title: Optimal space-time precoding of artificial sensory feedback through mutichannel microstimulation in bi-directional brain-machine interfaces.
abstract: Brain-machine interfaces (BMIs) aim to restore lost sensorimotor and cognitive function in subjects with severe neurological deficits. In particular, lost somatosensory function may be restored by artificially evoking patterns of neural activity through microstimulation to induce perception of tactile and proprioceptive feedback to the brain about the state of the limb. Despite an early proof of concept that subjects could learn to discriminate a limited vocabulary of intracortical microstimulation (ICMS) patterns that instruct the subject about the state of the limb, the dynamics of a moving limb are unlikely to be perceived by an arbitrarily-selected, discrete set of static microstimulation patterns, raising questions about the generalization and the scalability of this approach. In this work, we propose a microstimulation protocol intended to activate optimally the ascending somatosensory pathway. The optimization is achieved through a space-time precoder that maximizes the mutual information between the sensory feedback indicating the limb state and the cortical neural response evoked by thalamic microstimulation. Using a simplified multi-input multi-output model of the thalamocortical pathway, we show that this optimal precoder can deliver information more efficiently in the presence of noise compared to suboptimal precoders that do not account for the afferent pathway structure and/or cortical states. These results are expected to enhance the way microstimulation is used to induce somatosensory perception during sensorimotor control of artificial devices or paralyzed limbs.
authors.affiliation: Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48823, USA.
authors.forename: John
authors.initials: J
authors.lastname: Daly
authors.forename: Jianbo
authors.initials: J
authors.lastname: Liu
authors.forename: Mehdi
authors.initials: M
authors.lastname: Aghagolzadeh
authors.forename: Karim
authors.initials: K
authors.lastname: Oweiss
mesh_terms: D001676:Biofeedback, Psychology / Q000295:instrumentation*; D062207:Brain-Computer Interfaces; D004558:Electric Stimulation / Q000379:methods*; D005121:Extremities / Q000502:physiology; D008839:Microelectrodes; D009068:Movement; D009415:Nerve Net / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009622:Noise; D012677:Sensation / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology; D013788:Thalamus / Q000502:physiology