StimSync: Open-source hardware for behavioral and MRI experiments

BACKGROUND Many neuroscience experiments rely on presenting stimuli and measuring participants' responses to these events. Often computer screens, speakers and keyboards are sufficient. However, these devices are not appropriate for some situations. For example, some studies present tactile or olfactory stimuli or brain stimulation. Likewise, keyboard buttons are not appropriate for use with vocal responses, small animals or individuals with motor impairments. NEW METHOD We describe StimSync, which simulates USB keyboard inputs, allowing use with most experimental software. StimSync can measure button presses, optical signals from magnetic resonance imaging systems, changes in ambient light (e.g. synchronizing intracranial electrography), and auditory events (a voice key). In addition to the USB keyboard mode (necessarily millisecond precision), StimSync can also be set to provide higher precision timing. This feature can be used to validate timing, ensuring event synchronization (e.g. auditory events, visual events, brain stimulation). In addition to recording inputs, StimSync provides seven digital outputs for controlling external devices. Finally, StimSync can record analog inputs; we illustrate how this can be used to evaluate the rise time for computer displays. RESULTS We observed outputs with a mean latency of 2.1ms (sd=0.17ms) and USB inputs with a mean latency of 2ms (sd=0.54ms). COMPARISON WITH EXISTING METHOD(S) StimSync statistically outperforms two professional solutions and numerically outperforms other devices described in the literature. CONCLUSIONS StimSync (http://www.mccauslandcenter.sc.edu/CRNL/tools/stimsync) provides an open-source solution for controlling and validating neuroscience experiments. In addition to sharing the design, we have produced a batch of devices to demonstrate the market for professional implementations.