Adrenal medulla graft induced recovery of function in an animal model of Parkinson's disease: possible mechanisms of action

Following unilateral dopamine (DA) denervation of the striatum in animals, there is an asymmetry in the striatal DA system. Animals with such denervations will rotate vigorously when given dopaminergic drugs. Adrenal medulla grafts placed in the lateral ventricle adjacent to a DA-denervated striatum decrease rotational behaviour induced by DA receptor agonists or DA-releasing agents. This discussion reviews research on the use of adrenal medulla grafts to reverse behavioural deficits following DA-denervation of the striatum. Results from basic animal research and from the application of the procedure to patients with Parkinson's disease suggests that at least three different fundamental processes may mediate the functional effects of adrenal medulla grafts: (a) Adrenal medulla grafts may induce changes in the blood-brain barrier; (b) adrenal medulla grafts may induce an increase in serum DA; and (c) adrenal medulla grafts may have a trophic effect on the host brain. Hypotheses are proposed to explain the behavioural effects of adrenal medulla grafts in light of the processes that are thought to mediate their effects.     

Hippocampal deafferentation: transplantderived reinnervation and functional recovery

A brief review is provided of the capacity of neural tissue transplants to reinnervate the deafferented hippocampus and repair functional deficits induced by the lesion. The techniques for transplantation of solid pieces of embryonic septum, locus coeruleus or raphe nuclei, or tissue suspensions of embryonic septum, to the adult rat hippocampus are described. Such grafts manifest good long-term survival, provide a good reinnervation of the hippocampus that is histochemically and biochemically appropriate and specific, can establish ultrastructural synaptic contacts with the host, and are electrophysiologically active. Rats with septal grafts manifest recovery of the capacity to learn certain aspects of radial 8-arm maze, T-maze alternation and Morris water-maze tasks. Rats with locus coeruleus grafts manifest an amelioration of lesion-induced hyperactivity. It is concluded that neural tissue transplantation provides a powerful new tool in the study of the functional organization of the hippocampus and its various neurotransmitter-specific afferent systems.     

Neural representations during sleep: from sensory processing to memory traces

In the course of a day, the brain undergoes large-scale changes in functional modes, from attentive wakefulness to the deepest stage of sleep. The present paper evaluates how these state changes affect the neural bases of sensory and cognitive representations. Are organized neural representations still maintained during sleep? In other words, despite the absence of conscious awareness, do neuronal signals emitted during sleep contain information and have a functional relevance? Through a critical evaluation of the animal and human literature, neural representations at different levels of integration (from the most elementary sensory level to the most cognitive one) are reviewed. Recordings of neuronal activity in animals at presentation of neutral or significant stimuli show that some analysis of the external word remains possible during sleep, allowing recognition of behaviorally relevant stimuli. Event-related brain potentials in humans confirm the preservation of some sensory integration and discriminative capacity. Behavioral and neuroimaging studies in humans substantiate the notion that memory representations are reactivated and are reorganized during post-learning sleep; these reorganisations may account for the beneficial effects of sleep on behavioral performance. Electrophysiological results showing replay of neuronal sequences in animals are presented, and their relevance as neuronal correlates of memory reactivation is discussed. The reviewed literature provides converging evidence that structured neural representations can be activated during sleep. Which reorganizations unique to sleep benefit memory representations, and to what extent the operations still efficient in processing environmental information during sleep are similar to those underlying the non-conscious, automatic processing continually at work in wakefulness, are challenging questions open to investigation.     

