Intracellular recordings from single neurons provide functional information with unparalleled spatial and temporal resolution among known brain monitoring techniques in vivo. They have several well-known advantages over extra-cellular single neuronal recordings such as the ability to assess (a) membrane potentials of single neurons where the dynamic range of the signal is 2 or 3 orders of magnitude larger (b) dynamics of ion-channels and their role in specific neuronal functions (c) shapes of individual neuronal action potentials without the confounding occurences of overlapping action potentials from neurons in the proximity and (d) the potential to assess synaptic potentials such as excitatory post-synaptic potentials. The overall goal of the current proposal is to develop a head-mounted system for recording intracellular membrane potentials in vivo from ensembles of neurons in awake behaving animals. Current technologies to record intra-cellular potentials require extraordinary skill and tedious operations using cumbersome stereotactic, positioning systems for precise isolation and penetration or patching of single neurons in the central nervous system. The size and weight of such systems make it difficult for tracking specific clusters of neurons in a given functional region in awake, behaving animals and are therefore primarily used in anesthetized animals. We propose to use Micro-electromechanical systems (MEMS) based technologies to dramatically reduce the form factor and develop a head-mounted, autonomous nanoelectrode system that will (a) automate and minimize the art in intracellular recording experiments and (b) enable intracellular recordings from single neurons first in anesthetized animals and eventually in awake, behaving animals. We will build on our successful NIH funded program to develop MEMS based movable microelectrodes for recording single and multi-unit activity in chronic in vivo rodent experiments [1, 2]. The key hypothesis is that a confluence of 3 distinct technologies namely, (a) MEMS for precise positioning of brain implants in chronic experiments with significant reduction in form factor (b) nanoelectrodes for minimally invasive cell penetration and (c) closed-loop control to automate the positioning and compensation against disturbances will now enable the exciting possibility of stable intracellular recordings first in anesthetized animals and eventually in awake, behaving animals.The specific aims of the current proposed effort are: Aim #1. Design, develop and test a polysilicon nanoelectrode, electrothermal microactuator, integrated gear trains and closed-loop control technology that will enable the penetration and successful placement of the nanoelectrode inside xenopus oocyte cells. We will attempt two different approaches (a) focussed ion beam (FIB) milling and (b) growing gold nanowire(s) at the tip of polysilicon microelectrodes. We will optimize the force generated by the electrothermal microactuators, velocity of microelectrode at different positions relative to the single cell, displacement jitter for cell penetration, and closed-loop control system for autonomous placement of the nanoelectrode inside the cell. Aim #2. Design, develop and test the autonomous nanoelectrode system for intracellular recordings in (a) in vitro isolated abdominal ganglia neurons from Aplysia (b) rat hippocampal brain slice experiments and (c) rat experiments under different levels of anesthesia motivated by eventual testing in awake, behaving rats.
|Effective start/end date||9/1/13 → 8/31/16|
- HHS: National Institutes of Health (NIH): $582,041.00