Strategies to probe mechanoreception: From mechanical to optogenetic approaches

Abstract

There remain many questions about the rules governing the neural representation of touch; how the spatio-temporal patterns of points are integrated in the brain to generate the complex senses such as shape, size, weight, movement, and texture. Conventionally, the touch sense has been artificially generated mechanically or electrically with insufficient spatio-temporal resolution. Recently, the somatosensory system has been optogenetically investigated with the expression of optogenetic molecular reagents (OMRs) such as channelrhodopsin (ChR)-2 and halorhodopsin (Np HR). In a transgenic rat model that expresses ChR2 in peripheral mechanoreceptive neurons in the dorsal root ganglion (DRG) and the trigeminal ganglion (TG), blue light irradiation on skin or whiskers evoked a touch-dependent response in the cortex. Thus, various and reproducible patterned touch stimulations could be made by the patterned irradiations on the skin or whiskers. Optogenetic approaches could open a new avenue to investigate the neural representation of complex touch patterns using a combination of electrophysiological and imaging techniques.