Thursday, 17 November 2011
All bar one of the disabled participants had at least one dream in which they moved their legs, including all five of the congenital paraplegics. As a group, the disabled participants experienced dreams about walking twice as often as they had dreams featuring their paraplegia. Moreover, voluntary leg movements featured in the dreams of the disabled more often than in the dreams of the able-bodied (38.2 per cent of dreams vs. 28.7 per cent). "I was not in a wheelchair but walking to a night club, to go dancing," recalled a 22-year-old person with congenital paraplegia in one typical dream report. There were some dreams featuring wheelchairs - these were experienced by eight of the disabled group and none of the controls.
Of the leg-movement mentions in the disabled participants' dream reports, the majority (46 per cent) pertained to walking. This is a lower percentage than found in the able-bodied diaries (64 per cent), but that's because the disabled dreamt more often about dancing and standing up. Activities like running, cycling, swimming and driving featured equally often in the dreams of both groups.
The disabled participants dreamed of walking even though they'd either never walked or hadn't walked for years. For example, two of the participants had been paralysed since sustaining gun-shot wounds during World War II and the France-Algeria war. There was no evidence that walking dreams became less frequent with duration of paralysis.
How do people with paraplegia dream of walking if it's something they've never experienced or haven't done for years? The researchers, led by Marie-Thérèse Saurat, believe it could reflect the activity of a "genetic, inherent walking programme", or the action of mirror neurons, which are stimulated during the day by the sight of other people performing movements. The latter explanation is especially favoured for dreams about cycling and other complex activities - it's "difficult to imagine that there is an innate programme for riding a bicycle, as this is a highly specialised activity recently developed in human history," the researchers said.
Why do paralysed people dream of walking? The researchers dismiss the psychoanalytic idea that the dreams are an expression of a subconscious wish. They argue that people with paraplegia are open about their desires to walk, and that their dreams are not dominated by walking to the extent you'd expect if they were compensating for lack of walking in waking life (in fact their dreams contained less walking than the control participants). Saurat and her colleagues suggest instead that walking in dreams may have an adaptive function: helping "consolidate the relevant neuronal mapping ... Notably, motor imagery training improves the movement performance of the intact muscles and increases basal ganglia activation in subjects with spinal cord injury."
These new findings add to previous research that found people born blind have visual experiences in their dreams and people born deaf can hear spoken language in theirs.
Saurat, M., Agbakou, M., Attigui, P., Golmard, J., and Arnulf, I. (2011). Walking dreams in congenital and acquired paraplegia. Consciousness and Cognition, 20 (4), 1425-1432 DOI: 10.1016/j.concog.2011.05.015
Post written by Christian Jarrett for the BPS Research Digest.