Common pathways in mental imagery and pain perception: An fMRI study of a subject with an amputated arm

The present paper reviews data from two previous studies in our laboratory, as well as some additional new data, on the neuronal representation of mov ement and pain imagery in a subject with an amputated right arm. The subjec t imagined painful and non-painful finger movements in the amputated stump while being in a MRI scanner, acquiring EPI-images for fMRI analysis. In St udy I (Ersland et al., 1996) the Subject alternated tapping with his intact left hand fingers and imagining "tapping" with the fingers of his amputate d right arm. The results showed increased neuronal activation in the right motor cortex (precentral gyrus) when tapping with the fingers of the left h and, and a corresponding activation in the left motor cortex when imagining tapping with the fingers of the amputated right arm. Finger tappings of th e intact left hand fingers also resulted in a larger activated precentral a rea than imagery "finger tapping" of the amputated right arm fingers. In St udy II (Rosen ct nl., 2001 in press) the same subject imagining painful and pleasurable finger movements, and still positions of the fingers of the am putated arm. The results showed larger activations over the motor cortex fo r movement imagining versus imagining the hand being in a still position, a nd larger activations over the sensory cortex when imagining painful experi ences. It can therefore be concluded that not only does imagery activate th e same motor areas as real finger movements, but also that adding instructi ons of pain together with imaging moving the fingers intensified the activa tion compared with adding instructions about non-painful experiences. From these studies, it is clear that areas activated during actual motor executi on to a large extent also are activated during mental imagery of the same m otor commands. In this respect the present studies add to studies of visual imagery that have shown a similar correspondence in activation between act ual object perception and imagery of the same object.