We’re presenting two papers at the upcoming IEEE SMC 2022 conference in Prague! We presented two papers – the first detailing our experience using intracranial stimulation to deliver sensory feedback in a virtual reality environment, and the second detailing a new method for identifying time-varying neural responses to intracranial stimulation. If you’re going to SMC 2022 in Prague, come see our presentations!

Touching the Void: Intracranial Stimulation for NeuroHaptic Feedback in Virtual Reality
Courtnie Paschall, Jason Hauptman, Rajesh Rao, Jeffrey Ojemann, Jeffrey Herron
Abstract: Direct cortical stimulation of the somatosensory cortex (S1-DCS) has been shown to evoke distinct and localizable percepts, exploitable as neurohaptic feedback. In this study, we leveraged a novel virtual reality (VR) experimental platform to evaluate S1-DCS neurohaptic feedback during naturalistic object interaction. Two human subjects implanted with intracranial electrodes for seizure localization were asked to discriminate between visually identical virtual objects based on their distinct S1-DCS neurohaptic profiles. In a binary discrimination task, neurohaptic feedback was either present or absent while grasping a virtual object. In the ternary discrimination task, neurohaptic feedback was either present in one of two distinct neurohaptic sequences or absent. Both subjects performed significantly above chance in binary and ternary discrimination, demonstrating the efficacy of S1-DCS as neurohaptic feedback. Successful ternary discrimination also demonstrated that different sequences of amplitude-modulated S1-DCS at a single pair of electrodes can evoke discriminable neurohaptic percepts. Moreover, amplitude-modulated S1-DCS sequences were shown to elicit sensorimimetic percepts described as “bumpy” and “smooth” in Subject 1, and as a sensation of movement in the paralyzed hand of Subject 2. Our study demonstrates the reliability and discriminability of both simple and complex S1-DCS for neurohaptic feedback during immersive VR object interaction and supports the use of immersive VR for neurohaptic design towards the development of functional brain computer interface.

Human Intracortical Responses to Varying Electrical Stimulation Conditions Are Separable in Low-Dimensional Subspaces 
Samantha Sun, Lila Levinson, Courtnie Paschall, Jeffrey Herron, Kurt Weaver, Jason Hauptman, Andrew Ko, Jeffrey Ojemann, Rajesh Rao
Abstract: Electrical stimulation is a powerful tool for targeted neurorehabilitation, and recent work in adaptive stimulation where stimulation can be adjusted in real-time has shown promise in improving stimulation outcomes and reducing stimulation-induced side effects. Mapping the relationship between electrical stimulation input and neural activity response can help reveal interactions between stimulation and underlying neural activity and can give us tools to iterate and improve on our stimulation protocols. Here, we introduce methods for identifying low-dimensional subspaces of human intracortical responses to electrical stimulation in invasive electroencephalography. In epilepsy patients (n=4) undergoing clinical monitoring, we applied a stimulation protocol of varying stimulation amplitude and frequency in 5-second intervals to capture a range of responses to different stimulation conditions. We characterized these responses using time-frequency spectral power, applied baseline subtraction and outlier removal procedures, and performed principal component analysis across frequencies. We identified that intracortical responses to different stimulation conditions can be represented in a 3-dimensional subspace, accounting for more than 95% of the variance. Using pairwise support vector machine classification, we demonstrated separability of intracortical responses to different stimulation conditions across subjects, where this separability was contingent on performing baseline subtraction and outlier removal. Our results represent a first step towards building a mapping or predictive model from stimulation input to neural response, an important prerequisite for adaptive closed-loop stimulation for targeted neurorehabilitation.

At the upcoming EMBC 2021 we’re excited to present our latest research results from the fields of BCI and DBS. Congratulations to all students involved for getting their hard work published! Stay tuned for final paper links but this year we’ll be presenting two papers:

“Robustness of Beta Desynchronization from Chronically Implanted Cortical Electrodes on Multiple Time Scales” by Tomek Fraczek, Andrew Ko, Howard Chizeck, and Jeffrey Herron. Available here: https://ieeexplore.ieee.org/abstract/document/9629927

“A Platform for Virtual Reality Task Design with Intracranial Electrodes” by Co-first authors Maurice Montag and Courtnie Paschall, along with Jeff Ojemann, Rajesh Rao, and Jeffrey Herron. Available here: https://ieeexplore.ieee.org/abstract/document/9630231

Three papers are being presented at NER 2021 next week detailing ongoing work in the evaluating the sensing capabilities of directional DBS electrodes, stimulation ramp rate testing to support closed-loop DBS studies, and new architectures to support future research tool software development. Congratulations to all the students and collaborators who got their papers accepted to NER 2021!

