Pregled posta

*PHANTOM LIMB oder DEVOTEE

Phantoms in the Brain
Grief and Loss



HBO: What is a phantom limb?

Jay Rosenblatt: It's this experience of people who have lost a limb who have this sensation that the limb is still there. And many of them still feel pain where the limb was. So it seemed like the perfect metaphor for losing a loved one, where you have lost them but you still feel that they're there and you still feel the pain of the loss.


Phantom limb

A phantom limb is the sensation that an amputated or missing limb is still attached to the body and is moving appropriately with other body parts ( Mitchell 1871; Melzack 1992; Ramachandran & Hirstein 1998). Approximately 50 to 80% of amputees experience these phantom sensations in their amputated limb, and the majority of these people report that the sensations are painful (Sherman, Sherman & Parker 1984). Phantom sensations and phantom pain may also occur after the removal of body parts other than the limbs, e.g. after amputation of the breast, extraction of a tooth (phantom tooth pain) or removal of an eye (phantom eye syndrome).
Phantom pains can also occur in people who are born without limbs and people who are paralyzed ( Ramachandran 1993; Saadah & Melzack 1994). Phantom pains occur when the missing limb causes discomfort. Other induced sensations include warmth, cold, itching, squeezing and burning ( Ramachandran & Blakeslee 1998; Ramachandran & Hirstein 1998). The missing limb often feels shorter and may feel as if it is in a distorted and painful position. Occasionally, the pain can be made worse by stress, anxiety and weather changes.

Clinical description

Although not all phantom limbs are painful, patients will sometimes feel as if they are gesturing, feel itches, twitch or even try to pick things up. For example, Ramachandran and Blakeslee describe that some people's representations of their limbs don't actually match what they should be, for example, one patient reported that her phantom arm was about "6 inches too short" (Ramachandran & Blakeslee 1998).
Some people with phantom limbs find that the limb will gesticulate as they talk. Given the way that the hands and arms are represented on the motor cortex and language centers, this is not surprising. Some people find that their phantom limb feels and behaves as though it is still there, others find that it begins to take on a life of its own, and doesn't obey their commands.
I placed a coffee cup in front of John and asked him to grab it [with his phantom limb]. Just as he said he was reaching out, I yanked the cup away.
"Ow!" he yelled. "Don't do that!"
"What's the matter?"
"Don't do that", he repeated. "I had just got my fingers around the cup handle when you pulled it. That really hurts!"
Hold on a minute. I wrench a real cup from phantom fingers and the person yells, ouch! The fingers were illusory, but the pain was real - indeed, so intense that I dared not repeat the experiment.
—Ramachandran, Phantoms in the Brain, p. 43. (Ramachandran & Blakeslee 1998)

Neurological basis

Until recently, the dominant theory for cause of phantom limbs was irritation in the severed nerve endings (called "neuromas"). When a limb is amputated, many severed nerve endings are terminated at the remaining stump. These nerve endings can become inflamed, and were thought to send anomalous signals to the brain. These signals, being functionally nonsense, were thought to be interpreted by the brain as pain.
Treatments based on this theory were generally failures. In extreme cases, surgeons would perform a second amputation, shortening the stump, with the hope of removing the inflamed nerve endings and causing temporary relief from the phantom pain. But instead, the patients' phantom pains increased, and many were left with the sensation of both the original phantom limb, as well as a new phantom stump, with a pain all its own (Ramachandran & Blakeslee 1998). In some cases, surgeons even cut the sensory nerves leading into the spinal cord or in extreme cases, even removed the part of the thalamus that receives sensory signals from the body.
In the early 1990s, Tim Pons, at the National Institutes of Health (NIH), showed that the brain can reorganize if sensory input is cut off (Pons et al. 1991). Hearing about these results,V. S. Ramachandran realized that phantom limb sensations could be due to "crosswiring" in the somatosenory cortex, which is located in the postcentral gyrus ( Ramachandran & Blakeslee 1998; Ramachandran & Hirstein 1998), and which receives input from the limbs and body. Input from the left side of the body goes to the right hemisphere and vice versa. The input from extremities comes into the somatosensory cortex in an ordered way, the representation of which is referred to as the somatosensory homonculus. Input from the hand is located next to the input from the arm, input from the foot is located next to input from the hand, and so on. One oddity is input from the face is located next to input from the hand.
Ramachandran reasoned that if someone were to lose their right hand in an accident, they may then have the feelings of a phantom limb because the input that normally would go from their hand to the left somatosensory cortex would be stopped. The areas in the somatosensory cortex that are near to the ones of the hand (the arm and face) will take over (or "remap") this cortical region that no longer has input. Ramachandran and colleagues first demonstrated this remapping by showing that stroking different parts of the face led to perceptions of being touched on different parts of the missing limb (Ramachandran, Rogers-Ramachandran & Stewart 1992). Through magnetoencephalography (MEG), which permits visualization of activity in the human brain (Yang et al. 1994), Ramachandran verified the reorganization in the somatosensory cortex.



