In preparation for the HCP 900 subjects data release, we have identified previously unknown timing errors in the in the processed physiological log files (e.g., rfMRI_REST1_RL_Physio_log.txt). These errors have resulted in variable offsets in timing, sometimes amounting to hundreds of milliseconds.
We are currently correcting known timing issues for all scans including pulse oximetry data that was collected during diffusion MRI scans. Due to limitations in computational resources, it was not possible to correct the physio files in the packages being released. Therefore, the physio log files in those packages should not be used. The corrected processed physiological log files will be released in a patch available on the 900 Subjects Release Project page in ConnectomeDB in December 2015.