Hemispheric Activation Research Articles

Finding hidden treasures: A child-friendly neural test of task-following in individuals using functional Transcranial Doppler ultrasound

Despite growing interest in the mental life of individuals who cannot communicate verbally, objective and non-invasive tests of covert cognition are still sparse. In this study, we assessed the ability of neurotypical children to understand and follow task instructions by measuring neural responses through functional transcranial Doppler ultrasound (fTCD). We recorded blood flow velocity for the two brain hemispheres of twenty children (aged 9 to 12) while they performed either a language task or a visuospatial memory task, on identical visual stimuli. We extracted measures of neural lateralisation for the two tasks separately to investigate lateralisation, and we compared the left-minus-right pattern of activation across tasks to assess task-following. At the group level, we found that neural responses were left-lateralised when children performed the language task, and not when they performed the visuospatial task. However, with statistically robust analyses and controlled paradigms, significant lateralisation in individual children was less frequent than expected from the literature. Nonetheless, the pattern of hemispheric activation for the two tasks allowed us to confirm task-following in the group of participants, as well as in over half of the individuals. This provides a promising avenue for a covert and inexpensive test of children's ability to follow task instructions and perform different mental tasks on identical stimuli.

Levodopa Facilitates Prefrontal Cortex Activation During Dual Task Walking in Parkinson Disease

Background. Although dopaminergic medication improves dual task walking in people with Parkinson disease (PD), the underlying neural mechanisms are not yet fully understood. As prefrontal cognitive resources are involved in dual task walking, evaluation of the prefrontal cortex (PFC) is required. Objective. To investigate the effect of dopaminergic medication on PFC activity and gait parameters during dual task walking in people with PD. Methods. A total of 20 individuals with PD (69.8 ± 5.9 years) and 30 healthy older people (68.0 ± 5.6 years) performed 2 walking conditions: single and dual task (walking while performing a digit vigilance task). A mobile functional near infrared spectroscopy system and an electronic sensor carpet were used to analyze PFC activation and gait parameters, respectively. Relative concentrations of oxygenated hemoglobin (HbO2) from the left and right PFC were measured. Results. People with PD in the off state did not present changes in HbO2 level in the left PFC across walking conditions. In contrast, in the on state, they presented increased HbO2 levels during dual task compared with single task. Regardless of medication state, people with PD presented increased HbO2 levels in the right PFC during dual task walking compared with single task. The control group demonstrated increased PFC activity in both hemispheres during dual task compared with single task. People with PD showed increases in both step length and velocity in the on state compared with the off state. Conclusions. PD limits the activation of the left PFC during dual task walking, and dopaminergic medication facilitates its recruitment.

Brain Activation for Audiovisual Information in People With One Eye Compared to Binocular and Eye-Patched Viewing Controls.

Blindness caused by early vision loss results in complete visual deprivation and subsequent changes in the use of the remaining intact senses. We have also observed adaptive plasticity in the case of partial visual deprivation. The removal of one eye, through unilateral eye enucleation, results in partial visual deprivation and is a unique model for examining the consequences of the loss of binocularity. Partial deprivation of the visual system from the loss of one eye early in life results in behavioral and structural changes in the remaining senses, namely auditory and audiovisual systems. In the current study we use functional neuroimaging data to relate function and behavior of the audiovisual system in this rare patient group compared to controls viewing binocularly or with one eye patched. In Experiment 1, a whole brain analysis compared common regions of cortical activation between groups, for auditory, visual and audiovisual stimuli. People with one eye demonstrated a trend for increased activation for low-level audiovisual stimuli compared to patched viewing controls but did not differ from binocular viewing controls. In Experiment 2, a region of interest (ROI) analysis for auditory, visual, audiovisual and illusory McGurk stimuli revealed that people with one eye had an increased trend for left hemisphere audiovisual activation for McGurk stimuli compared to binocular viewing controls. This aligns with current behavioral analysis and previous research showing reduced McGurk Effect in people with one eye. Furthermore, there is no evidence of a correlation between behavioral performance on the McGurk Effect task and functional activation. Together with previous behavioral work, these functional data contribute to the broader understanding of cross-sensory effects of early sensory deprivation from eye enucleation. Overall, these results contribute to a better understanding of the sensory deficits experienced by people with one eye, as well as, the relationship between behavior, structure and function in order to better predict the outcome of early partial visual deafferentation.