中枢肥大细胞在脑功能和行为调节中的作用

已知肥大细胞作为免疫细胞在过敏反应和炎性疾病中发挥重要作用。肥大细胞在中枢亦有表达, 但对其作用了解不足。新近的研究发现中枢肥大细胞在脑功能和行为调节中发挥重要的内源性平衡作用。一方面, 中枢肥大细胞在维持相关脑区发育, 正常神经活动, 以及动机, 情绪和认知等多种行为中发挥保护性作用, 各种应激条件诱导的中枢肥大细胞表达和活动改变参与脑和行为的适应性反应过程。另一方面, 中枢肥大细胞过度激活或者过度抑制都可导致脑功能和行为异常, 并参与某些免疫相关心身疾病的病理过程。体外神经解剖学和功能学研究证据提示中枢肥大细胞与神经系统间存在结构性和功能性相互作用网络。肥大细胞和神经组织间通过形成类似突触的结构性联系直接影响相邻细胞的活动。肥大细胞还可以通过脱颗粒释放多种生物活性介质调节神经活动, 同时表达多种受体接受脑内免疫性和神经性分子调节。但是目前对于中枢肥大细胞-神经系统相互作用的认识主要基于体外研究, 其在脑内相互作用方式及其与特定脑区功能和行为表型的关系所知甚少, 开展相关研究可以为认识脑与行为的神经免疫调节机制提供新的视角。     

Steroid Hormone Modulation of Hippocampal Dependent Spatial Memory

Recent studies show that the adult CNS is capable of considerable re-structuring and re-growth, a property previously thought limited to the developmental period. Hormones play an important role in many of these plastic processes, and the hippocampus, as a target for all the major classes of steroid hormones, undergoes considerable remodeling. Since it is critical for mediating tasks requiring spatial memory, the hippocampus can serve as an important model for understanding not only the mechanisms underlying plasticity of brain circuits but also how these changes impact on a higher order function, spatial memory. In this review, the effects of steroid hormones on hippocampal remodeling are discussed, and the ability of estradiol to enhance spatial memory as well as the ability of both excessive or diminished corticosteroid levels to impair spatial memory are described. The neural mechanisms for these effects, as well as previous and current contributions of McEwen and colleagues to this expanding area of research, are discussed.     

A positron emission tomography study of short- and long-term treatment effects on functional brain activation in adults who stutter

Previous studies have shown that fluency-inducing techniques, such as choral speech, result in changes in neural activation as measured by functional neuroimaging. In the present study, positron emission tomography was used to investigate the effects of intensive behavioural treatment, followed by a 1-year maintenance program, on the pattern of cortical and subcortical activation in stuttering adults during silent and oral reading of single words. The results indicate changes in activation lateralisation, as well as a general reduction in overactivation, especially in the motor cortex, following treatment. The results are discussed in light of previous functional imaging studies with stuttering adults.

Educational objectives: The reader will learn about and be able to describe the: (1) use of functional neuroimaging PET in the study of stuttering; (2) differences in neural activation between stuttering and non-stuttering adults; and (3) effects of behavioural fluency treatment on cortical and subcortical activations in stuttering speakers.     

Cholinergic modulation of trace conditioning trained in serial compound: A developmental analysis

In four experiments the effects of serial compound conditioning on responding to a trace-conditioned CS were evaluated using a fear conditioning paradigm. The subjects were 18- and 25-day-old Sprague-Dawley rats, previously shown to exhibit little or no trace fear conditioning. Here, animals as young as 18 days of age were shown to be capable of trace conditioning between a visual CS1 and a shock US, provided the trace interval was filled with a non-target CS2 during serial conditioning trials (CS1-->CS2-->US). To explore cholinergic mechanisms involved in trace and serial conditioning, additional experiments assessed conditioned responding following pre-training administration of the muscarinic receptor antagonist scopolamine. Scopolamine produced a dose-dependent reduction in responding to the trace CS1, regardless of whether subjects were trained with standard trace (CS1-->trace interval-->US) or serial (CS1-->CS2-->US) trials. Responding to CS2 was unaffected by scopolamine. These data suggest that central cholinergic systems are functional in the young animals, but are not normally sufficiently activated by standard trace conditioning procedures. The results suggest that serial compound conditioning can promote trace conditioning in young rats, as it does in adults, perhaps by enhancing cholinergic activity during training. Implications for the late ontogenetic emergence of trace conditioning as it relates to maturation of neural pathways and their role in the potentiating effects of a gap filler are discussed.     

