Sentiments de présence dans la paralysie du sommeil et d'autres conditionsjanvier 5, 2020
“Felt presence” is a phenomenon where you feel that someone or some entity is near you, sometimes accompanied by an actual hallucination of some form. The phenomenon occurs in sleep paralysis (see this blog post) but also in certain neurological conditions. It can even be induced in healthy people while they’re awake.
A recent paper surveyed the available research on felt presence to uncover some commonalities in the experience across different studies and seek clues as to the biological basis of the phenomenon. The psychological quality of felt presence is typically associated with feelings of fear and anxiety. In the case of sleep paralysis, which is a state of paralysis that sometimes persists shortly upon waking from sleep, the feeling of presence often takes the form of a threatening intruder hovering near the sleeper. This threatening feeling of presence is persistent in most sleep paralysis episodes, and it has been associated with anxiety and depression.
Felt presence also occurs in certain neurological diseases such as epileptic auras or neurodegenerative diseases like Parkinson’s disease. Felt presence is also reported following Traumatic Brain Injury, and in these cases, it may be associated with changes in electrophysiology over the right temporal area of the brain.
In one case following Traumatic Brain Injury, a patient described felt presence as being preceded by an “electric shock” sensation, which is also commonly reported in cases of epileptic auras. It seems that changes in electrophysiology in the temporal area occurs across these varied diagnostic pathologies.
This commonality provides some support for a brain basis of felt presence as a neuropsychological phenomenon that involves electrophysiological glitches, particularly in temporal areas of the brain. There also seem to be some changes in activation in subcortical areas such as the amygdala and hippocampus. Even in sleep paralysis episodes, it’s possible that felt presence is enabled via high amygdala activation levels during REM sleep, which induce a hypervigilant state.
Besides these spontaneous episodes, felt presence can be artificially induced both behaviorally and biologically in healthy subjects, reinforcing the notion that it is a neuropsychological phenomenon. Magnetic stimulation in temporal areas of the brain can create illusions of felt presence. Or, a paradigm called the master-slave robotic system that leads to sensorimotor confusion can also induce feelings of presence.
In the Presence Detected Protocol, felt presence can be induced through wearing a helmet with solenoids over the temporal lobes. Weak magnetic stimulation is applied while the participant is in a state of sensory deprivation or relaxation, inducing feelings of presence. In the robotic master-slave mechanism, subjects perform movements with their finger on a touchpad, and the same movements are then applied to the subjects’ backs with a robotic arm. When the robotic arm diverges from the intended pattern, feelings or presence are reported.
In the majority of cases, felt presence is associated with unpleasant feelings like fear and sadness, although it sometimes takes a positive form, in which the presence feels like a friend, family member, or religious entity. Some have suggested that the feelings associated with the presence are determined by its felt location. For instance, a presence on the right side might be more associated with fear and anxiety whereas on the left side the presence is suggested to be less unpleasant. Nevertheless, most instances occurring during sleep paralysis are associated with negative feelings.
The electrical alterations in the temporal lobe and common qualities in experience provide evidence that cerebral alterations could induce feelings of presence across pathologies. Relative sensory deprivation, such as in the case of REM sleep, also seems to be a predisposing factor for feelings of presence.
Roballo, Francisco; Delgado, Ana R. Analysis of the empirical research on the feeling of presence. Dreaming Vol. 29, Iss. 4, (Dec 2019): 358-369. DOI:10.1037/drm0000113