Treatment

Some treatments include drugs such as antidepressants. Spinal cord stimulation (SCS) can be effective treatment for phantom pain. An electrical stimulator is implanted under the skin, and an electrode is placed next to the spinal cord. The nerve pathways in the spinal cord are stimulated by an electric current. This interferes with the impulses travelling towards the brain and lessens the pain felt in the phantom limb (Melzack 1992). Instead, amputees feel a tingling sensation in the phantom limb.
Vibration therapy, acupuncture, hypnosis and biofeedback may all be used to treat phantom pain but are often of little help. The pain can sometimes be helped by keeping busy and focusing attention on something else. Massaging the stump can sometimes help.
For planned amputation, phantom pain can reduced by preoperative pain management, effective control of pain by analgesic or neuroleptic is required. The brain seems to implant the sensations from the preoperative state.
One particularly novel treatment for phantom limb pain is the mirror box developed by Ramachandran and colleagues (Ramachandran, Rogers-Ramachandran & Cobb 1995). Through the use of artificial visual feedback it becomes possible for the patient to "move" the phantom limb, and to unclench it from potentially painful positions. Repeated training in some subjects has lead to long-term improvement, and in one exceptional case, even to the complete elimination of the phantom limb between the hand and the shoulder (so that the phantom hand was dangling from the shoulder).
More recently, virtual reality has been used to combat the discomfort caused by phantom limb syndrome, [1]. Scientists from the University of Manchester have shown that phantom limb pain can be relieved by attaching the sufferer's real limb to an interface that allows them to see two limbs moving in a computer-generated simulation. This works on a similar principle to the mirror box technique in that the somatosensory cortex is being ‘tricked’, except that the illusion is stronger.



GRANICE KAO FANTOMSKI UD - ISTOČNA I ZAPADNA NJEMAČKA

Berlinska granica je lokalitet reprezentativne arhitekture “nove države”. Unutarnja njemačka granica, duga 1380 kilometara, trebala bi se promijeniti iz mrtvog poteza u žilu kucavicu s 200 ugroženih vrsta, spomenik na otvorenom u sjećanje na granicu. 1989. na zapadnoj strani je 90% stanova imalo površinu od 39 kvadratnih metara, a na istoku 28. Danas je dvije trećine stanova modernizirano i obnovljeno > Mladi napuštaju istočna područja i idu na zapad, zanimljiv zbog radnih mjesta. Urbanističke dotacije povećat će se na 1.08 milijardi. U dekadi 2002.-2009., 5 milijardi DEM trebalo bi biti uloženo u istočnu građevinsku industriju, a 2,2 milijarde trebala bi potrošiti njemačka vlada > 1989., nakon 33 godine razdvajanja, rušenje Berlinskoga zida i unutarnje njemačke granice povezalo je istočni i zapadni dio Njemačke. Dotacije su iznosile oko 1200 milijardi DEM. S druge strane, dominacija zapada kod istočnjaka otkriva poteškoće u psihološkom i ljudskom prihvaćanju novoga stanja .


