Cerebellar plasticity: modification of Purkinje cell structure by differential rearing in monkeys

MRI morphometry of the anterior and posterior cerebellar vermis and its relationship to sensorimotor and cognitive functions in children

INTRODUCTION

The human cerebellum emerges as a posterior brain structure integrating neural networks for sensorimotor, cognitive, and emotional processing across the lifespan. Developmental studies of the cerebellar anatomy and function are scant. We examine age-dependent MRI morphometry of the anterior cerebellar vermis, lobules I-V and posterior neocortical lobules VI-VII and their relationship to sensorimotor and cognitive functions.

METHODS

Typically developing children (TDC; n=38; age 9-15) and healthy adults (HAC; n=31; 18-40) participated in high-resolution MRI. Rigorous anatomically informed morphometry of the vermis lobules I-V and VI-VII and total brain volume (TBV) employed manual segmentation computer-assisted FreeSurfer Image Analysis Program [http://surfer.nmr.mgh.harvard.edu]. The neuropsychological scores (WASI-II) were normalized and related to volumes of anterior, posterior vermis, and TBV.

RESULTS

TBVs were age independent. Volumes of I-V and VI-VII were significantly reduced in TDC. The ratio of VI-VII to I-V (∼60%) was stable across age-groups; I-V correlated with visual-spatial-motor skills; VI-VII with verbal, visual-abstract and FSIQ.

CONCLUSIONS

In TDC neither anterior I-V nor posterior VI-VII vermis attained adult volumes. The "inverted U" developmental trajectory of gray matter peaking in adolescence does not explain this finding. The hypothesis of protracted development of oligodendrocyte/myelination is suggested as a contributor to TDC's lower cerebellar vermis volumes.

Distinct gray matter abnormalities in children/adolescents and adults with history of childhood maltreatment

Gray matter (GM) abnormalities have been reported in both adults and children/adolescents with histories of childhood maltreatment (CM). A comparison of effects in youth and adulthood may be informative regarding life-span effects of CM. Voxel-wise meta-analyses of whole-brain voxel-based morphometry studies were conducted in all datasets and age-based subgroups respectively, followed by a quantitative comparison of the subgroups. Thirty VBM studies (31 datasets) were included. The pooled meta-analysis revealed increased GM in left supplementary motor area, and reduced GM in bilateral cingulate/paracingulate gyri, left occipital lobe, and right middle frontal gyrus in maltreated individuals compared to the controls. Maltreatment-exposed youth showed less GM in the cerebellum, and greater GM in bilateral middle cingulate/paracingulate gyri and bilateral visual cortex than maltreated adults. Opposite GM alterations in bilateral middle cingulate/paracingulate gyri were found in maltreatment-exposed adults (decreased) and children/adolescents (increased). Our findings demonstrate different patterns of GM changes in youth closer to maltreatment events than those seen later in life, suggesting detrimental effects of CM on the developmental trajectory of brain structure.

Multiple benefits of juvenile play: A ground squirrel's perspective

Adaptive functions of play can vary across species, and also within species, reflecting behavioral ecology and evolutionary history. We evaluated juvenile play in Belding's ground squirrels (Urocitellus beldingi), a species for which field studies have assessed play behavior in the context of the squirrels' ecology and life history. Social play behavior in U. beldingi appears not to have the range of adaptive benefits related to social behavior apparent in species with more complex social organization. Play in juvenile U. beldingi improves general motor skill, which may translate to more proficient performance of behaviors during and beyond the juvenile period. Social play in juvenile squirrels is associated with refinement of temperament and behavior, promoting behavioral shifts toward less docile responses as well as more cautious behavior. Social play also influences behavior of juvenile squirrels in novel situations, fostering greater exploration and adaptability of responses. Important life events in U. beldingi such as the timing of natal dispersal and defense of maternal territories can be influenced by juvenile play.

