Showing papers in "Progress in Brain Research in 2019"

Dispositional negativity, cognition, and anxiety disorders: An integrative translational neuroscience framework

Abstract: When extreme, anxiety can become debilitating. Anxiety disorders, which often first emerge early in development, are common and challenging to treat, yet the underlying mechanisms have only recently begun to come into focus. Here, we review new insights into the nature and biological bases of dispositional negativity, a fundamental dimension of childhood temperament and adult personality and a prominent risk factor for the development of pediatric and adult anxiety disorders. Converging lines of epidemiological, neurobiological, and mechanistic evidence suggest that dispositional negativity increases the likelihood of psychopathology via specific neurocognitive mechanisms, including attentional biases to threat and deficits in executive control. Collectively, these observations provide an integrative translational framework for understanding the development and maintenance of anxiety disorders in adults and youth and set the stage for developing improved intervention strategies.

Empathy and emotion regulation: An integrative account.

Abstract: How we understand and respond to others' emotions (i.e., empathy) may be influenced by the regulatory processes that are used to shape which emotions we and others have (i.e., emotion regulation). Empathy and emotion regulation are complex multidimensional constructs and the relationship between their component processes is not well characterized. To enable future work to examine their relationship more closely, this chapter presents an integrative framework of empathy and emotion regulation. We begin by delineating the component processes that underlie empathy and emotion regulation, and the neural underpinnings of these processes. We then present an integrative framework describing the processes of empathy and how these may be acted upon by distinct regulatory strategies. We conclude with a brief consideration of contextual influences on empathy and emotion regulation using a reward-based heuristic.

The neuroscience of meditation: classification, phenomenology, correlates, and mechanisms

Abstract: Rising from its contemplative and spiritual traditions, the science of meditation has seen huge growth over the last 30 years. This chapter reviews the classifications, phenomenology, neural correlates, and mechanisms of meditation. Meditation classification types are still varied and largely subjective. Broader models to describe meditation practice along multidimensional parameters may improve classification in the future. Phenomenological studies are few but growing, highlighting the subjective experience and correlations to neurophysiology. Oscillatory EEG studies are not conclusive likely due to the heterogeneous nature of the meditation styles and practitioners being assessed. Neuroimaging studies find common patterns during meditation and in long-term meditators reflecting the basic similarities of meditation in general; however, mostly the patterns differ across unique meditation traditions. Research on the mechanisms of meditation, specifically attention and emotion regulation is also discussed. There is a growing body of evidence demonstrating positive benefits from meditation in some clinical populations especially for stress reduction, anxiety, depression, and pain improvement, although future research would benefit by addressing the remaining methodological and conceptual issues. Meditation research continues to grow allowing us to understand greater nuances of how meditation works and its effects.

Evolution of the modern human brain

Abstract: When compared to the brains of our closest living relatives, chimpanzees and bonobos, the brains of modern humans are larger and differently shaped. This chapter reviews what we know about the evolutionary history of these differences. We can make an educated guess about the size and shape of the brains of the hypothetical common ancestor of modern humans and chimpanzees/bonobos, but between ca. 8 million years ago and the present day evidence about the size and shape of the brain comes from either natural endocasts, which are literally brain-shaped rocks, or from individuals for which enough of the brain case is preserved to provide estimates of endocranial volume and/or the relative proportions of the different regions of the cerebral hemispheres and the cerebellum. The tempo and mode of brain size increase in the hominin clade has been the subject of spirited debate, but we suggest that some of this controversy is the combination of an overreliance on frequentist statistical tests and researchers addressing these issues at different taxonomic scales. The existence and significance of shape changes are also controversial topics, made more so by the dearth of reliable evidence.

Nondual awareness: Consciousness-as-such as non-representational reflexivity.

Abstract: I introduce arguments toward a non-representational reflexivity theory of consciousness-as-such to address one of the key issues in the science of consciousness today: lack of understanding of the nature of consciousness itself. An expanded map of consciousness is outlined, which includes, in addition to the well-known contents of awareness and levels of arousal, the indeterminate substrate and consciousness-as-such or nondual awareness. The central idea presented is that consciousness-as-such is a non-conceptual nondual awareness, whose essential property is non-representational reflexivity. This property makes consciousness-as-such phenomenologically, cognitively and neurobiologically a unique kind, different from and irreducible to any contents, functions and states, including the indeterminate substrate. Our previous hypothesis on the precuneus network for nondual awareness is further discussed in relation to non-representational reflexivity, and in the light of other hypotheses on the neural correlates of consciousness-as-such.