Phantom Limb Disorder

The leap from silence to a whisper is infinite. A mind is quiet. Aside from the background hum of inactivity, oscillating in perfect waveform, not a disturbance can be detected from this intricately woven system. Then, with no provocation from any incoming source, a signal spontaneously sparks into being. There is no discernable context from which this proto-thought has emerged, but the jump from nothing to something is seemingly random and infinite. From there a cascade of neural activity takes place, amplifying the signal into a meaningful code which, when pumped through the appropriate machinery, emerges as an idea or a softly spoken word.
"I have a splinter in my toe," the man says, referring to the nagging prickle below. The brain is an organ with extraordinary information processing ability. A mechanical signal such as a tear in the skin can be transformed into an electrical code relayed to the central nervous system, processed by neural circuitry (which communicates by chemical signals), modulated by several association cortices, until finally perceived as a pain sensation. But what may be just as eerie as a thought emerging from a pool of nothing is when a sensation arrives from a body part that does not exist. Just as curious is when a lower-leg amputee begins to complain of a splinter in a toe that is no longer there. Somewhere in the depths of the brain an errant signal emerges and, like a whisper out of the silence, breaths life into a phantom appendage. Such phantom sensations challenge our views on how our brains create perceptions of the world we see and even the notion of our own selves. What is "me", may not necessarily be.

History

The phenomenon of phantom limb was first described by a French doctor, Ambroise Pare, in the 16th century. It wasn't until 1866, after the American Civil War, when Doctor Wier Mitchell published his first account of the malady, coining the term "Phantom Limb". (Melzack, 1992). As the name implies, phantom limb disorder is the persistent sensation of an appendage, after removal by amputation or simple denervation. The onset of sensation in the phantom limb is relatively fast, occurring within weeks or even days following amputation. Although the effects may be transient in some, the symptoms usually persist for years without diminishing. (Shreeve, 1993).
The rate of incidence has been reported as high as 80% of all amputees acquiring phantom limb (Melzack, 1992). Patients will often speak of their phantom limbs as if they were physical parts. To the patient, the appendage feels just as real as any other. Phantom arms will swing while a woman walks, phantom fingers will grasp for a cup as a man aims his stump toward the table, a man reportedly even had a problem of falling out of bed in the morning when he tried to bear weight on his phantom leg. Interestingly, the sensation of an accessory such as a watch or ring can often be felt on the phantom limb as well (Shreeve, 1993).
Occasionally a more disturbing analogue of phantom limb manifests whereby the patient can not only feel the missing limb, but it is in constant pain. The most common descriptions of this pain are crushing, burning, itching or shooting sensations (Miles, 1989). Other reports include a distortion of the appendage such as a painful twisting of a foot, or fingernails pushing through the flesh of the palm in a tight fist which never releases (Shreeve, 1993).
Naturally the earliest explanations for this disorder were mental psychosis resulting from the traumatic loss of a limb. In effect the sensations were regarded as "not real," stemming only from the mind. (Though the sensations are now regarded as very real, they may have been right that "the mind" is their origin). Another classic explanation for phantom limb placed the root of ghostly sensation at the severed sensory neurons themselves. When a sensory nerve is severed during amputation, a nodule called a neuroma will form near the end of the stump. These neuromas can be very sensitive to the touch and were thus believed to generate the mysterious signals. Although surgically removing the neuromas occasionally provided temporary relief, the phantom limb always returned (Shreeve, 1993).
A wide range of remedies have been attempted to abate the phantom limb/phantom pain sensations. Many involve stimulation of the stump in some fashion to diminish the phantom pain (see pain gate theory later on), while others rely on surgery or some other means. Some examples include: percussion of the stump, transcutaneous electrical stimulation, massage, ultrasound applied at the stump (Anderson, 1981), electric stimulation of the brain, surgery and chemical pain blocks such as propranolol. Some of the more unusual remedies include electroshock therapy, acupuncture, "nerve strangulation" (where the nerves are literally tied off at the ends a few inches above the amputation line), administration of LSD, hypnosis, psychotherapy and prefrontal lobotomies (Sherman, 1980). Most of the treatments worked temporarily for about 1/3 of the recipients, but were ineffective upon a 1-year follow-up. In almost all cases, because the numbers of success were so similar, regardless of the type of treatment, and because of the eventual return of phantom limb, the temporary relief has been attributed to the placebo effect. (Sherman, 1980).

