c-Fos immunoreactivity and variation of neuronal units in rat's motor cortex after chronic implants

Recovering of people suffering from spinal cord and brain lesion is a medical challenge. Brain-machine interface (BMI) emerges as a potential candidate, by allowing patients to use their own brain activity to reestablish sensorimotor control of paralyzed body parts. BMI can be divided in two main groups: non-invasive, based in the capture of the neuronal signal over the cranium, and invasive, much more effective in generating high resolution brain-derived motor control signals, despite requiring a brain surgery for implantation of recording microelectrodes. Accordingly, chronic multielectrodes implants define the fundamental component of an invasive BMI. However, it is important to characterize the impact of microwire arrays' implant on the nervous tissue before this technique can be available to human clinical trials. Here we evaluated the expression of immediate early-gene c-fos and inflammatory response (astrogliosis), as well as the quality of the neuronal signal comparing the variation of the total number and the amplitude of the recorded units after long-lasting chronic multielectrode implants. Electrode recordings remained viable for 6 months after implant, and did not alter the general physiology of the implanted tissue, as revealed by normal c-Fos expression in implanted sites. Moreover, there was a small inflammatory response across implanted regions. Our findings suggest that tungsten microwire arrays can be viable candidates to future human BMI interventions.