Longitudinal study of infants receiving extra motor stimulation, full‐term control infants, and infants born preterm: High‐density EEG analyses of cortical activity in response to visual motion

Electroencephalography was used to investigate the effects of extrastimulation and preterm birth on the development of visual motion perception during early infancy. Infants receiving extra motor stimulation in the form of baby swimming, a traditionally raised control group, and preterm born infants were presented with an optic flow pattern simulating forward and reversed self‐motion and unstructured random visual motion before and after they achieved self‐produced locomotion. Extrastimulated infants started crawling earlier and displayed significantly shorter N2 latencies in response to visual motion than their full‐term and preterm peers. Preterm infants could not differentiate between visual motion conditions, nor did they significantly decrease their latencies with age and locomotor experience. Differences in induced activities were also observed with desynchronized theta‐band activity in all infants, but with more mature synchronized alpha–beta band activity only in extrastimulated infants after they had become mobile. Compared with the other infants, preterm infants showed more widespread desynchronized oscillatory activities at lower frequencies at the age of 1 year (corrected for prematurity). The overall advanced performance of extrastimulated infants was attributed to their enriched motor stimulation. The poorer responses in the preterm infants could be related to impairment of the dorsal visual stream that is specialized in the processing of visual motion.

Putative neural consequences of captivity for elephants and cetaceans

The present review assesses the potential neural impact of impoverished, captive environments on large-brained mammals, with a focus on elephants and cetaceans. These species share several characteristics, including being large, wide-ranging, long-lived, cognitively sophisticated, highly social, and large-brained mammals. Although the impact of the captive environment on physical and behavioral health has been well-documented, relatively little attention has been paid to the brain itself. Here, we explore the potential neural consequences of living in captive environments, with a focus on three levels: (1) The effects of environmental impoverishment/enrichment on the brain, emphasizing the negative neural consequences of the captive/impoverished environment; (2) the neural consequences of stress on the brain, with an emphasis on corticolimbic structures; and (3) the neural underpinnings of stereotypies, often observed in captive animals, underscoring dysregulation of the basal ganglia and associated circuitry. To this end, we provide a substantive hypothesis about the negative impact of captivity on the brains of large mammals (e.g., cetaceans and elephants) and how these neural consequences are related to documented evidence for compromised physical and psychological well-being.

Aging, lifestyle and dementia

Aging is the greatest risk factor for most diseases including cancer, cardiovascular disorders, and neurodegenerative disease. There is emerging evidence that interventions that improve metabolic health with aging may also be effective for brain health. The most robust interventions are non-pharmacological and include limiting calorie or protein intake, increasing aerobic exercise, or environmental enrichment. In humans, dietary patterns including the Mediterranean, Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) and Okinawan diets are associated with improved age-related health and may reduce neurodegenerative disease including dementia. Rapamycin, metformin and resveratrol act on nutrient sensing pathways that improve cardiometabolic health and decrease the risk for age-associated disease. There is some evidence that they may reduce the risk for dementia in rodents. There is a growing recognition that improving metabolic function may be an effective way to optimize brain health during aging.

Enriching Communicative Environments: Leveraging Advances in Neuroplasticity for Improving Outcomes in Neurogenic Communication Disorders

Purpose Research manipulating the complexity of housing environments for healthy and brain-damaged animals has offered strong, well-replicated evidence for the positive impacts in animal models of enriched environments on neuroplasticity and behavioral outcomes across the lifespan. This article reviews foundational work on environmental enrichment from the animal literature and considers how it relates to a line of research examining rich communicative environments among adults with aphasia, amnesia, and related cognitive-communication disorders. Method Drawing on the authors' own research and the broader literature, this article first presents a critical review of environmental complexity from the animal literature. Building on that animal research, the second section begins by defining rich communicative environments for humans (highlighting the combined effects of complexity, voluntariness, and experiential quality). It then introduces key frameworks for analyzing and designing rich communicative environments: distributed communication and functional systems along with sociocultural theories of learning and development in humans that support them. The final section provides an overview of Hengst's and Duff's basic and translational research, which has been designed to exploit the insights of sociocultural theories and research on environmental complexity. In particular, this research has aimed to enrich communicative interactions in clinical settings, to trace specific communicative resources that characterize such interactions, and to marshal rich communicative environments for therapeutic goals for individuals with aphasia and amnesia. Conclusions This article concludes by arguing that enriching and optimizing environments and experiences offers a very promising approach to rehabilitation efforts designed to enhance the reorganization of cognitive-communicative abilities after brain injury. Such interventions would require clinicians to use the principles outlined here to enrich communicative environments and to target distributed communication in functional systems (not the isolated language of individuals).