Southern hemisphere tropical cyclones: A critical analysis of regional characteristics

AbstractThe destructive nature of tropical cyclones poses a risk to the regions where they occur during and after landfall. Southern hemisphere countries are usually more vulnerable to these risks and impacts due to their lower adaptive capacity. Research for the northern hemisphere has comprehensively explored the nature of tropical cyclones. This information has since been applied to long‐term adaptation plans and short‐term evacuation plans. This study interrogates the characteristics and nature of Southern Hemisphere tropical cyclones and critically explores their differences to Northern Hemisphere storm characteristics. The differences found between the hemispheric storm activities include seasonality, number of storms and the latitudinal position at which these storms undergo genesis and intensification. Similarities were found in storm intensity, which was observed to increase with the time taken to reach maximum lifetime intensity. Higher sea surface temperatures were similarly found to be a major factor associated with increased intensity and lifetime of Southern Hemisphere tropical cyclones. Tropical cyclone seasonality is also centred around the warmer months within each hemisphere. Compared to the Northern Hemisphere the tropical cyclone seasonal length indicates no increase. The magnitude of sea surface temperature increase is also lower in the Northern Hemisphere. These fundamental links observed with temperature in both hemispheres implicates climate warming and its impact on tropical cyclones in both hemispheres, regardless of their seasonality and frequency.

Musical mirror-symmetrical movement tasks: comparison of rhythm versus melody-playing.

Bimanual mirror-symmetrical movement (MSM) is relatively easy to control movement. Different MSM tasks may have different activations and interhemispheric interactions. The purpose of this study is to compare anatomo-physiological features such as hemispheric activations and dominance of two different MSMs, namely melody-playing and rhythm. We examined functional MRI (fMRI) recordings in a group of fifteen right-handed pianists performing two separate tasks: bimanual rhythm and bimanual melody-playing on two different keyboards with standard key order for right hand and reversed for left hand, which allows homolog fingers' movements. Activations and laterality indices on fMRI were examined. The results show that significant cerebellar activations (especially in anterior cerebellum) in both groups. Significant primary sensorimotor cortical activations are observed in the melody-playing group. While there are also bilaterally symmetric activations, and laterality indices suggest overall lateralization towards the left hemisphere in both groups. Activations in the left fronto-parietal cortex, left putamen and left thalamus in conjunction with right cerebellar activations suggest that the left cortico-thalamo-cerebellar loop may be a dominant loop. Dynamic causal modeling (DCM) indicates the presence of causal influences from the left to the right cerebral cortex. In conclusion, melody-playing with bimanual MSM is a complex in-phase task and may help activate the bilateral cortical areas, and left hemisphere is dominant according to laterality indices and DCM results. On the other hand, bimanual rhythm is a simpler in-phase task and may help activate subcortical areas, which might be independent of the voluntary cortical task.

The Application of the Rorschach Inkblot Test in the Study of Neural and Cognitive Aging

Abstract. The Rorschach Inkblot test has been adopted and adapted by many researchers to assess and predict different aspects of human experience and cognitive performance. The present review examines research that incorporates the Rorschach to evaluate neural and cognitive aging as well as decline in age-related disease. Specifically, differences in amygdala and cortical regions, as well as mirror neuron and asymmetrical hemisphere activity that correlate with specific responses to Rorschach stimuli are discussed in the context of typical changes in brain structure and function in the course of aging. In addition, the present review provides a proposed framework for expanding the use of the Rorschach to evaluate other domains of neural and cognitive function. The authors conclude that, despite a need for increased research, the Rorschach is a viable measure to evaluate certain aspects of cognitive function and decline throughout the lifespan.

The effect of unilateral hand contractions on psychophysiological activity during motor performance: Evidence of verbal-analytical engagement