Explanations & Mechanisms



In order to understand the current explanations for phantom limb disorder, it is important to consider the normal pathways involved in sensation. Both hemispheres of the brain contain a deep fissure called the central sulcus (see fig. 1). This crevice is flanked on either side, rostrally by the precentral gyrus (motor cortex), and caudally by the postcentral gyrus (somatosensory cortex), (see fig. 2). Incoming sensory afferents from the contralateral (opposite) side of the body will synapse at the somatosensory cortex after routing through the thalamus (see fig. 7). The somatosensory cortex (S1) is highly ordered in a roughly topographic fashion, containing a receptive field for every body part, with larger receptive fields devoted to areas that are more highly innervated such as the hands and lips. The receptive fields are laid out in an ordered fashion along the length of S1, representing the entire body surface in an abstract map known as a homunculus (Latin = diminutive human), (see fig. 3). When a sensation comes in from a particular location, the corresponding receptive field will become active. Likewise, if an area of S1 is stimulated, the person will feel a sensation in the corresponding body part. (Kandel, 324-329).
But what happens when an appendage and its incoming sensory afferents are severed? One would expect the corresponding receptive field to go silent, however this is not entirely the case. Interestingly, shortly after deafferentation those fields become active again. Using imaging techniques such as magnetoencephalography (MEG) and magnetic source imaging, researchers have found that these areas of S1 are not only active, but respond to stimulus from other parts of the body (Flor, 1995, Yang, 1994). Typically an area of the cortical map on the homunculus adjacent to the deafferented (severed) section will expand following deafferentation (Barinaga, 1992, Flor, 1995, Yang, 1994). As a result of this cortical reorganization, the newly recruited cells respond to the body part represented by this expanded receptive field. The encroachment actually takes place on either side of the deafferented location so that two receptive fields enlarge, filling in the area (Ramachandran, 1992).
The observable result of cortical reorganization has been studied extensively by Dr. Vilayanur Ramachandran at the University of California, San Diego. While probing the entire body surface with a Q-tip, certain areas would evoke a strong sensation in the phantom limb. These "referred sensations" were highly localized with one to one correspondence between points on the reference field and points on the phantom limb. (Ramachandran, 1992). The most common locations for reference fields are the chest for leg amputations (the two are adjacent in S1) and the face for arm amputations. By carefully probing the skin surface, one could map out an entire phantom appendage onto a body location--for instance a phantom hand, fingers and all, mapped across the chin and jawline of an arm amputee (see fig. 6). Touching a particular area on the person's body will evoke a phantom sensation, but what is very interesting is that the sensations are modality specific (Ramachandran, 1992, Yang, 1994). Put a drop of water on the body reference field, and the corresponding phantom limb will feel wet; apply pressure, and the sense of pressure is perceived on the phantom.
Michael B. Calford and Rowan Tweedale showed that permanent amputation is not required for transient cortical reorganization. In their study, the somatosensory cortices on both hemispheres of flying foxes were mapped using electrodes. Then a single digit was temporarily anesthetized with an injection of 2% lignocain. What was unique about this experiment is that plasticity induced in one hemisphere by receptive field expansion from a small peripheral denervation was immediately mirrored in the other hemisphere. Receptive fields are normally shaped by lateral inhibition; denervation allowed for previously inhibited/masked fields to appear. The reason cortical expansion occurred on both hemispheres in this case was that the normally inhibitory ipsilateral influence was released following temporary denervation for the duration of the anesthetic. (Calford & Tweedale, 1990).



