An LCD Tachistoscope With Sub-Millisecond Precision

Tachistoscopes allow brief visual stimulation delivery, crucial for experiments where subliminal presentation is required. Up to now, tachistoscopes have shortcomings regarding timing accuracy, reliability, and flexibility of use. Here, we present a new and inexpensive 2-channel tachistoscope which allows for exposure durations in the sub-millisecond range with an extremely high timing accuracy. The tachistoscope consists of two standard liquid-crystal display (LCD) monitors of the light-emitting diode (LED) backlight type, a semipermeable mirror, a mounting rack, and an experimental personal computer (PC). The monitors have been modified to provide external access to the LED backlights which are controlled by the PC via the standard parallel port. Photodiode measurements confirm reliable operation of the tachistoscope and reveal switching times of 3 microseconds.