1. Background - phantom limbs, subjective reality, phantom limb pain, referred sensations
2. Basic principles - a general theory of consciousness
3. Phantom limbs
4. Phantom limb pain
5. Discussion
   
6. References
   

Comments on our work are welcome! Please feel free to comment on our Discussion Group on the Self-Conscious Mind.

Robert and Suzanne Mays

• 11/21/09 - started page

A phantom limb is the vivid subjective experience that a limb that has been amputated is still present. Between 90% and 98% of all amputees experience a vivid phantom almost immediately after the loss, particularly if the loss was due to a sudden, traumatic event, as opposed to a planned amputation of a non-painful limb. The onset of phantom sensation is usually immediate, as soon as the anesthetic wears off, but may be delayed by a few days or weeks. The phantom limb is perceived to be an integral part of the body, with a distinct shape and occupying a habitual position or posture. If the limb was deformed or painful prior to amputation, the deformity or pain is often carried over into the phantom. Many patients are able to move the phantom limb at will, but in some the limb is stuck in a fixed posture (Ramachandran and Hirstein, 1998).

Subjective reality
The phantom limb appears to the patient as subjectively very real, especially shortly after the amputation, and as part of their body. The patient can use the phantom to reach for a cup, extend to shake hands, gesticulate when talking or count on the phantom fingers. Such experiences occur even when the phantom appears in a limb that was congenitally absent (Ramachandran, 1993; Poeck, 1964). The phantom limb can become paralyzed and stiff, or stuck in an awkward position. Because of the sense of the phantom’s reality, the patient usually acts to accommodate these sensations by moving so as not to interfere with the phantom’s position. Sensations in the limb prior to amputation can also be carried forward to the phantom, such as the presence of a ring that fits tightly on a finger (Melzack, 1992). These phenomena all imply that the phantom limb is integrated into the patient’s body as much as the intact limb was prior to amputation.

In many cases, the phantom is experienced vividly for a few days or weeks, but then gradually fades from consciousness. In other patients, the phantom persists for years or decades. Some patients can recall a faded phantom by focusing attention on it or by some form of stimulation to the stump. For about half of the patients in whom the phantom fades, it does so by the limb gradually growing shorter or “telescoping” in. This occurs especially for the upper limbs: only the experience of the phantom hand remains, extending from the end of the stump or the hand may disappear into the stump. Some patients can telescope their phantom arm out or in at will, for example, when they reach for an object.

Phantom limb pain
More than 70% of amputees experience pain in their phantom. The pain appears in the form of cramping or a clenching spasm, or as a painful burning, tingling, shooting or tearing sensation. When pain is present, movement of the phantom is also painful. In the case of a clenching hand, the patient frequently also feels the fingernails digging into the palm. The pain does not result from the existing somatosensory neural pathways because cutting these pathways at every level from the stump to the spine to the thalamus and cortex has been attempted. The pain may be alleviated for a while in these cases, even for months or years, but usually returns. Moreover, the sense of the phantom limb itself persists even when these nerves are severed (Melzack, 1992). Phantom pain may lessen in the months following amputation, but in general, phantom pain that persists more than 6 months after the operation is very difficult to treat. Analgesic drug therapy is often used but is not very effective. 

Referred sensations to other parts of body
Subjects frequently can feel sensations in their phantom when other parts of the body are stimulated. These sensations are thus referred sensations and are also called “dual percepts” or “mislocalizations”. For example, gently stroking the ipsilateral (on the same side) cheek or lip with a cotton swab produces a touch sensation on the cheek, as one would expect, and a sensation of tingling on a finger or the palm of the phantom hand. In some patients, these referred sensations are “mapped”, that is, the regions that show referred sensation on the face are contiguous and correspond to different fingers appearing on different parts of the cheek, lips and jaw. There may also be a similar mapping of the phantom hand on the regions surrounding the amputation such as on the arm stump or shoulder and occasionally also on the contralateral limb (Ramachandran and Rogers-Ramachandran, 1996). Also, in some subjects, the sensations are multi-modal, so the subject can distinguish touch, hot or cold, pain, and complex sensations such as water trickling (Ramachandran, 1993).

One reported subject (F.A.) had his right arm amputated 8 cm below the elbow after a boating accident. F.A. showed a striking ability to move his phantom at will. He experienced a referral of sensation on the face and at two different arm locations, on the stump and the biceps, which formed two complete “maps” of his phantom hand. When F.A. subjectively rotated (pronated) his phantom hand to the left, the touch sensation of the biceps map shifted 1.5 cm to the left (toward the body) and shifted back on return to the original hand position. As a demonstration of this, if a drop of water was placed, say, on the pinkie finger region on the arm, when F.A. rotated the phantom hand, he felt the water moving from the pinkie to the ring finger (Ramachandran, 1993, p. 10419). 