Oligodendrocyte precursor cells as a therapeutic target for demyelinating diseases.

Abstract: The mechanisms regulating differentiation of multipotent oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes (OLs) are critical to our understanding of myelination and remyelination Following acute demyelination in the central nervous system, adult OPCs migrate to the injury site, differentiate into OLs and generate new myelin sheaths A common feature of regenerative processes is the fact that remyelination efficiency declines with aging and, accounts for the observation that chronic demyelinating diseases like multiple sclerosis (MS) are characterized by an ineffective remyelination Without doubt, impairment of OPC differentiation is an essential determinant of the aging effects in remyelination However, spontaneous remyelination is limited in demyelinating diseases such as MS, owing in part to the failure of adult OPCs to differentiate into myelinating OLs The inability to restore myelin after injury compromises axon integrity and renders them vulnerable to degeneration Although the genes that regulate the proliferation and differentiation of OPCs during development have been intensively studied, relatively little is known about the molecular signals that regulate the function of adult OPCs after demyelination Elucidating the mechanisms regulating OPC differentiation are key to identifying pharmacological targets for remyelination-enhancing therapy This review will discuss OPC biology, myelination, and possible pharmacological targets for promoting the differentiation of OPCs as a strategy to enhance remyelination, including the potential for nanoscale delivery

The impact of sleep deprivation on declarative memory.

Abstract: Sleep plays a crucial role in memory stabilization and integration, yet many people obtain insufficient sleep. This review assesses what is known about the level of sleep deprivation that leads to impairments during encoding, consolidation and retrieval of declarative memories, and what can be determined about the underlying neurophysiological processes. Neuroimaging studies that deprived sleep after learning have provided some of the most compelling evidence for sleep's role in the long-term reorganization of memories in the brain (systems consolidation). However, the behavioral consequences of losing sleep after learning-shown by increased forgetting-appear to recover over time and are unaffected by more common forms of partial sleep restriction across several nights. The capacity to encode new memories is the most vulnerable to sleep loss, since long-term deficits have been observed after total and partial sleep deprivation, while retrieval mechanisms are relatively unaffected. The negative impact of sleep loss on memory has been explored extensively after a night of total sleep deprivation, but further research is needed on the consequences of partial sleep loss over many days so that impairments may be generalized to more common forms of sleep loss.

Nanomedicine in Alzheimer's disease: Amyloid beta targeting strategy

Abstract: The treatment of Alzheimer's disease (AD) is up to today one of the most unsuccessful examples of biomedical science. Despite the high number of literature evidences detailing the multifactorial and complex etiopathology of AD, no cure is yet present on the market and the available treatments are only symptomatic. The reasons could be ascribed on two main factors: (i) lack of ability of the majority of drugs to cross the blood-brain barrier (BBB), thus excluding the brain for any successful therapy; (ii) lack of selectivity and specificity of drugs, decreasing the efficacy of even potent anti-AD drugs. The exploitation of specifically engineered nanomedicines planned to cross the BBB and to target the most "hot" site of action (i.e., β-amyloid) is one of the most interesting innovations in drug delivery and could reasonably represent an promising choice for possible treatments and even early-diagnosis of AD. In this chapter, we therefore outline the most talented approaches in AD treatment with a specific focus on the main advantages/drawbacks and future possible translation to clinic application.

Toward a brain theory of meditation.

