If you create events that indicate your event of interest, you'd be able to epoch your data according these events. You can create them either:
- manually. https://neuroimage.usc.edu/brainstorm/Tutorials/EventMarkers
- or automatically, based on one of the detection processes available in the process menu "Events" (these processes are intended primarily to detect artifacts, but they can be used to detect peaks in any signal).
https://neuroimage.usc.edu/brainstorm/Tutorials/EventMarkers#Other_menus
https://neuroimage.usc.edu/brainstorm/Tutorials/ArtifactsDetect