1. The human being consists of (1) a “self-conscious mind”,* a physical, non-material entity, united with (2) a physical brain and body. The self-conscious mind is the seat of conscious experience.
   Evidence: during near-death experience (NDE), the locus of consciousness appears to separate from the physical body and operate independent of the brain, having heightened, lucid awareness, logical thought processes, and vivid perceptions including veridical perceptions of the surroundings.


2. The self-conscious mind is a physical “field of consciousness”. It is non-material (does not consist of material atoms, etc.) but rather is a “structured” region of space that can interact with material processes.
   Evidence: (1) during the out-of-body component of NDE, the locus of consciousness has a particular position in space and a particular visual perspective; (2) the out-of-body mind appears to pass readily through solid objects and is invisible to ordinary sight, but it also appears to interact in subtle ways with physical processes, including physical objects, light, sound, and other persons’ bodies; (3) the out-of-body mind can apparently be “seen” by animals.


3. All cognitive functions (perception, thinking, feelings, volition, memory and self-awareness) reside in the non-material mind entity, not in the brain.
   Evidence: (1) during NDE, the locus of consciousness retains all cognitive functions while apparently operating independent of the brain; (2) in the ordinary case, if a person loses brain electrical activity, they become unconscious.


4. The mind is united with the brain and body and interacts directly with the brain, probably via electrical interactions with the cortical and other dendritic structures.
   Evidence: (1) people generally feel that their locus of consciousness extends throughout their physical body; (2) electrical brain activity is correlated with conscious experiences (e.g., electrical brain stimulation, EEG, brain imaging technologies); (3) some NDEs suggest an electrical nature to the NDEr “body” (e.g., interaction with fog), (4) one after-effect of NDE is abnormally high electrostatic charges around the person's body, which can interfere with watches and electronic equipment.


5. When the mind is united with the physical body, it takes the shape of the body and is completely co-extensive with it. When the mind is separated from the body (e.g., during an NDE), it generally retains a shape similar to the physical body but the shape may be different, for example an ovoid.
   Evidence: (1) people generally feel that their locus of consciousness extends throughout their physical body but stops at the skin; (2) during the NDE, NDErs usually experience their non-material “body” as having the shape of their physical body or of an ovoid.


6. The non-material mind entity has an internal structure which probably follows the structure of the neurons exactly.
   Evidence:(1) In at least some NDErs, the out-of-body “body” appears to have an intricate, luminous structure, for example with tiny structures in the hands and tubes of light up the arms (Moody & Perry, 1988, p. 10); (2) (from #4 previous) the interaction of the mind with the body is probably via electrical interactions with neurons; (3) in order to interact, the mind structure needs to be in close proximity with the neurons.


7. When the mind is united with the physical body, cognitive functions (perception, thinking,feelings, volition and memory) become conscious only when there is sufficient electrical brain activity. If the electrical activity is not sufficient, the percept or other mental event remains subliminal. If the electrical activity in sensory brain regions is excessive or is “displaced” from its ordinary cortical regiion, the person experiences pain. When the mind is separated from the body, cognitive functions are experienced as happening “instantaneously”.
   Evidence:(1) sensations become conscious only after a sufficient duration of electrical brain activity (Libet, 1973; Libet, et al., 1975); (2) pain results from higher voltage electrical brain stimulation; (3) a neural correlate of pain is a high level of electrical brain activity or displaced electrical activity; (4) NDErs report “instantaneous” responses to volitions and telepathic thoughts.


8. The mind can initiate electrical brain activity and thereby serves as the agent that initiates volitional activity, exerts “mental force” and alters brain neural patterns plastically.
   Evidence: A non-neural mental agency is suggested by the apparent backward referral of sensations (Libet, ), by “mental force” with CBT (Schwartz, ), long-distance neural synchrony in which gamma frequency electrical impulses associated with conscious experiences is synchronized cross-hemispherically from posterior to anterior brain regions. (Doesburg, ).

