Photoactivatable genetically encoded calcium indicators for targeted neuronal imaging.

Circuit mapping requires knowledge of both structural and functional connectivity between cells. Although optical tools have been made to assess either the morphology and projections of neurons or their activity and functional connections, few probes integrate this information. We have generated a family of photoactivatable genetically encoded Ca(2+) indicators that combines attributes of high-contrast photolabeling with high-sensitivity Ca(2+) detection in a single-color protein sensor. We demonstrated in cultured neurons and in fruit fly and zebrafish larvae how single cells could be selected out of dense populations for visualization of morphology and high signal-to-noise measurements of activity, synaptic transmission and connectivity. Our design strategy is transferrable to other sensors based on circularly permutated GFP (cpGFP)

Driving Opposing Behaviors with Ensembles of Piriform Neurons

SummaryAnatomic and physiologic studies have suggested a model in which neurons of the piriform cortex receive convergent input from random collections of glomeruli. In this model, odor representations can only be afforded behavioral significance upon experience. We have devised an experimental strategy that permits us to ask whether the activation of an arbitrarily chosen subpopulation of neurons in piriform cortex can elicit different behavioral responses dependent upon learning. Activation of a small subpopulation of piriform neurons expressing channelrhodopsin at multiple loci in the piriform cortex, when paired with reward or shock, elicits either appetitive or aversive behavior. Moreover, we demonstrate that different subpopulations of piriform neurons expressing ChR2 can be discriminated and independently entrained to elicit distinct behaviors. These observations demonstrate that the piriform cortex is sufficient to elicit learned behavioral outputs in the absence of sensory input. These data imply that the piriform does not use spatial order to map odorant identity or behavioral output.PaperCli

A 3D Monte Carlo Photoionization Code for Modeling Diffuse Ionized Gas

We have developed a three dimensional Monte Carlo photoionization code tailored for the study of Galactic H II regions and the percolation of ionizing photons in diffuse ionized gas. We describe the code, our calculation of photoionization, heating & cooling, and the approximations we have employed for the low density H II regions we wish to study. Our code gives results in agreement with the Lexington H II region benchmarks. We show an example of a 2D shadowed region and point out the very significant effect that diffuse radiation produced by recombinations of helium has on the temperature within the shadow.Comment: MNRAS accepte

Twinship in mythology and science: Ambivalence, differentiation, and the magical bond

This article has attempted to show parallels and continuities between mythological traditions dealing with twinship and modern scientific approaches that either study twinship itself or use twin studies to answer more general questions. We do not mean to imply that modern research on twins is just a continuation of mythological concepts. What we have tried to show is the continuity in some of the questions being asked and in some of the answers being given. The explanation we would like to offer here for these parallels is that there are common psychological elements in both mythological and scientific approaches to twinship. The two major elements are fascination and ambivalence. Fascination with twin births has always been combined with a great deal of apprehension and ambivalence. In both primitive and modern societies, multiple births have been viewed as a potential source of familial and social conflict and complication. The Old Testament mythological tradition, which emphasized competition and individuation in twin pairs, and the Greek mythological tradition, which emphasized fusion and intimacy, are both reflected in modern approaches to the study of twinship.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22324/1/0000769.pd

The Processing of Pitch Combinations

In this chapter, we shall examine ways in which pitch combinations are ab-stracted by the perceptual system. First, we shall inquire into the types of abstrac-tion that give rise to the perception of local features, such as intervals, chords, and pitch classes. Such features can be considered analogous to those of orientatio

Determination of sheath heat transmission coefficient in NSTX discharges with applied lithium coatings

Recycled particle flux can be a significant contributor to tokamak edge plasma density, and lead to reductions in edge temperature. Previous measurements have shown that solid evaporated lithium coatings can lead to lowered edge recycling, corresponding decreases in edge plasma density, and a radial broadening of the electron temperature profile. During the 2010 run campaign, The National Spherical Torus Experiment operated with both solid and liquid lithium coatings on its plasma-facing components. A section of graphite outer divertor tiles was replaced with a substrate designed to hold liquid lithium coatings. While the lithium coatings on the graphite remain solid, the plates can be heated to render the lithium into a liquid state. In preparation for this campaign, a 99-tip dense Langmuir probe array was installed in the outboard divertor to measure scrape-off layer density and temperature. The probe array was located so as to radially span these two different divertor surfaces and measure their respective effects on the temperature and density. A dual-band fast IR camera was also installed to provide surface temperature and heat flux measurements. The use of two-color IR thermography allows for an assessment of effects due to the uncertain, phase- and purity-dependent emissivity of the lithium coatings. The present study compares the derived heat fluxes from these diagnostics to determine an effective classical sheath heat transmission coefficient γ, a measure of the heat flow reaching the device surfaces as a function of plasma parameters, namely the edge temperature and density - quantities which should be modified by lithium coatings. The sheath heat transmission is of great interest to future devices, which can expect to see large steady-state and transient heat fluxes to material surfaces. The value of γ was measured to be 2.49 +/- 0.04, a factor of ∼3 smaller than the expected classical result of ∼7. The implications of this measurement and the changes to edge plasma profiles that are possible causes of the lower observed value are discussed. Supported by US-DOE Contract DE-AC02-09CH11466

