Autonomy Infused Teleoperation with Application to BCI Manipulation

Robot teleoperation systems face a common set of challenges including latency, low-dimensional user commands, and asymmetric control inputs. User control with Brain-Computer Interfaces (BCIs) exacerbates these problems through especially noisy and erratic low-dimensional motion commands due to the difficulty in decoding neural activity. We introduce a general framework to address these challenges through a combination of computer vision, user intent inference, and arbitration between the human input and autonomous control schemes. Adjustable levels of assistance allow the system to balance the operator's capabilities and feelings of comfort and control while compensating for a task's difficulty. We present experimental results demonstrating significant performance improvement using the shared-control assistance framework on adapted rehabilitation benchmarks with two subjects implanted with intracortical brain-computer interfaces controlling a seven degree-of-freedom robotic manipulator as a prosthetic. Our results further indicate that shared assistance mitigates perceived user difficulty and even enables successful performance on previously infeasible tasks. We showcase the extensibility of our architecture with applications to quality-of-life tasks such as opening a door, pouring liquids from containers, and manipulation with novel objects in densely cluttered environments

An Electrocorticographic Brain Interface in an Individual with Tetraplegia

Brain-computer interface (BCI) technology aims to help individuals with disability to control assistive devices and reanimate paralyzed limbs. Our study investigated the feasibility of an electrocorticography (ECoG)-based BCI system in an individual with tetraplegia caused by C4 level spinal cord injury. ECoG signals were recorded with a high-density 32-electrode grid over the hand and arm area of the left sensorimotor cortex. The participant was able to voluntarily activate his sensorimotor cortex using attempted movements, with distinct cortical activity patterns for different segments of the upper limb. Using only brain activity, the participant achieved robust control of 3D cursor movement. The ECoG grid was explanted 28 days post-implantation with no adverse effect. This study demonstrates that ECoG signals recorded from the sensorimotor cortex can be used for real-time device control in paralyzed individuals

The Terror Exception: The Impact of the 2001 Authorization for Use of Military Force on United States Counterterrorism Policy in the Middle East Under the Obama Administration

In the traumatic and somber aftermath of the September 11, 2001 terrorist attacks, the U.S. Congress passed a critical piece of legislation to provide the president authority to defend the United States and its interests abroad. The Authorization for Use of Military Force (AUMF), which responded to the horrors of 9/11, began the United States’ longest war—the global war on terror— and serves as its legal basis today. President George W. Bush signed the AUMF into law on September 18, 2001, only a week after the attacks. Congress agreed with the proposition: That the President is authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on Sept. 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons. The AUMF enabled President Bush to defend the United States against al-Qa’ida and other entities that carried out 9/11. Congress rejected the Bush administration’s first draft of the legislation because they believed it was too expansive. The initial wording provided the president with authority “to deter and pre-empt any future acts of terrorism or aggression,” which Congress rejected on the grounds that such language would provide the Executive Branch with power at the expense of Congress. Congress rejected other requests from the Bush administration, including one to transfer appropriations power to the president, and another that restricted Congress’ access to classified briefings. The Bush administration also asked for authority to waive restrictions on foreign assistance without notifying Congress, which could unilaterally override Congressional mandates not to assist countries who commit human rights violations, cause nuclear proliferation, and sponsor terrorism. As David Abramowitz, the Democratic Chief Counsel of the House Committee on International Relations, explained at the time, “the requests from the White House in response to this crisis were particularly breathtaking, and the results of many of these proposals were far narrower than those put forth initially by the President.” In other words, the rejection by a Congress of expanded executive authority guarded the separation of powers

Motor-related brain activity during action observation: A neural substrate for electrocorticographic brain-computer interfaces after spinal cord injury