Abstract: The rapidly progressing science of meditation has led to insights about the neural correlates of focused attention meditation (FAM), open monitoring meditation (OMM), compassion meditation (CM) and loving kindness meditation (LKM), in terms of states and traits. However, a unified theoretical understanding of the brain mechanisms involved in meditation-related functions, including mindfulness, is lacking. After reviewing the main forms of meditation and their relationships, the major brain networks and brain states, as well as influential theoretical views of consciousness, we outline a Brain Theory of Meditation (BTM). BTM takes the lead from considerations about the roles of the major brain networks, i.e., the central executive, salience and default mode networks, and their interplay, in meditation, and from an essential energetic limitation of the human brain, such that only up to 1% of the neurons in the cortex can be concurrently activated. The development of the theory is also guided by our neuroscientific studies with the outstanding participation of Theravada Buddhist monks, with other relevant findings in literature. BTM suggests mechanisms for the different forms of meditation, with the down-regulation of brain network activities in FAM, the gating and tuning of network coupling in OMM, and state-related up-regulation effects in CM and LKM. The theory also advances a leftward asymmetry in top-down regulation, and an enhanced inter-hemispheric integration, in meditation states and traits, also with implications for a theoretical understanding of conscious access. Meditation thus provides a meta-function for an efficient brain/mind regulation, and a flexible allocation of highly limited and often constrained (e.g., by negative emotion and mind wandering) brain activity resources, which can be related to mindfulness. Finally, a series of experimental predictions is derived from the theory.

Adolescent sleep restriction effects on cognition and mood

Abstract: Adolescents throughout the world do not obtain adequate sleep. A recent proliferation of experimental and quasi-experimental studies has considerably clarified the relationships between sleep loss and neurobehavioral function suggested by earlier epidemiological and cross-sectional studies. These new studies concur in finding that multiple successive nights of restricted sleep can impair multiple cognitive and affective functions. These effects cumulate from night to night, may not fully recover after weekend recovery sleep and may even be compounded by re-exposure to sleep restriction. An hour long afternoon nap reduces sleepiness in addition to improving vigilance, memory encoding and mood without interfering with nocturnal sleep when the latter is shortened. However, this does not detract from the point that adolescents require approximately 9h of sleep per night for optimal neurobehavioral function, a message that more need to embrace.

Short-term mindful breath awareness training improves inhibitory control and response monitoring.

Abstract: Mindfulness meditation is thought to lead to positive changes in cognitive and affective functioning. However, the mechanisms underlying these changes are not well understood. One reason for this is that so far only very few studies considered the effects of specific meditation practices. We thus investigated the effects of engaging in one specific form of mindfulness meditation for a brief time period on behavioral and neural indicators of inhibitory control and metacognition. Performance on the Go/No-Go task and concurrent neural activity (EEG) was assessed before and after participants engaged in 3 weeks of mindful breath awareness meditation. Compared to a waitlist control group, meditation training enhanced the N2 event-related potential in No-Go trials and the error-related negativity (ERN) after error responses. As these two components reflect conflict and response monitoring, respectively, our results support the notion that mindfulness meditation improves metacognitive processes. The changes in the ERN were correlated with the accumulated amount of meditation time, highlighting the importance of meditation practice. Furthermore, meditation improved a behavioral marker of impulsive responding, indicating the relevance of mindfulness-based approaches for supporting health-related behaviors that are associated with deficits in impulsive control, such as substance abuse or over-eating. This study demonstrated that investigating one particular meditation practice rather than complex mindfulness-based interventions can contribute to a deeper understanding of mindfulness meditation mechanisms.

Functional connectivity and the sleep-deprived brain.

Abstract: Resting state functional connectivity (rsFC) evaluated by detecting temporal co-variation of BOLD signals across multiple brain regions undergoes three major changes following sleep deprivation that indicate the occurrence of sleep intrusions; a loss of integration within networks like the default mode network as well as between networks like the salience and dorsal attention systems; a loss of segregation between networks, for example, between the dorsal attention and default mode networks; and an increase in global signal. Changes in vigilance affect rsFC and these likely occur in many scans involving persons with neuropsychiatric conditions. Ensuring "healthy" or "control" participants do not fall asleep in the scanner is increasingly acknowledged as a being important for proper inference in fMRI studies. Dynamic functional connectivity analyses evaluating the relative proportion of time spent in "low" or "high" arousal states during the well-rested state can predict propensity for vigilance decline when sleep deprived.

Mindfulness training as cognitive training in high-demand cohorts: An initial study in elite military servicemembers.

