Summary:Purpose: Electric field stimulation can interact with brain activity in a subthreshold manner. Electric fields have been previously adaptively applied to control seizures in vitro. We report the first results from establishing suitable electrode geometries and trajectories, as well as stimulation and recording electronics, to apply this technology in vivo.Methods: Electric field stimulation was performed in a rat kainic acid injection seizure model. Radial electric fields were generated unilaterally in hippocampus from an axial depth electrode. Both sinusoidal and multiphasic stimuli were applied. Hippocampal activity was recorded bilaterally from tungsten microelectrode pairs. Histologic examination was performed to establish electrode trajectory and characterize lesioning.Results: Electric field modulation of epileptiform neural activity in phase with the stimulus was observed in five of six sinusoidal and six of six multiphasic waveform experiments. Both excitatory and suppressive modulation were observed in the two experiments with stimulation electrodes most centrally placed within the hippocampus. Distinctive modulation was observed in the period preceding seizure-onset detection in two of six experiments. Short-term histologic tissue damage was observed in one of six experiments associated with high unbalanced charge delivery.Conclusions: We demonstrated in vivo electric field modulation of epileptiform hippocampal activity, suggesting that electric field control of in vivo seizures may be technically feasible. The response to stimulation before seizure could be useful for triggering control systems, and may be a novel approach to define a preseizure state. Key Words: Electric field-Neural prosthesis-Seizure-HippocampusPreseizure state-Epilepsy.Although control system technology has made extraordinary advances during the past century, our efforts to apply sophisticated control strategies to epilepsy have been limited. Such limitations arise both from the lack of a flexible control parameter that would permit us to increase or decrease activity in the brain rapidly and reversibly, and the lack of stimulation and recording amplifiers designed for simultaneous monitoring of neuronal activity during control stimulation. Uninterrupted monitoring would allow a control system to use ongoing information about the dynamics to prescribe the control perturbations as continuous feedback. The application of continuous feedback would allow a controller to modify spe- cific patterns of neuronal activity selectively while minimizing the impact on other more normal activities. This approach is in contrast to "reversible lesions" associated with high-frequency stimulation, which more indiscriminately suppresses neuronal activity in the neighborhood of stimulation. We here demonstrate in vivo some technical solutions required for future implementation of continuous feedback control of seizures by using electric field stimulation.Early strategies for controlling epileptic seizures through electrical stimulation focus...

Headwater riparian wetlands are relatively small in size but functionally significant as expected "hot spots" of microbial activity in the landscape. Despite their roles as biogeochemical drivers, little is known about how microbial communities in headwater riparian wetlands are affected by surrounding land-uses and land-covers (LULCs). The primary objective of this study was to determine if and how wetland soil microbial abundance and community composition varied as a function of landscape metrics as mediated through on-site edaphic properties. Forty-two soil samples, collected from eight headwater riparian wetlands in the Ridge and Valley Region of central Pennsylvania, were used for phospholipid fatty acid (PLFA) profiling of soil microbial communities. These samples were used to create microbial habitat models describing plot-level relationships between edaphic properties and microbial measures (i.e., microbial biomarker abundances, ratios and composition). Soil organic matter (SOM) content was a strong predictor of microbial biomarker abundances and fungi / bacteria ratios, while soil pH was a strong predictor of microbial composition (i.e., relative abundance of individual fatty acids) and potential microbial stress indices (i.e., cy19:0a/18:1ω7c and cy17:0/16:1ω7c). Soil texture, soil moisture, and litter total nitrogen had smaller, but significant effects in these empirical microbial habitat models. Microbial habitat models were subsequently used to estimate microbial measures for a larger regional headwater riparian wetland dataset (n = 87), where edaphic property information was compiled. Site-average microbial measures were correlated with wetland elevation, and with landscape composition metrics in a landscape assessment area (i.e., 125,664 m 2). Wetland elevation explained high among-site variability in microbial abundance measures, as mediated through SOM content, in headwater riparian wetlands in forested landscapes. However, wetland elevation was confounded by landscape composition, for