Psychische Faktoren gastrointestinaler Erkrankungen

The list of potential or proven associations between psychological and intestinal functions in healthy subjects and in patients with functional and organic bowel disorders demonstrates that although these associations are manifold they are to a large extent incompletely understood, primarily of academic interest and not yet ready to be integrated into everyday clinical practice. However, of immediate practical relevance are psychotherapeutic as well as psychopharmacological approaches. It is, however, required that clinicians, both medical and psychological, are aware of the mechanisms of regulation of intestinal functions through central (CNS) and peripheral (ENS) neural circuits.     

How Does it STAC Up? Revisiting the Scaffolding Theory of Aging and Cognition

“The Scaffolding Theory of Aging and Cognition (STAC)”, proposed in 2009, is a conceptual model of cognitive aging that integrated evidence from structural and functional neuroimaging to explain how the combined effects of adverse and compensatory neural processes produce varying levels of cognitive function. The model made clear and testable predictions about how different brain variables, both structural and functional, were related to cognitive function, focusing on the core construct of compensatory scaffolding. The present paper provides a revised model that integrates new evidence about the aging brain that has emerged since STAC was published 5 years ago. Unlike the original STAC model, STAC-r incorporates life-course factors that serve to enhance or deplete neural resources, thereby influencing the developmental course of brain structure and function, as well as cognition, over time. Life-course factors also influence compensatory processes that are engaged to meet cognitive challenge, and to ameliorate the adverse effects of structural and functional decline. The revised model is discussed in relation to recent lifespan and longitudinal data as well as emerging evidence about the effects of training interventions. STAC-r goes beyond the previous model by combining a life-span approach with a life-course approach to understand and predict cognitive status and rate of cognitive change over time.     

Transplantation of fetal brain tissue

Fetal brain tissue transplanted to the brain of an adult mammalian host is known to develop within this environment. The grafted tissue also forms connections with the host brain and can produce recovery from behavioral deficits associated with destruction of parts of the host brain. The ability of grafts of fetal brain tissue to both develop in and form electrophysiologically viable connections with brains previously exposed to neurotoxins is discussed in this review. Restoration of neurotoxin-induced behavioral dysfunction by fetal brain grafts is also discussed. Finally, several uses for neural transplantation in neurotoxicological research are suggested. These uses include restoration of behavioral function, identification of the particular structures responsible for observed behavioral deficits, from among several structures damaged by an environmental neurotoxin, and identification of mechanisms underlying neurotoxicity.     

A critical review of ERP and fMRI evidence on L2 syntactic processing

The current review focuses on recent event-related brain potential (ERPs) and functional magnetic resonance imaging (fMRI) in L2 syntactic processing data. To this end, critical factors influencing both the dynamics of neural mechanisms (ERPs) and critical functional brain correlates (fMRI) are discussed. These entail the critical period hypothesis, levels of proficiency, cross-linguistic syntactic similarities and dissimilarities as well as brain bases that may or may not be shared during syntactic processing in a first (L1) and a second (L2) language. The data to date reveal that (i) the critical period hypothesis plays less of a significant role than initially discussed, (ii) L2 proficiency is a driving factor influencing peak and extent of activation in brain correlates and in neurophysiological mechanisms as a function of learning, and (iii) language transfer effects (i.e., positive transfer effects when L1 and L2 are structurally similar or negative transfer effects when L1 and L2 are structurally dissimilar) primarily from the L1 to the L2 and potentially vice versa need to be critically considered in future research.     

The functional state of the central nervous system in chemical stress

The psychosocial and physical factors, including chemical ones, which affect the human organism are considered by some authors to be stress factors which affect the functional state (FS) of the central nervous system (CNS). We calculated correlations among the clinical, psychological/psychometric, and quantitative electropsychological (QEEG) variables of the functional changes of the CNS in chemical stress. These data were based on occupational contact with lead as experienced by 402 workers, with styrene by 96, with shale-oil products by 252, with organic solvents by 77 workers, and a control group of 145 workers in different age groups. The QEEG data of 77 patients were analyzed to determine the chronic neurotoxic effects of industrial chemical substances by diagnosing the functional changes at the syndrome level. We concluded that occupational chemical factors impact the functional state of the CNS. During chemical stress -activity and total cerebral bioelectrical activity (BA) decreases. The use of psychometric/ psychological and QEEG methods makes it possible to diagnose the changes of the CNS as hypersthenic, hyposthenic, and organic psychosyndromes.     

