We are investigating the consequences of bidirectional connections produced by an autonomous implantable recurrent brain-computer interface [R-BCI] that operates continuously during free behavior and generates activity-dependent stimulation of the brain or muscles. This device consists of battery-powered electronics connected to electrodes that record the activity of motor cortex cells and/or muscles. The neural activity is processed by a programmable computer chip and can be converted in real-time to activity-contingent stimuli delivered to nervous system sites or muscles.