Abstract: Cognitive ability is a key selection criterion for entry into many elite professions. Herein, we investigate whether mindfulness training (MT) can enhance cognitive performance in elite military forces. The cognitive effects of a short-form 8-h MT program contextualized for military cohorts, referred to as Mindfulness-Based Attention Training (MBAT), were assessed. Servicemembers received either a 2-week (n=40) or 4-week (n=36) version of MBAT or no training (NTC, n=44). Sustained attention and working memory task performance along with self-reported cognitive failures were assessed at study onset (T1) and 8-weeks later (T2). In contrast to both the NTC and 2-week MT groups, the 4-week MT group significantly improved over time on attention and working memory outcome measures. Among the 4-week more so than the 2-week MBAT participants, working memory performance improvements were correlated with their amount of out-of-class MT practice. In addition to these group-wise effects, all participants receiving MBAT decreased in their self-reported cognitive failures from T1 to T2. Importantly, none of these improvements were related to self-reported task motivation. Together, these results suggest that short-form MT, when delivered over a 4-week delivery schedule, may be an effective cognitive training tool in elite military cohorts.

The contemplative exercise through the lenses of predictive processing: A promising approach.

Abstract: The theory of predictive processing in the comprehensive articulation proposed by Karl Friston is a framework that boasts an impressively wide explanatory power in neurobiology, where processes apparently as diverse as perception, action, attention, and learning unfold, and are coherently orchestrated, according to the single general mandate of free-energy minimization. In the present opinion piece, I argue that the adoption of this theoretical perspective can provide a much needed unitary framework for contemplative research as well, whose explosive growth in terms of the number of published studies and amount of collected data has not been matched yet by a similarly extensive effort to theoretically organize the findings, so that a deeper understanding of meditation-related processes can be attained. After an introduction to the basic notions of predictive processing, a tentative application of the latter to the meditative exercise is discussed, taking as a paradigmatic example the Japanese Zen meditation practice of shikantaza. Finally, I provide a short list of experimental paradigms that seem particularly useful to test the hypotheses born out of the predictive processing approach to contemplative research.

Mathematical models for dynamic, multisensory spatial orientation perception.

Abstract: Mathematical models have been proposed for how the brain interprets sensory information to produce estimates of self-orientation and self-motion. This process, spatial orientation perception, requires dynamically integrating multiple sensory modalities, including visual, vestibular, and somatosensory cues. Here, we review the progress in mathematical modeling of spatial orientation perception, focusing on dynamic multisensory models, and the experimental paradigms in which they have been validated. These models are primarily "black box" or "as if" models for how the brain processes spatial orientation cues. Yet, they have been effective scientifically, in making quantitative hypotheses that can be empirically assessed, and operationally, in investigating aircraft pilot disorientation, for example. The primary family of models considered, the observer model, implements estimation theory approaches, hypothesizing that internal models (i.e., neural systems replicating the behavior/dynamics of physical systems) are used to produce expected sensory measurements. Expected signals are then compared to actual sensory afference, yielding sensory conflict, which is weighted to drive central perceptions of gravity, angular velocity, and translation. This approach effectively predicts a wide range of experimental scenarios using a small set of fixed free parameters. We conclude with limitations and applications of existing mathematical models and important areas of future work.

Emotion regulation and emotion perception in aging: A perspective on age-related differences and similarities.

Abstract: The aim of this chapter is to review recent literature describing how developments in cognition may contribute to age-related changes in emotional processes, specifically emotion regulation and emotion perception. In general, older adults are more likely than young adults to report feeling positive. Prominent conceptual models of cognitive and emotional development in aging attempt to explain why the affective lives of older adults might not undergo similar age-related declines as other cognitive and physical systems. In this chapter, we will discuss predictions of cognitive and emotional development from several leading conceptual models of aging. We will then examine how closely the evidence from the fields of emotion regulation and emotion perception coincides with conceptual predictions. Finally, we will attempt to negotiate findings of age differences and age similarities in emotional processes as well as provide suggestions for future studies of emotion and cognition in aging.

Self-regulation and social behavior during sleep deprivation.

