Reported in Nature:
When the patient sat up, leaned forward and clasped her knees, she felt that the figure was also sitting, embracing her in its arms – a feeling she described as “unpleasant”.
The temporoparietal junction is known to be involved in creating the concept of ‘self’, and the distinction between ‘self’ and ‘other’. According to the researchers, stimulation of this region interfered with the patient’s ability to integrate information about her own body, leading to her experience of a ‘shadow person’.
Although the woman was aware of the similarity between her own movements and those of her doppelganger, she didn’t recognise the experience as an illusion of her own body.