In one embodiment of this system aspect of the invention, the first, second, and third anesthesia levels correspond to {HEAD ~ respective BIS levels}, the anesthesia effect level is a BIS level, and {TAIL ~ the combined anesthesia signal} is a combined BIS level signal 
In one embodiment of this system aspect of the invention , the first , second , and third anesthesia levels correspond to { HEAD ~ respective BIS levels } , the anesthesia effect level is a BIS level , and { TAIL ~ the combined anesthesia signal } is a combined BIS level signal
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH