title: Decoding hand gestures from primary somatosensory cortex using high-density ECoG.
abstract: Electrocorticography (ECoG) based Brain-Computer Interfaces (BCIs) have been proposed as a way to restore and replace motor function or communication in severely paralyzed people. To date, most motor-based BCIs have either focused on the sensorimotor cortex as a whole or on the primary motor cortex (M1) as a source of signals for this purpose. Still, target areas for BCI are not confined to M1, and more brain regions may provide suitable BCI control signals. A logical candidate is the primary somatosensory cortex (S1), which not only shares similar somatotopic organization to M1, but also has been suggested to have a role beyond sensory feedback during movement execution. Here, we investigated whether four complex hand gestures, taken from the American sign language alphabet, can be decoded exclusively from S1 using both spatial and temporal information. For decoding, we used the signal recorded from a small patch of cortex with subdural high-density (HD) grids in five patients with intractable epilepsy. Notably, we introduce a new method of trial alignment based on the increase of the electrophysiological response, which virtually eliminates the confounding effects of systematic and non-systematic temporal differences within and between gestures execution. Results show that S1 classification scores are high (76%), similar to those obtained from M1 (74%) and sensorimotor cortex as a whole (85%), and significantly above chance level (25%). We conclude that S1 offers characteristic spatiotemporal neuronal activation patterns that are discriminative between gestures, and that it is possible to decode gestures with high accuracy from a very small patch of cortex using subdurally implanted HD grids. The feasibility of decoding hand gestures using HD-ECoG grids encourages further investigation of implantable BCI systems for direct interaction between the brain and external devices with multiple degrees of freedom.
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Mariana P
authors.initials: MP
authors.lastname: Branco
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Zachary V
authors.initials: ZV
authors.lastname: Freudenburg
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Aarnoutse
authors.affiliation: Neuropsychology Lab, Department of Psychology, Cluster of Excellence Hearing4all, University of Oldenburg, Oldenburg, Germany.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Bleichner
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Mariska J
authors.initials: MJ
authors.lastname: Vansteensel
authors.affiliation: Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands. Electronic address: N.F.Ramsey@umcutrecht.nl.
authors.forename: Nick F
authors.initials: NF
authors.lastname: Ramsey
mesh_terms: D000328:Adult; D001931:Brain Mapping; D062207:Brain-Computer Interfaces; D000069280:Electrocorticography / Q000379:methods*; D004567:Electrodes, Implanted; D004827:Epilepsy / Q000601:surgery; D005260:Female; D065818:Gamma Rhythm; D005868:Gestures; D006225:Hand; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology; D012813:Sign Language; D013003:Somatosensory Cortex / Q000502:physiology*; D058067:Wavelet Analysis; D055815:Young Adult
keywords: Brain-computer interface; Decoding; Electrocorticography; Primary motor cortex; Primary somatosensory cortex