the ergonomics community and for military/aviation domains. Further, the outcomes also offer an unprecedented attempt towards the development of a novel microstates-based resting hemispheric asymmetry model for bringing forth the relationship of resting EEG based asymmetry with psychological measures of affect and approach/withdrawal behavior Also, the key findings of subcortical regions and their interaction with cortical regions dominating the affect and approach/withdrawal measure can be further explored in clinical as well as task-based studies.

Abstract Upper-atmospheric processes under different space weather conditions are still not well understood, and the existing models are far away from the desired operational requirements due to the lack of in-situ measurements input. The ionospheric perturbation of electromagnetic signals affects the accuracy and reliability of Global Navigation Satellite Systems (GNSS), satellite communication infrastructures, and Earth observation techniques. Furthermore, the variable aerodynamic drag, due to variable thermospheric mass density, disturbs orbital tracking, collision analysis, and re-entry calculations of Low Earth Orbit (LEO) objects, including manned and unmanned artificial satellites. In this paper, we use the Principal Component Analysis (PCA) technique to study and compare the main driver-response relationships and spatial patterns of total electron content (TEC) estimates from 2003 to 2018, and total mass density (TMD) estimates at 475 km altitude from 2003 to 2015. Comparison of the first TEC and TMD PCA mode shows a very similar response to solar flux, but annual cycle shown by TEC is approximately one order of magnitude larger. A clear hemispheric asymmetry is shown in the global distribution of TMD, with higher values in the southern hemisphere than in the northern hemisphere. The hemispheric asymmetry is not visible in TEC. The persistent processes including a favorable solar wind input and particle precipitation over the southern magnetic dip may produce a higher thermospheric heating, which results in the hemispheric asymmetry in TMD.

The Interaural Time Difference is one of the primary localiza- tion cues for 3D sound. However, due to differences in head and ear anthropometry across the population, ITDs related to a sound source at a given location around the head will differ from sub- ject to subject. Furthermore, most individuals do not possess sym- metrical traits between the left and right pinnae. This fact may cause an angle-dependent ITD asymmetry between locations mir- rored across the left and right hemispheres. This paper describes an exploratory analysis performed on publicly available databases of individually measured HRIRs. The analysis was first performed separately for each dataset in order to explore the impact of dif- ferent formats and measurement techniques, and then on pooled sets of repositories, in order to obtain statistical information closer to the population values. Asymmetry in ITDs was found to be consistently more prominent in the rear-lateral angles (approxi- mately between 90° and 130° azimuth) across all databases inves- tigated, suggesting the presence of a sensitive region. A signifi- cant difference between the peak asymmetry values and the aver- age asymmetry across all angles was found on three out of four examined datasets. These results were further explored by pooling the datasets together, which revealed an asymmetry peak at 110° that also showed significance. Moreover, it was found that within the region of sensitivity the difference between specular ITDs ex- ceeds the just noticeable difference values for perceptual discrim- ination at all frequency bands. These findings validate the sta- tistical presence of ITD asymmetry in public datasets of individ- ual HRIRs and identify a significant, perceptually-relevant, region of increased asymmetry. Details of these results are of interest for HRIR modeling and personalization techniques, which should consider implementing compensation for asymmetric ITDs when aiming for perceptually accurate binaural displays. This work is part of a larger study aimed at binaural-audio personalization and user-characterization through non-invasive techniques.

A generalization of the results of the analysis of the electrical activity of the brain of patients with tumor lesions of diencephalic and limbic structures made it possible to replenish the set of diagnostic EEG signs of damage to regulatory structures and expand the clinic's accepted interpretation of interhemispheric asymmetry of EEG in cerebral pathology.

Starting from the sense that laterality represents the functional innegality of cerebral hemispheres asymmetry, and from the sumption that this functional asymmetry although can be subdued by training, it not receed completly,we will try to emphasize these aspects on advanced athletes practicing martial arts, black belt level. The hypothesis of this researchis that laterality can be highlighted bytheinstrumentalityof cinematic parameters analysys of the movements that we consider automatized. For this purpose we used MOVEN from Xsens equipment for human motion tracking using inertial navigation sensors. We have done position aquisitions for the subject's segments and these data underlied on callculation of fist's pathway and joint angles further analized. Data aquisitions took place in Biomotry department in National Institute for Sport Research from Bucharest. Equipped with MOVEN Xsens equipament, four athletes karate Shotokan practitioners, registered at Sports Club AIKO Bucharest, with an experience of 5 to 15 yearsof practice, performed Heian Nidan kata. On each athlete has been done three data aquisition sessions. Then, having an eye on the avatar recording offered by the dedicated software of the MOVEN equipment, we choose the time sequencesin which we analyzed and compared joint angles on elbow (arm - forearm) and in shoulder (arm vertical axis) and knee (upper leg - lower leg) boyh on the left and right side for emphasize the differences in identic postures (times 1, 2, 3 to the left and 4, 5 and 6 to the right). This angles has been calculated both for the right and left limbs.

Recent deep learning-based Brain-Computer Interface (BCI) decoding algorithms mainly focus on spatial-temporal features, while failing to explicitly explore spectral information which is one of the most important cues for BCI. In this paper, we propose a novel regional attention convolutional neural network (RACNN) to take full advantage of spectral-spatial-temporal features for EEG motion intention recognition. Time-frequency based analysis is adopted to reveal spectral-temporal features in terms of neural oscillations of primary sensorimotor. The basic idea of RACNN is to identify the activated area of the primary sensorimotor adaptively. The RACNN aggregates a varied number of spectral-temporal features produced by a backbone convolutional neural network into a compact fixed-length representation. Inspired by the neuroscience findings that functional asymmetry of the cerebral hemisphere, we propose a region biased loss to encourage high attention weights for the most critical regions. Extensive evaluations on two benchmark datasets and real-world BCI dataset show that our approach significantly outperforms previous methods.

This study examines the acoustic behavior in forward speeds of 0, 15, 30, and 60 knots of manned-size, multi-rotor, eVTOL aircraft in quadcopter, hexacopter, and octocopter configurations. The rotors are assumed to have constant RPM and are controlled through collective pitch, with orthogonal phasing between rotors. All configurations share the same disk loading and hover tip Mach, with the rotor radius decreasing and the RPM increasing as the number of rotors increase. The simulations use the Rensselaer Multicopter Analysis Code (RMAC) for the aerodynamic loads coupled with the PSUWOPWOP code for noise predictions at an observer hemisphere. From the results, it is shown that at higher forward flight speeds, where loading noise becomes more dominant, high elevation angles (below the vehicle) show peak noise for all configurations. Asymmetry in the number of outside advancing blades, such as on the plus quadcopter, causes higher noise levels for the left (advancing) side. In-plane directivity patterns that show large decreases due to signal cancellations in inter-boom noise are shown to progressively diminish at larger forward speeds, with lower reductions for the hexacopter and octocopter configurations. The total acoustic radiated power is also compared with the single rotor for all multicopter configurations. The comparison shows that the acoustic power versus the single rotor power is decreasing as we increase the number of rotors or the forward speed.