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Article

Effects of Early Visual Deprivation  

Brigitte Röder and Ramesh Kekunnaya

As a consequence of congenital blindness, compensatory performance in the intact sensory modalities has been documented in humans in many domains, including auditory and tactile perception, auditory localization, voice and language processing, and memory. Both changes of the neural circuits associated with the intact sensory systems (intramodal plasticity) and an activation of deprived visual cortex (crossmodal plasticity) have been observed in blind humans. Compensation in congenitally blind and late-blind individuals involves partially different neural mechanisms. If sight is restored in patients who were born with dense bilateral cataracts (opaque lenses preventing patterned light to reach the retina), considerable visual recovery has been observed in basic visual functions even after long periods of visual deprivation. Functional recovery has been found to be lower for higher-order visual processes, which has been linked to deficits in the functional specialization of neural circuits. First evidence has suggested that crossmodal plasticity largely retracts after sight restoration but that crossmodal activity does not seem to fully dissolve. In contrast, intramodal adaptations in the auditory system have been observed to persist after sight restoration. Except for predominantly subcortically mediated multisensory functions, many multisensory processes have been found to be altered even many years after sight restoration. On the one hand, research in permanently blind humans has documented a high capability of the human neurocognitive system to adapt to an atypical environment. On the other hand, research in sight recovery individuals who had suffered a transient phase of visual deprivation following birth has demonstrated functional specific sensitive periods in the development of visual and multisensory neural circuits.

Article

NMDA Receptor Mediated Plasticity in Learning and Memory  

Robert J. McDonald and Ellen G. Fraser

One view of the organization of learning and memory functions in the mammalian brain is that there are multiple learning and memory networks that acquire and store different kinds of information. Each neural network is thought to have a central structure. The hippocampus, amygdala, perirhinal cortex, and dorsal striatum are thought to be central structures for different learning and memory networks important for spatial/relational, emotional, visual objects, and instrumental memory respectively. These central structures are part of a complex network including cortical and subcortical brain regions containing areas important for sensory, motivational, modulatory, and output functions. These networks are thought to encode and store information obtained during experiences via a general plasticity mechanism in which the relationship between synapses in these regions are changed. This view suggests that that memory has a physical manifestation in the brain, which allows for synapses to communicate more effectively as a result of activation. One form of synaptic plasticity called long-term potentiation (LTP) is considered a fundamental form of changes in synaptic efficacy mediating learning and long-term memory functions. One of the biochemical mechanisms for initiating LTP is triggered when a type of glutamate receptor, N-methyl-D-aspartate receptor (NMDAR), found in all of these memory networks is activated and various biochemical pathways that can produce long-term enhancements to the efficacy of that synapse are recruited. NMDAR-mediated LTP processes appear to be important for learning and memory processes in these different networks, but there are clear differences. None of the networks require NMDAR functions during expression of new learning. All the networks required NMDAR function during encoding of new information, except the network centered on perirhinal cortex. Finally, all of the networks required NMDAR-mediated plasticity processes for long-term consolidation of new information, except the one centered on the amygdala.

Article

Psychoneuroendocrinology and Physical Activity  

Anthony C. Hackney and Eser Ağgön

Stress is encountered by every individual on a daily basis. Such encounters can be of a negative (distress) or a positive (eustress) nature. Excessive and chronic distress exposure is associated with numerous health problems affecting both physiological and psychological components of a person’s well-being. One mediating aspect of these occurrences is the responses of the neuroendocrine system with the body. Physical activity (i.e., exercise) produces large and dramatic changes in the neuroendocrine system as it serves as a “stressor” to the system. To this end, though, chronic engagement in physical activity leads to exercise training-induced adaptations within the neuroendocrine system that potentiate an individual’s ability to deal with distressful experiences and exposures. Therefore, becoming more physically fit and exercise trained is one potential adjunctive therapy available for clinicians to recommend in the treatment of health problems associated with chronic exposure to distress.