A perceptual correlate of the interhemispheric field expansion experiment was done by Yigal Gross and Ronald Melzack. They cut off the sensation in the arms of participants with a tightly fastened pressure-cuff (pressure-cuff ischemia), (see fig. 5). After 40 minutes of ischemia, the perceived location of the arm was strikingly different from its actual position. The premise behind this experiment is that our perceptions of limbs are determined by activity in neural cell assemblies (see Hebb's cell assemblies later in text) that are derived by earlier sensory-motor activity of the real limb. When modulatory inputs are abolished, cell assembly activity becomes increasingly independent of the position of the real limb. Therefore the reduction of sensory input is one essential condition for the appearance of phantom limb (Gross & Melzack, 1978).
The most pressing issue is finding an insight into the mechanisms behind these perceptual shifts and cortical reorganizations. The puzzle has not been solved; there are several dominant theories explaining phantom limb, but all are yet to be proven equivocally. Consider the expansion of cortical fields in the somatosensory cortex. One of the most prevalent theories for this brain plasticity is that deafferented areas of S1 become reactivated and receptive field expansion occurs because of the unmasking of latent circuits (Calford, 1991, Calford & Tweedale, 1990, Barinaga, 1992). There are many systems in the brain and PNS that make use of neuronal competition. Through either a superior firing rate or actual feedback/feedforward inhibition, "stronger" synapses will tend to "dominate" or "weaken" nearby synapses which effectively become masked (Kandel, 106-107). Many of the observed S1 cortical expansions have occurred within a range of 1-2 millimeters (Calford, 1991), so one possible source of underlying circuits could simply be the wide arborization of thalamocortical afferents (Calford & Tweedale, 1990). The axon terminals of the thalamocortical cells, bringing signals from the thalamus to S1, have a wide branching pattern which spans between 1-2 millimeters. The idea is that when one thalamocortical afferent goes silent, an adjacent one--previously inhibited in the location of interest--becomes unmasked, thus encroaching a neighboring receptive field into the deafferented area (Calford, 1991).