1. In an amputation, the physical limb is removed but the corresponding “mind limb” remains and forms a field of sensation where the physical limb was. A similar situation occurs in some cases of congenital limb deficiency. The mind limb (phantom limb) is objectively real and has a specific location at any time.
   Evidence: (1) the phantom limb is subjectively felt as real, having a particular location in space; (2) the mind “field of consciousness” is an objectively real entity of which the “mind limb” is a part.
2. Non-painful and painful sensations:
3. Phantom mind-limb is changeable and is sometimes distorted from normal anatomical positions, usually accompanied by pain (telescoping, felt in odd positions, some parts are not felt -- phantom hand but not the phantom arm)
4. Subjective phantom sensations (location, movement, pain) associated with neurons in stump: neural activity (electrical stimulation --> movement, sodium enhancer --> pain, anesthetic --> loss of phantom sensations, loss of pain, sensation of numbness)
5. "Touch" of phantom region can invoke phantom sensations; feeling can be felt in stump and up the limb (M.G. when touched) or in TT treatment; M.G. feels sensations in finger buds and up the arm; TT on amputees: can feel where therapist is "touching")
6. Subtle interactions with mind-limb induce electrical brain acitivty and result in


7. The amputee subjectively experiences pain located in the phantom mind-limb region when excessive or “displaced” electrical brain activity occurs in the somatosensory region of the brain which maps to the
   Evidence: (1) during the out-of-body component of NDE, the locus of consciousness has a particular position in space and a particular visual perspective; (2) the out-of-body mind appears to pass readily through solid objects and is invisible to ordinary sight, but it also appears to interact in subtle ways with physical processes, including physical objects, light, sound, and other persons’ bodies; (3) the out-of-body mind can apparently be “seen” by animals.

1. The human being consists of (1) a “self-conscious mind”,* a physical, non-material entity, united with (2) a physical brain and body. The self-conscious mind is the seat of conscious experience.
   Evidence: during near-death experience (NDE), the locus of consciousness appears to separate from the physical body and operate independent of the brain, having heightened, lucid awareness, logical thought processes, and vivid perceptions including veridical perceptions of the surroundings.


2. The self-conscious mind is a physical “field of consciousness”. It is non-material (does not consist of material atoms, etc.) but rather is a “structured” region of space that can interact with material processes.
   Evidence: (1) during the out-of-body component of NDE, the locus of consciousness has a particular position in space and a particular visual perspective; (2) the out-of-body mind appears to pass readily through solid objects and is invisible to ordinary sight, but it also appears to interact in subtle ways with physical processes, including physical objects, light, sound, and other persons’ bodies; (3) the out-of-body mind can apparently be “seen” by animals.

• Libet, B. (1973). Electrical stimulation of cortex in human subjects, and conscious sensory aspects. In A. Iggo (ed.), Handbook of sensory physiology, volume II: Somatosensory system (pp. 743–790). Berlin, Germany: Springer-Verlag.
• Libet, B., Alberts, W. W., Wright, E. W., Lewis, M., and Feinstein, B. (1975). Cortical representation of evoked potentials relative to conscious sensory responses, and of somatosensory qualities – in man. In H. H. Kornhuber (ed.), The somatosensory system (pp. 291–308). Acton, MA: Publishing Sciences Group.
• Mays, R. G., and Mays, S. B. (2008). The phenomenology of the self-conscious mind. Journal of Near-Death Studies, 27(1), 5-45. Reprint (PDF, 250 KB, 41 pages).
• Melzack, R. (1992). Phantom limbs. Scientific American, 266, 120-126.
• Moody, Jr., R. A., and Perry, P. (1988). The light beyond. New York: Bantam Books.
• Poeck, K. (1964). Phantoms following amputation in early childhood and in congenital absence of limbs. Cortex, 1, 269-275.
• Popper, K. R., and Eccles, J. C. (1977). The self and its brain: An argument for interactionism. London: Routledge.
• Ramachandran, V. S. (1993). Behavioral and magnetoencephalographic correlates of plasticity in the adult human brain. Proceedings of the National Academy of Sciences, 90, 10413-10420.
• Ramachandran, V. S., and Hirstein, W. (1998). The perception of phantom limbs: The D. O. Hebb lecture. Brain, 121, 1603-1630.
• Ramachandran, V. S., and Rogers-Ramachandran, D. (1996). Synaesthesia in phantom limbs induced with mirrors. Proceedings Royal Society of London. Biological sciences, 263, 377-386.

Birbaumer, N., Lutzenberger, W., Montoya, P., Larbig, W., Unertl, K., Töpfner, S., Grodd, W., Taub, E., and Flor, H. (1997). Effects of regional anesthesia on phantom limb pain are mirrored in changes in cortical reorganization. The Journal of Neuroscience, 17, 5503-5508.

Brugger, P., Kollias, S. S., Müri, R. M., Crelier, G., Hepp-Reymond, M.-C., and Regard, M. (2000). Beyond re-membering: phantom sensations of congenitally absent limbs. Proceedings of the National Academy of Sciences, 97, 6167-6172.

Flor, H., Elbert, T., Knecht, S., Wienbruch, C., Pantev, C., Birbaumer, N., Larbig, W., and Taub, E. (1995). Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation. Nature, 375, 482-484.