ObjectivesConscious engagement in movement control can influence motor performance. In most cases, the left hemisphere of the brain plays an important role in verbal-analytical processing and reasoning, so changes in the balance of hemispheric activation may influence conscious engagement in movement. Evidence suggests that unilateral hand contractions influence hemispheric activation, but no study has investigated whether there is an associated effect of hand contractions on verbal-analytical processing during motor performance. This study utilized psychophysiological (and behavioural) measures to examine whether pre-performance unilateral hand contraction protocols change verbal-analytical engagement during motor performance. DesignA repeated measures crossover design was employed. MethodsTwenty-eight participants completed three hand contraction protocols in a randomised order: left-, right- and no-hand contractions. Electroencephalography (EEG) measures of hemispheric asymmetry were computed during hand contractions. A golf putting task was conducted after each protocol. EEG connectivity between sites overlying the left verbal-analytical temporal region (T7) and the motor planning region (Fz) was computed for the 3 sec prior to movement initiation. Additionally, electrocardiography (ECG) and electromyography (EMG) signals were analysed 6 sec prior to movement initiation until 6 sec after. Golf putting performance (distance from the target) and putter swing kinematics were measured. ResultsContralateral hemisphere activity was revealed for the left-hand and right-hand contraction conditions. During motor planning, the left-hand contraction protocol led to significantly lower T7-Fz connectivity, and the right-hand contraction protocol led to significantly higher T7-Fz connectivity than the other conditions. EMG, ECG and kinematic measures did not differ as a function of condition. Importantly, T7-Fz connectivity mediated the relationship between hand squeezing and motor performance (distance from the target). ConclusionThe EEG results suggest that pre-performance unilateral hand contractions influence the extent of verbal-analytical engagement during motor planning, which in turn influences motor performance. However, the hand contractions did not influence cardiac activity, muscle activity or kinematics.

Unveilling the cerebral and sensory contributions to automatic postural control during dual-task standing

The postural control dual-task literature has demonstrated greater postural stability during dual-task in comparison to single task (i.e., standing balance alone through the examination of multiple kinetic and kinematic measures. This improve stability is thought to reflect an automatic mode of postural control during dual-task. Recently, sample entropy (SampEn) and wavelet discrete transform have supported the claim of automaticity, as higher SampEn values and a shift toward increased contributions from automatic sensory systems have been demonstrated in dual-task settings. In order to understand the cortical component of postural control, functional near-infrared spectroscopy has been used to measure cortical activation during postural control conditions. However, the neural correlates of automatic postural behaviour have yet to be fully investigated. Therefore, the purpose of this study is to confirm the presence of automatic postural control through static and dynamic balance measures, and to investigate the prefrontal cortex activation when concurrently performing quiet standing and the auditory cognitive tasks of varied difficulty. Eighteen healthy young adults (21.4±3.96yo), 12 females and 6 males, with no balance deficits were recruited. Participants were instructed to either quietly stand on a force platform (SM), perform three cognitive tasks while seated (SC) or perform both aforementioned tasks concurrently (DT). Results supported automatic postural control with lower area and standard deviation of center-of-pressure in DT conditions compared to SM. As for SampEn and the wavelet analysis, DT conditions demonstrated greater values than SM, and a shift from vision to a cerebellar contribution. For the most difficult cognitive task, the DNS task, a trend toward significantly lower right hemisphere prefrontal cortex activation compared to left hemisphere activation in DT was found, potentially representing a decrease in cognitive control, and the presence of automaticity. These findings suggest that the simultaneous performance of a difficult cognitive task and posture yields automatic postural behaviour, and provides insight into the neural correlates of automaticity.

Anterior temporal lobe is necessary for efficient lateralised processing of spoken word identity

In the healthy human brain, the processing of language is strongly lateralised, usually to the left hemisphere, while the processing of complex non-linguistic sounds recruits brain regions bilaterally. Here we asked whether the anterior temporal lobes, strongly implicated in semantic processing, are critical to this special treatment of spoken words. Nine patients with semantic dementia (SD) and fourteen age-matched controls underwent magnetoencephalography and structural MRI. Voxel based morphometry demonstrated the stereotypical pattern of SD: severe grey matter loss restricted to the anterior temporal lobes, with the left side more affected. During magnetoencephalography, participants listened to word sets in which identity and meaning were ambiguous until word completion, for example PLAYED versus PLATE. Whereas left-hemispheric responses were similar across groups, patients demonstrated increased right hemisphere activity 174–294 msec after stimulus disambiguation. Source reconstructions confirmed recruitment of right-sided analogues of language regions in SD: atrophy of anterior temporal lobes was associated with increased activity in right temporal pole, middle temporal gyrus, inferior frontal gyrus and supramarginal gyrus. Overall, the results indicate that anterior temporal lobes are necessary for normal and efficient lateralised processing of word identity by the language network.

