Eberhard E. Fetz, University of Washington

Bidirectional interactions between the brain and implantable computers

Closed-loop interactions between the brain and implantable computers open new opportunities for brain research and clinical applications. We are investigating the consequences of direct connections produced by an autonomous implantable bidirectional brain-computer interface [B-BCI]. This device consists of battery-powered electronics connected to electrodes that record the activity of motor cortex cells and/or muscles. It operates continuously during free behavior and generates activity-dependent stimulation of the brain or spinal cord. The neural activity is processed by a programmable computer chip and can be converted in real-time to activity-contingent stimuli. A promising application is to bridge impaired biological connections, a paradigm that was demonstrated for cortically controlled electrical stimulation of paralyzed forearm muscles (Moritz et al, Nature, 2008), and cortically controlled intraspinal stimulation (Nishimura et al, Frontiers in Neuroscience, 2013). Given sufficient time to adapt to an implanted B-BCI the brain could learn to incorporate such artificial recurrent connections into normal behavior. A second application of the B-BCI is to produce Hebbian plasticity through spike-triggered stimulation; this can strengthen neural connections, as demonstrated for neighboring motor cortical sites (Jackson et al, Nature, 2006). Similar plastic changes can be produced in motor cortex by EMG-triggered stimulation (Lucas & Fetz, J. Neurosci. 2013). The strength of corticospinal connections can be modified by cortically triggered intraspinal stimulation, in a manner consistent with spike-timing dependent plasticity (Nishimura et al, Neuron, 2013). Such activity-dependent stimulation has clinical potential for targeted strengthening of neural connections weakened by stroke or injury (Edwardson et al Exp. Brain Res. 2013). A third application of the B-BCI is to deliver intracranial reinforcing stimuli contingent on patterns of neural or muscular activity, thus implementing prolonged periods of operant conditioning during free behavior. The novel B-BCI paradigm has numerous potential applications, depending on the input signals, the computed transform and the output targets.

Organized by

Klaus-Robert Müller