ABSTRACT
By stimulating or recording electrical activity, microelectrode arrays implanted in the brain have created a renaissance in the treatment of neurological diseases and injuries. Likewise, these devices are an enabling technology to understand normal brain function and behavior. However, questions remain regarding the relationship between the biological response to implanted electrodes, their chronic performance, and features of their design. It is my lab’s goal to understand the basic science underlying the interaction between implanted electrodes and brain cells, and to provide guiding principles to improve device design and performance as a result. Recently, we have found novel effects of implanted silicon and polyimide-based electrode arrays on the structure and function of local neurons, including alterations in ion channel expression, synaptic transporter expression, dendritic spine density, and excitability. Results of quantitative immunohistochemistry demonstrate a progressive local increase in the expression of potassium ion channels and inhibitory transporters surrounding devices implanted in the brains of rats over time, indicating a potential shift toward hypoexcitability over the 6-week time course studied. Two-photon laser scanning microscopy in brain slice preparations revealed profound local spine loss surrounding implants, coupled with observations of reduced responsiveness to injected current during whole cell intracellular recordings, where preliminary observations indicate particularly pronounced effects surrounding silicon-based devices. More recently, we have pursued RNA-sequencing to understand the molecular identity and function of neurons and non-neurons surrounding implanted electrodes. Our results suggest a novel role of local plasticity surrounding devices in chronic signal loss and instability, and we are currently working to assess and perturb local gene expression to reveal potential underlying mechanisms.
BIOGRAPHY
Dr. Erin Purcell studied neural engineering during her graduate work with Dr. Daryl Kipke in the Department of Biomedical Engineering at the University of Michigan, where her work focused on developing ways to improve the integration of neural implants with the surrounding brain tissue. She became interested in neural regeneration and plasticity, developing techniques to deliver stem cells and drugs with the implant and characterizing the effects of those treatments using histology and extracellular electrophysiology. Following graduation, Erin joined the Kresge Hearing Research Institute as a Research Fellow in Dr. Keith Duncan's laboratory at the University of Michigan, where she trained in intracellular (patch clamp) neural recordings. Erin joined the faculty at Michigan State University in 2014 as an Assistant Professor in the Department of Electrical and Computer Engineering. In 2016, she became the first tenure-track faculty member of the new Department of Biomedical Engineering at MSU. As the P.I. of the Regenerative Electrode Interface Lab, Dr. Purcell is pursuing new approaches to characterize, modulate, and regenerate neuronal responses at the interface of electrodes implanted in the brain. Dr. Purcell's lab is funded by an R01 recently awarded by the NIH.