Franz, E. A., and Ramachandran, V. S. (1998). Bimanual coupling in amputees with phantom limbs. Nature Neuroscience, 1, 443-444.

Giraux, P., and Sirigu, A. (2003). Illusory movements of the paralyzed limb restore motor cortex activity. NeuroImage, 20, S107-S111.

Grüsser, S. M., Winter, C., Mühlnickel, W., Denke, C., Karl, A., Villringer, K., and Flor, H. (2001). The relationship of perceptual phenomena and cortical reorganization in upper extremity amputees. Neuroscience, 102, 263-272.

Karl, A., Birbaumer, N., Lutzenberger, W., Cohen, L. G., and Flor, H. (2001). Reorganization of motor and somatosensory cortex in upper extremity amputees with phantom limb pain. The Journal of Neuroscience, 21, 3609-3618.

Karl, A., Mühlnickel, W., Kurth, R., and Flor, H. (2004). Neuroelectric source imaging of steady-state movement-related cortical potentials in human upper extremity amputees with and without phantom limb pain. Pain, 110, 90-102.

Lotze, M., Grodd, W., Birbaumer, N., Erb, M., Huse, E., and Flor, H. (1999). Does use of a myoelectric prosthesis prevent cortical reorganization and phantom limb pain? Nature Neuroscience, 2, 501-502.

Melzack, R. (1992). Phantom limbs. Scientific American, 266, 120-126.

Melzack, R., Israel, R., Lacroix, R., and Schultz, G. (1997). Phantom limbs in people with congenital limb deficiency or amputation in early childhood. Brain, 120, 1603-1620.

Moody, Jr., R. A. and Perry, P. (1988). The light beyond. New York, NY: Bantam Books.

Poeck, K. (1964). Phantoms following amputation in early childhood and in congenital absence of limbs. Cortex, 1, 269-275.

Ramachandran, V. S. (1993). Behavioral and magnetoencephalographic correlates of plasticity in the adult human brain. Proceedings of the National Academy of Sciences, 90, 10413-10420.

Ramachandran, V. S., and Blakeslee, S. (1998). Phantoms in the brain: probing the mysteries of the human mind. New York, NY: William Morrow.

Ramachandran, V. S., and Hirstein, W. (1998). The perception of phantom limbs: The D. O. Hebb lecture. Brain, 121, 1603-1630.

Ramachandran, V. S., and Rogers-Ramachandran, D. (1996). Synaesthesia in phantom limbs induced with mirrors. Proceedings Royal Society of London. Biological sciences, 263, 377-386.

Weiss, T., Miltner, W. H., Adler, T., Bruckner, L., and Taub, E. (1999). Decrease in phantom limb pain associated with prosthesis-induced increased use of an amputation stump in humans. Neuroscience Letters, 10, 131-134.

Yang, T. T., Gallen, C. C., Ramachandran, V. S., Cobb, S., Schwartz, B. J., and Bloom, F. E. (1994). Noninvasive detection of cerebral plasticity in adult human somatosensory cortex. Neuroreport, 5, 701-704.

A phantom limb is the vivid subjective experience that a limb that has been amputated is still present. Between 90% and 98% of all amputees experience a vivid phantom almost immediately after the loss, particularly if the loss was due to a sudden, traumatic event, as opposed to a planned amputation of a non-painful limb. Phantoms occur less often in early childhood, with a gradual increase in incidence from 20% in children less than 2 years old, increasing to 25% at ages 2-4, 61% at ages 4-6, 75% at ages 6-8, and 100% in children older than 8 years. The onset of phantom sensation is usually immediate, as soon as the anesthetic wears off, but may be delayed by a few days or weeks. The phantom limb is perceived to be an integral part of the body, with a distinct shape and occupying a habitual position or posture. If the limb was deformed or painful prior to amputation, the deformity or pain is often carried over into the phantom. Many patients are able to move the phantom limb at will, but in some the limb is stuck in a fixed posture (Ramachandran and Hirstein, 1998).  

The phantom limb appears to the patient as subjectively very real, especially shortly after the amputation, and as part of their body. The patient can use the phantom to reach for a cup, extend to shake hands, gesticulate when talking or count on the phantom fingers. Such experiences occur even when the phantom appears in a limb that was congenitally absent (Ramachandran, 1993; Poeck, 1964). Sensations in the phantom can be invoked by the sight of the phantom interacting with objects, such as a feeling of wetness when the phantom foot “steps” in a puddle (Melzack, 1992). V. S. Ramachandran and Sandra Blakeslee (1998) described a patient who grasped a cup handle with his phantom fingers and felt strong pain when the cup was pulled away.

