Prefrontal Compensatory Engagement in TBI is due to Altered Functional Engagement Of Existing Networks and not Functional Reorganization

Functional neuroimaging studies of traumatic brain injury (TBI) have demonstrated altered neural recruitment, specifically within prefrontal cortex (PFC). This is manifest typically as increased recruitment of homologous regions of PFC (e.g., right ventrolateral PFC during performance of a verbal working memory task, possibly in response to damage involving the left PFC). The behavioral correlates of these functional changes are poorly understood. We used fMRI and multivariate analytic methods to investigate changes in spatially distributed activity patterns and their behavioral correlates in a sample of TBI patients with diffuse axonal injury (DAI, but without focal injury) and matched healthy controls. Participants performed working memory tasks with varying memory load and executive demand. We identified networks within left and right PFC that uniquely and positively correlated with performance in our control and TBI samples respectively, providing evidence of compensatory functional recruitment. Next we combined brain–behavior and functional connectivity analyses to investigate whether compensatory brain changes were facilitated by functional reorganization (i.e., recruitment of brain regions not engaged by our control sample) or altered functional engagement (i.e., differential recruitment of similar brain regions between the two groups based on task demands). In other words, does altered recruitment represent the instantiation of novel neural networks to support working memory performance after injury or the unmasking of extant, but behaviorally latent, functional connectivity? Our results support an altered functional engagement hypothesis. Areas within PFC that are normally coactivated during working memory are behaviorally relevant at an earlier stage of difficulty for TBI patients as compared to controls. This altered functional engagement, also evident in the aging literature, is attributable to distributed changes owing to significant DAI

Evaluation of diffusive gradients in thin-films using a Diphonix® resin for monitoring dissolved uranium in natural waters

Commercially available Diphonix® resin (TrisKem International) was evaluated as a receiving phase for use with the diffusive gradients in thin-films (DGT) passive sampler for measuring uranium. This resin has a high partition coefficient for actinides and is used in the nuclear industry. Other resins used as receiving phases with DGT for measuring uranium have been prone to saturation and significant chemical interferences. The performance of the device was evaluated in the laboratory and in field trials. In laboratory experiments uptake of uranium (all 100% efficiency) by the resin was unaffected by varying pH (4–9), ionic strength (0.01–1.00 M, as NaNO3) and varying aqueous concentrations of Ca2+ (100–500 mg L−1) and HCO3− (100–500 mg L−1). Due to the high partition coefficient of Diphonex®, several elution techniques for uranium were evaluated. The optimal eluent mixture was 1 M NaOH/1 M H2O2, eluting 90% of the uranium from the resin. Uptake of uranium was linear (R2 = 0.99) over time (5 days) in laboratory experiments using artificial freshwater showing no saturation effects of the resin. In field deployments (River Lambourn, UK) the devices quantitatively accumulated uranium for up to 7 days. In both studies uptake of uranium matched that theoretically predicted for the DGT. Similar experiments in seawater did not follow the DGT theoretical uptake and the Diphonix® appeared to be capacity limited and also affected by matrix interferences. Isotopes of uranium (U235/U238) were measured in both environments with a precision and accuracy of 1.6–2.2% and 1.2–1.4%, respectively. This initial study shows the potential of using Diphonix®-DGT for monitoring of uranium in the aquatic environment

The effect of organic management on soil quality indicators

This report was presented at the UK Organic Research 2002 Conference. A range of physical, biological and chemical parameters were measured in organic soil that had been managed in different ways and in a conventional control. Factors were identified that could be used to construct an index of soil quality

Prefrontal Engagement and Reduced Default Network Suppression Co-occur and Are Dynamically Coupled in Older Adults: The Default-Executive Coupling Hypothesis of Aging

Abstract ■ Reduced executive control is a hallmark of neurocognitive aging. Poor modulation of lateral pFC activity in the context of increasing task challenge in old adults and a "failure to deactivate" the default network during cognitive control tasks have been observed. Whether these two patterns represent discrete mechanisms of neurocognitive aging or interact into older adulthood remains unknown. We examined whether altered pFC and default network dynamics co-occur during goal-directed planning over increasing levels of difficulty during performance on the Tower of London task. We used fMRI to investigate taskand age-related changes in brain activation and functional connectivity across four levels of task challenge. Frontoparietal executive control regions were activated and default network regions were suppressed during planning relative to counting performance in both groups. Older adults, unlike young, failed to modulate brain activity in executive control and default regions as planning demands increased. Critically, functional connectivity analyses revealed bilateral dorsolateral pFC coupling in young adults and dorsolateral pFC to default coupling in older adults with increased planning complexity. We propose a default-executive coupling hypothesis of aging. First, this hypothesis suggests that failure to modulate control and default network activity in response to increasing task challenge are linked in older adulthood. Second, functional brain changes involve greater coupling of lateral pFC and the default network as cognitive control demands increase in older adults. We speculate that these changes reflect an adaptive shift in cognitive approach as older adults come to rely more upon stored representations to support goal-directed task performance.