Consequences of early adverse rearing experience(EARE) on development: insights from non-human primate studies

Early rearing experiences are important in one's whole life, whereas early adverse rearing experience(EARE) is usually related to various physical and mental disorders in later life. Although there were many studies on human and animals, regarding the effect of EARE on brain development, neuroendocrine systems, as well as the consequential mental disorders and behavioral abnormalities, the underlying mechanisms remain unclear. Due to the close genetic relationship and similarity in social organizations with humans, non-human primate(NHP) studies were performed for over 60 years. Various EARE models were developed to disrupt the early normal interactions between infants and mothers or peers. Those studies provided important insights of EARE induced effects on the physiological and behavioral systems of NHPs across life span, such as social behaviors(including disturbance behavior, social deficiency, sexual behavior, etc), learning and memory ability, brain structural and functional developments(including influences on neurons and glia cells, neuroendocrine systems, e.g., hypothalamic-pituitary-adrenal(HPA) axis, etc). In this review, the effects of EARE and the underlying epigenetic mechanisms were comprehensively summarized and the possibility of rehabilitation was discussed.

General and specific effects of early-life psychosocial adversities on adolescent grey matter volume

Exposure to childhood adversities (CA) is associated with subsequent alterations in regional brain grey matter volume (GMV). Prior studies have focused mainly on severe neglect and maltreatment. The aim of this study was to determine in currently healthy adolescents if exposure to more common forms of CA results in reduced GMV. Effects on brain structure were investigated using voxel-based morphometry in a cross-sectional study of youth recruited from a population-based longitudinal cohort. 58 participants (mean age = 18.4) with (n = 27) or without (n = 31) CA exposure measured retrospectively from maternal interview were included in the study. Measures of recent negative life events (RNLE) recorded at 14 and 17 years, current depressive symptoms, gender, participant/parental psychiatric history, current family functioning perception and 5-HTTLPR genotype were covariates in analyses. A multivariate analysis of adversities demonstrated a general association with a widespread distributed neural network consisting of cortical midline, lateral frontal, temporal, limbic, and cerebellar regions. Univariate analyses showed more specific associations between adversity measures and regional GMV: CA specifically demonstrated reduced vermis GMV and past psychiatric history with reduced medial temporal lobe volume. In contrast RNLE aged 14 was associated with increased lateral cerebellar and anterior cingulate GMV. We conclude that exposure to moderate levels of childhood adversities occurring during childhood and early adolescence exerts effects on the developing adolescent brain. Reducing exposure to adverse social environments during early life may optimize typical brain development and reduce subsequent mental health risks in adult life.

Symptoms as solutions: hypnosis and biofeedback for autonomic regulation in autism spectrum disorders

The Autonomic Dysregulation Theory of autism posits that a phylogenetically early autonomic defect leads to overarousal and impairments in language and social engagement. Cognitive rigidity and repetitive behaviors manifest as mitigating efforts. Focusing on the implications of this premise may provide more productive therapeutic approaches than existing methods. It suggests that self-regulation therapy using hypnosis and biofeedback should be highly effective, especially for young people. Hypnotic strategies can utilize restrictive repetitive behaviors in trance as resources for comfort and control. Biofeedback training can be tailored to focus on autonomic regulation. The authors develop this theory and describe methods of integrating hypnosis and biofeedback that have been therapeutic for people with autism. Directions for future research to validate this approach are discussed.