About 20% of people who were born without a limb experience a phantom (Melzack, Israel, Lacroix, and Schultz, 1997). The cases of phantoms in subjects with congenital limb deficiency can be striking: the use of the phantom fingers to count and solve simple arithmetic problems like other children, the use of the phantom arms to gesticulate during conversation, and the sprouting of phantom fingers to “assist” the stump in manipulating objects. The sensation of a phantom as an integral part of the body can be among the earliest memories of a subject (Brugger, Kollias, Müri, Crelier, Hepp-Reymond, and Regard, 2000). On the other hand, in other subjects with congenital absence, no phantom sensations are felt initially for the missing limb, but may be awakened later in life by a blow to the stump or after minor surgery. Phantom limb pain occurs in relatively fewer congenitally limb-deficient subjects than in amputees. 

Elizabeth Franz and Ramachandran (1998) described an experiment that demonstrated bimanual coupling between the phantom arm and the intact arm. Ordinarily a person cannot perform two “contradictory” actions with both hands simultaneously, such as twirling the finger of one hand and drawing a vertical line with the other, because the hand and arm movements are coupled together. When this experiment was performed on an amputee, the phantom arm and hand still showed bimanual coupling, as if phantom was actually present. Thus the operation of the phantom appears still to be integrated with the patient’s overall motor function.

The phantom limb can become paralyzed and stiff, or stuck in an awkward position. Because of the sense of the phantom’s reality, the patient usually acts to accommodate these sensations by moving so as not to interfere with the phantom’s position. Sensations in the limb prior to amputation can also be carried forward to the phantom, such as the presence of a ring that fits tightly on a finger (Melzack, 1992). These phenomena all imply that the phantom limb is integrated into the patient’s body as much as the intact limb was prior to amputation.  

In many cases, the phantom is experienced vividly for a few days or weeks, but then gradually fades from consciousness. In other patients, the phantom persists for years or decades. Some patients can recall a faded phantom by focusing attention on it or by some form of stimulation to the stump. For about half of the patients in whom the phantom fades, it does so by the limb gradually growing shorter or “telescoping” in. This occurs especially for the upper limbs: only the experience of the phantom hand remains, extending from the end of the stump or the hand may disappear into the stump. Some patients can telescope their phantom arm out or in at will, for example, when they reach for an object.

More than 70% of amputees experience pain in their phantom. The pain appears in the form of cramping or a clenching spasm, or as a painful burning, tingling, shooting or tearing sensation. When pain is present, movement of the phantom is also painful. In the case of a clenching hand, the patient frequently also feels the fingernails digging into the palm. The pain does not result from the existing somatosensory neural pathways because cutting these pathways at every level from the stump to the spine to the thalamus and cortex has been attempted. The pain may be alleviated for a while in these cases, even for months or years, but usually returns. Moreover, the sense of the phantom limb itself persists even when these nerves are severed (Melzack, 1992). Phantom pain may lessen in the months following amputation, but in general, phantom pain that persists more than 6 months after the operation is very difficult to treat. Analgesic drug therapy is often used but is not very effective. 

Ramachandran and Diane Rogers-Ramachandran (1996) described a novel treatment for phantom pain using a “virtual reality box”. The patient inserts the intact arm and the phantom arm in the box which has a mirror installed lengthwise between the arms. The image of the intact arm is seen in a mirror so that it coincides visually with the position of the missing arm behind the mirror. The amputated arm now appears to be present. The subject is usually surprised and pleased to see an image of his missing arm, now resurrected. The patient is asked to make mirror symmetric movements with both hands and generally experiences vivid sensations of movement in the muscles and joints of the phantom. When the eyes are closed or the mirror is removed, the patient’s phantom arm remains frozen as before. The visual feedback of movement in response to volitional motor commands restores phantom limb movement and sensations. If the phantom hand has been clenched or frozen, it can be unclenched and the related pain is relieved. In general, the phantom pain is reduced or eliminated following a number of short mirror-box sessions and in some cases the phantom recedes completely.

The procedure of matching voluntary “movements” can also be done using computer generated images rather than a mirror (Giraux and Sirigu, 2003). With training in these movements, a dramatic increase in motor cortex (M1) activation was detected in some subjects, with a corresponding decrease in pain. Subjects not showing the increase in motor cortical activation had little or no pain relief. With these virtual reality therapies, pain is generally reduced in clenching, cramping and constriction, that is, for proprioceptive and motor related pain, but not burning, tingling, electric discharge or shooting pains, that is, sensory nerve related pain. 

