254 research outputs found

    Participatory Development of a Forage Grass Cultivar

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    Perennial forage grasses exist in both nature and agriculture as a highly heterogeneous mixture of genotypes. Extreme environments, fluctuating environments, and severe managements can impose selection pressures that will result in loss of unadapted genotypes. Mortality of unadapted genotypes leads to dominance of fewer highly adapted genotypes which may be useful as superior germplasm in other similar environments

    Selection for Field Survival Increases Freezing Tolerance in Festulolium

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    Festulolium (Festulolium braunii K.A.) is marginally adapted to the north central and northeastern USA and southern Canada. The purpose of this study was to evaluate four festulolium populations selected for field survival under harsh winter conditions for their freezing tolerance in controlled environments. Progenies of all four populations showed some improvement in freezing tolerance compared to their parents. Improvements were dependent on the temperature at which measurements were made and varied among germplasms. Improvements were manifested in both decreased plant mortality and decreased injury to surviving plants. Genetic variation for freezing tolerance appears to be a viable mechanism for enhancing field survival of festulolium

    Hippocampal sequencing mechanisms are disrupted in a maternal immune activation model of schizophrenia risk

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    Episodic memory requires information to be stored and recalled in sequential order, and these processes are disrupted in schizophrenia. Hippocampal phase precession and theta sequences are thought to provide a biological mechanism for sequential ordering of experience at timescales suitable for plasticity. These phenomena have not previously been examined in any models of schizophrenia risk. Here, we examine these phenomena in a maternal immune activation (MIA) rodent model. We show that while individual pyramidal cells in the CA1 region continue to precess normally in MIA animals, the starting phase of precession as an animal enters a new place field is considerably more variable in MIA animals than in controls. A critical consequence of this change is a disorganization of the ordered representation of experience via theta sequences. These results provide the first evidence of a biological-level mechanism that, if it occurs in schizophrenia, may explain aspects of disorganized sequential processing that contribute to the cognitive symptoms of the disorder

    The hippocampus and entorhinal cortex encode the path and Euclidean distances to goals during navigation

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    BACKGROUND Despite decades of research on spatial memory, we know surprisingly little about how the brain guides navigation to goals. While some models argue that vectors are represented for navigational guidance, other models postulate that the future path is computed. Although the hippocampal formation has been implicated in processing spatial goal information, it remains unclear whether this region processes path- or vector-related information. RESULTS We report neuroimaging data collected from subjects navigating London's Soho district; these data reveal that both the path distance and the Euclidean distance to the goal are encoded by the medial temporal lobe during navigation. While activity in the posterior hippocampus was sensitive to the distance along the path, activity in the entorhinal cortex was correlated with the Euclidean distance component of a vector to the goal. During travel periods, posterior hippocampal activity increased as the path to the goal became longer, but at decision points, activity in this region increased as the path to the goal became closer and more direct. Importantly, sensitivity to the distance was abolished in these brain areas when travel was guided by external cues. CONCLUSIONS The results indicate that the hippocampal formation contains representations of both the Euclidean distance and the path distance to goals during navigation. These findings argue that the hippocampal formation houses a flexible guidance system that changes how it represents distance to the goal depending on the fluctuating demands of navigation

    The psychological and social impact of the digital self-support system ‘Brain in Hand’ on autistic people: prospective cohort study in England and Wales

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    Background Brain in Hand (BIH) is a UK-based digital self-support system for managing anxiety and social functioning. Aims To identify the impact of BIH on the psychological and social functioning of adults with autism. Method Adults with diagnosed or suspected DSM-5 (level 1) autism, identified by seven NHS autism services in England and Wales, were recruited for a 12-week prospective mixed-methods cohort study. The primary quantitative outcome measures were the Health of the Nation Outcome Scales for People with Learning Disabilities (HONOS-LD) and the Hospital Anxiety and Depression Scale (HADS). Fisher's exact test explored sociodemographic associations. Paired t-test was utilised for pre–post analysis of overall effectiveness of BIH. Multivariable linear regression models, univariable pre–post analysis, Wilcoxon signed-rank test, logistic regression analysis, Bonferroni correction and normative analysis were used to give confidence in changes identified. A thematic analysis of semi-structured exist interviews following Braun and Clarke's six-step process of 10% of participants who completed the study was undertaken. Results Sixty-six of 99 participants completed the study. There was significant reduction in mean HONOS-LD scores, with 0.65 s.d. decrease in those who used BIH for 12 weeks. Significant positive changes were identified in HONOS-LD subdomains of ‘self-injurious behaviours’, ‘memory and orientation’, ‘communication problems in understanding’, ‘occupation and activities’ and ‘problems with relationship’. A significant reduction in the anxiety, but not depression, component of the HADS scores was identified. Thematic analysis showed high confidence in BIH. Conclusions BIH improved anxiety and other clinical, social and functioning outcomes of adults with autism. </jats:sec