C. Paschall, L. Levinson, J. Ojemann, A. Ko, J. Herron “Data-Driven Spectral Features of Directional DBS Electrodes and dDBS-ECoG Connectivity”

M. Petrucci, K. Wilkins, G. Orthlieb, Y. Kehnemouyi, J. O’Day, J. Herron, H. Bronte-Stewart “Ramp Rate Evaluation and Configuration for Safe and Tolerable Closed-Loop Deep Brain Stimulation”

B. Roarr, R. Perrone, F. Jamshed, R. Gilron, T. Denison, P. Starr, J. Herron, D. Borton “OMNI: Open Mind Neuromodulation Interface for Accelerated Research and Discovery“

Master’s student Kazi (Sabrina) Sonnet will be presenting her work on classifying essential tremor symptom classification using drawing task data at the IEEE BIBE2020 Conference on Monday, October 26th!

Five papers are going to be presented at EMBC covering ongoing work associated with closed-loop deep brain stimuilation (DBS) for Parkinson’s Disease and Essential Tremor, automated movement disorder symptom assessment techniques using mobile applications, and sleep stage classification based on invasive electrocorticography signals in epilepsy patients. Congratulations to all the students at University of Washington and our collaborators at Stanford who wrote these papers that were accepted to EMBC!

S. Cooper, B. Ferleger, A. Ko, J. Herron, H. Chizeck, “Rebound effect in deep brain stimulation for essential tremor and symptom severity estimation from neural data”

B. Ferleger, K. Sonnet, T. Morriss, A. Ko, H. Chizeck, J. Herron, “A tablet- and mobile-based application for remote diagnosis and analysis of movement disorder symptoms”

S. Sun, L. Jiang, S. Peterson, J. Herron, K. Weaver, A. Ko, J. Ojemann, R. Rao, “Unsupervised Sleep and Wake State Identification in Long-Term Neural Recordings”

J. O’Day, Y. Kehnemouyi, M. Petrucci, R. Anderson, J. Herron, H. Bronte-Stewart, “Demonstration of Kinematic-Based Closed-Loop Deep Brain Stimulation for Mitigating Freezing of Gait in People with Parkinson’s Disease”

M. Petrucci, R. Anderson, J. O’Day, Y. Kehnemouyi, J. Herron, H. Bronte-Stewart, “A Closed-Loop Deep Brain Stimulation Approach for Mitigating Burst Durations in People with Parkinson’s Disease”

A poster detailing work done in collaboration with Dr. Greg Worrell and Dr. Ben Brinkmann at the Mayo Clinic will be presented at the upcoming American Epilepsy Society meeting. The poster, titled “Epilepsy Personal Assistant Device – A Mobile Platform for Brain State, Dense Behavioral and Physiology Tracking, and Controlling Adaptive Stimulation” details work on a chronic monitoring system leveraging the Medtronic Summit System. See the full abstract here.

PhD student Ben Ferleger and undergraduate researcher Sarah Cooper will be at the annual Society for Neuroscience meeting in Chicago this year presenting a poster on some of our recent work using the Activa PC+S. The research project being presented is an investigation into the ‘rebound effect’ whereby essential tremor patients with a deep brain stimulator can have worse-than-normal symptoms immediately following the removal of electrical stimulation. Due to the fact that in future closed-loop DBS  systems may automatically turn on and off stimulation in response to sensed neural biomarkers, the fact that symptoms get worse temporarily with the removal of stimulation needs to inform future algorithm design to ensure effective control of symptoms.

The full SFN Conference Poster information is available here: https://www.abstractsonline.com/pp8/#!/7883/presentation/44957