Subjects frequently can feel sensations in their phantom when other parts of the body are stimulated. These sensations are thus referred sensations and are also called “dual percepts” or “mislocalizations”. For example, gently stroking the ipsilateral (on the same side) cheek or lip with a cotton swab produces a touch sensation on the cheek, as one would expect, and a sensation of tingling on a finger or the palm of the phantom hand. In some patients, these referred sensations are “mapped”, that is, the regions that show referred sensation on the face are contiguous and correspond to different fingers appearing on different parts of the cheek, lips and jaw. There may also be a similar mapping of the phantom hand on the regions surrounding the amputation such as on the arm stump or shoulder and occasionally also on the contralateral limb (Ramachandran and Rogers-Ramachandran, 1996). Also, in some subjects, the sensations are multi-modal, so the subject can distinguish touch, hot or cold, pain, and complex sensations such as water trickling (Ramachandran, 1993).

One reported subject (F.A.) had his right arm amputated 8 cm below the elbow after a boating accident. F.A. showed a striking ability to move his phantom at will. He experienced a referral of sensation on the face and at two different arm locations, on the stump and the biceps, which formed two complete “maps” of his phantom hand. When F.A. subjectively rotated (pronated) his phantom hand to the left, the touch sensation of the biceps map shifted 1.5 cm to the left (toward the body) and shifted back on return to the original hand position. As a demonstration of this, if a drop of water was placed, say, on the pinkie finger region on the arm, when F.A. rotated the phantom hand, he felt the water moving from the pinkie to the ring finger (Ramachandran, 1993, p. 10419). 

The referred sensations are not exactly like normal touch or temperature sensations, because there is a 2-3 second latency before the sensation is felt in the phantom hand, and when the stimulus is removed, an “echo” of the sensation persists for 8-10 seconds afterward in the phantom. The sensory latency and echo, of course, do not occur in the direct touch sensations from the direct stimulus to the face or arm (Ramachandran, 1993). Thus, the referral of ipsilateral sensory stimulation to the phantom hand appears to be an “invasion” of the phantom hand into the face and upper arm, with a phantom-like delay of the sensation and echo of sensation.

The referral of stimuli from the face and upper arm to the phantom limb was also studied with magnetoencephalography (MEG). The MEG image of the sensory cortex representing the amputation side showed that sensory information from stimulation of the face and upper arm had shifted in the brain toward or into the region of the hand (the hand region happens to fall between these two regions in the map of the sensory cortex). In the other hemisphere, representing the intact side, the mapping of sensory stimulation appeared normal. The absence of the amputated arm and hand seems to allow the neural pathways from the adjacent regions of the face and upper arm to expand and “invade” the neural structures of the missing limb (Yang, Gallen, Ramachandran, Cobb, Schwartz, and Bloom, 1994; Ramachandran and Hirstein, 1998). At the same time, of course, there is delayed referred sensation from stimulation of the face and upper arm to the phantom hand. Anke Karl and colleagues (Karl, Birbaumer, Lutzenberger, Cohen, and Flor, 2001) found that there is a similar reorganization of the primary motor cortex in upper limb amputees, where the motor neural areas for the lip and biceps muscles are similarly displaced toward the motor hand region. 

This cortical reorganization happens within hours or days, so it is unlikely to be due to new neural synaptic growth. Furthermore, a very strong correlation was found between phantom limb pain and the observed cortical reorganization (Flor, Elbert, Knecht, Wienbruch, Pantev, Birbaumer, Larbig, and Taub, 1995; Birbaumer, Lutzenberger, Montoya, Larbig, Unertl, Töpfner, Grodd, Taub, and Flor, 1997; Karl, Birbaumer, Lutzenberger, Cohen, and Flor, 2001). The greater the shifts were in cortical electrical activity from their expected neural pathways, the greater was the phantom limb pain experienced by the patient.

Thus, we have outwardly an apparent invasion, in some subjects, of delayed sensory feelings of the phantom hand into the face and upper arm and, at the same time, we can observe through brain imaging an apparent invasion and reorganization of the sensory and motor neural structures of the face and arm into the adjacent region of the missing limb. In at least one subject (F.A.), the sensory map of the hand on the arm can shift with the subjective movement of the phantom hand. Along with the cortical reorganization of neural pathways, the amputees experience both proprioceptive and motor related pain (clenching, cramping or constriction) and sensory related pain (burning, tingling, electric discharge or shooting pains). The former types of pain, but not the latter, can be alleviated by phantom limb movements that are enabled when an image of the phantom limb’s movements can be seen and copied by the patient. 