The problem with the thalamocortical arborization hypothesis is that it is limited to the width of a projection zone of a single thalamocortical axon--1 to 2mm. However, cortical encroachments have certainly been observed over areas much greater than this limit. For example, in a study on the perceptual correlate of cortical reorganization using magnetic source imaging, H. Flor, et. al. found a mean shift in the focus of cortical responsivity of 0.43 centimeters in phantom limb subjects, and a mean shift of 2.05 centimeters in phantom pain subjects (1995). (Though note, they were looking at the shift in focus of responsivity, not the actual shift of boundaries).
Probably the most cited study in cortical reorganization and phantom limb to date is the "Massive Cortical Reorganization" in the Silver Spring Monkeys by Timothy Pons, et. al. What they found closed the door on many of the hidden pathway theories. In 1971 a group of macaques, the Silver Spring Monkeys, were involved in an unrelated experiment under Edward Taub in which the sensory nerves from one arm were cut where they entered the spinal cord. The monkeys then became a center of animal rights attention, after which time the experiment was halted and the macaques were held, off-limits to research. Before they were put to sleep 12 years later, Pons requested permission to take recordings from the animals' cortices (Shreeve, 1993). What they found was unexpected. The entire deafferented zone responded to the stimulation of the face in a highly systematic pattern of reorganization. The area of the face representing the lower jaw and chin stretched into a cortical sheet 10-14mm long, extending the upper limit of cortical reorganization by an order of magnitude. Rather than unmasking hidden circuits, Pons believes the magnitude of this plasticity can only be explained by neuronal growth; although evidence for the sprouting could occur in subcortical areas where modest growth would be amplified by divergence. (Pons, et. al., 1991).
Few scientists currently support the neuronal sprouting theory. Mike Calford feels the massively extended cortical fields in the Silver Monkeys is not evidence enough to suggest neuronal growth. Based on work with cortical representation of raccoon hands (which have large receptive fields in S1), deafferentation will result in neural responses in S1 that seem to come from existing connections from other areas of the somatosensory cortex which do not have quite the precision of the primary field. These preexisting cortico-cortical connections, according to Calford, are responsible for such plasticity on a larger scale. (Calford, 1991).
As seen with the temporarily anesthetized digits of flying foxes, deafferentation is not required to observe cortical reorganization. In the mid 1980's Michael Merzenich and his colleagues severed a nerve supplying sensory input from the palm of a monkey's hand. They found that over time (a month or so), cortical neurons that used to receive information from that nerve began to respond to stimulation from the back of the hand instead (Barinaga, 1992). This finding was important in overturning the hard-wired brain view established by David Hubel and Thorsten Wiesel, who discovered immutable (in adulthood) ocular dominance columns in the visual systems of cats in the 1960's (Barinaga, 1992, Kandel 470-477). The outcome of Merzenich's experiment--a more pliable brain circuitry--revealed that not all cortical systems are as unyielding as the primary visual cortex. But in a more recent experiment, Merzenich and his colleagues taught fully-intact monkeys to discriminate vibrations of differing frequency with their middle fingers. As the animals became more adept at this activity, neural connections devoted to the middle finger in S1 became stronger and the receptive fields also began to expand (Barinaga, 1992, Shreeve, 1993, Kandel 329-333).
Charles Gilbert of Rockefeller University believes a working model of such cortical plasticity can be found, ironically enough, in the visual system. These are the so-called "horizontal connections", first found by Gilbert. His experiment involved creating a lesion (blind spot) in a cat's retina with a laser. Within a matter of minutes, the silent cortical cells began to expand their receptive fields until they responded to signals from areas of the retina surrounding the blind spot (see fig. 8). (Barinaga, 1992).
"The classical receptive field is the tip of a floating iceberg," illustrates Vilayanur Ramachandran. "If the tip of the iceberg is cut off--by creating a blind spot that covers the receptive field--the iceberg can ride a bit higher in the water, exposing a new and broader receptive field." (Barinaga, 1992). Ramachandran has done a lot of interesting work lately with phantom limb and other perceptual disorders. He likes to point out that many systems in the brain behave in a fashion similar to the visual filling in of a blind spot. (Shreeve, 1993). The brain is a feature detector which, in the absence of meaningful information, will often fill in the blanks with whatever surrounds. A proponent of the unmasked silent synapse idea, Ramachandran is currently investigating the effect of vision of phantom limb sensations. This investigation involves a mirror box containing two holes on the side where a person can stick his hands. The left and right halves of the box are divided by a mirror which has been placed over the top of the box in a manner such that the participant can only see into one of the two halves from the top. When, for instance, the participant places his right hand into the box (left compartment is covered), a sterioisomeric image resembling a "virtual" left hand appears in the mirror. From here, a multitude of manipulations can be done. Recall that many patients complain of a tightly clenched phantom fist sensation. When both "hands" are placed into the box--superimposing the virtual mirror image left-hand over the phantom hand--the patient is asked to make a fist, which would resemble the phantom contortion. He is then asked to unclench the fist (with both hands) while watching in the mirror. Four of the five patients experienced immediate relief upon observing the phantom hand unclench in the mirror. This did not work when the eyes were closed. (Ramachandran, 1995).
In similar versions of the same experiment, patients were asked to move their real hands inside the box. Whenever the phantom hand was visually perceived to move, the patients would actually feel the proprioceptive movement in the phantom. Ramachandran explains for the two experiments, that motor commands sent from the motor cortex are usually damped by error feedback and proprioception. However such dampening is not possible in a phantom limb; this may result in a continually amplified motor output eventually perceived as a painful spasm. The visual feedback (which is an important sense in proprioception) seems to interrupt the amplified loop. (Ramachandran, 1995). An equally interesting finding was that touching the real hand in the mirror box, evoked the same sensation at the same location in the phantom hand (recall Calford's interhemispheric transfer of plasticity in flying foxes). Two of the patients had to actually witness the event on the phantom for the effect to work. But what is most fascinating is that these symmetrical referred sensations (not to be confused with "referred sensations" discussed earlier from reference fields plotted onto the face or chest) were modality-specific for most sensations such as pressure, wetness, vibration, etc. Heat, cold and pain however were not referred. When a patient's real hand was placed in a bucket of ice, the phantom would perceive the shape and texture of the cubes, but not the cold. Ramachandran believes these referred sensations are due to unidentified commissural pathways to mirror-symmetrical points in the opposing cerebral hemisphere. Pain and temperature may not have been referred because there may be no commissural pathways for these modalities. The observed vision-touch interactions suggest that the current modular hierarchy view of the brain must be replaced with a more dynamic model. (Ramachandran, 1995).



