Sustainable Water Management Using Environmental Flows In The Connecticut River

There is significant evidence demonstrating that altering river flows downstream of impoundments harms native aquatic ecosystems and decreases the ability of native species to strive and survive. Innovative water management practices are needed to improve the health of native aquatic species and their surrounding ecosystems while maintaining the benefits from historic operating policies at these facilities. The impacts of individual reservoir operations on ecosystem health are often masked by the compounding influence of multiple upstream impoundments, making it difficult to analyze an individual facility’s impact within the larger system. This study presents an optimization model that investigates the value of coordinated reservoir management practices for ecological benefits in a dynamic system with several major reservoirs operating for hydropower production. An application of this model is presented for five hydropower facilities along the Connecticut River using The Connecticut River Environmental Assessment Model (CREAM). The Connecticut River Basin is the largest river basin in New England and one of the most impounded rivers in the United States. Five hydropower facilities along the Connecticut River are undergoing Federal Energy Regulatory Commission (FERC) re-licensing

The ‘laws’ of binocular rivalry: 50 years of Levelt’s propositions

It has been fifty years since Levelt’s monograph On Binocular Rivalry (1965) was published, but its four propositions that describe the relation between stimulus strength and the phenomenology of binocular rivalry remain a benchmark for theorists and experimentalists even today. In this review, we will revisit the original conception of the four propositions and the scientific landscape in which this happened. We will also provide a brief update concerning distributions of dominance durations, another aspect of Levelt’s monograph that has maintained a prominent presence in the field. In a critical evaluation of Levelt’s propositions against current knowledge of binocular rivalry we will then demonstrate that the original propositions are not completely compatible with what is known today, but that they can, in a straightforward way, be modified to encapsulate the progress that has been made over the past fifty years. The resulting modified, propositions are shown to apply to a broad range of bistable perceptual phenomena, not just binocular rivalry, and they allow important inferences about the underlying neural systems. We argue that these inferences reflect canonical neural properties that play a role in visual perception in general, and we discuss ways in which future research can build on the work reviewed here to attain a better understanding of these propertie

Neural mechanisms for reducing uncertainty in 3D depth perception

In order to navigate and interact within their environment, animals must process and interpret sensory information to generate a representation or ‘percept’ of that environment. However, sensory information is invariably noisy, ambiguous, or incomplete due to the constraints of sensory apparatus, and this leads to uncertainty in perceptual interpretation. To overcome these problems, sensory systems have evolved multiple strategies for reducing perceptual uncertainty in the face of uncertain visual input, thus optimizing goal-oriented behaviours. Two available strategies have been observed even in the simplest of neural systems, and are represented in Bayesian formulations of perceptual inference: sensory integration and prior experience. In this thesis, I present a series of studies that examine these processes and the neural mechanisms underlying them in the primate visual system, by studying depth perception in human observers. Chapters 2 & 3 used functional brain imaging to localize cortical areas involved in integrating multiple visual depth cues, which enhance observers’ ability to judge depth. Specifically, we tested which of two possible computational methods the brain uses to combine depth cues. Based on the results we applied disruption techniques to examine whether these select brain regions are critical for depth cue integration. Chapters 4 & 5 addressed the question of how memory systems operating over different time scales interact to resolve perceptual ambiguity when the retinal signal is compatible with more than one 3D interpretation of the world. Finally, we examined the role of higher cortical regions (parietal cortex) in depth perception and the resolution of ambiguous visual input by testing patients with brain lesions

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Hierarchically Variable Deference to Agency Interpretations

