A brain wave pattern or brain circuitry pattern (BCP) was a readout of a patient's hyperencephalogram, exhibited on a viewscreen as different linear changes of the subject's brain activity. The BCP was considered a unique characteristic for every individual, akin to fingerprints, making that individual's hyperencephalogram an important part of his or her medical record.
While monitoring the sedated Trip Tucker and Hoshi Sato, Doctor Phlox observed them talking and moving about. Although at the time he did not know they were being inhabited by two Organian observers, he was able to record their brain wave patterns and discovered that they were not Human. When he attempted to report the impossibility to Captain Jonathan Archer and T'Pol, he discovered they were then inhabited by the Organians, who noted that Phlox' discovery must have been accomplished with Denobulan technology. (ENT: "Observer Effect")