Such a scenario warrants a close look why it occurred: head motion? subject anticipation? coding mistake in stimulus timing? Just throw in an option. If you don't believe that the brain should respond at the stimulus onset time point, simply use TENTzero (or CSPLINzero) instead of TENT (or CSPLIN). However, if you do see some large amount of signal at the onset time, consider adding a regressor of 1's at those time points (or censoring them out) to account for the unexplained data variability (e.g., head motion).
Gang
Edited 3 time(s). Last edit at 03/13/2013 10:41AM by Gang.