Brain signal variability within individually defined alpha frequency range as a marker of cognitive performance

General description

Eight subjects with severe acquired brain injury and fourteen healthy participants took part in the study. EEG was recorded at 19 international standard 10-20 system locations with a sampling frequency of 256 Hz, using an ear-linked reference and the Fpz location as ground.

For all participants three-minute baseline recordings were obtained, one with eyes open and one with eyes closed. Both groups participated in the same sustained attention task while EEG data was being collected. Healthy participants underwent 10 blocks of 225 trials while ABI patients were given 7 blocks of 225 trials.

Content of the zip files uploaded here

Each zip file contains matlab files with raw EEG data plus a channel that contains information of the triggers used in the sustained attention task. In addition, log files contain the latency of the experimental events and responses.

Description of the task

The Continuous Temporal Expectancy Task (CTET), developed by O’Connell et al. (2009), is a computerized task that measures sustained attention. Participants are required to notice and respond with a click of the mouse when an alternating pattern (Fig. 1) is randomly displayed for a longer interval than the regular interval (800ms). Participants practiced the experiment initially to ensure they obtained 100% accuracy at the end of the training trials. Longer target duration should be easily detected during the training block, but challenging when performed over an extended period of time. The healthy group detected the target difference at 1120ms (duration 40% longer than the standard), whereas the ABI group detected a difference at 1200ms latency (duration 50% longer than the standard). The hand that responded to the longer stimulus with a mouse-click was counterbalanced in each block.