Rethinking the reaction time

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Whether stepping on the brake pedal when a hazard appears in the road ahead, beginning a sprint in response to the starter's pistol, or reaching to catch a tipping glass, we possess a remarkable ability to respond rapidly and accurately to demands for action. These responses occur within a reaction time of around 250 milliseconds, during which we must perceive the need to act, decide precisely what action to take, and generate motor commands to coordinate the activity of dozens of muscles to make the movement. It is currently not clearly understood what steps in this pathway take the greatest amount of time, which brain regions are responsible for which computations, and whether or not the reaction time could be reduced even lower. With support from the National Science Foundation, Dr. John Krakauer and colleagues Dr. Adrian Haith, Dr. Pablo Celnik and Dr. Joshua Ewan will use innovative behavioral experiments with human participants to stress the limits of the reaction time and tease apart its constituent processes and limitations. They will record brain activity during these same tasks (using EEG) in order to identify the underlying brain networks responsible and will apply non-invasive brain stimulation to establish the specific function of these brain networks in generating rapid motor responses.A number of neurological disorders, such as Parkinson disease, are associated with slowing of motor responses. Such symptoms are not well-understood at present. The knowledge gained from this study will yield important insights as to why this slowing may occur and what, if anything, could be done to treat it from a therapeutic and/or clinical perspective. A deeper understanding of the reaction time will also be of significant interest to those seeking to push the limits of human performance, such as athletes and race car drivers, or amateurs seeking to better their own performance. Furthermore, data collected in this study are likely to be of broad interest and therefore will be made available to other researchers. EEG recordings will be of particular interest to researchers developing advanced analytical techniques for mapping human brain activity. Finally, students from under-represented minorities, including those from economically disadvantaged backgrounds, will have the opportunity to directly participate in this project and gain valuable research experience through the Johns Hopkins Diversity Summer Internship Program.