Diode probes for spatiotemporal optical control of multiple neurons in freely moving animals

Abstract

Stark E, Koos T, Buzsáki G. Diode probes for spatiotemporal optical control of multiple neurons in freely moving animals.

State-of-the-art MEMS and microsystem tools for brain research

“…Using MEMS-based arrays to improve software tools for neuroscientists also involves neuronal location information 9,24,29,31 and cell classification of neurons 4,83 , which are critical in brain mapping. The need for technologies to enable cell typing in brain research was highlighted as the number one priority by the U.S.…”

“…Early work involving in vivo optogenetics relied on the manual assembly of commercially available components such as microwires and optical fibers, which are not only bulky but can also experience large misalignments due to human error 9,159 . Since then, engineering efforts have gradually evolved towards MEMS technologies for miniaturization, high-density integration, and precise definition of the probe dimensions with lithographic resolution.…”

“…However, no recording electrodes were integrated on these devices; therefore, they could not support both optical stimulation and electrophysiology. Stark et al 9 reported a hybrid approach for manually assembling optical fibers onto MEMS recording probes. Coupled to laser diodes of various emission wavelengths, this device could excite and silence neural populations monitored by a high-density electrode array 161 .…”

“…Calculating the volume of excitable tissue also requires that some assumptions be made. First, one must estimate the irradiance threshold at which a neuron can be stimulated or silenced, which is a function of the opsin type, the consistency of expression in a cell, and local neuron orientation 9,169 . A second assumption must be made about the maximum irradiance allowed in tissue before heating 170 and cellular 155 changes occur.…”

“…Beginning in 2005, seminal studies on optogenetics introduced methods for exciting and inhibiting neurons in ways specific to genetic and chemical markers of a particular cell type 7,8 . Optical control of genetically engineered ion channels is a powerful tool for parsing circuit elements and cell types in the dense heterogeneous populations surrounding a microelectrode recording site 4,9 . Biotechnologists are rapidly discovering new opsins (light-activated ion channels) [10][11][12] , and neurotechnologists are racing to scale light-delivery instruments, while simultaneously scaling electrical recording capabilities in the illuminated regions of tissue.…”