Working memory is an essential component of human cognition and determines to a large extent an individual's intellectual ability. In this paper, the human brain oscillatory response system associated with working memory performance is evaluated in an experimental and analysis setting involving 10 volunteers performing a visual 2-back task. Event-related dynamics in three bands: theta (3.5-7 Hz), alpha (7.5-12 Hz) and upper beta (17-29 Hz) at 32 locations distributed over the scalp are examined analyzing the event-related desynchronization (ERD)/synchronization (ERS) in these bands. Both global dynamics as well as trial- and subject-specific trends were considered. The overall across participants trend shows that the theta level synchronizes during working memory engagement, whereas beta and alpha desynchronizes. While common features seem to emerge, different subjects exhibit equally significant but opposite in direction correlation between reaction time and power dynamics.