sentences:  The hemodynamic response occurs within seconds of the presented stimuli, but it is essential to space out the events in order to ensure that the response being measured is from the event that was presented and not from a prior event.Presenting stimuli in a more rapid sequence allows experimenters to run more trials and gather more data, but this is limited by the slow course of hemodynamic response, which generally must be allowed to return baseline before the presentation of another stimulus.According to Burock “as the presentation rate increases in the random event related design, the variance in the signal increases thereby increasing the transient information and ability to estimate the underlying hemodynamic response”.