Synchronization with other equipment (EEG, MRI, MEG)
Synchronisation between other equipment and the PC or Mac you are running your experiment on is a typical source of timing error.
Due to inherent timing errors in your other equipment, e.g. TFT, soundcard, response device, it can be difficult to align an event marker from an EEG machine or sync signal from an MRI machine accurately. For example, if you instruct the experiment to send an event marker to coincide with the onset of an image it is fairly certain the marker will actually be sent before the images appears due to input lag on your TFT monitor. How much sooner the event marker is sent can only be determined empirically with a Black Box ToolKit. Once the error is determined you would need to correct for it on a post hoc basis.
The Black Box ToolKit can also help you identify EEG acquisition artefacts and apply the correct post hoc corrections.
A Neurovisor-BMM 40 computer-based electroencephalograph (image courtesy of Masloboev Yury Petrovich)
For more information on EEG timing errors when using a combination of different manufactures equipment consult:
Jing et al (2004), "Timing errors in auditory event-related potentials"
Mulert and Lemieux (2010), "EEG- FMRI: Physiology, Technique and Applications"
Ritter et al (2010), "EEG Quality:The Image Acquisition Artefact"