My Research

Compiling large databases of neural simulations
Computer simulations are an important tool for neuroscience. Part of their power comes from the ability to test the simulation under a variety of conditions and parameters. The number of conditions tested, however, is limited by computing power?a matrix of even a few experimental variables can involve millions of simulation runs, requitring months of dedicated computing time. I have developed a software tool called NeuronPM that creates a ?screen-saver cluster?, allowing millions of simulation runs to be distributed across hundreds of computers and completed during idle time. I gave an invited talk presenting this software at this year?s computational neuroscience meeting, and it is gaining users in the neuroscience community. A paper describing the project appeared in the December issue of Neural Computation. The software is available at: http://neuronpm.homeip.net....more

Unlocking Behaviors through Neuromodulation
Neuromodulators are often thought of as ?shaping? circuits and behavior. Recent evidence from Tritonia suggests, however, that neuromodulators can also transform the capabilities of a circuit and unlock certain behaviors. Tritonia flee from predators by executing an escape swim. In an unperturbed animal, the circuit controlling swim is non-functional?it does not osciallate no matter how strongly activated. Upon predator contact, serotonin is released in the circuit, changing many of its neural and synaptic properties. These serotonin-induced changes unlock circuit oscillation and swim behavior; blocking serotonin receptors prevents oscillation and swim behavior. To understand how serotonin unlocks swim behavior, I am studying a computer model of the Tritonia swim circuit, and testing it under different conditions of simulated serotonin exposure. By testing many (~3 million) circuit configurations, I have been able to show that 2 synapses in the swim circuit function as switches for circuit oscillation. I am following up with physiological and behavioral experiments to document the effects of serotonin on these synapses and how these effects influence behavior. A manuscript describing this research has been prepared for submission to the Journal of Neurophysiology. ...more

NeuronBank: A Knowledge Base of Identified Neurons and Synaptic Connections
Part of the progress of neuroscience depends on tracing circuits of neurons and synaptic connections within a nervous system. Currently, however, there is no standard way of representing, storing, searching, or sharing our knowledge of neural circuits. I am working as part of a team of neuroscientists and computer programmers at GSU to develop NeuronBank?an online repository of identified neurons and synaptic connections. The project aims to be a ?gene bank? of neuroscience?a common gateway where our understanding of neural circuits can be indexed, updated, and analyzed. I serve as project-manager for the group?coordinating the interface between the neuroscience users and the programming team that is implementing the project. The project website is at: http://neuronbank.org. I was co-author on a poster presenting this work at the 2005 Annual Meeting of the Society for Neuroscience and at the 2006 International Protege Users Conference.? I was also co-author on a paper describing the query-language developed for this system (Tian et al., 2006) ...more

Neuromodulation of Synaptic Strength
Dr. Akira Sakurai, a post-doc in the Katz lab, has shown that neuromodulators can have complex effects on synapses. Specifically, he has shown that activation of serotonergic neurons can cause a bi-phasic change in local synapses, producing an initial enhancement followed by a persistent depression. To better understand these effects, I have developed a computer model of synaptic transmission. By fitting the model to Dr. Sakurai?s data, I have been able to show that serotonin?s enhancement of synapses is best modeled as an increase in release fraction (% of releasable pool activated / spike). I was co-author on a poster presenting this work at the 2005 Annual Meeting of the Society for Neuroscience.? A manuscript describing this research has been prepared for Journal of Neurophysiology....more

Neural mechanisms of adaptation
Organisms living in a dynamic environment must regulate their behavior to match the conditions of the environment. A ubiquitous strategy for coping with environmental change is adaptation?a decrease in responsiveness due to a sustained stimulus. Although much is known about adaptation at the level of sensory receptors and individual neurons, less is known about how these mechanisms contribute to changes in behavior. Adaptation is particularly interesting because it is a transient behavioral change, and little is known about the neural mechanisms underlying temporary alterations of behavior. For my doctoral project, I integrated physiological, behavioral, and computational techniques to develop a complete account of a simple form of adaptation in Aplysia californica. Specifically, I explored environmental adaptation of the siphon-withdrawal reflex (SWR)?a decrease in SWR duration produced by exposure to water turbulence, an ethologically relevant environmental stimulus Aplysia frequently encounter in the wild....more

Explaining and Learning
High-school students learn better when they are required to explain sample problems presented by their teachers or textbooks. This technique is known as ?self-explaining?, and it is a simple but powerful way to increase the effectiveness of a student?s study time. Self-explaining can also be applied to pre-readers (kindergartners and elementary school) by asking them to explain the actions of an adult expert. However, it is still unclear exactly how explaining alters learning....more

Influence of Emotion on Speech Processing
I contributed to a series of experiments designed to explore the role of emotion cues in speech perception. Specifically, we explored how two different emotive signals are integrated to influence a spoken-word lexical decision task: tone of voice (happy, scared, disgusted, and neutral) and meaning (happy, scary, disgusting). We found that congruent emotional stimuli (e.g. happy tone of voice and happy word) are processed faster than neutral and incongruent stimuli, but only when tone of voice is predictable from trial-to-trial. This project resulted in a publication in an a peer-reviewed publication in Cognition and Instruction. link.? This project was completed in the psycholinguistics lab of Dr. Lee Wurm at Wayne State University, in conjunction with Shannon Ross and Maureen Strausser in the lab and Dr. Doug Vakoch....more