Hi all,

IF YOU USE PRESENTATION IN fMRI PLEASE READ THIS!

We have recently been experiencing issues with the synchronisation of stimulus code in Presentation with pulses from the scanner. This problem has been intermittent and inconsistent. As many scans rely on precise timings by synch-ing with specific pulses from the scanner, we have had to come up with an alternate solution.

Without boring you with the fine detail, we are using a different port on the scanner to provide us with the pulse information. After extensive testing this afternoon, this port seems to give consistent output while the other does not.

Anyone using pulses from the scanner to synchronise their presentation stimuli should note the following:

Change "pulses_per_scan" in your scenario header (.sce files) to the actual number of slices you are acquiring. In the past this has been set to half the number (e.g. if you were acquiring 38 slices per TR you had pulses_per_scan = 19). Just to make that clear, YOU SHOULD DOUBLE THE NUMBER YOU CURRENTLY HAVE IN pulses_per_scan.

N.B. YOU MUST CHANGE THESE NUMBERS WITH IMMEDIATE EFFECT OR YOUR TIMINGS WILL BE INCORRECT.

Also note that when you run your pulses calibration scan you will now get twice the number of pulses you got before.

This will not affect your data in any way, it simply means that you are getting a pulse for every slice from the scanner, rather than every second slice.

This will work for all TRs, and the back room settings should now be the same for all researchers.

If you have any queries, please contact me.

Andre'