Faculty Bibliography

A scalable adaptive optics (AO) control system architecture composed of asynchronous control clusters based on the stochastic parallel gradient descent (SPGD) optimization technique is discussed. It is shown that subdivision of the control channels into asynchronous SPGD clusters improves the AO system performance by better utilizing individual and/or group characteristics of adaptive system components. Results of numerical simulations are presented for two different adaptive receiver systems based on asynchronous SPGD clusters-one with a single deformable mirror with Zernike response functions and a second with tip-tilt and segmented wavefront correctors. We also discuss adaptive wavefront control based on asynchronous parallel optimization of several local performance metrics-a control architecture referred to as distributed adaptive optics (DAO). Analysis of the DAO system architecture demonstrated the potential for significant increase of the adaptation process convergence rate that occurs due to partial decoupling of the system control clusters optimizing individual performance metrics

BACKGROUND: Maturation of prefrontal circuits during adolescence contributes to the development of cognitive processes such as decision-making. Recent theories suggest that these neural changes also play a role in the shift from generalized anxiety disorder (GAD) to depression that often occurs during this developmental period. Cognitive models of the development of GAD highlight the role of intolerance of uncertainty (IU), which can be characterized behaviorally by impairments in decision-making. The present study examines potential developmental differences in frontal regions associated with uncertain decision-making, and tests the impact of IU on these circuits. METHODS: Twelve healthy adults (ages 19-36) and 12 healthy adolescents (ages 13-17) completed a decision-making task with conditions of varied uncertainty while fMRI scans were acquired. They also completed measures of worry and IU, and a questionnaire about their levels of anxiety and certainty during the task. RESULTS: Combined group analyses demonstrated significant linear effects of uncertainty on activity within anterior cingulate cortex (ACC). Region of interest (ROI)-based analysis found a significant interaction of group and IU ratings in ACC. Increased IU was associated with robust linear increases in ACC activity only in adolescents. An ROI analysis of feedback-related processing found that adolescents demonstrated greater activation during incorrect trials relative to correct trials, while the adults showed no difference in neural activity associated with incorrect and correct feedback. CONCLUSIONS: This decision-making task was shown to be effective at eliciting uncertainty-related ACC activity in adults and adolescents. Further, IU impacts ACC activity in adolescents during uncertain decision-making, providing preliminary support for a developmental model of GAD.

Sonic hedgehog has received an enormous amount of attention since its role as a morphogen that directs ventral patterning in the spinal cord was discovered a decade ago. Since that time, a bewildering array of information has been generated concerning both the components of the hedgehog signalling pathway and the remarkable number of contexts in which it functions. Nowhere is this more evident than in the nervous system, where hedgehog signalling has been implicated in events as disparate as axonal guidance and stem cell maintenance. Here we review our present knowledge of the hedgehog signalling pathway and speculate about areas in which further insights into this versatile pathway might be forthcoming

Recent advances in molecular genetics have produced many novel strategies for directing the expression of both functional and regulatory elements in transgenic mice. With the application of such approaches, the specific populations that comprise CNS networks can be both visualized and manipulated. Transgenic methods now range from the use of specific enhancer elements and large genomic regions assembled using BACs and PACs, to the use of gene targeting to a specific locus. In addition, the advent of transactivators and site-specific recombinases has provided unprecedented spatial and temporal control for directing expression in the CNS using a combination of appropriate alleles. As a result, the promise of being able to use transgenics to target specific neuronal populations is now being realized

One of the earliest steps of embryonic development is the establishment of polarity along the anteroposterior axis. Extensive studies of Drosophila embryonic development have elucidated mechanisms for establishing polarity, while studies with other model systems have found that many of these molecular components are conserved through evolution. One exception is Bicoid, the master organizer of anterior development in Drosophila and higher dipterans, which is not conserved. Thus, the study of anteroposterior patterning in insects that lack Bicoid can provide insight into the evolution of the diversity of body plan patterning networks. To this end, we have established the long germ parasitic wasp Nasonia vitripennis as a model for comparative studies with Drosophila. Here we report that, in Nasonia, a gradient of localized caudal mRNA directs posterior patterning, whereas, in Drosophila, the gradient of maternal Caudal protein is established through translational repression by Bicoid of homogeneous caudal mRNA. Loss of caudal function in Nasonia results in severe segmentation defects. We show that Nasonia caudal is an activator of gap gene expression that acts far towards the anterior of the embryo, placing it atop a cascade of early patterning. By contrast, activation of gap genes in flies relies on redundant functions of Bicoid and Caudal, leading to a lack of dramatic action on gap gene expression: caudal instead plays a limited role as an activator of pair-rule gene expression. These studies, together with studies in short germ insects, suggest that caudal is an ancestral master organizer of patterning, and that its role has been reduced in higher dipterans such as Drosophila.