In the present view, the non-material SCM has a shape similar to the physical body and this shape includes “mind-limbs”, which are visible to many NDErs during the OBE (Moody and Perry, 1988, p. 10). The phantom limb is the continued conscious experience of the mind-limb when the physical limb is not present. The SCM is whole and complete from birth even though it may be united with a physical body that has deformities. Thus we would expect that phantom limbs would be experienced by subjects with congenital limb deficiencies. However, because the deficient limb was never physically present, the mind-limb in many cases will not be engaged by the subject during infancy and childhood but will rather lie dormant. Similarly for young children who have limb amputation, the younger the age of the operation the more likely that the mind-limb will be dormant because the mind-limb will have had less time to unite and integrate with the physical limb through ordinary physical movement. This implies that during infancy and early childhood, the SCM becomes more and more intimately united with the physical body until the age of 7 or 8, through normal use of the limbs and body.

The mind-limb projects into and throughout the physical limb, probably via the limb’s neural pathways. The cortical electrical activity that we observe in the motor and somatosensory cortex is a reflection of the mind-limb activity in the body rather than the cause. Thus, the activity of the phantom mind-limb, both sensory and motor, can result in measurable cortical electrical activity even though parts of the neural pathways are missing due to amputation. The phantom mind-limb must still be able to induce electrical activity, including sensory activity from purely mental constructs such as “seeing” one’s phantom hand move in a mirror, “feeling” one’s phantom finger nails digging into the palm, “feeling” one’s phantom foot step in a puddle, or “seeing” the cup pulled away with the phantom fingers wrapped around the handle.  

Note that these phantom limb sensations all result from mind-to-brain inductions, whereas we usually associate sensation with brain-to-mind induction via neural sensory stimulation. In the case of the phantom mind-limb, the SCM is inducing neural stimulation at some point in the neural sensory pathways. This kind of induction is not the normal sensory induction but involves both a long latency and a very long echo sensation. Thus the neural induction from the phantom mind-limb must be influencing the sensory neural pathways at unusual locations and via an unusual form of induction. However, the operation of the phantom mind-limb may provide insight into how mind-limbs normally operate when the neural pathways are intact.

Normally there are thresholds before neural electrical activity reaches conscious awareness: a certain minimum intensity of stimulation and a minimum duration of electrical activity (usually 500 msec) must occur before we become aware of the stimulus. Since the amputee’s SCM is still united with the brain, these requirements must still hold. Thus, we can expect to see thresholds of phantom sensations, both non-painful and painful. Indeed, data from Sabine Grüsser and colleagues (Grüsser, Winter, Mühlnickel, Denke, Karl, Villringer, and Flor, 2001, p. 269, lower right) suggest that there is a threshold of phantom limb pain associated with cortical reorganization >8 mm but not ≤8 mm. Similar thresholds may account for the variations reported in the literature in subjects who have or do not have phantom limb sensations, referred sensations, referred mappings, and so on. 

In normal physical development, the mind-limb is usually well formed and coincident with the physical limb. However, when there is a loss of a limb, especially through a sudden traumatic event, the mind-limb becomes a phantom limb. The subject continues to experience of mind-limb even though the physical limb is not present. The subject experiences the phantom within hours or days of the amputation because the mind still works to project the mind-limb into the missing limb. The process of projection is not a neural process but a mind process, which normally uses neural pathways. The subject will not experience a phantom if the mind-limb has retreated and isn’t active. However, the phantom can be “called out”, usually with a blow or other stimulation to the stump.

The patient can still feel the phantom and move it, but the non-material phantom does not interact with the physical environment. When a prosthesis is used, the patient usually experiences that the phantom fills the mechanical prosthesis as it would the physical limb. The phantom then interacts through the prosthesis with the environment much as a blind person uses a cane to sense the area in front of him. The prosthesis becomes integrated into the patient’s body sense through movement of the prosthesis-embodied mind-limb. Klaus Poeck (1964) reported that a man with a leg amputation so well integrated his leg and foot that he could feel the unevenness of the ground through the prosthesis as well as he could through the shoe on the intact foot. 

When there is the sudden loss of an arm, say, the mind-arm’s projection into the body can become “diffuse”, because there is no physical arm to project into. Then we observe the related phenomena of (1) an apparent invasion, in some subjects, of the sensory aspect of the mind-arm into other parts of the body, (2) an apparent invasion or reorganization, in all subjects, of neural sensory activity into the missing arm and hand’s cortical region, and (3) sensory and motor related pain. The mind-arm seeks its normal neural pathways but they now reach only to the stump; the mind-arm becomes diffuse and disorganized. Indeed, the degree of neural reorganization and pain both appear to be related to the length of the remaining arm: the shorter the residual arm, the greater in general is both the motor neural reorganization and the phantom limb pain (Karl, Mühlnickel, Kurth, and Flor, 2004). With a greater length of limb loss, the mind-arm projection becomes ever more diffuse and disorganized.