Dendritic structural plasticity

Dendrites represent the compartment of neurons primarily devoted to collecting and computating input. Far from being static structures, dendrites are highly dynamic during development and appear to be capable of plastic changes during the adult life of animals. During development, it is a combination of intrinsic programs and external signals that shapes dendrite morphology; input activity is a conserved extrinsic factor involved in this process. In adult life, dendrites respond with more modest modifications of their structure to various types of extrinsic information, including alterations of input activity. Here, the author reviews classical and recent evidence of dendrite plasticity in invertebrates and vertebrates and current progress in the understanding of the molecular mechanisms that underlie this plasticity. Importantly, some fundamental questions such as the functional role of dendrite remodeling and the causal link between structural modifications of neurons and plastic processes, including learning, are still open.

Plasticity of gray matter volume: the cellular and synaptic plasticity that underlies volumetric change

Fifty years ago, Mark Rosenzweig and coworkers described environmental effects on brain chemistry and gross brain weight. William Greenough then used stereological tools, electron microscopy, and the Golgi stain to demonstrate that enrichment led to dendritic growth and synapse addition. Together these forms of plasticity accounted for cortical expansion and a reduction in cell density. In parallel with other investigators, Greenough demonstrated that these effects were not limited to the rodent, the cortex, or development, but instead generalize to many species, brain regions, and life stages. Studies of the anatomical effects of enrichment foreshadowed the recent empirical evidence for cortical volumetric increases after environmental experience and training in humans. Since research in humans is limited to regional effects, the analysis of the cellular and synaptic effects of enrichment, and their contribution to volumetric increases can inform us of the potential cellular and subcellular plasticity the leads to volume change in humans.

Identifying key features of early stressful experiences that produce stress vulnerability and resilience in primates

This article examines the complex role of early stressful experiences in producing both vulnerability and resilience to later stress-related psychopathology in a variety of primate models of human development. Two types of models are reviewed: Parental Separation Models (e.g., isolate-rearing, peer-rearing, parental separations, and stress inoculation) and Maternal Behavior Models (e.g., foraging demands, variation in maternal style, and maternal abuse). Based on empirical evidence, it is argued that early life stress exposure does not increase adult vulnerability to stress-related psychopathology as a linear function, as is generally believed, but instead reflects a quadratic function. Features of early stress exposure including the type, duration, frequency, ecological validity, sensory modality, and developmental timing, within and between species, are identified to better understand how early stressful experiences alter neurobiological systems to produce such diverse developmental outcomes. This article concludes by identifying gaps in our current knowledge, providing directions for future research, and discussing the translational implications of these primate models for human development and psychopathology.

A psychobiological theory of attachment

This article describes a neurobiological basis for the “first attachment” of the primate infant to its caretaker. The infant normally internalizes a neurobiological “image” of the behavioral and emotional characteristics of its caregiver that later regulates important features of its brain function. Current models of sensorimotor analysis and its relation to emotion suggest that sensorimotor systems are also habit and memory systems, their functional status and lability regulated in part by biogenic amine systems. The intertwined development of neural and social functions can sometimes go awry. If the attachment process fails or the caregiver is incompetent, the infant may become socially dysfunctional. This helps explain the developmental psychopathology and later vulnerability to adult psychopathology that result from disruptions of social attachment.

Neural plasticity: the biological substrate for neurorehabilitation

Decades of basic science have clearly demonstrated the capacity of the central nervous system (CNS) to structurally and functionally adapt in response to experience. The field of neurorehabilitation has begun to use this body of work to develop neurobiologically informed therapies that harness the key behavioral and neural signals that drive neural plasticity. The present review describes how neural plasticity supports both learning in the intact CNS and functional improvement in the damaged or diseased CNS. A pragmatic, interdisciplinary definition of neural plasticity is presented that may be used by both clinical and basic scientists studying neurorehabilitation. Furthermore, a description of how neural plasticity may act to drive different neural strategies underlying functional improvement after CNS injury or disease is provided. The understanding of the relationship between these different neural strategies, mechanisms of neural plasticity, and changes in behavior may facilitate the development of novel, more effective rehabilitation interventions.

