Time frequency spectral representation of EEG

A study that uses a time frequency spectral representation (TFSR) with an exponential kernel to relate the changes in EEG spectrum to the depth of anesthesia is discussed. The level of anesthesia in the patient (dog) was changed by varying the halothane and tested using the tail clamp stimulus. The TFSR of the EEG did not change appreciably over the period of tail clamp when the patient was in deep sleep. For an awake patient the TFSR was localized in time and frequency. The energy was concentrated in the delta and the theta band frequencies and complete α - blocking was observed. This shows that TFSR can be used as a possible aid to the anesthesiologist in detecting consciousness and hence prevent patient awareness