In the cases where referred sensations are felt by the subject, for example from tactile stimulation to the lower face, the neural pathways leading from the sensory cortex to the hand become involved. Adjacent pathways, which are neurally close together to the hand at points along the path, for example in the thalamus (cf. Ramachandran, 1993, p. 10418; Grüsser, Winter, Mühlnickel, Denke, Karl, Villringer, and Flor, 2001, p. 270), are induced by the mind-arm in these subjects to project sensory receptivity to the face, upper arm and other areas. Sensory stimuli above the requisite threshold at these face and arm locations are then projected both to the primary face or arm area and to the referred phantom location. The induction across adjacent neural pathways is not the usual neural connection and so results in a 2-3 second latency and an 8-10 second echo of the referred sensation.  

The projection of the mind-arm still carries the neural structural form of the hand, so the associated induction results in contiguous sensory maps of the fingers and arm forming on the face and upper arm. The limb projection is a dynamic mind process and thus we can occasionally see a movement in the sensory mapping when the subjective mind-arm changes position. Over time the cross-neural induction weakens in many subjects, probably because the projection of the mind-arm becomes less diffuse and more focused in its proper place, namely in the location where the arm was. The absence of referred sensations in many subjects is due both to the induced sensations failing to reach the requisite threshold, and, particularly in congenitally limb-deficient subjects, to the focused organization of the mind-arm.

The normal neural processes for the face and upper arm areas continue to function. However, additional neural activity from the mind-arm induction is superimposed on the normal neural electrical activity. This extra electrical activity would ordinarily project to the hand regions of the sensory and motor cortex. Thus we see an anomalous shift of the face and upper arm electrical activity toward the hand region because it is reflecting the combination of normal tactile sensations and motor activity of the face and upper arm as well as the induced sensory and motor activity of the mind-arm. The result is both a diffuse neural activity in the cortex and, frequently, subjective sensations of pain. We would expect the motor related pains of cramping, clenching or constriction to be associated with the anomalous shifts in the motor cortex (Karl, Birbaumer, Lutzenberger, Cohen, and Flor, 2001), and are probably caused by anomalous induction of electrical activity in proprioceptive pathways. Similarly, we would expect the sensory related burning, tingling or shooting pains to be associated with the anomalous shifts in the somatosensory cortex, and are probably caused by anomalous induction of electrical activity in sensory pathways. The induction by the mind-arm is clearly demonstrated by the non-material, clenched fingers digging into the non-material palm and inducing the real sensation of pain via neural pathways. 

Thus, the observed shifts of neural activity in the cortex is not a cortical “reorganization”, but rather is the abnormal projection of mind-limb into the body via a neural induction which is then reflected back as a shift in neural electrical activity. The rule then appears to be that when the SCM cannot “connect” to a limb via ordinary neural pathways, the SCM will initially induce adjacent neural pathways using an abnormal induction which will cause phantom limb pain. Such pain will not be conducive to ordinary pain management via analgesic drug therapy because it involves an unusual kind of neural induction which the ordinary therapies do not affect. Similarly, severing the nerve pathway to the painful limb will also not help because the pain is occurring via the adjacent induced neural pathways leading to the referred areas.

Nevertheless, alternate therapies are possible, which can reorganize and “focus” the phantom mind-limb and reduce or eliminate the pain. In the virtual reality mirror box (or an equivalent computer generated display), when the subject sees a mirror image of his hand projected where the amputated hand would be, the mind-arm projection immediately focuses from a diffuse projection into the hand image that is actually seen. This reduces the diffusion and focuses the mind-arm projection in the proper place in space. We would expect that this focusing would feel pleasant to the subject and this is what subjects report. With movements of the hand image and corresponding subjective movements of the mind-limb, the mind-limb can begin to follow the normal motor neural pathways. Some of the pain can be alleviated, especially pain that is related to the spatial placement and proprioceptive sense of the limb (i.e., clenching, cramping and unnatural posture or position). The mind-limb can now focus and project properly into the presented image of the limb. The practice of movement of the phantom reorganizes the placement and the motor function of the mind-limb. 

However, we would expect that not all pain is reduced because this sort of focusing is only via an image and the subjective hand movement that follows and mimics the moving image. The process of refocusing the mind-limb is similar to the learning that an infant does to integrate her mind-limbs with the body in the first place. The infant does not learn to use her arm and hand by looking at an image of it, but rather by actually using it in the world. Therefore we would expect that a much more effective therapy would be to use a prosthesis, where the subject could work with the prosthetic arm and hand in the world. This would be much more effective in refocusing the mind-limb properly and should eliminate all diffuse neural activity, including pain that is related to the sensory functions of the limb (i.e., burning, tingling and shooting pains). The mind-limb can now focus and project properly into a physical representation of the limb (the prosthesis). The use of the prosthesis reorganizes the sensory function as well as the motor function of the mind-limb.