Preoperative evaluation by functional magnetic resonance imaging in patients with dysembryoplastic neuroepithelial tumours: A case series

IntroductionDysembryoplastic neuroepithelial tumours (DNET) are a type of benign glioneuronal neoplasia of typically temporal location that produce drug-resistant epileptic seizures in children and young adults. AimsThis work aims to assess the usefulness of functional magnetic resonance imaging (fMRI) in the preoperative study in four patients with DNET. A Philips Intera 3.0 Tesla magnetic resonance imaging scanner and the Blood-Oxygen-Level-Dependent (BOLD) technique were used to obtain the images, making it possible to locate the eloquent areas for language and motor areas through the application of specific paradigms. ResultsIn one case the tumour was adjacent to Broca’s area, in two cases it coincided with Wernicke’s area, in one patient it was <1 cm from the motor area for the hand and in another close to memory. Only two of the patients were operated on, without postoperative functional deficit. Hemispheric activation contralateral to the tumour suggestive of neuroplasticity was observed in one of the patients. ConclusionsfMRI is a non-invasive method that allows us to assess the proximity of lesions to eloquent areas, which is key in the evaluation of surgical risk. In addition, it allowed the detection of probable neuroplasticity in one case, which guaranteed the success of the surgery

Obstetric Brachial Plexus Palsy: Can a Unilateral Birth Onset Peripheral Injury Significantly Affect Brain Development?

ABSTRACT Purpose: Examine brain structure and function in OBPP and relate to clinical outcomes to better understand the effects of decreased motor activity on early brain development. Methods: 9 OBPP, 7 controls underwent structural MRI scans. OBPP group completed evaluations of upper-limb function and functional near-infrared spectroscopy (fNIRS) during motor tasks. Results: Mean primary motor area volume was lower in both OBPP hemispheres. No volume differences across sides seen within groups; however, Asymmetry Ratio in supplementary motor area differed between groups. Greater asymmetry in primary somatosensory area correlated with lower ABILHAND-Kids scores. fNIRS revealed more cortical activity in both hemispheres during affected arm reach. Conclusion: Cortical volume differences or asymmetry were found in motor and sensory regions in OBPP that related to clinical outcomes. Widespread cortical activity in fNIRS during affected arm reach suggests reorganization in both hemispheres and is relevant to rehabilitation of those with developmental peripheral and brain injuries.

Effects of Small Temperature Differences Detected in Callosal Circuits of the Anterior Cingulate Cortex

We measured the sensitivity of cortical circuit activity to small differences in local cortical environments by studying how temperature affects the trajectory of epileptiform events (EEs). EEs evoked via blockade of GABA-A receptors were recorded extracellularly from mouse coronal brain slices containing both hemispheres of anterior cingulate cortex synaptically connected by corpus callosum axons. Preferentially illuminating one hemisphere with the microscope condenser produced temperature differences of 0.1 °C between the hemispheres. The relatively warmer hemisphere typically initiated the EEs that then propagated to the contralateral side, demonstrating temperature directed propagation. Severing the callosum following one hour of EEs showed that the warmer hemisphere possessed a higher rate of EE generation. Further experiments implied that intact callosal circuits were required for the increased EE generation in the warmer hemisphere. We propose a hypothesis whereby callosal circuits can amplify differences in respective hemispheric activity, promoting this directionality in seizure propagation.

Gross motor adaptation benefits from sleep after training.

Sleep has been shown to facilitate the consolidation of newly acquired motor memories. However, the role of sleep in gross motor learning, especially in motor adaptation, is less clear. Thus, we investigated the effects of nocturnal sleep on the performance of a gross motor adaptation task, i.e. riding an inverse steering bicycle. Twenty‐six male participants (M = 24.19, SD = 3.70 years) were randomly assigned to a PM‐AM‐PM (n = 13) or an AM‐PM‐AM (n = 13) group, i.e. they trained in the evening/morning and were re‐tested the next morning/evening and the following evening/morning (PM‐AM‐PM/AM‐PM‐AM group) so that every participant spent one sleep as well as one wake interval between the three test sessions. Inverse cycling performance was assessed by speed (riding time) and accuracy (standard deviation of steering angle) measures. Behavioural results showed that in the PM‐AM‐PM group a night of sleep right after training stabilized performance (accuracy and speed) and was further improved over the subsequent wake interval. In the AM‐PM‐AM group, a significant performance deterioration after the initial wake interval was followed by the restoration of subjects' performance levels from right after training when a full night of sleep was granted. Regarding sleep, right hemispheric fast N2 sleep spindle activity was related to better stabilization of inverse cycling skills, thus possibly reflecting the ongoing process of updating the participants' mental model from “how to ride a bicycle” to “how to ride an inverse steering bicycle”. Our results demonstrate that sleep facilitates the consolidation of gross motor adaptation, thus adding further insights to the role of sleep for tasks with real‐life relevance.

Individual Response to Stressors and Efficiency in Project Activities.

This article investigates the way a graded approach can be implemented in the organization of the project-based learning process in accordance with the personality characteristics of subjects. This study is based on the results analysis of the key features of project-based learning as one of the methods for developing human resources. The assessment of subjects’ individual response to stressors at different project stages is justified to be relevant in order to improve project efficiency in the framework of the learning process. The assessment of the individual response of subjects to stressors was carried out according to the activation dynamics of cerebral hemispheres. The research target was to determine features of the subjects’ individual responses to the project activity stressors and to identify specifics of the individual responding at each of its stages. The study involved 56 final-year students of different majors. Aktivatsiometr ATs-9K, a device for comprehensive psychophysiological diagnosis designed by Yu. A. Tsagarelli, was used to monitor hemispheric activation. This hardware and software complex consists of a device diagnosing the activation of cerebral hemispheres based on the galvanic skin response and PC software for automatic data processing. The individual typological indicators of activation (13 measurements in a familiar environment) and activity-situational indicators of activation (seven single measurements at different stages of the project activity) were calculated. The stress response was diagnosed if the activity-situational activation indicators of the cerebral hemispheres exceeded the individual typological activation indices by more than 1.5 times. The results of the empirical study show different types of individual responses to stressors at different stages of the project activity. The analysis of the profiles of individual responses to stressors made it possible to differentiate subjects, and also identify groups of students with the maximum resources for each stage of activity.

COMPLEX DIAGNOSTICS OF GIFTED CHILDREN OF PRESCHOOL AGE

The article describes a set of diagnostic tools to identify the natural potential of a gifted preschooler, it presents the results of diagnosing children and their parents using these tools, as well as their interpretation. The relevance of the formation of a comprehensive diagnosis of giftedness of preschool children is determined by the task of promoting preservation and development of child giftedness, the national gene pool of gifted people in Russia. The novelty of the considered approach to solving the problem of diagnosing children’s giftedness lies in the use of an original set of techniques for determining the profile of the dominant hemispheres of the brain, a psychotype and natural inclinations of the child. The aim of the study is to find an answer to the question concerning the potential of giftedness with which a person is born and the percentage of children endowed with it. Among the research methods employed were such empirical methods as observation and testing with the help of a set of questionnaires and tests, as well as a statistical method for the initial collection and primary processing of quantitative data on natural inclinations, psychotypes, dominant profiles of hemispheric brain activity. The following diagnostic tools were applied: A. I. Savenkov’s questionnaire “Palette of interests” - to determine the natural inclinations of preschoolers,” Psychogeometric test of S. Dellinger (in the adaptation of G. I. Kolesnikova) - to determine a psychotype and the technique of Carla Hannaford - to determine the dominant profile of hemispheric activity of the brain. Among the results obtained, the most significant conclusion is the possibility of identifying a diverse and rich palette of natural inclinations in each child, which will allow individualizing the content aspect of the program and serve as a basic condition for the successful development of natural inclinations of each child. In the total sample of children (1669 questionnaires) more than 82% demonstrated inclinations to 3-4 types of human activity. Also revealed are more poorly developed areas, such as the communicative sphere, which is associated with the lack of live interaction (communication) of the child with adults and peers, and humanitarian, requiring more attention to the speech development of the child. Thus, children of 4-7 years old of both sexes with a dominant profile were characterized by a weak interest in the communicative sphere, the most preferred area for girls was art, and for boys - mathematics and technology

Polar flux imbalance at the sunspot cycle minimum governs hemispheric asymmetry in the following cycle

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-fieldα-effect and meridional circulation can have finite contributions in this regard.

No Evidence of Improved Emotion Perception Through Unilateral Hand Contraction.

Previous studies have identified improved cognitive performance from unilateral hand contraction to effect contralateral hemisphere activation. As little is known of whether this activation can improve emotion perception, this study examined any differences in perception accuracy and reaction times of matching photographs of human facial expressions presented to the left or right visual fields after left versus right hemisphere activation triggered by unilateral hand contractions. We used photographs of happy, sad, and neutral facial expressions presented briefly and simultaneously (two photographs in each presentation) either unilaterally (intrahemisphere condition) or bilaterally (interhemisphere condition). We recruited 68 university student participants (aged 19–23 years) and randomly assigned half of them to squeeze a dynamometer with the right hand, while the other half squeezed with the left hand, prior to performing the Dimond face-matching task. Matching of happy faces was faster than matching of sad faces. In females (but not males), perception accuracy was higher when stimuli were presented in the right (vs. left) visual field. We found no difference in emotion perception of photographs in either unilateral (intrahemispheric) or bilateral (interhemispheric) stimuli presentations as a function of hand contractions.

