Delays in blood collection and drug toxicology results among crash-involved drivers arrested for impaired driving.

OBJECTIVE: The concentration of drugs in a driver's system can change between an impaired driving arrest or crash and the collection of a biological specimen for drug testing. Accordingly, delays in specimen collection can result in the loss of critical information that has the potential to affect impaired driving prosecution. The objectives of the study were: (1) to identify factors that influence the time between impaired-driving violations and specimen collections (time-to-collection) among crash-involved drivers, and (2) to consider how such delays affect measured concentrations of drugs, particularly with respect to common drug per se limits. METHOD: Study data included blood toxicology results and crash-related information from 8,923 drivers who were involved in crashes and arrested for impaired driving in Wisconsin between 2019 and 2021. Analyses examined how crash timing and severity influenced time-to-collection and the effects of delays in specimen collection on blood alcohol concentrations (BACs) and blood delta-9-tetrahydrocannabinol (THC) concentrations. RESULTS: The mean time-to-collection for the entire sample was 1.80 h. Crash severity had a significant effect on time-to-collection with crashes involving a fatality having the longest duration (M = 2.35 h) followed by injury crashes (M = 2.06 h) and noninjury crashes (M = 1.69 h). Time of day also affected time-to-collection; late night and early morning hours were associated with shorter durations. Both BAC (r = -0.11) and blood THC concentrations (r = -0.16) were significantly negatively correlated with time-to-collection. CONCLUSIONS: Crash severity and the time of day at which a crash occurs can result in delays in the collection of blood specimens after impaired driving arrests. Because drugs often continue to be metabolized and eliminated between arrest and biological specimen collection, measured concentrations may not represent the concentrations of drugs that were present at the time of driving. This has the potential to affect drug-impaired driving prosecution, particularly in jurisdictions whose laws specify per se impairment thresholds.

A binary method for simple and accurate two-dimensional cursor control from EEG with minimal subject training.

BACKGROUND: Brain-computer interfaces (BCI) use electroencephalography (EEG) to interpret user intention and control an output device accordingly. We describe a novel BCI method to use a signal from five EEG channels (comprising one primary channel with four additional channels used to calculate its Laplacian derivation) to provide two-dimensional (2-D) control of a cursor on a computer screen, with simple threshold-based binary classification of band power readings taken over pre-defined time windows during subject hand movement. METHODS: We tested the paradigm with four healthy subjects, none of whom had prior BCI experience. Each subject played a game wherein he or she attempted to move a cursor to a target within a grid while avoiding a trap. We also present supplementary results including one healthy subject using motor imagery, one primary lateral sclerosis (PLS) patient, and one healthy subject using a single EEG channel without Laplacian derivation. RESULTS: For the four healthy subjects using real hand movement, the system provided accurate cursor control with little or no required user training. The average accuracy of the cursor movement was 86.1% (SD 9.8%), which is significantly better than chance (p = 0.0015). The best subject achieved a control accuracy of 96%, with only one incorrect bit classification out of 47. The supplementary results showed that control can be achieved under the respective experimental conditions, but with reduced accuracy. CONCLUSION: The binary method provides naïve subjects with real-time control of a cursor in 2-D using dichotomous classification of synchronous EEG band power readings from a small number of channels during hand movement. The primary strengths of our method are simplicity of hardware and software, and high accuracy when used by untrained subjects.

Mechanisms underlying reversal of motor unit activation order in electrically evoked contractions after spinal cord injury.

Extracellular stimulation normally activates larger-diameter axons, innervating motor units producing higher force, at lower stimulation intensities than required to activate small-diameter axons innervating motor units producing low force. However, activation of weaker thenar motor units at lower stimulation intensities than required to activate strong motor units has been reported during extracellular stimulation of the median nerve in persons with chronic cervical spinal cord injury. We used a computational model that reproduced this experiment to identify the potential mechanisms for the observed reversal of the inverse recruitment order, including preferential death of large motoneurons, demyelination and remyelination, and denervation and reinnervation of muscle fibers. Five sets of simulations assessed these mechanisms with seven simulated subjects. Preferential reinnervation, with small-diameter axons reinnervating more abandoned muscle fibers than larger-diameter axons, accounted for the apparent reversal of the inverse recruitment order observed previously. Preferential death of larger axons enhanced the reversal, but alone could not account for the observed reversal. Further, demyelination and remyelination, even in an extreme case and when combined with preferential death of large motoneurons, could not reproduce the reversal of inverse recruitment order. Thus, the apparent reversal of the inverse recruitment order was not a reversal of activation order across different diameter nerve fibers, but rather was a consequence of the redistributed force-generating capacity of the motor units resulting from denervation and reinnervation.