第二语言学习与脑可塑性

脑可塑性指人脑会因为环境刺激、认知需求和行为经验而产生功能或结构改变。近10年来的单双语者对比和语言训练研究结果表明, 不论儿童、青年或老年人, 第二语言学习和使用都能改变其脑运行模式并带来相应结构变化, 包括灰质(GM)体积和白质(WM)密度增加, 且长期持续的双语经验还能形成认知优势, 帮助抵制由老化导致的负面认知影响。基于脑可塑性概念及其研究证据, 从双语经验与语言训练两方面, 对比分析了长期和短期第二语言学习引起脑功能或结构变化及其内在机制, 并对未来相关研究进行了展望。     

A model of amygdala–hippocampal–prefrontal interaction in fear conditioning and extinction in animals

Empirical research has shown that the amygdala, hippocampus, and ventromedial prefrontal cortex (vmPFC) are involved in fear conditioning. However, the functional contribution of each brain area and the nature of their interactions are not clearly understood. Here, we extend existing neural network models of the functional roles of the hippocampus in classical conditioning to include interactions with the amygdala and prefrontal cortex. We apply the model to fear conditioning, in which animals learn physiological (e.g. heart rate) and behavioral (e.g. freezing) responses to stimuli that have been paired with a highly aversive event (e.g. electrical shock). The key feature of our model is that learning of these conditioned responses in the central nucleus of the amygdala is modulated by two separate processes, one from basolateral amygdala and signaling a positive prediction error, and one from the vmPFC, via the intercalated cells of the amygdala, and signaling a negative prediction error. In addition, we propose that hippocampal input to both vmPFC and basolateral amygdala is essential for contextual modulation of fear acquisition and extinction. The model is sufficient to account for a body of data from various animal fear conditioning paradigms, including acquisition, extinction, reacquisition, and context specificity effects. Consistent with studies on lesioned animals, our model shows that damage to the vmPFC impairs extinction, while damage to the hippocampus impairs extinction in a different context (e.g., a different conditioning chamber from that used in initial training in animal experiments). We also discuss model limitations and predictions, including the effects of number of training trials on fear conditioning.     

Computational studies of the development of functionally specialized neural modules

Three hypotheses about the activity-dependent development of functionally specialized neural modules are discussed in this review. These hypotheses state that: (1) a combination of structure function correspondences plus the use of competition between neural modules leads to functional specializations; (2) parcellation is due to a combination of neural selectionism, the idea that learning results from a stabilization of some neural connections and the elimination of others, and a locality constraint, which states that connections between nearby neurons are more easily stabilized than those between distant neurons; and (3) a temporal and spatial modulation of plasticity can induce higher functional development in later-developing parts of the nervous system relative to earlier-developing parts. All three hypotheses have been implemented and evaluated in computational models. Limitations of current neuroscientific methodologies mean that computer simulation provides one of the only tools available for evaluating and refining our large-scale theories of the development of functionally specialized neural modules.     

Activity Versus Reactivity in Psychology and Neurophysiology

The traditional reflex approach in neurophysiology is incompatible with modern psychology's concern with goal-directed activity. We try to show that a ne~roph~siological approach based on the theory of functional systems may help to solve this problem. According to functional systems theory, all the elements of the organism are organized in systems that are neither sensory nor motor, but functional; the elements of these systems are defined in terms of how they enable the achievement of useful results of behavior. To make our case for this functional systems approach, experimental data are reviewed to illustrate the significance of the behavioral context in determining the activity of both central and peripheral neurons. One key indicator of the functionally specific organization of neural elements is the role of efferent influences in the coordination of the central and peripheral neural processes, and this is discussed at some length here. We offer the present approach as a basis for a new integration of neurophysiology and psy- chology (systemic psychophysiology), an integration which aims not at correla- tions of psychological with neural phenomena, but at their methodologically consistent unification through an understanding of the organization of different levels of the organism-environment system.     

