BCS Jr. Faculty Research Talks
Description
Assistant Professor Steven Flavell
Title: Neural Mechanisms that Generate Persistent Behavioral States
Abstract: Action potentials and synaptic transmission occur over the timescale of milliseconds, yet the brain can generate behaviors that last for seconds, minutes, or hours. In my talk, I will describe our efforts to understand how neural circuits are able to generate coherent behavioral outputs that persist for long stretches of time. We examine this problem in the simple nervous system of the nematode C. elegans, where we are able to use a multi-disciplinary approach that combines genetics, optogenetics, large-scale imaging of neural activity, and quantitative behavioral analysis. These mechanistic studies have revealed how neuromodulators supplement fast motor circuits with slow temporal dynamics, organizing motor actions into long-lasting behavioral states.
Assistant Professor Gloria Choi
Title: Elucidating neural circuits underlying social behaviors using Maternal Immune Activation model of autism
Abstract: Viral infection during pregnancy has been correlated with increased frequency of neurodevelopmental disorders, such as autism spectrum disorder (ASD), in offspring. This phenomenon has been modeled in mice prenatally subjected to maternal immune activation (MIA). We previously showed that the T helper 17 (Th17) cell/interleukin-17a (IL-17a) pathway is crucial for the induction of both cortical and behavioral abnormalities observed in MIA-affected offspring. However, it remains unclear if and how cortical abnormalities serve as causative factors for the aberrant behavioral phenotypes. We now provide evidence showing that cortical abnormalities are preferentially localized to a sub-region of the primary somatosensory cortex in the adult MIA offspring and that the presence and size of cortical patches tightly correlate with manifestation and severity of MIA-driven behavioral phenotypes. More specifically, we demonstrate that the selective loss of parvalbumin (PV)-expressing interneurons and a concomitant increase in neural activity is causal to the emergence of MIA behavioral phenotypes. Furthermore, we identify downstream targets involved in the selective modulation of sociability phenotypes versus repetitive behaviors. Our work identifies a cortical region centered on a sub-region of S1 as the major node of a neural network whose increased neural activity mediates ASD-like behavioral abnormalities observed in offspring exposed to maternal inflammation.
Assistant Professor Mehrdad Jazayeri
Title: A short trip from neural code to neural dynamics and back while you are waiting to clap
Abstract: Sensorimotor, cognitive and motor functions enjoy a remarkable level of temporal flexibility. A pianist can play the same piece at different tempos, a speaker can flexibly control the cadence of a speech, and children can flexibly alter expectations of events happening around them. How do neurons confer temporal flexibility to our behavioral repertoire? Cortical electrophysiology in awake, behaving monkeys has led us to a simple answer rooted in the dynamics of cortical networks. Neurons’ activity patterns stretch in time for longer intervals and compress for short ones. This suggests that flexible temporal control is achieved by unraveling the same neural dynamics over time, but at different speeds. This raises the question of how can the brain control the speed of cortical dynamics. Using a recurrent neural network model, I will demonstrate that the answer might be found in the nonlinearities of individual neurons. When an input pushes some of the neurons in the network toward their saturating nonlinearity, they slow down and cause an overall drop in the speed of dynamics in the network. These findings demonstrate a novel and general mechanism operating at the level of single neurons that confers temporal flexibility to recurrent cortical networks and behavior.
Speaker Bio
Steve Flavell completed his undergraduate work at Oberlin College, majoring in Neuroscience. He then pursued graduate studies in Harvard University’s PhD program in Neuroscience. Working the lab of Michael Greenberg, Steve investigated the mechanisms by which neuronal activity alters gene expression to regulate synapse development and function. His work blended molecular and cellular neurobiology with genomic approaches and was recognized with the Weintraub Graduate Student Award. Steve then worked as a postdoctoral fellow in Cori Bargmann’s lab at Rockefeller University, supported by a fellowship from the Helen Hay Whitney Foundation. Using a combination of behavioral recordings, genetics, in vivo calcium imaging, and optogenetics, Steve characterized a neural circuit capable of generating persistent locomotor states that last from minutes to hours. He will be joining the faculty of MIT in January 2016, as an assistant professor in Brain and Cognitive Sciences and the Picower Institute for Learning and Memory.
Gloria Choi received her bachelor’s degree from University of California, Berkeley, and her Ph.D. from Caltech, where she studied with David Anderson. She was a postdoctoral research scientist in the laboratory of Richard Axel at Columbia University.
Mehrdad Jazayeri joined the MIT faculty in January 2013 as an assistant professor in the Department of Brain and Cognitive Sciences and an Investigator in the McGovern Institute. Jazayeri, who is originally from Iran, obtained a B.Sc in Electrical Engineering from Sharif University of Technology in Tehran. He received his PhD from New York University, where he studied with J. Anthony Movshon, winning the 2007 Dean’s award for the most outstanding dissertation in the university. After graduating, he was awarded a Helen Hay Whitney fellowship to join the laboratory of Michael Shadlen at the University of Washington, where he was a postdoctoral researcher.