Abstract: An emerging literature is specifically focusing on the effects of sleep deprivation on aspects of social functioning and underlying neural changes. Two critical facets of social behavior emerge that are negatively impacted by sleep deprivation-self-regulation, which includes behavioral and emotional regulation, and social monitoring, which includes perceiving and interpreting cues relating to self and others. Sleep deprived individuals performing tasks with social components show altered brain activity in areas of the prefrontal cortex implicated in self-control, inhibition, evaluation, and decision-making, in proximity to mesocorticolimbic pathways to reward and emotional processing areas. These cognitive changes lead to increased reward seeking and behaviors that promote negative health outcomes (such as increased consumption of indulgence foods). These changes also lead to emotional disinhibition and increased responses to negative stimuli, leading to reductions in trust, empathy, and humor. Concomitant attentional instability leads to impaired social information processing, impairing individual and team performance and increasing likelihood of error, incident, and injury. Together, changes to reward seeking, the foundational components of social interaction, and interpretation of social cues, can result in unpleasant or deviant behavior. These behaviors are perceived and negatively responded to by others, leading to a cycle of conflict and withdrawal. Further studies are necessary and timely. Educational and behavioral interventions are required to reduce health-damaging behaviors, and to reduce emotionally-laden negative interpretation of sleep-deprived exchanges. This may assist with health, and with team cohesion (and improved performance and safety) in the workplace and the home.

Nanoparticles and neurotoxicity: Dual response of glutamatergic receptors.

Abstract: Although the use of nanoparticles for neuro-diagnostic and neurotherapeutic purposes provides superior benefits than the conventional approaches, it may be potentially toxic in central nervous system. In this respect, nanotechnological research focuses on nanoneurotoxicity-nanoneurosafety concepts. Despite these efforts, nanoparticles (NPs) may cause neurotoxicity, neuroinflammation, and neurodegeneration by penetrating the brain-olfactory route and blood-brain barrier (BBB). Indeed, due to their unique structures nanomaterials can easily cross biological barriers, thus avoid drug delivery problems. Despite the advancement of nanotechnology for designing therapeutic agents, toxicity of these nanomaterials is still a concern. Activation of neurons by astrocytic glutamate is a result of NPs-mediated astrocyte-neuron crosstalk. Increased extracellular glutamate levels due to enhanced synthesis and reduced reuptake may induce neuronal damage by abnormal activation of extrasynaptic N-methyl d-aspartate receptor (NMDAR) subunits. NMDAR is the key factor that mediates the disturbances in intracellular calcium homeostasis, mitochondrial dysfunction and generation of reactive oxygen species in NPs exposed neurons. While some NPs cause neuronal death by inducing NMDARs, others may be neurotoxic through the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors or protect the neurons via blocking NMDARs. However, mechanisms of dual effects of NPs, neurotoxicity or neuroprotection are not precisely known. Some NPs present neuroprotective effect either by selectively inhibiting extrasynaptic subunit of NMDARs or by attenuating oxidative stress. NPs-related proinflammatory activation of microglia contributes to the dysfunction and cytotoxicity in neurons. Therefore, investigation of the interaction of NPs with the neuronal signaling molecules and neuronal receptors is necessary for the better understanding of the neurotoxicity or neurosafety of nanomaterials.

Nanowired delivery of cerebrolysin with neprilysin and p-Tau antibodies induces superior neuroprotection in Alzheimer's disease.

Abstract: Alzheimer's disease (AD) is estimated to be afflicting over 55 millions of individual worldwide in 2018-19 for which no suitable clinical therapeutic measures have been developed so far. Thus, there is an urgent need to explore novel therapeutic strategies using nanodelivery of drugs and agents either alone or in combination for superior neuroprotection in AD and enhanced quality of life of the affected individuals. There are reports that AD is often associated with diminished neurotrophic factors and neprilysin together with enhancement of phosphorylated Tau (p-Tau) within the brain and in the cerebrospinal fluid (CSF). Thus, studies aiming to enhance neurotrophic factors and neprilysin together with neutralizing p-Tau within the central nervous system (CNS) may alleviate brain pathology in AD. In this review these strategies are discussed using nanotechnological approaches largely based on our own investigations in relation to current literature in the field.

Nanodelivery of cerebrolysin reduces pathophysiology of Parkinson's disease.