Contact with maternal parent and siblings affects hunting behavior,learning, and central nervous system development in spiderlings of <Emphasis Type="Italic">Hogna carolinensis</Emphasis> (Araeneae: Lycosidae)

The purpose of this study was to determine the effects of early experience (rearing conditions) on the central nervous system (CNS) and behavior of spiderlings of Hogna carolinensis (Lycosidae). We were interested in whether or not spiderlings that were allowed to remain in contact with their maternal parent and siblings (enriched condition, EC) would exhibit differences in CNS development or subsequent behavior when compared with those reared in isolation (impoverished condition, IC). Spiderlings emerged from their egg sacs and climbed onto the dorsal surface of their mother's abdomen where they remained until their yolk supply was depleted (5 days). They dispersed on day 6 after emergence. We compared the ability of 16-day-old EC and IC spiderlings to capture prey in a linear runway and to learn a complex maze (spatial learning). We also compared certain aspects of CNS development (brain weight, total number of brain cells, volume of central body and protocerebral neuropil) in EC and IC spiderlings. Results indicated that EC subjects are more efficient at capturing moving prey (crickets) and exhibited improved performance (significantly fewer blind alley errors) in the maze. The volume of the protocerebral neuropil in 6-day-old EC animals increased 30% over a 5-day period after emergence as compared to IC animals of the same age. The volume of the central body of EC animals increased 34.8% over the same time period. On day 6 after emergence, the weight of the protocerebrum was significantly greater in EC versus IC subjects. There were no significant effects of rearing condition (EC vs IC) or age (1- and 6-day-old spiderlings) on the total number of nerve cells in the protocerebrum, suggesting that the difference in protocerebral weight was due primarily to differences in supporting glial tissues and neuropil matrix. In conclusion, the data suggest that early contact with the maternal parent and siblings is of vital importance to CNS development in lycosid spiderlings and can influence the capacity for spatial learning as well as the ability to capture prey. Electronic Publication     

Fetal brain tissue transplants reduce visual deficits in adult rats with bilateral lesions of the occipital cortex

Fetal brain tissue from the occipital or the frontal cortex was implanted into the damaged occipital cortex of adult rats. The animals receiving grafts of embryonic frontal cortex showed partial restoration of brightness discrimination while recipients given homologous implants of occipital cortex were as impaired as those animals with lesions alone. Neither frontal nor occipital grafts aided in the performance of a pattern discrimination problem; both groups of brain-damaged animals were unable to learn the task. Nonetheless, both groups of animals had viable and enlarged grafts with similar neuronal and glial profiles.     

青少年风险决策的发展认知神经机制

随着认知神经科学技术的发展, 青少年风险决策的发展认知神经机制成为了新近的一个热点课题。从双系统理论模型(社会情感神经网络系统、认知控制神经网络系统)出发, 对与青少年风险决策相关的大脑结构、功能的变化进行了阐述, 重点分析了新近的大脑功能连接、脑网络的研究; 阐述了青少年风险决策认知神经机制的主要理论模型：双系统模型和三角模型。未来研究还应加强对认知神经机制理论模型的检验、整合和创新, 从社会认知神经科学的角度深入研究社会参照系统(同伴关系、亚文化等)在青少年风险决策中的作用及机制, 以及从认知神经层面如何预防和干预青少年高风险行为。     

Category effects on the processing of plane-rotated objects

We examined the effects of plane rotations on the identification of exemplars of three semantic categories. In the first two experiments line drawings belonging to three categories (animals, inanimate objects, and vegetables) were presented at four orientations (0 degree, 60 degrees, 120 degrees, and 180 degrees of clockwise rotation). The response time was found to depend on stimulus category. In particular, whereas rotation effects were shown for animals, no effect at all was found for vegetables and only partial effects were found for inanimate objects. The unclear pattern found for inanimate objects was further examined in experiment 3 where the orientation effects on the identification of two subsets of the inanimate category were studied. The hypothesis of view-observation frequency was confirmed. In experiment 4, line drawings of objects at different orientations were presented in physically degraded versions. The minimum amount of visual information necessary to identify rotated stimuli was found to vary as a function of stimulus category as well. Results are discussed, combining current research on both viewpoint-dependence/independence and neural systems involved in category processing.