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.