Multichannel planar microelectrode array for somatic mapping in rats

Planar electrode array is an important tool to evaluate perceptual or cognitive functions of the cortex and prosthetic applications. Many construction methods have been developed. To maximize the usefulness of an array electrode, a low-cost, precise, and flexible microelectrode array with low man power and short construction duration is crucial. In this study, we introduced an 8 × 8 microelectrode array on a flexible polyimide film through microelectronics fabrication. The array dimension was capable of covering the primary somatosensory cortex of a rat. The microelectrode array was insulated with biocompatible Parylene-C except of microelectrode tip. Each electrode tip was 66 μm height and separated with 0.5 mm to refine a detail somatic sensory processing. In pentobarbital anesthetized rats, stable spontaneous brain activity was successfully recorded through the electrode array. In addition, positive peaks of somatosensory evoked potentials (SEPs) elicited by stimulating rat's whisker pad, forepaw, hindpaw, and tail were obviously and consistently recorded. Latencies of SEPs increased as caudal part of the body was stimulated. The SEPs from stimulation of 4 body parts revealed different spatiotemporal patterns, which indicated a somatotopic organization of the rat. Our results demonstrated the superiority of the planar microelectrode array on the application of simultaneous recording and analysis of the brain activity in rats.