    Acceleration and Deceleration in the Internationalization Process of the Firm

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    By adopting a processual and dynamic view on internationalization, we develop the concepts of acceleration and deceleration, providing analytical tools to enhance our understanding of the non-linearity and multidimensionality of internationalization. We argue that acceleration and deceleration are embedded in the internationalization process and are a consequence of the firm’s capability to absorb and integrate acquired knowledge, and to find and exploit opportunities. In addition, we advance the idea that changes in speed are further influenced by how the firm integrates and coordinates the resources it has deployed within and across various internationalization dimensions. Thus, it emerges that the overall evolution of commitment to internationalization is more complex than received theories tend to present; therefore, empirical studies should aim to include a wide set of international activities and processes embedded in time

    Impact of Dendritic Size and Dendritic Topology on Burst Firing in Pyramidal Cells

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    Neurons display a wide range of intrinsic firing patterns. A particularly relevant pattern for neuronal signaling and synaptic plasticity is burst firing, the generation of clusters of action potentials with short interspike intervals. Besides ion-channel composition, dendritic morphology appears to be an important factor modulating firing pattern. However, the underlying mechanisms are poorly understood, and the impact of morphology on burst firing remains insufficiently known. Dendritic morphology is not fixed but can undergo significant changes in many pathological conditions. Using computational models of neocortical pyramidal cells, we here show that not only the total length of the apical dendrite but also the topological structure of its branching pattern markedly influences inter- and intraburst spike intervals and even determines whether or not a cell exhibits burst firing. We found that there is only a range of dendritic sizes that supports burst firing, and that this range is modulated by dendritic topology. Either reducing or enlarging the dendritic tree, or merely modifying its topological structure without changing total dendritic length, can transform a cell's firing pattern from bursting to tonic firing. Interestingly, the results are largely independent of whether the cells are stimulated by current injection at the soma or by synapses distributed over the dendritic tree. By means of a novel measure called mean electrotonic path length, we show that the influence of dendritic morphology on burst firing is attributable to the effect both dendritic size and dendritic topology have, not on somatic input conductance, but on the average spatial extent of the dendritic tree and the spatiotemporal dynamics of the dendritic membrane potential. Our results suggest that alterations in size or topology of pyramidal cell morphology, such as observed in Alzheimer's disease, mental retardation, epilepsy, and chronic stress, could change neuronal burst firing and thus ultimately affect information processing and cognition

    Incipient Social Groups: An Analysis via In-Vivo Behavioral Tracking

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    Social psychology is fundamentally the study of individuals in groups, yet there remain basic unanswered questions about group formation, structure, and change. We argue that the problem is methodological. Until recently, there was no way to track who was interacting with whom with anything approximating valid resolution and scale. In the current study we describe a new method that applies recent advances in image-based tracking to study incipient group formation and evolution with experimental precision and control. In this method, which we term "in vivo behavioral tracking," we track individuals' movements with a high definition video camera mounted atop a large field laboratory. We report results of an initial study that quantifies the composition, structure, and size of the incipient groups. We also apply in-vivo spatial tracking to study participants' tendency to cooperate as a function of their embeddedness in those crowds. We find that participants form groups of seven on average, are more likely to approach others of similar attractiveness and (to a lesser extent) gender, and that participants' gender and attractiveness are both associated with their proximity to the spatial center of groups (such that women and attractive individuals are more likely than men and unattractive individuals to end up in the center of their groups). Furthermore, participants' proximity to others early in the study predicted the effort they exerted in a subsequent cooperative task, suggesting that submergence in a crowd may predict social loafing. We conclude that in vivo behavioral tracking is a uniquely powerful new tool for answering longstanding, fundamental questions about group dynamics

    Influence of country and city images on students’ perception of host universities and their satisfaction with the assigned destination for their exchange programmes

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    ABSTRACT: This research focuses on the effect that country image, city image and university image has on students’ a priori satisfaction with the assigned destination for their international exchange programme (Bachelor and Master). In particular, this study establishes six hypotheses related to the causal relationships among the different typologies of image and their effects on students’ satisfaction with the assigned destination to study at least one semester in a host university. In order to contrast these hypotheses, a quantitative research was carried out in the Spanish city of Santander (Spain), by obtaining a sample of 245 international students who participated in an exchange programme at the University of Cantabria. The research findings are: (1) students’ satisfaction with the assigned destination is positively influenced by the university image; (2) the university image is positively influenced by the city image; and (3) the city image is positively influenced by the country image
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