Operant conditioning is implemented in brain-machine interfaces (BMI) to induce rapid volitional modulation of single neuron activity to control arbitrary mappings with an external actuator. However, intrinsic factors of the volitional controller (i.e. the brain) or the output stage (i.e. individual neurons) might hinder performance of BMIs with more complex mappings between hundreds of neurons and actuators with multiple degrees of freedom. Improved performance might be achieved by studying these intrinsic factors in the context of BMI control. In this study, we investigated how neuron subtypes respond and adapt to a given BMI task. We conditioned single cortical neurons in a BMI task. Recorded neurons were classified into bursting and non-bursting subtypes based on their spike-train autocorrelation. Both neuron subtypes had similar improvement in performance and change in average firing rate. However, in bursting neurons, the activity leading up to a reward increased progressively throughout conditioning, while the response of non-bursting neurons did not change during conditioning. These results highlight the need to characterize neuron-subtype-specific responses in a variety of tasks, which might ultimately inform the design and implementation of BMIs.
The ability to select neurons with high utility will be important to minimize training times and maximize information yield in future clinical BMI applications. The highly contrasting utility observed between fast-spiking and bursting neurons versus regular-spiking neurons allows for the hypothesis to be advanced that intrinsic electrophysiological properties may be useful criteria that predict neuron utility in BMI implementation.
Context/Objective Functional electrical stimulation (FES) is commonly used in rehabilitation to generate electrically-induced muscle contractions. FES has been shown to assist in the recovery of voluntary motor functions after stroke or spinal cord injury. However, discomfort associated with FES can motivate patients to withdraw their participation from FES therapy despite its benefits. To address this issue, a functional electrical stimulator, called MyndMove™ (MyndTec Inc., Canada), has been developed to generate more comfortable contractions than conventional stimulators. Design Cross-sectional, interventional, with two treatment arms. Setting A laboratory within a rehabilitation center. Participants Twelve able-bodied participants. Intervention FES delivered with two different stimulators, MyndMove™ and Compex Motion (Compex, Switzerland), during muscle contractions of high, moderate and low stimulation intensity. Outcome Measures Comfort-related preference to a given stimulator and the discomfort score rated through a Numeric Rating Scale (NRS-101) for both stimulators. Results Participants perceived a reduction in discomfort during high-intensity stimulation generated using MyndMove™. In addition, MyndMove™ stimulations were preferred in 60% of all contractions. The reduction in discomfort associated with MyndMove™ might be due the fact that MyndMove™ delivers less charge to generate contractions of equivalent intensity, compared to Compex Motion. Conclusion Reducing discomfort during FES may help in generating stronger and more clinically useful contractions, increasing accessibility of FES therapy to include individuals with low tolerance to FES.
Background/Objectives: To identify and compare effective means of managing obesity in individuals with chronic spinal cord injury (SCI). Methods/Overview: This review included English and non-English articles, published prior to January 2017 found in PubMed/Medline, Embase, Cinahl, Psychinfo and Cochrane databases. Studies evaluating any obesity management strategy alone or in combination including diet therapy, physical exercises, passive exercises such as neuro-muscular electric stimulation (NMES), pharmacotherapy, and surgery, among individuals with chronic SCI were included. Outcomes of interest were declines in waist circumference, body weight, body mass index and Total Fat Mass (TFM) and increases in total lean body mass (TLBM). From 3553 retrieved titles and abstracts, 34 articles underwent full-text review and 23 articles selected for data abstraction. Weight loss due to inflammation, cancer or B12 deficiency was excluded. The quality of the selected studies was evaluated by Downs and Black tool and found to be generally poor to medium with 4 exceptions. Results: Bariatric surgery produced the greatest permanent weight reduction and BMI correction followed by combinations of physical exercise and diet therapy. Generally NMES and pharmacotherapy did not reduce weight but improved body composition (increases in TLBM and reductions in TFM). Conclusions: Due to link between adiposity and all-cause mortality; obesity is a legitimate therapeutic target. A trial of diet and exercise therapy is recommended prior to definitive bariatric surgery.
Objective. Volitional modulation of single cortical neurons holds great potential for the implementation of brain–machine interfaces (BMIs) because it can induce a rapid acquisition of arbitrary associations between machines and neural activity. It can also be used as a framework to study the limits of single-neuron control in BMIs. Approach. We tested the control of a one-dimensional actuator in two BMI tasks which differed only in the neural contingency that determined when a reward was dispensed. A thresholded activity task, commonly implemented in single-neuron BMI control, consisted of reaching or exceeding a neuron activity level, while the second task consisted of reaching and maintaining a narrow neuron activity level (i.e. windowed activity task). Main findings. Single neurons in layer V of the motor cortex of rats improved performance during both the thresholded activity and windowed activity BMI tasks. However, correct performance during the windowed activity task was accompanied by activation of neighboring neurons, not in direct control of the BMI. In contrast, only neurons in direct control of the BMI were active at the time of reward during the thresholded activity task. Significance. These results suggest that thresholded activity single-neuron BMI implementations are more appropriate compared to windowed activity BMI tasks to capitalize on the adaptability of cortical circuits to acquire novel arbitrary skills.
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