Abstract: Parkinson's disease (PD) is affecting >10 million people worldwide for which no suitable cure has been developed so far. Roughly, about two people per thousand populations are affected with PD like symptoms especially over the age of 50. About 1% of the populations above 60 years suffer from PD-like disease. The prevalence of the disease is increasing over the years, and future projections by 2020 could be 12-14 millions people affected by the disease. Thus, exploration of suitable therapeutic measures is the need of the hour to enhance quality of the life of PD patients. PD induced brain pathology includes loss of dopaminergic neurons in the substantia niagra that could later extends to other cortical regions causing loss of voluntary motor control. Deposition of α-synuclein in the brain further leads to neurodegeneration. However, the exact cause of PD is still unknown. It appears that breakdown of the blood-brain barrier (BBB) and leakage of serum component into the brain could lead to neurodegeneration in PD. Thus, novel treatment strategies that are able to restore BBB breakdown and enhance neuronal plasticity and neuroregeneration in PD could be effective in future therapy. With the advancement of nanotechnology, it is worthwhile to understand the role of nanodelivery of selected agents in PD to enhance neuroprotection. In this review new role of BBB, brain edema, and neuropathology in PD is discussed. In addition, superior neuroprotection induced by nanowired delivery of a multimodal drug cerebrolysin in PD is summarized based on our own investigations.

Unraveling the genetic underpinnings of sleep deprivation-induced impairments in human cognition

Abstract: The biobehavioral phenomena of sleep and cognition involve complex phenotype-genotype associations, i.e., complex relationships between observable traits and the genetic variants that contribute to the expression of those traits. There is a general belief that investigating such relationships requires large sample sizes. However, sleep- and cognition-related phenotype-genotype associations may be strengthened through carefully controlled laboratory studies that amplify a given cognitive phenotype by perturbing the biobehavioral system through sleep deprivation and/or pharmacogenetic interventions. Utilization of performance tasks that dissociate cognitive processes allows for cognitive endophenotyping, that is, making precise measurements that capture the essence of a cognitive phenotype. This enables assessment of the genetic underpinnings of cognitive impairment due to sleep deprivation without necessarily requiring large samples. Theory-driven gene selection, selective population sampling techniques to avoid underrepresentation of rare genetic variants, and modern statistical techniques informed by prior knowledge further enhance statistical power. Here we illustrate these approaches on the basis of recent findings, supplemented with some new results, as well as a discussion of modern regression methods for statistical analysis. Ongoing research employing these methods is driving advancements in the understanding of the genetic underpinnings of cognitive impairment associated with sleep loss.

The origin and evolution of neocortex: From early mammals to modern humans.

Abstract: Human neocortex evolved in a series of ancestors with less neocortex and fewer cortical areas. Thus, early mammals had little neocortex and roughly 20 cortical areas, while early primates had much more cortex and around 50 cortical areas. Humans have the largest of primate brains that is 80% neocortex with about 200 areas. Other changes include more and more complex cortical networks, such as those for language, and modular and cellular specializations within areas. These and other changes allow the impressive mental abilities of humans.

Sleep deprivation, effort allocation and performance

Abstract: Sleep deprivation causes physiological alterations (e.g., decreased arousal, intrusion of micro-sleeps), that negatively affect performance on a wide range of cognitive domains. These effects indicate that cognitive performance relies on a capacity-limited system that may be more challenged in the absence of sleep. Additionally, sleep loss can result in a lower willingness to exert effort in the pursuit of performance goals. Such deficits in motivation may interact with the effects of capacity limitations to further stifle cognitive performance. When sleep-deprived, cognitive performance is experienced as more effortful, and intrinsic motivation to perform dwindles. On the other hand, increasing motivation extrinsically (e.g., by monetary incentives) can inspire individuals to allocate more task-related effort, and can partially counter performance deficits associated with sleep deprivation. In this chapter, we review current research on the interplay between sleep deprivation, effort and performance. We integrate these findings into an effort-based decision-making framework in which sleep-related performance impairments may result from a voluntary decision to withdraw effort. We conclude with practical implications of this framework for performance in healthy populations (e.g., work productivity) and clinical conditions.

Evolution of cerebral asymmetry.

Abstract: The human brain is often characterized in terms of a duality, with the left and right brains serving complementary functions, and even individuals are sometimes classified as either "left-brained" or "right-brained." Recent evidence from brain imaging shows that hemispheric asymmetry is multidimensional, comprised of independent lateralized circuits. Cerebral asymmetries, which include handedness, probably arise in phylogenesis through the fissioning of ancestral systems that divided and lateralized with increasing demand for specialization. They also vary between individuals, with some showing absent or reversed asymmetries. It is unlikely that this variation is controlled by a single gene, as sometimes assumed, but depends rather on complex interplay among several, perhaps many, genes. Hemispheric asymmetry has often been regarded as a unique mark of being human, but it has also become evident that behavioral and cerebral asymmetries are not confined to humans, and are widespread among animal species. They nevertheless exist against a fundamental background of bilateral symmetry, suggesting a tradeoff between the two. Individual differences in asymmetry, moreover, are themselves adaptive, contributing to the cognitive and behavioral specializations necessary for societies to operate efficiently.