Using animal models of enriched environments to inform research on sensory integration intervention for the rehabilitation of neurodevelopmental disorders

The field of behavioral neuroscience has been successful in using an animal model of enriched environments for over five decades to measure the rehabilitative and preventative effects of sensory, cognitive and motor stimulation in animal models. Several key principles of enriched environments match those used in sensory integration therapy, a treatment used for children with neurodevelopmental disorders. This paper reviews the paradigm of environmental enrichment, compares animal models of enriched environments to principles of sensory integration treatment, and discusses applications for the rehabilitation of neurodevelopmental disorders. Based on this review, the essential features in the enriched environment paradigm which should be included in sensory integration treatment are multiple sensory experiences, novelty in the environment, and active engagement in challenging cognitive, sensory, and motor tasks. Use of sensory integration treatment may be most applicable for children with anxiety, hypersensitivity, repetitive behaviors or heightened levels of stress. Additionally, individuals with deficits in social behavior, social participation, or impairments in learning and memory may show gains with this type of treatment.

Visual experience and age affect synaptic organization in the mushroom bodies of the desert ant Cataglyphis fortis

Desert ants of the genus Cataglyphis undergo an age-related polyethism from interior workers involved in brood care and food processing to short-lived outdoor foragers with remarkable visual navigation capabilities. The quick transition from dark to light suggests that visual centers in the ant's brain express a high degree of plasticity. To investigate structural synaptic plasticity in the mushroom bodies (MBs)-sensory integration centers supposed to be involved in learning and memory-we immunolabeled and quantified pre- and postsynaptic profiles of synaptic complexes (microglomeruli, MG) in the visual (collar) and olfactory (lip) input regions of the MB calyx. The results show that a volume increase of the MB calyx during behavioral transition is associated with a decrease in MG numbers in the collar and, less pronounced, in the lip. Analysis of tubulin-positive profiles indicates that presynaptic pruning of projection neurons and dendritic expansion in intrinsic Kenyon cells are involved. Light-exposure of dark-reared ants of different age classes revealed similar effects. The results indicate that this structural synaptic plasticity in the MB calyx is primarily driven by visual experience rather than by an internal program. This is supported by the fact that dark-reared ants age-matched to foragers had MG numbers comparable to those of interior workers. Ants aged artificially for up to 1 year expressed a similar plasticity. These results suggest that the high degree of neuronal plasticity in visual input regions of the MB calyx may be an important factor related to behavior transitions associated with division of labor.

Does play matter? Functional and evolutionary aspects of animal and human play

In this paper I suggest that play is a distinctive behavioural category whose adaptive significance calls for explanation. Play primarily affords juveniles practice toward the exercise of later skills. Its benefits exceed its costs when sufficient practice would otherwise be unlikely or unsafe, as is particularly true with physical skills and socially competitive ones. Manipulative play with objects is a byproduct of increased intelligence, specifically selected for only in a few advanced primates, notably the chimpanzee.

The adaptiveness of play in pongid evolution is traced through the probable changes in selective pressures that occurred in hominid evolution. It is argued that fantasy was an emergent property in hominids, made possible by symbolic intelligence and language, and serving to make play complex enough to continue to provide useful practice for increasingly complex later skills.

The advent of organised instruction and education has meant that play's unplanned, intrinisic goal-setting could be replaced by extrinsic goal-setting in the systematic development of particular skills. However, the need to ensure adequate motivation has continued to give play educational value. In addition, its capacity to enhance innovative behaviour seems to be a residual function of play which has acquired a new cultural importance.