Characterizing the correlation between motor cortical neural firing and grasping kinematics

The hand has evolved to allow specialized interactions with our surroundings that define much of what makes us human. Comprised of numerous joints allowing 23 separate degrees-of-freedom (DoF) (joint motions) of movement, the hand and wrist are exceedingly complex. In order to better understand the constraints and principles underlying the neural control of the hand, we have carried out a series of neurophysiological experiments with monkeys performing a variety of reaching and grasping tasks. This work uses linear regression and low dimensional analysis to probe the neural representation of hand kinematics.We find that the kinematics of the three wrist DoFs (flexion, abduction and rotation) are rashly independent from hand-shape DoFs, and are considered separately. With respect to the wrist DoF, we show that the firing patterns of individual motor cortical cells are more linearly related to joint position than joint angular velocity. Using tuning functions from multivariate linear regressions, the firing rates from a population of cells accurately predicted three DoF of wrist orientation. We used principal components analysis to simplify the complex kinematics of the hand. Although the majority of the variability in hand kinematics can be explained with a small number (~7) of characteristic hand shapes (synergies), we find that these synergies do not capture the majority of neural variability. Both higher-order and lower-order synergies are well represented in the neural data. Although the kinematic synergies do not fully characterize neural firing, they can be utilized to simplify hand shape decoding. Using an optimal linear estimator, we predicted the average wrist and hand shape from the firing rates of 327 motor cortical cells with an accuracy as high as 92%. Individual motor cortical neurons are not well correlated with single joint variables; rather, they correlate with a number of joints in a complex way. This work provides evidence that hand movements are likely controlled through an intricate network of motor systems, of which motor cortical neurons contribute by making fine adjustments to a basic substrate. Further understanding of the control system will be gained by establishing a model that captures both the hand kinematic and neural variability

Biomimetic grasp planning for cortical control of a robotic hand

In this paper we outline a grasp planning system designed to augment the cortical control of a prosthetic arm and hand. A key aspect of this system it the ability to combine online user input and autonomous planning to enable the execution of stable grasping tasks. While user input can ultimately be of any modality, the system is being designed to adapt to partial or noisy information obtained from grasp-related activity in the primate motor cortex. First, principal component analysis is applied to the observed kinematics of physiologic grasping to reduce the dimensionality of hand posture space and simplify the planning task for on-line use. The planner then accepts control input in this reduced-dimensionality space, and uses it as a seed for a hand posture optimization algorithm based on simulated annealing. We present two applications of this algorithm, using data collected from both primate and human subjects during grasping, to demonstrate its ability to synthesize stable grasps using partial control input in real or near-real time

Outcomes in patients with gunshot wounds to the brain.

Introduction:Gunshot wounds to the brain (GSWB) confer high lethality and uncertain recovery. It is unclear which patients benefit from aggressive resuscitation, and furthermore whether patients with GSWB undergoing cardiopulmonary resuscitation (CPR) have potential for survival or organ donation. Therefore, we sought to determine the rates of survival and organ donation, as well as identify factors associated with both outcomes in patients with GSWB undergoing CPR. Methods:We performed a retrospective, multicenter study at 25 US trauma centers including dates between June 1, 2011 and December 31, 2017. Patients were included if they suffered isolated GSWB and required CPR at a referring hospital, in the field, or in the trauma resuscitation room. Patients were excluded for significant torso or extremity injuries, or if pregnant. Binomial regression models were used to determine predictors of survival/organ donation. Results:825 patients met study criteria; the majority were male (87.6%) with a mean age of 36.5 years. Most (67%) underwent CPR in the field and 2.1% (n=17) survived to discharge. Of the non-survivors, 17.5% (n=141) were considered eligible donors, with a donation rate of 58.9% (n=83) in this group. Regression models found several predictors of survival. Hormone replacement was predictive of both survival and organ donation. Conclusion:We found that GSWB requiring CPR during trauma resuscitation was associated with a 2.1% survival rate and overall organ donation rate of 10.3%. Several factors appear to be favorably associated with survival, although predictions are uncertain due to the low number of survivors in this patient population. Hormone replacement was predictive of both survival and organ donation. These results are a starting point for determining appropriate treatment algorithms for this devastating clinical condition. Level of evidence:Level II

Systematic review to evaluate algorithms for REBOA use in trauma and identify a consensus for patient selection.

BACKGROUND: Patient selection for resuscitative endovascular balloon occlusion of the aorta (REBOA) has evolved during the last decade. A recent multicenter collaboration to implement the newest generation REBOA balloon catheter identified variability in patient selection criteria. The aims of this systematic review were to compare recent REBOA patient selection guidelines and to identify current areas of consensus and variability. METHODS: In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we conducted a systematic review of clinical practice guidelines for REBOA patient selection in trauma. Published algorithms from 2015 to 2022 and institutional guidelines from a seven-center REBOA collaboration were compiled and synthesized. RESULTS: Ten published algorithms and seven institutional guidelines on REBOA patient selection were included. Broad consensus exists on REBOA deployment for blunt and penetrating trauma patients with non-compressible torso hemorrhage refractory to blood product resuscitation. Algorithms diverge on precise systolic blood pressure triggers for early common femoral artery access and REBOA deployment, as well as the use of REBOA for traumatic arrest and chest or extremity hemorrhage control. CONCLUSION: Although our convenience sample of institutional guidelines likely underestimates patient selection variability, broad consensus exists in the published literature regarding REBOA deployment for blunt and penetrating trauma patients with hypotension not responsive to resuscitation. Several areas of patient selection variability reflect individual practice environments. LEVEL OF EVIDENCE: Level 5, systematic review