An Accurate Measure of Reaction Time can Provide Objective Metrics of Concussion

Evaluation of a Field-Ready Neurofunctional Assessment Tool for Use in a Military Environment

INTRODUCTION

The Office of Naval Research sponsored the Blast Load Assessment Sense and Test (BLAST) program to develop a rapid, in-field solution that could be used by team leaders, commanders, and medical personnel to provide a standardized approach to operationally relevant monitoring and analysis of service members exposed to single or repeated low-level blast. A critical piece of the BLAST team's solution was the development of the Brain Gauge technology which includes a cognitive assessment device that measures neurofunctional changes by testing sensory perceptions and a suite of mathematical algorithms that analyze the results of the test. The most recent versions of the technology are easily portable; the device is in the size and shape of a computer mouse. Tests can be administered in a matter of minutes and do not require oversight by a clinician, making Brain Gauge an excellent choice for field use. This paper describes the theoretical underpinnings and performance of a fieldable Brain Gauge technology for use with military populations.

MATERIALS AND METHODS

The methods used by the Brain Gauge have been documented in over 80 peer-reviewed publications. These papers are reviewed, and the utility of the Brain Gauge is described in terms of those publications.

RESULTS

The Brain Gauge has been demonstrated to be an effective tool for assessing blast-induced neurotrauma and tracking its recovery. Additionally, the method parallels neurophysiological findings of animal models which provide insight into the sensitivity of specific metrics to mechanisms of information processing.

CONCLUSIONS

The overall objective of the work was to provide an efficient tool, or tools, that can be effectively used for (1) determining stand-down criteria when critical levels of blast exposure have been reached and (2) tracking the brain health history until return-to-duty status is achieved. Neurofunctional outcome measures will provide the scientific link between blast sensors and the impact of blast on biological health. This calibration process is strengthened with outcome measures that have a biological basis that are paralleled in animal models. The integrative approach that utilizes the Brain Gauge technology will provide a significant advance for assessing the impact of blast exposure and support rapid, science-based decision-making that will ensure mission success and promote the protection of brain health in service members.

Methodological Problems With Online Concussion Testing

Reaction time testing is widely used in online computerized concussion assessments, and most concussion studies utilizing the metric have demonstrated varying degrees of difference between concussed and non-concussed individuals. The problem with most of these online concussion assessments is that they predominantly rely on consumer grade technology. Typical administration of these reaction time tests involves presenting a visual stimulus on a computer monitor and prompting the test subject to respond as quickly as possible via keypad or computer mouse. However, inherent delays and variabilities are introduced to the reaction time measure by both computer and associated operating systems that the concussion assessment tool is installed on. The authors hypothesized systems that are typically used to collect concussion reaction time data would demonstrate significant errors in reaction time measurements. To remove human bias, a series of experiments was conducted robotically to assess timing errors introduced by reaction time tests under four different conditions. In the first condition, a visual reaction time test was conducted by flashing a visual stimulus on a computer monitor. Detection was via photodiode and mechanical response was delivered via computer mouse. The second condition employed a mobile device for the visual stimulus, and the mechanical response was delivered to the mobile device's touchscreen. The third condition simulated a tactile reaction time test, and mechanical response was delivered via computer mouse. The fourth condition also simulated a tactile reaction time test, but response was delivered to a dedicated device designed to store the interval between stimulus delivery and response, thus bypassing any problems hypothesized to be introduced by computer and/or computer software. There were significant differences in the range of responses recorded from the four different conditions with the reaction time collected from visual stimulus on a mobile device being the worst and the device with dedicated hardware designed for the task being the best. The results suggest that some of the commonly used visual tasks on consumer grade computers could be (and have been) introducing significant errors for reaction time testing and that dedicated hardware designed for the reaction time task is needed to minimize testing errors.