Analysis of the empirical research on the feeling of presence.

Abstract

The feeling of presence consists of the feeling that another person or entity is detected near the extrapersonal space without any clear sensory evidence. Its symptoms include visual hallucinations and wrong coding of sensorial input. The phenomenon is sometimes present in pathologies such as sleep paralysis or neurodegenerative diseases, but it can also be found in healthy subjects. It has been associated with folk beliefs, but there is now enough evidence of its brain basis. A total of 72 studies from Web of Science and Scopus were analyzed considering 12 classificatory variables that were constructed bottom-up. Prevalence of neurodegenerative disease was higher for males, whereas sleep paralysis was prevalent for females. Twenty-one studies included participants with multiple pathologies. The episodes were generally associated to fear and anxiety. Some structural and functional alterations were found in neuroimaging case studies. Scale validation studies were scarce, usually showing scores with good psychometric properties. Diverse scales comprised different dimensions according to their objectives. Feeling of presence is a neuropsychological phenomenon, as failures in perception and self-concept are due to brain electric maladjustment. Evidence corroborates that mismatches are localized in cortical areas such as the temporal-parietal or insular cortex, as well as in subcortical areas, such as the hippocampus. The phenomenon main characteristics, associated factors, and measurement scales vary according to the studied pathological entity. Given that most scales have not been validated, a more empirical approach that takes into account the variety of associated pathologies is needed.