Neural Circuits Underlying Mating Behavior in Drosophila

Reproduction is essential for the survival of animal species. Males and females exhibit innate sex-specific reproductive behaviors, which are established developmentally and do not require previous experience. Because mating can be energetically costly, animals have evolved mechanisms to distinguish between reproductively viable and futile conspecifics that rely largely on sex-specific pheromones. How these complex, often antagonistic cues are transmitted from the periphery to the higher brain, the neural circuits they activate, or the computational principles by which they are integrated remain unclear. In the first part of this dissertation, I investigate the neural circuits underlying mating behavior in the fruit fly Drosophila melanogaster, leading to a novel model of decision-making. I employ anatomical, calcium-imaging, optogenetic, and behavioral studies to demonstrate that sensory neurons that detect female pheromones, but not male pheromones, activate a novel class of neurons in the ventral nerve cord to cause activation of P1 neurons, male-specific command neurons that trigger courtship. In addition, I show that sensory neurons that detect male pheromones, as well as those that detect female pheromones, activate GABAergic mAL neurons to inhibit P1 neurons. These data support a model in which the balance of excitatory and inhibitory inputs onto central courtship-promoting neurons regulates the decision to court.In the second part of this dissertation, I develop methods to visualize the morphology of neurons in taste processing in the fly brain. I employ large-scale calcium imaging coupled to cell labeling to identify sweet- or bitter-responsive neurons in the subesophageal zone (SEZ), the primary taste relay in the fly brain. I successfully use this approach to label SEZ motor neurons and demonstrate that they are tuned to a single taste modality, arguing for labeled-line processing of taste from sensory input to motor output. Nonetheless, reliably labeling single, non-motor SEZ neurons using this strategy has been difficult. Using a modified approach incorporating a nuclear-localized calcium indicator, I reproducibly label a cluster of putative bitter-responsive SEZ neurons. Based on their morphology, these neurons appear to be inhibitory olfactory projection neurons (iPNs), which transmit information from the antennal lobe to the lateral horn, suggesting that taste inputs may modulate the processing of odors

Identification of a Single Pair of Interneurons for Bitter Taste Processing in the Drosophila Brain

Drosophila has become an excellent model system for investigating the organization and function of the gustatory system due to the relatively simple neuroanatomical organization of its brain and the availability of powerful genetic and transgenic technology. Thus, at the molecular and cellular levels, a great deal of insight into the peripheral detection and coding of gustatory information has already been attained. In contrast, much less is known about the central neural circuits that process this information and induce behaviorally appropriate motor output. Here, we combine functional behavioral tests with targeted transgene expression through specific driver lines to identify a single bilaterally homologous pair of bitter-sensitive interneurons that are located in the subesophageal zone of the brain. Anatomical and functional data indicate that these interneurons receive specific synaptic input from bitter-sensitive gustatory receptor neurons. Targeted transgenic activation and inactivation experiments show that these bitter-sensitive interneurons can largely suppress the proboscis extension reflex to appetitive stimuli, such as sugar and water. These functional experiments, together with calcium-imaging studies and calcium-modulated photoactivatable ratiometric integrator (CaMPARI) labeling, indicate that these first-order local interneurons play an important role in the inhibition of the proboscis extension reflex that occurs in response to bitter tastants. Taken together, our studies present a cellular identification and functional characterization of a key gustatory interneuron in the bitter-sensitive gustatory circuitry of the adult fly

Representations of Taste Modality in the Drosophila Brain

Gustatory receptors and peripheral taste cells have been identified in flies and mammals, revealing that sensory cells are tuned to taste modality across species. How taste modalities are processed in higher brain centers to guide feeding decisions is unresolved. Here, we developed a large-scale calcium-imaging approach coupled with cell labeling to examine how different taste modalities are processed in the fly brain. These studies reveal that sweet, bitter, and water sensory cells activate different cell populations throughout the subesophageal zone, with most cells responding to a single taste modality. Pathways for sweet and bitter tastes are segregated from sensory input to motor output, and this segregation is maintained in higher brain areas, including regions implicated in learning and neuromodulation. Our work reveals independent processing of appetitive and aversive tastes, suggesting that flies and mammals use a similar coding strategy to ensure innate responses to salient compounds