杏吧原创

The able-bodied dreams of people with a variety of disabilities challenge the theory that dreams are mere echoes of your day

鈥淲E HAD to flee. After a frantic race I started walking, carrying my daughter in my arms鈥︹�� No matter how exciting to the dreamer, listening to people recount their dreams is notoriously dull. But reports such as this one, from someone who was born paralysed from the waist down, are perhaps more interesting.

This is because a flurry of recent dream studies in people with disabilities are challenging our understanding of why we dream. The results seem to suggest that dreams, besides being a surreal echo of our waking lives, have a reality of their own: they may even spring from innate, fully functional representations of our body and sensory perceptions that do not always match real-life situations.

鈥淒reams are tapping into representations of our bodies that are independent of reality鈥�

The idea that dreams are linked to our waking reality 鈥� known as the continuity hypothesis 鈥� can be traced back to Sigmund Freud. The basic premise is that our dreams are determined by the thoughts, feelings and events that we have experienced during our waking hours, whether recently or further into the past.

While this hypothesis cannot account for everything 鈥� why we occasionally fly in our dreams, for example 鈥� it is the dominant idea, says dream researcher Martin Schredl at the Central Institute of Mental Health in Mannheim, Germany. He says there is a thematic continuity between waking and dreaming: 鈥淒reams evoke specific emotions and reactions within the dreamer, and these are very closely related to actual waking-life issues.鈥�

To explore whether dreams are indeed a one-way street from the outside in, Alan Hobson of Harvard Medical School in Boston and Ursula Voss at the University of Bonn in Germany, and colleagues, collected dream reports from four people born with paraplegia, 10 people who were born deaf and did not speak, and 36 able-bodied people acting as controls. The volunteers were asked to write down their dreams for two weeks, paying particular attention to the frequency and intensity of their movements and sensory experiences.

When the team analysed the dream reports, they were in for a surprise. About 80 per cent of the dream narratives of the deaf participants gave no indication of their impairment: many spoke in their dreams, while others could hear and understand spoken language. The dream reports of the people born paralysed revealed something similar: they often walked, ran or swam, none of which they had ever done in their waking lives (see 鈥淲hose dream is it anyway?鈥�). Most importantly, there was no difference between the number of such bodily movements in the dream reports of the people with paraplegia and in those of the deaf and able-bodied subjects (Consciousness and Cognition, ).

鈥淩eports from people born with paraplegia reveal that they often walk, run and swim in their dreams鈥�

In June, another group reported similar results. A team led by Marie-Th茅r猫se Saurat of the Piti茅-Salp锚tri猫re Hospital in Paris, France, analysed the dreams of 15 people who were either born with paraplegia or acquired it as a result of a spinal-cord injury, and compared them with dreams of 15 able-bodied volunteers. Dream reports collected over six weeks showed that all but one person with paraplegia dreamed of being physically active and voluntarily moved their legs in their dreams. And people with paraplegia 鈥� even those born with the disability 鈥� dreamed of walking just as often as the healthy controls (Consciousness and Cognition, ).

Voss admits that while it is likely that the dreams of the people with disabilities would have been influenced by witnessing able-bodied people doing what the dreamer could not, she thinks it runs deeper than that. Why? Because some of the deaf, non-speaking participants said that rather than seeing themselves speak in their dream, they simply knew that they were doing it. Voss reckons this implies that 鈥渄reams are tapping into representations of limbs and movements that exist in the brain and which are independent of our waking reality鈥�.

She and Hobson argue that rapid-eye-movement (REM) sleep, the period in which we dream, prepares the brain for motor and sensory experiences before we encounter these experiences in real life. Babies and fetuses also experience REM sleep. The pair say the recent dream studies suggest that our brain has the genetically determined ability to generate experiences that mimic life, including having fully functioning limbs and senses, and that people who are born deaf or paralysed are likely tapping into these parts of the brain when they dream about things they cannot do while awake.

Ivan Limosani, a psychiatrist and dream researcher at the San Paolo Hospital in Milan, Italy, also reckons we need to rethink dream theory. 鈥淚 don鈥檛 agree with the continuity hypothesis,鈥� he says. 鈥淚 think that the activation of the brain during dreams is always the same鈥� regardless of daily experience. He adds that it is a state of the mind that arises from 鈥渁 primitive part of our brain鈥�.

Schredl is far from convinced the continuity hypothesis is dead, however. He thinks that continuity between dreams and waking life might lie in the basic emotions and thinking patterns experienced in dreams, rather than in the particulars such as whether or not the dreamer鈥檚 body is fully functional. He reasons that if you were feeling a certain way during the day, then those feelings and emotions are likely to show up in dreams, even if the scenarios do not match the physical reality.

Hobson, meanwhile, describes the relationship between dreams and wakefulness as a two-way street, but 鈥渁 two-way street that is first travelled from inside out鈥�. In other words, dreams influence waking life more significantly than the other way around. This reversal of the conventional view has profound implications, he says. Dreams could be laying the groundwork for real life, and without them our brain may not be prepared for waking experiences. But Hobson admits 鈥渢hat鈥檚 an intuition鈥� that needs to be empirically tested.

The next step for Voss and her colleagues is to match EEG signals to dream reports, allowing them to investigate how the brain activity of their subjects ties in with what they report to be dreaming about.

Voss also plans to use a technique that delivers a mild electric current to parts of dreamers鈥� brains, disrupting activity without waking them, to see if this changes the nature of their dreams. 鈥淲e are going beyond the subjective dream report by actively altering the dreams,鈥� she says.