Positive emotions have a unique capacity to capture attention

Abstract: Most of the previous research in the area of cognitive psychology or cognitive neuroscience focused on studying negative emotions and argued that the negative emotional stimuli capture attention involuntarily as compared to neutral stimuli. However, in the last decades, researchers started paying attention in studying positive emotions also as positive emotions have evolutionary significance and are essential for many aspects of our life. The theme of this chapter is to present an overview of research in the area of positive emotions, and make a case that positively-valenced stimulus is prioritized over others. Primarily, when attentional resources are not constrained, many studies have shown that similar to negative stimuli, positive stimuli also capture attention automatically irrespective of whether they are relevant or irrelevant to the primary task. It suggests a fundamental prioritization of these stimuli by the cognitive/motivational system. However, when attentional resources are constrained, only positive or high rewarding stimuli win the competition for attentional resources compared to negative or stimuli associated with high punishment. Positive or high rewarding stimuli also receive priority in temporal selection, when attention is constrained. Theoretical implications of these results have been discussed. Possible cognitive and neural mechanisms have been proposed underlying these effects.

Central positional vertigo: A clinical-imaging study.

Abstract: The diagnosis of central positional vertigo (CPV) is challenging, mainly because symptoms overlap with the common variants of benign paroxysmal positional vertigo (BPPV). Recent correlations of imaging with neurotologic exams have improved our understanding of CPV and ability differentiate it from BPPV. Yet, there is still a need to develop better diagnostic algorithms to improve timely diagnosis and early intervention. Here we present a retrospective review of the clinical characteristics, neurotologic evaluation and imaging of CPV in a cohort of 27 patients and propose a diagnostic algorithm to be tested in future prospective fashion. Most patients had positional nystagmus (downbeat and apogeotropic horizontal), cerebellar ocular motor abnormalities and truncal ataxia indicative of a central lesion. 61.5% of our cohort had paroxysmal CPV, 30.5% had a non-paroxysmal CPV and 8% paroxysmal-evolving-to-non-paroxysmal CPV. The most common pattern of positional nystagmus evoked with maneuvers was positional downbeat nystagmus (pDBN, 69.2%), apogeotropic horizontal nystagmus (42.3%), geotropic (7.69%) and multiplanar (23.0%). Notably, 13 (50%) of patients had cerebral imaging prior to CPV being on the differential diagnosis, whereas another 50% of patients had CPV diagnosis preceding their work-up. Unilateral lesions on imaging were 4× less likely to exhibit nausea and vomiting, nearly 2× less likely to exhibit paroxysmal nystagmus, and 2× less likely to exhibit nystagmus with habituality. Findings of pDBN or apogeotropic nystagmus alone were enough to diagnose CPV in 50% of our patient cohort, underscoring the importance of clinical evaluation in a time when an "imaging-first" philosophy is gaining popularity in Neurology.

Central positional nystagmus: Characteristics and model-based explanations.

Abstract: The central vestibular system operates to precisely estimate the rotational velocity and gravity orientation using the inherently ambiguous information from peripheral vestibular system. Therefore, any lesions disrupting this function can generate positional nystagmus. Central positional nystagmus (CPN) can be classified into the paroxysmal (transient) and persistent forms. The paroxysmal CPN has the features suggesting a semicircular canal origin regarding the latency, duration, and direction of nystagmus. Patients with paroxysmal CPN commonly show several different types of nystagmus classified according to the provoking positioning. The persistent form of CPN mostly appears as downbeat nystagmus while prone or supine, or apogeotropic or geotropic horizontal nystagmus when the head is turned to either side while supine. CPN may be ascribed to erroneous neural processing within the velocity-storage circuit that functions in estimating angular head velocity, gravity direction, and inertia. Paroxysmal CPN appears to be post-rotatory rebound nystagmus due to lesions involving the cerebellar nodulus and uvula. In contrast, persistent CPN may arise from erroneous gravity estimation. The overlap of lesion location responsible for both paroxysmal and persistent CPN may account for the frequent coexistence of both forms of nystagmus in a single patient.