Such a dynamic model is the neuromatrix, proposed by Ronald Melzack of McGill university. According to him, any suitable explanation for phantom sensation and phantom pain must look beyond the somatosensory cortex, into highly integrated systems involving higher processing centers. He believes this neuromatrix must contain at least three systems: 1) the classical sensory pathway from the thalamus to S1, 2) emotion pathways such as those through the reticular formation to the limbic system, and 3) regions for the recognition of "self" such as the parietal lobe (see fig. 4). This neuromatrix forms a continuously generating pattern--a neurosignature--indicating a body part as one's own. Whenever a new signal comes in from sensory pathways it must pass through all three systems of the neuromatrix in parallel, where it is compared with the self-regenerating neurosignature--usually with no conflict. In the absence of incoming signals, concept and literal sensation of a limb is continuously generated by the neuromatrix. (Melzack, 1992). Melzack's neuromatrix is similar to the idea of Donald Hebb's cell assemblies whereby cells, and later systems of cells, that fire together in a given pattern will wire together in associated assemblies (synapse). The biggest difference in Melzack's idea is that the neuromatrix is largely genetic and present from birth (babies born without limbs often experience vivid phantoms). According to Melzack, this neuromatrix can then be sculpted by experience (recall those who could feel rings or watches on their phantom hands). From there the neurosignature is modulated by experience over time, but locked in place once experiences cease to form. (Melzack, 1993).
In 1965 Melzack proposed the gate-control theory of pain. This theory involves a neural mechanism in the dorsal horn of the spine which can increase or decrease the strength of impulses entering the CNS. The degree to which this gate acts depends on the relative activity of large-diameter and small diameter fibers as well as descending pathways from the brain. (Melzack, 153-158). This has a bearing when the act of patting or stimulating the stump to abate phantom pain is considered. The incoming signals from the stimulated stump activate the gating mechanisms in the spinal cord, diminishing a phantom pain pathway generated by the neuromatrix. Not only that, but presumably the incoming signal itself will interact with the neuromatrix, threading through the parallel pathways, and quelling the internally amplified neurosignature. Supporting the notion of a neuromatrix which can be modified with experience is the breakdown of the numbers of phantom limb patients with pain and without. Those who experienced a lot of pain in the limb prior to deafferentation (hospital patients who experience pre-surgical pain before the procedure), tend to often exhibit phantom limb pain. conversely, those who lose a limb suddenly with no prior pain (war amputees) rarely exhibit phantom limb pain. This finding makes intuitive sense in light of a modifiable neuromatrix. (Melzack, 55).

