Past events

A fundamental problem in brain research is how distributed brain systems work together to give rise to behavior. I seek to advance our understanding of principles underlying the dynamic interaction between multiple neural systems, how the different systems co-operate and/or compete to give rise to goal-directed behavior, and the dynamics of the system when one or more of its components fail. Magnetic resonance imaging (MRI) methods allow us to simultaneously measure the function of multiple brain systems. In humans we can characterize the functional organization and specialization, and compare the system between health and disease. In animal models we can further dissect the circuits underlying these dynamics. In my work I aim to identify functional networks that span multiple cortical and subcortical regions, characterize their responses in the presence and absence of overt behavior, and modulate the observed dynamics. To advance these goals, I am developing new tools that will allow us to study large-scale neural systems across species. In this talk, I will review recent studies that use functional neuroimaging in humans and animal models. I will describe how spontaneous fluctuations of the blood oxygenation level-dependent (BOLD) signal measured with MRI in awake resting humans, reveal functional subdivisions in the medial temporal lobe memory system and parietal and prefrontal cortical components linked to it. I will describe results from non-human primates demonstrating that this functional organization persists across the species, highlighting cortical components that have undergone considerable areal expansion in humans relative to non-human primates, how this method can be used to identify homologue regions, and more generally, what can be learned from a comparative perspective. In the second part of my talk I will describe recent efforts to selectively modulate system dynamics. A lentivirus was used to target excitatory neurons in the rat cortex with light-activated cation channel channelrhodopsin-2. Using photostimulation to activate these neurons we were able to drive the BOLD response locally and in regions anatomically connected to the infected site in a variety of stimulation paradigms. I will discuss implications for understanding the BOLD signal and prospects for this approach in studying the microcircuit as well as large-scale brain dynamics. Finally, I will discuss the challenges and promises of whole-brain imaging in small animals, and how this work can provide avenues to bridge between a basic understanding of human behavior, large-scale neural dynamics, and psychiatric disorders where such dynamics are disrupted.

Retinal neuroprosthetics can potentially be used to address some of the major degenerative disorders that cause blindness, including Retinitis Pigmentosa and Macular Degeneration, by bypassing the degenerated photoreceptor layer, and interfacing directly the more viable Retinal Ganglion Cells (RGCs). I will describe the development of new optical and computational tools aimed at allowing controlled experimental emulation of activity patterns in a large population of retinal ganglion cells and their correlation structure. First, we introduce new optical systems allowing control of increasingly complex spatiotemporal activity patterns in neural populations, focusing on holographic photo-stimulation which has several fundamental advantages in this application. Next, we introduce a general new computational strategy based on correlation distortions, for controlling and analyzing the pair-wise correlation structure (defined in terms of auto- and cross-correlation functions) in multiple synthetic spike trains. This approach can be used to generate stationary or non-stationary network activity patterns with predictable spatio-temporal correlations. In a final part of the talk I will describe a new approach for exact, flexible control of neurite outgrowth in three-dimensional neural structures, and its possible applications.