Article

Brain Effects of Environmental Enrichment and Deprivation  

Bryan Kolb

The role of experience in brain organization and function can be studied by systematically manipulating developmental experiences. The most common protocols use extremes in experiential manipulation, such as environmental deprivation and/or enrichment. Studies of the effects of deprivation range from laboratory studies in which animals are raised in the absence of sensory or social experiences from infancy to children raised in orphanages with limited caregiver interaction. In both cases there are chronic perceptual, cognitive, and social dsyfunctions that are associated with chronic changes in neuronal structure and connectivity. Deprivation can be more subtle too, such as being raised in a low socioeconomic environment, which is often associated with poverty. Such experience is especially detrimental to language development, which in turn, limits educational opportunities. Unfortunately, the effects of some forms of socioemotional deprivation are often difficult, if not impossible, to ameliorate. In contrast, adding sensory or social experiences can enhance behavioral functions. For example, placing animals in environments that are cognitively, motorically, and/or socially more complex than standard laboratory housing is associated with neuronal changes that are correlated with superior functions. Enhanced sensory experiences can be relatively subtle, however. For example, tactile stimulation with a soft brush for 15 minutes, three times daily for just two weeks in infant rats leads to permanent improvement in a wide range of psychological functions, including motoric, mnemonic, and other cognitive functions. Both complex environments and sensory stimulation can also reverse the negative effects of many other experiences. Thus, tactile stimulation accelerates discharge from hospital for premature human infants and stimulates recovery from stroke in both infant and adult rats. In sum, brain and behavioral functions are exquisitely influenced by manipulation of sensory experiences, especially in development.

Article

Physical Activity and Inactivity Impacts on Cognitive and Emotional Functioning in Later Life  

Patrick D. Gajewski and Michael Falkenstein

Healthy aging is associated with changes in sensory, motor, cognitive, and emotional functions. Such changes depend on various factors. In particular, physical activity not only improves physical and motor but also cognitive and emotional functions. Observational (i.e., associations) and cross-sectional studies generally show a positive effect of regular physical exercise on cognition in older adults. Most longitudinal randomized controlled intervention studies also show positive effects, but the results are inconsistent due to large heterogeneity of methodological setups. Positive changes accompanying physical activity mainly impact executive functions, memory functions, and processing speed. Several factors influence the impact of physical activity on cognition, mainly the type and format of the activity. Strength training and aerobic training yield comparable but also differential benefits, and all should be used in physical activities. Also, a combination of physical activity with cognitive activity appears to enhance its effect on cognition in older age. Hence, such combined training approaches are preferable to homogeneous trainings. Studies of brain physiology changes due to physical activity show general as well as specific effects on certain brain structures and functions, particularly in the frontal cortex and the hippocampus, which are those areas most affected by advanced age. Physical activity also appears to improve cognition in patients with mild cognitive dysfunction and dementia and often ameliorates the disease symptoms. This makes physical training an important intervention for those groups of older people. Apart from cognition, physical activity leads to improvement of emotional functions. Exercise can lead to improvement of psychological well-being in older adults. Most importantly, exercise appears to reduce symptoms of depression in seniors. In future intervention studies it should be clarified who profits most from physical activity. Further, the conditions that influence the cognitive and emotional benefits older people derive from physical activity should be investigated in more detail. Finally, measures of brain activity that can be easily applied should be included as far as possible.

Article

Perceptual Learning: Perception and Experience  

Barbara Anne Dosher and Zhong-Lin Lu

Perceptual learning is the training-induced improvement in the accuracy or speed of relevant perceptual decisions about what is seen, heard, or felt. It occurs in all sensory modalities and in most tasks. The magnitude and generalizability of this learning may, however, depend on the stimulus modality, the level of sensory representation most aligned to the task, and the methods of training, including attention, feedback, reward, and the training protocol. What is known about perceptual learning in multiple modalities has been advanced based on behavioral studies and consideration of physiology and brain imaging, and the theoretical and computational models that systematize and promote understanding of the complex patterns of perceptual learning. Perceptual training might be used in translational applications, such as education, remediation of perceptual deficits, or maintenance of performance.

