Advanced Technologies for Measuring Brain Activity in Behaving Animals

While the primary focus has been the understanding of the physical mechanisms that give rise to cognitive and motor sequences, an essential part of our research program is the continued development of novel technologies for extracellular recording, intracellular recording, and functional imaging in behaving animals. W have recently developed an extremely lightweight motorized microdrive that permits three chronically implanted electrodes to be manipulated by remote control without interfering with naturally occurring behaviors. The motorized microdrive has resulted in a two order-of-magnitude increase in the number of neurons that can be recorded in the behaving songbird. We are continuing to develop new chronic recording techniques.

We have also recently developed a system to actively stabilize an intracellular recording electrode relative to the brain using laser interferometric measurement of brain motion. Intracellular recording is a powerful technique that has revealed most of what is known about the biophysical properties of neurons. Unfortunately, this technique is extremely sensitive to movement of the tissue relative to the recording electrode. Thus intracellular recording has largely been limited to recordings in brain slice and anesthetized animals. However, neuronal properties are strongly affected by activity-dependent and modulatory influences, making it desirable to study these biophysical properties, as well as circuit dynamics, in behaving animals. The laser-interferometric electrode stabilizer has permitted stable intracellular recordings from neurons in awake behaving rats and zebra finches.We are collaborating with Mark Schnitzer at Stanford to develop a fiber-optic based electrode stabilizer that can compensate for tissue motion in deep brain structures in awake behaving animals.