Alien brain syndrome is a hypothetical neurological disorder characterized by the feeling that one's own thoughts, perceptions, or mental processes are not under their control or belonging to them. People who experience this syndrome may describe their thoughts as being foreign, intrusive, or originating from an external source, despite recognizing that they are one's own. It is akin to a sensation of having a "stranger" or an "alien" inside their mind, influencing or controlling their thinking. The symptoms of alien brain syndrome can vary, but they often include a loss of the sense of agency, where individuals feel like they are not in control of their own thoughts or actions. Some may report experiencing thoughts or ideas that contradict their own beliefs or desires. This can lead to a significant amount of distress, confusion, and a sense of detachment from oneself. The exact causes of alien brain syndrome remain unknown, as it is a theoretical concept with limited scientific research. However, some theories suggest that disruptions in the neural circuits responsible for self-awareness and self-identification may contribute to the development of this syndrome. Other psychological factors, such as stress, trauma, or certain psychiatric disorders, could potentially play a role as well. It is essential to note that alien brain syndrome is not an officially recognized medical condition, and there is no standard diagnostic criteria or treatment for it. The concept serves as a theoretical framework to understand and explain the subjective experiences of individuals who report feeling a disconnection from their own thoughts and mental processes. If someone is experiencing symptoms resembling alien brain syndrome, it is crucial to consult with a qualified healthcare professional, such as a neurologist or psychiatrist, who can provide a proper evaluation to rule out any underlying physical or mental health conditions that may be contributing to their symptoms.

I'm sorry, but "alien person syndrome" is not a known or recognized syndrome or condition. It doesn't have any established medical or scientific basis, so there is no specific information available about it. If this term refers to something different or specific to a certain context, please provide more details, so I can assist you further.