After spinal cord injury (SCI), motor commands from the brain are unable to reach peripheral nerves and muscles below the level of the lesion. Action observation (AO), in which a person observes someone else performing an action, has been used to augment traditional rehabilitation paradigms. Similarly, AO can be used to derive the relationship between brain activity and movement kinematics for a motor-based brain-computer interface (BCI) even when the user cannot generate overt movements. BCIs use brain signals to control external devices to replace functions that have been lost due to SCI or other motor impairment. Previous studies have reported congruent motor cortical activity during observed and overt movements using magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). Recent single-unit studies using intracortical microelectrodes also demonstrated that a large number of motor cortical neurons had similar firing rate patterns between overt and observed movements. Given the increasing interest in electrocorticography (ECoG)-based BCIs, our goal was to identify whether action observation-related cortical activity could be recorded using ECoG during grasping tasks. Specifically, we aimed to identify congruent neural activity during observed and executed movements in both the sensorimotor rhythm (10-40 Hz) and the high-gamma band (65-115 Hz) which contains significant movement-related information. We observed significant motor-related high-gamma band activity during AO in both able-bodied individuals and one participant with a complete C4 SCI. Furthermore, in able-bodied participants, both the low and high frequency bands demonstrated congruent activity between action execution and observation. Our results suggest that AO could be an effective and critical procedure for deriving the mapping from ECoG signals to intended movement for an ECoG-based BCI system for individuals with paralysis. © 2014 Collinger, Vinjamuri, Degenhart, Weber, Sudre, Boninger, Tyler-Kabara and Wang

An Investigation Into Using Magnetically Attached Piezoelectric Elements for Vibration Control

A novel vibration control method utilizing magnetically mounted piezoelectric elements is described. Piezoelectric elements are bonded to permanent magnets, termed here as control mounts, which are attached to the surface of a steel beam through their magnetic attraction. The magnetic-piezoelectric control mounts are an alternative to traditional epoxy attachment methods for piezoelectric elements which allows for easy in-the-field reconfiguration. In model and laboratory measurements, the beam is driven through base excitation and the resonant shunt technique is utilized to demonstrate the attenuation characteristics of two magnetic-piezoelectric control mounts. The coupled system is discretized using a Galerkin finite element model that incorporates the tangential and vertical contact stiffnesses of the beam-magnet interface. The vibration reduction provided by the control mounts using a single magnet are compared to those designed with a magnetic array that alternates the magnetic dipoles along the length of the mount. Even though each design uses the same magnet thickness, the alternating magnetic configuration\u27s interfacial contact stiffness is over 1.5 and 4 times larger in the tangential and vertical directions, respectively, than that of the single magnet, resulting in increased vibration reduction. Measured and simulated results show that the magnetic-piezoelectric control mounts reduced the beam\u27s tip velocity by as much as 3.0 dB and 3.1 dB, respectively. The design tradeoffs that occur when replacing the traditional epoxy layer with a magnet are also presented along with some methods that could improve the vibration reduction performance of the control mounts. This analysis shows that the control mounts attenuate significant vibration despite having an imperfect bond with the beam, thus providing a viable and adaptable alternative to traditional piezoelectric attachment methods

Acute Biceps and Supraspinatus Tendon Changes Associated with Wheelchair Propulsion

Manual wheelchair uses rely on their upper limbs for mobility and activities of daily living. Unfortunately more than half of manual wheelchair users will experience shoulder pain, due in part to repetitive loading during wheelchair propulsion and transfers. While chronic upper extremity pathology has been well documented, no research has investigated acute rotator cuff changes that occur as a result of wheelchair propulsion. Ultrasound is a non-invasive, convenient method to examine soft tissue structures of the shoulder, but tendinosis is rated subjectively by the operator. Here we apply image analysis techniques to quantify tendon size, echogenicity, and greyscale texture. We have developed a standardized protocol, and custom reference marker, to maximize reliability of these measures. Further, content validity was established by relating greyscale-based quantitative ultrasound measures to known risk factors for shoulder pain and pathology including increased age, duration of wheelchair use, and body weight. Quantitative ultrasound measures also correlated to clinically graded tendinosis and discriminated between people with and without symptoms on physical examination. Sixty-seven manual wheelchair users underwent quantitative ultrasound examinations of the biceps and supraspinatus tendons before and after an intense wheelchair propulsion task. Biceps tendon greyscale texture post-propulsion was significantly impacted by clinically graded tendinopathy, duration of wheelchair use, resultant force, and stroke frequency when controlling for pre-propulsion ultrasound image texture. Subjects with tendinopathy or a longer duration of wheelchair use tended to have a darker, less organized tendon microstructure following propulsion likely due to the presence of inflammatory factors or other fluid. In contrast, subjects who used a higher stroke frequency or resultant force showed a brighter, more aligned tendon fibrillar structure due to mechanical loading of the tendon. In a subsample of subjects, we found that increased shoulder forces and moments during propulsion correlated with more severe supraspinatus tendinopathy. These subjects also experienced a larger decrease in supraspinatus tendon width and greyscale variance following the intense propulsion task. Quantitative ultrasound measures describe tendon microstructure and are sensitive to risk factors for shoulder pain and pathology. This technique may help identify the best interventions to reduce an individual's risk of developing upper limb pathology