Intrinsic Architecture Underlying the Relations among the Default, Dorsal Attention, and Frontoparietal Control Networks of the Human Brain

Human cognition is increasingly characterized as an emergent property of interactions among distributed, functionally specialized brain networks. We recently demonstrated that the antagonistic “default” and “dorsal attention” networks—subserving internally and externally directed cognition, respectively—are modulated by a third “frontoparietal control” network that flexibly couples with either network depending on task domain. However, little is known about the intrinsic functional architecture underlying this relationship. We used graph theory to analyze network properties of intrinsic functional connectivity within and between these three large-scale networks. Task-based activation from three independent studies were used to identify reliable brain regions (“nodes”) of each network. We then examined pairwise connections (“edges”) between nodes, as defined by resting-state functional connectivity MRI. Importantly, we used a novel bootstrap resampling procedure to determine the reliability of graph edges. Furthermore, we examined both full and partial correlations. As predicted, there was a higher degree of integration within each network than between networks. Critically, whereas the default and dorsal attention networks shared little positive connectivity with one another, the frontoparietal control network showed a high degree of between-network interconnectivity with each of these networks. Furthermore, we identified nodes within the frontoparietal control network of three different types—default-aligned, dorsal attention-aligned, and dual-aligned—that we propose play dissociable roles in mediating internetwork communication. The results provide evidence consistent with the idea that the frontoparietal control network plays a pivotal gate-keeping role in goal-directed cognition, mediating the dynamic balance between default and dorsal attention networks.Psycholog

Goal-directed attention alters the tuning of object-based representations in extrastriate cortex

Humans survive in environments that contain a vast quantity and variety of visual information. All items of perceived visual information must be represented within a limited number of brain networks. The human brain requires mechanisms for selecting only a relevant fraction of perceived information for more in-depth processing, where neural representations of that information may be actively maintained and utilized for goal-directed behavior. Object-based attention is crucial for goal-directed behavior and yet remains poorly understood. Thus, in the study we investigate how neural representations of visual object information are guided by selective attention. The magnitude of activation in human extrastriate cortex has been shown to be modulated by attention; however, object-based attention is not likely to be fully explained by a localized gain mechanism. Thus, we measured information coded in spatially distributed patterns of brain activity with fMRI while human participants performed a task requiring selective processing of a relevant visual object category that differed across conditions. Using pattern classification and spatial correlation techniques, we found that the direction of selective attention is implemented as a shift in the tuning of object-based information representations within extrastriate cortex. In contrast, we found that representations within lateral prefrontal cortex (PFC) coded for the attention condition rather than the concrete representations of object category. In sum, our findings are consistent with a model of object-based selective attention in which representations coded within extrastriate cortex are tuned to favor the representation of goal-relevant information, guided by more abstract representations within lateral PFC

Age differences in functional brain networks associated with loneliness and empathy

AbstractLoneliness is associated with differences in resting-state functional connectivity (RSFC) within and between large-scale networks in early- and middle-aged adult cohorts. However, age-related changes in associations between sociality and brain function into late adulthood are not well understood. Here, we examined age differences in the association between two dimensions of sociality—loneliness and empathic responding—and RSFC of the cerebral cortex. Self-report measures of loneliness and empathy were inversely related across the entire sample of younger (mean age = 22.6y, n = 128) and older (mean age = 69.0y, n = 92) adults. Using multivariate analyses of multi-echo fMRI RSFC, we identified distinct functional connectivity patterns for individual and age group differences associated with loneliness and empathic responding. Loneliness in young and empathy in both age groups was related to greater visual network integration with association networks (e.g., default, fronto-parietal control). In contrast, loneliness was positively related to within- and between-network integration of association networks for older adults. These results extend our previous findings in early- and middle-aged cohorts, demonstrating that brain systems associated with loneliness, as well as empathy, differ in older age. Further, the findings suggest that these two aspects of social experience engage different neurocognitive processes across human life-span development

Comparison of Observed and Simulated Grow-Finish Swine Performance Under Summer Conditions

As a part of a National Pork Producers Council educational program, our research and extension team at the University of Kentucky was linked with an independent commercial swine producer to test the NCPIG model against observed commercial on-farm data. This experience provided improved information for model development as well as increased producer insight into the data input needs and potential benefits of modeling. Detailed production information comparisons between the NCPIG model and producer data are presented for summer time conditions to assess the validity of the NCPIG model for simulation of grow-finish swine performance. Results demonstrated that the NCPIG model accurately simulated performance

Imprints of Short Distance Physics On Inflationary Cosmology

We analyze the impact of certain modifications to short distance physics on the inflationary perturbation spectrum. For the specific case of power-law inflation, we find distinctive -- and possibly observable -- effects on the spectrum of density perturbations.Comment: Revtex 4, 3 eps figs, 4 page