Therefore, Braid defined hypnotism as a state of mental concentration that often leads to a form of progressive relaxation, termed "nervous sleep". Later, in his The Physiology of Fascination (1855), Braid conceded that his original terminology was misleading, and argued that the term "hypnotism" or "nervous sleep" should be reserved for the minority (10%) of subjects who exhibit amnesia, substituting the term "monoideism", meaning concentration upon a single idea, as a description for the more alert state experienced by the others.[23]
Finally, the neural underpinnings of PHA will be even clearer when we incorporate its most important aspect in imaging studies—the dissociation between implicit and explicit memory. In PHA (and in functional amnesia) the person is unable to explicitly recall certain information, yet we see evidence of this material on implicit measures. For instance, a participant given PHA may fail to recall the word “doctor,” learned earlier, but will have no trouble completing the word fragment “d _ _ t _ r”. Mendelsohn et al. did not assess implicit memory. Rather, they tested recognition, which in a sense confounds explicit and implicit memory. We’d like to compare brain scans of a PHA group trying to explicitly recall the movie (they should show reduced activation, as above) with brain scans of the same group completing an implicit memory measure of the movie (they should show normal activation). This would be tricky to do—implicit measures of complex material such as movies and autobiographical memories are hard to find or construct. But it would contribute to a more complete neural picture of the processes involved in these fascinating forms of forgetting. 
Hypnosis is not a psychotherapeutic treatment or a form of psychotherapy, but rather a tool or procedure that helps facilitate various types of therapies and medical or psychological treatments. Only trained health care providers certified in clinical hypnosis can decide, with their patient, if hypnosis should be used along with other treatments. As with psychotherapy, the length of hypnosis treatment varies, depending on the complexity of the problem.