The human amygdala disconnecting from auditory cortex preferentially discriminates musical sound of uncertain emotion by altering hemispheric weighting

How do humans discriminate emotion from non-emotion? The specific psychophysical cues and neural responses involved with resolving emotional information in sound are unknown. In this study we used a discrimination psychophysical-fMRI sparse sampling paradigm to locate threshold responses to happy and sad acoustic stimuli. The fine structure and envelope of auditory signals were covaried to vary emotional certainty. We report that emotion identification at threshold in music utilizes fine structure cues. The auditory cortex was activated but did not vary with emotional uncertainty. Amygdala activation was modulated by emotion identification and was absent when emotional stimuli were chance identifiable, especially in the left hemisphere. The right hemisphere amygdala was considerably more deactivated in response to uncertain emotion. The threshold of emotion was signified by a right amygdala deactivation and change of left amygdala greater than right amygdala activation. Functional sex differences were noted during binaural uncertain emotional stimuli presentations, where the right amygdala showed larger activation in females. Negative control (silent stimuli) experiments investigated sparse sampling of silence to ensure modulation effects were inherent to emotional resolvability. No functional modulation of Heschl’s gyrus occurred during silence; however, during rest the amygdala baseline state was asymmetrically lateralized. The evidence indicates changing hemispheric activation and deactivation patterns between the left and right amygdala is a hallmark feature of discriminating emotion from non-emotion in music.

Variations in the Winter Troughs' Position With Local Time, Longitude, and Solar Activity in the Northern and Southern Hemispheres

AbstractComprehensive pattern of ionospheric troughs' location in winter for all local times, longitudes, high (HSA), and low (LSA) solar activity, in both hemispheres, is at first investigated. Statistical analysis based on a large dataset of Interkosmos‐19, CHAMP, and Kosmos‐900 satellites was performed for quiet geomagnetic conditions Kp = 1–3. Three troughs were considered: high‐latitude trough (HLT) located inside the auroral oval, main ionospheric trough (MIT) located equatorward from the auroral oval, that is, at subauroral latitudes, and mid‐latitude ring ionospheric trough (RIT). The main purpose was to study the formation of the troughs' diurnal pattern in different conditions. The main problem was to distinguish MIT from RIT and MIT from HLT. For this purpose, early morning hours (04–06 LT), late morning hours (07–10 LT), day, evening, and night conditions were examined. In the early morning sector, RIT was separated from MIT and eliminated from the dataset. In the late morning sector, MIT and HLT were first clearly divided, although only for HSA. During the day, in the Northern Hemisphere under all conditions, HLT is mainly observed, in the Southern Hemisphere at poorly lit longitudes only the daytime MIT, and at well‐lit longitudes only the HLT is observed. The division of MIT and HLT was carried out according to the (statistical) position of the equatorial boundary of the auroral oval precipitation. At night, longitudinal variations in the MIT position determine the asymmetry of the hemispheres. Thus, the occurrence and position of MIT and HLT depend on the hemisphere, longitude, and solar activity.

Improved Accuracy on Lateralized Spatial Judgments in Healthy Aging.

Healthy young adults often demonstrate a leftward spatial bias called "pseudoneglect" which often diminishes with aging. One hypothesis for this phenomenon is an age-related deterioration in right hemisphere functions (right hemi-aging). If true, then a greater rightward bias should be evident on all spatial attention tasks regardless of content. Another hypothesis is a decrease in asymmetrical hemispheric activation with age (HAROLD). If true, older participants may show reduced bias in all spatial tasks, regardless of leftward or rightward biasing of specific spatial content. Seventy right-handed healthy participants, 33 younger (21-40) and 37 older (60-78), were asked to bisect solid and character-letter lines as well as to perform left and right trisections of solid lines. Both groups deviated toward the left on solid line bisections and left trisections. Both groups deviated toward the right on right trisections and character line bisections. In all tasks, the older participants were more accurate than the younger participants. The finding that older participants were more accurate than younger participants across all bisection and trisection conditions suggests a decrease in the asymmetrical hemispheric activation of these specialized networks important in the allocation of contralateral spatial attention or spatial action intention.