Jason Bourne, Matt Damon's fictional character from the movie series Bourne Identity, is the most famous 'person' who suffers from this rare amnesia. The name Bourne was taken from Ansel Bourne, the first recorded case of the dissociative fugue in 1887.
Dissociative fugue is a very rare form of amnesia, whereby the person loses complete memory of their identity and personality, but have full mental functioning for all other purposes. It's so fascinating, especially since the fugue state is associated with travel, and people sometimes end up across continents, not knowing how they got there. Psychiatrists attribute the onset of a fugue state with extreme stress, resulting in the person 'running away' or 'hiding' from their problems. In a recent story, a woman in a fugue state was able to go into an Apple store and check her email, but not remember who she was or what she was doing. She was eventually found three weeks after she went missing, floating in the water miles from where she lived.
In modern TCM theory, there is not one soul or consciousness, but five separate and distinct ones, each housed in the five major organs of the body. The 神 Shen, 意 Yi, 魄 Po, 志 Zhi, and 魂 Hun have their independent characteristics, but work together to form the mental-spiritual aspect of an individual.
From The Foundations of Chinese Medicine, by Giovanni Macciocia:
The Mind (Shen) is the consciousness that is responsible for thought, feeling, emotions, perceptions, and cognition. The Mind resides in the Heart and it is primarily for this reason that the Heart is called the 'Emperor' in relation to all the other Internal Organs. As the Mind is the consciousness that defines us as individual human beings and that is responsible for thinking, willing and feeling, the Heart plays a leading role among the Internal Organs.
The Intellect (Yi) is responsible for memory, concentration, thinking, logical thinking, capacity for studying, and application. In pathology, the capacity for thinking may become pensiveness, overthinking, obsessive thining, fantasizing or brooding. The intellect resides in the Spleen.
The Corporeal Soul (Po) is responsible for physical sensations, feelings, and generally somatic expressions. It resides in the Lungs and it plays a role in all physiological processes of the body. It is formed at conception, it is Yin in nature, and, at death, it dies with the body returning to the Earth. The Corporeal Soul is described as the 'entering and exiting of the Essence (Jing)'.
The Will-power (Zhi) resides in the Kidneys and it is responsible for will-power, drive, determination and constancy.
The Ethereal Soul (Hun) is a soul that is Yang in nature and that, according to Chinese culture, enters the body three days after birth and is imparted to the baby by the father. After death, the Ethereal Soul survives the body and returns to a world of spirit. The Chinese character for Hun confirms the spiritual, non-material nature as it is made up by the radical gui, which means 'spirit' or 'ghost', and the radical yun, which means 'clouds'. The Ethereal Soul resides in the Liver and particularly in the Blood and Yin of the Liver where it should be 'anchored'; if Liver-Blood is deficient and the Ethereal Soul is not anchored in the Liver, it 'wanders' at night and causes the person to dream a lot. The Ethereal Soul is described as 'the coming and going of the Mind (Shen)'.
So if a person were to lose complete memory of their identity, which soul would be the one affected, and how would Chinese medicine proceed in the treatment of an individual who has had a fugue state experience?
My guess would be the Hun. If the Shen were to go on vacation, all mental faculties would cease. If the Po were to leave the body, the person would die, since it is in charge of all things physical and only returns to Earth upon death. The Hun is the only one known for 'wandering', and is the one most immediately affected by stress and deficiency. A person in a dissociative fugue state could be said then to be suffering from a case of their Hun going out to party during the day when it should be at home in the Liver. It's like being in an extended dream that ultimately can't be remembered.
To treat this individual, one would have to Nourish Liver Blood and Yin, and Soothe the Liver. Without a look at the tongue and pulse, I would guess that the base formula for such a condition would be 酸枣仁汤 Suan Zao Ren Tang, with the addition of herbs like 熟地黄 Shu Di Huang, 夜交藤 Ye Jiao Teng, 白芍 Bai Shao and 当归 Dang Gui to more strongly tonify Blood. 柴胡 Chai Hu could be added and 赤芍 Chi Shao could substitute for Bai Shao if there is more Qi stagnation, and 茯神 Fu Shen for 茯苓 Fu Ling to more strongly calm the shen. 远志 Yuan Zhi and 石菖蒲 Shi Chang Pu can be added to calm the spirit and clear the head, in the same way they're used in 定志丸 Ding Zhi Wan.
Acupuncture could include points like 曲泉 LV-8, 太冲 LV-3, 三阴交 SP-6, 足三里 ST-36, 手三里 LI-10, 四化 Four Flowers, 神堂 UB-44, 魂门 UB-47, and 四神聪 Si Shen Cong. Other points would be added or subtracted according to tongue and pulse and symptom pattern.