APIG (Harris Lab)

Intracellular recordings provide the most fundamental information about electrical activity in neurons. These measurements are extremely delicate and very sensitive to mechanical disturbances, and therefore nearly impossible in active neural systems. The primary goal in this project is to provide the neuroscientists at Janelia with new devices that allow them to reliably measure intracellular electrical properties of active neural circuits with single-cell resolution. Images below show the performance of a novel device as compared to the standard patch electrode when subject to a mechanical impact.

We continually look at opportunities to utilize modern advances in semiconductor fabrication, optoelectronics, and microdevice development (shown below) to advance the field of experimental electrophysiology at Janelia. We believe that in miniaturizing present neural recording systems, by integration of novel micro-devices into complete recording systems, shown below, new opportunities will arise in obtaining fundamental intracellular information from active neural systems with single-cell resolution.


Optics and electrophysiology are becoming more intertwined, as neuroscientists look at novel ways to access information from single cells in active brains. As part of our efforts to provide the tools they need, we are developing two-photon visible patch-clamp electrodes (shown below) that will help Janelia neuroscientists target neural cells of interest with increasing precision and reliability.

Researchers strive to make measurements on animals in a way that does not inhibit or modify the behavior under study. Anthony Leonardo here at Janelia is investigating the neural basis for prey capture by dragonflies in midflight, a behavior requiring untethered and unrestricted motion of the animal. He and colleagues Reid Harrison and Rob Olberg have developed and demonstrated a lightweight telemetry circuit powered by a small battery that when combined with custom electrical probes, can record and transmit extracellular and neuromuscular signals from the dragonfly to a stationary receiver.
 
In collaboration with Anthony, we are exploring ways to provide a long-life source of lightweight and untethered power for the dragonfly electronics, as an alternative to the rather heavy batteries commercially available.  One approach we are pursuing involves using solar cells, which are photodiodes that generate a current and voltage proportional to the amount of light falling on the active area of the device.  While ambient light is a convenient source of optical power, in order to keep the size of the solar cells small, a near-IR light source that cannot be seen by the animal can illuminate the body-mounted solar cell while the dragonfly is perched.  An additional component, a small lightweight supercapacitor, is added to store electrical energy required for the telemetry circuit during the brief period of flight of the dragonfly during prey capture.  This is a rechargeable process; each time the dragonfly returns to the perch it is illuminated with near-IR light, which is converted to electrical power by the solar cell, recharging the supercapacitor for the next flight. 

Devices have been constructed and used to successfully record neural activity in perched dragonflies, and experiments are under way to map the complex dynamical behavior and the underlying neural computations involved in midflight prey capture.