When courts review agency action, they typically accord agency decisions a degree of deference. As many courts and commentators have recognized, the law in this area is complicated because it features numerous standards of review, including several distinct regimes for evaluating agencies’ legal interpretations. There is, however, at least one important respect in which uniformity rather than variety prevails: the applicable standards of review do not vary depending on which court is reviewing the agency. Whichever standard governs a particular case—Chevron, Skidmore, or something else—all courts in the judicial hierarchy are supposed to apply that same standard. This Article proposes instead that the law should take into account the varying institutional circumstances and competencies of courts at different positions in the judicial hierarchy. More specifically, lower courts should be more deferential to agencies than should higher courts. The argument divides into two parts. Part I, which presents the theoretical case, lays out a series of common rationales for judicial deference and explains how those rationales actually support a regime of hierarchically variable deference. Part II then turns to questions of institutional implementation. As it turns out, our system already manifests a few features of hierarchically variable deference, though it does not do so openly. Thus, this Article helps to explain and justify some current practices. Prescriptively, Part II suggests a number of ways in which the judicial system could more systematically implement a regime of hierarchically variable review. One possibility is that different courts should employ somewhat different doctrinal standards, but hierarchical variation can also manifest itself through non-doctrinal means, such as through decisions about how to allocate jurisdiction

Individual-level contact limits phonological complexity: Evidence from bunched and retroflex /ɹ/

We compare the complexity of idiosyncratic sound patterns involving American English /ɹ/ with the relative simplicity of clear/dark /l/ allophony patterns found in English and other languages. For /ɹ/, we report an ultrasound-based articulatory study of 27 speakers of American English. Two speakers use only retroflex /ɹ/, 16 use only bunched /ɹ/, and nine use both /ɹ/ types, with idiosyncratic allophonic distributions. These allophony patterns are covert, because the difference between bunched and retroflex /ɹ/ is not readily perceived by listeners. We compare this typology of /ɹ/ allophony patterns to clear/dark /l/ allophony patterns in 17 languages. On the basis of the observed patterns, we show that individual-level /ɹ/ allophony and language-level /l/ allophony exhibit similar phonetic grounding, but that /ɹ/ allophony patterns are considerably more complex. The low complexity of language-level /l/ allophony patterns, which are more readily perceived by listeners, is argued to be the result of individual-level contact in the development of sound patterns. More generally, we argue that familiar phonological patterns (which are relatively simple and homogeneous within communities) may arise from individual-level articulatory patterns, which may be complex and speaker-specific, by a process of koineization. We conclude that two classic properties of phonological rules, phonetic naturalness and simplicity, arise from different sources.published_or_final_versio

Changes of Mind in voluntary action – Flexibility vs. stability of intentions

Changes of Mind’ can provide insights into the dynamic and continuous processes underlying decision making and action selection. Previous studies on Changes of Mind have exclusively focused on either perceptual or value-based choice. This thesis investigates the flexible neurocognitive mechanisms that shape voluntary actions, which require integration of internally-generated (endogenous) intentions and externally-cued (exogenous) sensory or value-based information. When information is noisy or changes dynamically, agents sometimes change their voluntary intentions and/or change the movements that are required to implement intentions into action. Continuous movement trajectories were used to capture both types of Change of Mind during ongoing action execution, revealing that ‘Changes of Intention’ are more frequent when intentions are weak or when the cost of pursuing an intention is high. These findings could be qualitatively reproduced by an attractor network model that continuously integrates endogenous and exogenous information over time, occasionally switching from one attractor state to a different one later on. In an fMRI study, the neural dynamics of intention reversals were investigated, providing evidence that neural patterns in a fronto-parietal network change dynamically to incorporate new decision- and action-relevant evidence after action onset. Finally, while behavioural flexibility is advantageous in many situations, an important hallmark of voluntary control is intention pursuit despite external changes or challenges. For example, people often need to persevere in the face of effort. Patients with post-stroke fatigue showed reduced perseverance compared to healthy controls when goal pursuit required continuous effort, which may cause adverse health-related outcomes. In conclusion, this thesis provides new insights into the continuous neurocognitive mechanisms that shape voluntary actions as they unfold. Reversibility of intentions allows agents to adjust their own actions to the current context, while stability of intentions is necessary for successful goal pursuit. Hence, volition requires balanced integration of endogenous intentions with dynamically-changing exogenous information

Activity in area V3A predicts positions of moving objects

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