Contemplative neuroscience, self-awareness, and education

Abstract: Accumulating research in education shows that contemplative practices contribute to and foster well-being of individuals in sustainable ways. This bears special importance for teachers, as it affects not only them but also their students. Based on accumulating behavioral and neuroscientific findings, it has been suggested that a key process by which mindfulness meditation enhances self-regulation is the altering of self-awareness. Indeed, accumulated work shows that the underlying networks supporting various types of self-awareness are malleable following meditative practice. However, the field of education has developed independently from the study of the self and its relation to contemplative neuroscience thus far, and to date there is no systematic account linking this accumulating body of knowledge to the field of education or discussing how it might be relevant to teachers. Here we show how incorporating insights from contemplative neuroscience-which are built on the conceptualization and neuroscience of the self-into contemplative pedagogy can inform the field and might even serve as a core underlying mechanism tying together different empirical evidence. This review points to potential neural mechanisms by which mindfulness meditation helps teachers manage stress and promote supportive learning environments, resulting in improved educational outcomes, and thus it has significant implications for educational policy regarding teachers.

Vestibular roll tilt thresholds partially mediate age-related effects on balance.

Abstract: Background: It has been well-established that both vestibular function and balance degrade with age and that balance degradation contributes to falls. While multiple causes contribute to balance declines, there have been few empirical investigations of the specific sensory contributors to balance that mediate (i.e., explain a significant fraction of) the effect of age on balance. Objective: To determine if vestibular function significantly mediates the effect of age on balance, and to quantify the fraction of any such statistically significant age-effect on balance using previously published vestibular threshold and balance data. Methods: Balance was quantified as complete/incomplete on a standard Romberg 4-condition foam balance test. Vestibular thresholds were determined using standard methods with motion provided by a Moog 6DOF motion platform. Standard mediation analyses were performed to determine if any of the five vestibular thresholds measured (0.2 Hz roll tilt and 1 Hz roll tilt, yaw rotation, y-translation, and z-translation) significantly mediated the previously reported age-effect on balance. Results: 0.2 Hz roll tilt thresholds were found to significantly mediate the relationship between age and balance, whether we considered all subjects or just the subjects above the age of 40 (above which vestibular thresholds increase with age). Depending on the exact age cut-off implemented between 37 and 42 years of age, 0.2 Hz roll tilt thresholds explained (mediated) between 33% and 55% of the total age-effect on balance. Conclusion: Vestibular function may mediate approximately 50% of the widely-reported age-effect on balance. If confirmed by future studies, this may provide an opportunity to improve balance (and presumably reduce fall risk) via specific therapies tailored to improve vestibular function.

Fixation instability in amblyopia: Oculomotor disease biomarkers predictive of treatment effectiveness

Abstract: Amblyopic patients are known to have fixation instability, particularly of the amblyopic eye. The stability of the fixation is affected by the presence of nystagmus, the frequency and amplitude of fixational saccades and inter-saccadic drifts. Amblyopic patients without nystagmus have increased amplitude of the fixational saccades with reduced frequency of the physiologic microsaccades and have increased inter-saccadic drifts. Amblyopia patients who have experienced a disruption in binocularity in early infancy develop fusion maldevelopment nystagmus (FMN) previously called latent nystagmus as it is more evident during monocular viewing conditions. We have found that some amblyopic patients can have nystagmus with slow phases that are not directed nasally and without the reversal in direction on ocular occlusion, features seen in patients with FMN. The current mainstay of amblyopia treatment comprises of part-time occlusion therapy of the non-amblyopic eye. The amount of patching treatment is in the range of 2-6h/day as determined by the severity of amblyopia. Despite treatment, up to 40% of patients have residual amblyopia. We analyzed the effectiveness of part-time occlusion therapy in amblyopic patients as a function of fixation instability. We categorized amblyopic patients based on their eye movement waveforms obtained during a visual fixation task into those lacking nystagmus, those with FMN and those with nystagmus but no FMN. We did a retrospective chart review to gather information about their clinical characteristics and treatment response. We found that patients with FMN require a more prolonged duration of treatment and have a poorer recovery of stereopsis compared to patients with nystagmus but no FMN and patients lacking nystagmus. This study suggests that eye movement assessment provides valuable information in the management of amblyopia.