Sensory Phenomena · 6 min read
Heavy gravity, chest pressure and the sense of a presence
Shallow REM breathing plus a threat-activated amygdala plus a blurred body map produce the classic 'someone is sitting on me' experience.
Quick facts
In REM sleep your breathing becomes shallow and mostly diaphragmatic, and the intercostal muscles are inhibited. When you wake inside that state you consciously feel a breath that is far shallower than your waking normal. The brain reads shallow breathing as weight.
Meanwhile the amygdala is highly active. It is scanning for threat and finds no explanation, so the parietal areas that build your body map generate one: a shape, a figure, a presence at the edge of the bed.
Studies of body-map disruption show that stimulating parietal regions can create a felt presence in fully awake people. The presence is a construction of your own body-mapping system.
You are not being suffocated. Your diaphragm is fully functional throughout; only your voluntary chest muscles are inhibited, and the automatic breathing rhythm never stops.
- Shallow REM breathing feels like weight.
- The 'presence' is generated by your body map.
- Slow, deliberate exhalations shorten the panic.
Sources & further reading
Links to peer-reviewed research and recognised medical organisations.
- How to Make the Ghosts in my Bedroom Disappear? MR Therapy for sleep paralysis
Frontiers in Psychology, 2016
- A clinician's guide to recurrent isolated sleep paralysis
Neuropsychiatric Disease and Treatment, 2016