Article

Brain Development  

Robbin Gibb

The process of brain development begins shortly after conception and in humans takes decades to complete. Indeed, it has been argued that brain development occurs over the lifespan. A complex genetic blueprint provides the intricate details of the process of brain construction. Additional operational instructions that control gene and protein expression are derived from experience, and these operational instructions allow an individual to meet and uniquely adapt to the environmental demands they face. The science of epigenetics provides an explanation of how an individual’s experience adds a layer of instruction to the existing DNA that ultimately controls the phenotypic expression of that individual and can contribute to gene and protein expression in their children, grandchildren, and ensuing generations. Experiences that contribute to alterations in gene expression include gonadal hormones, diet, toxic stress, microbiota, and positive nurturing relationships, to name but a few. There are seven phases of brain development and each phase is defined by timing and purpose. As the brain proceeds through these genetically predetermined steps, various experiences have the potential to alter its final form and behavioral output. Brain plasticity refers to the brain’s ability to change in response to environmental cues or demands. Sensitive periods in brain development are times during which a part of the brain is particularly malleable and dependent on the occurrence of specific experiences in order for the brain to tune its connections and optimize its function. These periods open at different time points for various brain regions and the closing of a sensitive period is dependent on the development of inhibitory circuitry. Some experiences have negative consequences for brain development, whereas other experiences promote positive outcomes. It is the accumulation of these experiences that shape the brain and determine the behavioral outcomes for an individual.

Article

Bilingualism: A Cognitive and Neural View of Dual Language Experience  

Judith F. Kroll and Guadalupe A. Mendoza

There has been an upsurge of research on the bilingual mind and brain. In an increasingly multilingual world, cognitive and language scientists have come to see that the use of two or more languages provides a unique lens to examine the neural plasticity engaged by language experience. But how? It is now uncontroversial to claim that the bilingual’s two languages are continually active, creating a dynamic interplay across the two languages. But there continues to be controversy about the consequences of that cross-language exchange for how cognitive and neural resources are recruited when a second language is learned and used actively and whether native speakers of a language retain privilege in their first acquired language. In the earliest months of life, minds and brains are tuned differently when exposed to more than one language from birth. That tuning has been hypothesized to open the speech system to new learning. But when initial exposure is to a home language that is not the majority language of the community—the experience common to heritage speakers—the value of bilingualism has been challenged, in part because there is not an adequate account of the variation in language experience. Research on the minds and brains of bilinguals reveals inherently complex and social accommodations to the use of multiple languages. The variation in the contexts in which the two languages are learned and used come to shape the dynamics of cross-language exchange across the lifespan.

Article

Cognitive Reserve in the Aging Brain  

Michael J. Valenzuela

Cognitive reserve refers to the many ways that neural, cognitive, and psychosocial processes can adapt and change in response to brain aging, damage, or disease, with the overarching effect of preserving cognitive function. Cognitive reserve therefore helps to explain why cognitive abilities in late life vary as dramatically as they do, and why some individuals are brittle to degenerative pathology and others exceptionally resilient. Historically, the term has evolved and at times suffered from vague, circular, and even competing notions. Fortunately, a recent broad consensus process has developed working definitions that resolve many of these issues, and here the evidence is presented in the form of a suggested Framework: Contributors to cognitive reserve, which include environmental exposures that demand new learning and intellectual challenge, genetic factors that remain largely unknown, and putative G × E interactions; mechanisms of cognitive reserve that can be studied at the biological, cognitive, or psychosocial level, with a common theme of plasticity, flexibility, and compensability; and the clinical outcome of (enriched) cognitive reserve that can be summarized as a compression of cognitive morbidity, a relative protection from incident dementia but increased rate of progression and mortality after diagnosis. Cognitive reserve therefore has great potential to address the global challenge of aging societies, yet for this potential to be realized a renewed scientific, clinical, and societal focus will be required.