Understanding that the brain constructs the ‘reality’ in which we live has been a vital step forward in neuroscience. One of the best studied illusions is the rubber hand illusion (RHI) (see a video here) in which the brain takes ownership of a false hand. In fact, the brain can take ownership of any number of inanimate objects. The prop is taken on as part of ‘self’ and feels like it is part of the individual subject to the illusion. A more common example of ownership is wearing a pair glasses and when removed they continue to feel as if they are in situ. All that we see and all that we feel is created by our brains, meaning that our experiences, albeit very real, are unique to us and hence an illusion.
As an example, a recent study by Banakou created an illusion whereby the subjects were placed in the virtual body of a 4 year old. They viewed the environment from a first person perspective (as you looking out as opposed to looking from the outside). The outcome was fascinating:
An illusory sensation of ownership over a surrogate limb or whole body can be induced through specific forms of multisensory stimulation, such as synchronous visuotactile tapping on the hidden real and visible rubber hand in the rubber hand illusion. Such methods have been used to induce ownership over a manikin and a virtual body that substitute the real body, as seen from first- person perspective, through a head-mounted display. However, the perceptual and behavioral consequences of such transformed body ownership have hardly been explored. In Exp. 1, immersive virtual reality was used to embody 30 adults as a 4-year-old child (condition C), and as an adult body scaled to the same height as the child (condition A), experienced from the first-person perspective, and with virtual and real body movements synchronized. The result was a strong body-ownership illusion equally for C and A. Moreover there was an overestimation of the sizes of objects compared with a nonembodied baseline, which was significantly greater for C compared with A. An implicit association test showed that C resulted in significantly faster reaction times for the classification of self with child-like compared with adult-like attributes. Exp. 2 with an additional 16 participants extinguished the ownership illusion by using visuomotor asynchrony, with all else equal. The size-estimation and implicit association test differ- ences between C and A were also extinguished. We conclude that there are perceptual and probably behavioral correlates of body-ownership illusions that occur as a function of the type of body in which embodiment occurs. Read the full paper here
Illusionists have created amazing tricks for hundreds of years. Without necessarily understanding the neuroscience, these impressive individuals have been able to manipulate the brains of audiences, using methods of distraction and attentional blindness.
When it comes to pain, we can use certain illusions to trick the brain into perceiving that the body is in a different state. The RHI we have already described and is well studies as is mirror therapy whereby the affected body part is concealed whilst the individual looks at a mirror reflection of the healthy side. This tricks the brain into seeing normal tissue and movement in many cases but not all. Mirror therapy is part of the graded motor imagery programme (see here), an approach grounded in neuroscience that targets the brain. In part, GMI evolved from witnessing that mirror therapy can in fact make some people experience more pain despite the fact that they are moving their unaffected side. The pain is due to the brain perceiving activity and threat in the affected side because of the reflective image. The pain is very real but created by an illusion. Actually it is an illusion of an illusion because as already stated, what we see is an illusion created by the brain.
Although this science may come as a surprise, the fact that our brains can be manipulated is very useful in rehabilitation. We can apply these methods to develop normal, healthy movement in many cases as part of a comprehensive treatment and training programme.
For further information or to book an appointment, please visit our clinic site: Specialist Pain Physio Clinics
t. 07932 689081