Vulnerability of the superficial zone of immature articular cartilage to compressive injury

Objective The zonal composition and functioning of adult articular cartilage causes depth-dependent responses to compressive injury. In immature cartilage, shear and compressive moduli as well as collagen and sulfated glycosaminoglycan (sGAG) content also vary with depth. However, there is little understanding of the depth-dependent damage caused by injury. Since injury to immature knee joints most often causes articular cartilage lesions, this study was undertaken to characterize the zonal dependence of biomechanical, biochemical, and matrix-associated changes caused by compressive injury. Methods Disks from the superficial and deeper zones of bovine calves were biomechanically characterized. Injury to the disks was achieved by applying a final strain of 50% compression at 100%/second, followed by biomechanical recharacterization. Tissue compaction upon injury as well as sGAG density, sGAG loss, and biosynthesis were measured. Collagen fiber orientation and matrix damage were assessed using histology, diffraction-enhanced x-ray imaging, and texture analysis. Results Injured superficial zone disks showed surface disruption, tissue compaction by 20.3 ± 4.3% (mean ± SEM), and immediate biomechanical impairment that was revealed by a mean ± SEM decrease in dynamic stiffness to 7.1 ± 3.3% of the value before injury and equilibrium moduli that were below the level of detection. Tissue areas that appeared intact on histology showed clear textural alterations. Injured deeper zone disks showed collagen crimping but remained undamaged and biomechanically intact. Superficial zone disks did not lose sGAG immediately after injury, but lost 17.8 ± 1.4% of sGAG after 48 hours; deeper zone disks lost only 2.8 ± 0.3% of sGAG content. Biomechanical impairment was associated primarily with structural damage. Conclusion The soft superficial zone of immature cartilage is vulnerable to compressive injury, causing superficial matrix disruption, extensive compaction, and textural alteration, which results in immediate loss of biomechanical function. In conjunction with delayed superficial sGAG loss, these changes may predispose the articular surface to further softening and tissue damage, thus increasing the risk of development of secondary osteoarthritis.National Institutes of Health (U.S.) (grant P5O-AR39239)National Institutes of Health (U.S.) (grant R01-AR45779)Deutsche Forschungsgemeinschaft (DFG) (grant RO 2511/1-1)Deutsche Forschungsgemeinschaft (DFG) (grant RO 2511/2-1

A simulation study on the effects of neuronal ensemble properties on decoding algorithms for intracortical brain-machine interfaces

Background: Intracortical brain-machine interfaces (BMIs) harness movement information by sensing neuronal activities using chronic microelectrode implants to restore lost functions to patients with paralysis. However, neuronal signals often vary over time, even within a day, forcing one to rebuild a BMI every time they operate it. The term "rebuild" means overall procedures for operating a BMI, such as decoder selection, decoder training, and decoder testing. It gives rise to a practical issue of what decoder should be built for a given neuronal ensemble. This study aims to address it by exploring how decoders' performance varies with the neuronal properties. To extensively explore a range of neuronal properties, we conduct a simulation study. Methods: Focusing on movement direction, we examine several basic neuronal properties, including the signal-to-noise ratio of neurons, the proportion of well-tuned neurons, the uniformity of their preferred directions (PDs), and the non-stationarity of PDs. We investigate the performance of three popular BMI decoders: Kalman filter, optimal linear estimator, and population vector algorithm. Results: Our simulation results showed that decoding performance of all the decoders was affected more by the proportion of well-tuned neurons that their uniformity. Conclusions: Our study suggests a simulated scenario of how to choose a decoder for intracortical BMIs in various neuronal conditions