Phosphorus (P) has been identified as the primary nutrient limiting phytoplankton biomass in the Laurentian Great Lakes, and thus phytoplankton biomass varies as a function of P loading. While management efforts have reduced point sources of P, a recent rise in non-point source loadings and the introduction of dreissenid mussels to the Great Lakes are factors suspected to have direct and indirect impacts on nutrient cycling. We re-evaluated nutrient limitation of phytoplankton in the central basin of Lake Erie over spatial (i.e. 3 offshore stations) and temporal (i.e. monthly from June to October) scales. The nutrient limitation of the phytoplankton was evaluated using biomass response measurements to nutrient enrichment bioassays in a complete factorial of P, nitrogen (N), and silicon (Si). Nutrient additions yielded classic growth curves after 7 to 12 d of incubation. Treatments with added P had higher final biomass yields than treatments without P at all stations and during all months. During spring overturn, P+ Si yielded higher phytoplankton biomass than did P additions without Si at 2 of the 3 stations. During the late stratification to autumn overturn (August to October), P+N promoted higher phytoplankton biomass than did P additions without N; this was true at all stations. A quantitative assessment of the bioassays indicated that 63 to 94% of the biomass yield during spring overturn could be attributed to Si, while 48 to 68% of the biomass yield during late stratification and autumn overturn could be attributed to N. Water chemistry data collected in 2002 and 2003 predicted similar seasonal trends in nutrient limitation. These results suggest that seasonal variation in phytoplankton nutrient limitation is a probable factor in predicting changes in phytoplankton biomass and taxonomic composition in the central basin of Lake Erie. KEY WORDS: Phytoplankton · Lake Erie · Nutrient status Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 48: [61][62][63][64][65][66][67][68][69][70][71] 2007 important for effective management initiatives, an area of research where effort has been limited in the past (Elser et al. 1990). Moreover, the Great Lakes Fisheries Commission (GLFC) recognizes that, since the enactment of TP controls and the introduction of non-native dreissenids, many of the changes at the lower trophic levels appear to have influenced both the composition and productivity of the fish communities in the lake, yet little is known about the response at lower trophic levels (GLFC 1998).Nutrient enrichment bioassays have been widely used to evaluate nutrient limitations of phytoplankton (Lin & Schelske 1981). Therefore, we implemented 2 × 3 factorial nutrient enrichment bioassays (NEB) experiments using natural phytoplankton assemblages from Lake Erie to achieve 3 objectives. First, we evaluated the main and interactive effects of P, N, and Si in regulating phytoplankton biomass. Second, we characterized the seasonal and spatial variation of phytop...

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. 2017. Model application niche analysis: assessing the transferability and generalizability of ecological models. Ecosphere 8(10):e01974. 10. 1002/ecs2.1974 Abstract. The use of models by ecologists and environmental managers, to inform environmental management and decision-making, has grown exponentially in the past 50 yr. Due to logistical, economical, and theoretical benefits, model users frequently transfer preexisting models to new sites where data are scarce. Modelers have made significant progress in understanding how to improve model generalizability during model development. However, models are always imperfect representations of systems and are constrained by the contextual frameworks used during their development. Thus, model users need better ways to evaluate the possibility of unintentional misapplication when transferring models to new sites. We propose a method of describing a model's application niche for use during the model selection process. Using this method, model users synthesize information from databases, past studies, and/or past model transfers to create model performance curves and heat maps. We demonstrated this method using an empirical model developed to predict the ecological condition of plant communities in riverine wetlands of the Appalachian Highland physiographic region, USA. We assessed this model's transferability and generalizability across (1) riverine wetlands in the contiguous United States, (2) wetland types in the Appalachian Highland physiographic region, and (3) wetland types in the contiguous United States. With this methodology and a discussion of its critical steps, we set the stage for further inquiries into the development of consistent and transparent practices for model selection when transferring a model.

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