Considerations and Implications

The undeniable bulk of speculation about phantom limb lies in the theories of the unmasking of latent circuits; but the door has not been closed on the idea of neural growth. Studies have shown neuronal growth after lesions in the mammalian CNS, not from regenerated axons, but from collateral sprouting of nearby axons (Kuno, 128-129). Such sprouting may in the future sufficiently explain receptive field revival after deafferentation, or at the very least serve as an important compliment to the strengthening of latent circuits.
Probably one of the most important facets of phantom limb, that will have to be addressed in the future when considering a potential mechanism, is the specificity of sensation modality in this disorder. The somatosensory cortex contains a separate map (homunculus) for each modality of sensation (see fig. 3). (Kandel 328). Of the four areas illustrated, a particular modality tends to dominate that locale (3a responds to muscle stretch-proprioception, 3b responds to superficial skin receptors, 2 responds to deep pressure, and 1 responds to rapidly adapting skin receptors). (Kandel 32-329). An explanation for encroachment of any sort (hidden layers, sprouting, etc.) will have to be symmetrical for all four submodalities and their corresponding somatosensory locations.
Final Thoughts
Phantom limb disorder is not merely a parlor-room curiosity. It gives us a glimpse into the little, dark box where the secrets of memory, learning, the notion of "self" and consciousness are hidden. Insights into how cortical maps expand will shed light onto areas such as how a blind person learns to discriminate with her fingers, tiny Braille dots (remember the monkeys who learned to discriminate vibrations). Certainly the body I feel, whether it is there or not, is an integral association with my conscious notion of "self" and who I am. Resisting the temptation to quote Descartes, I must marvel at the universe and all its parts that exist not out there, but in here--and is aware.
Phantom limb is surreal--a twitching appendage that you cannot see, a ring on a finger that doesn't exist, a tightly clenched fist that never lets go. We brush our teeth, fall in love and dream up ghosts from the same matter capable of producing phantom limbs. If the phantom sensation were a shadow, then the flesh from which it perfuses would be a block, obscuring the source of illumination from which it derives.

AKROTOMOFILIJA



Acrotomophilia je seksualna sklonost prema osobama koje nemaju nogu ili ruku. Pojavljuje se kod oba pola, ali najveći broj akrotomofila su heteroseksualni muškarci. Mada akrotomofile mogu seksualno uzbuđivati osobe suprotnog pola koje su doživele razne vrste amputacija udova, od amputacije prsta do višestrukih amputacija ruku i nogu, za većinu su iz nekog razloga daleko najprivlačnije žene kojima je amputirana samo jedna noga iznad kolena. Neki akrotomofili su više skloni ženama koje koriste protezu, ali većinu najviše privlače žene koje hodaju sa štakama.
Dugo se vode polemike o tome da li je akrotomofilija vrsta seksualnog fetišizma ili ne. Na neki način tačno je oboje. Neke akrotomofile snažno, možda čak isključivo, privlači patrljak amputiranog uda i u takvim slučajevima se najverovatnije zaista radi o podvrsti fetišizma delova tela. Neke akrotomofile na sličan način uzbuđuje proteza ruke ili noge i u takvim slučajevima se najverovatnije radi o podvrsti fetišizma neživih predmeta. Izgleda da, ipak, veliki broj akrotomofila ne privlače samo patrljak ili proteza, nego ih, na neki način, privlači cela osoba koja je doživela amputaciju. U takvim slučajevima je svođenje akrotomofilije na puki fetišizam verovatno potpuno pogrešno.
Ništa kraće ne traju ni rasprave o tome da li je akrotomofilija seksualna perverzija ili običan i normalan (mada ne čest) seksualni varijetet koji se u suštini ne razlikuje od sklonosti prema ženama sa velikim grudima ili plavušama. Ima argumenata i za jedan i za drugi stav, a najverovatnije istina, kao i u prethodnom slučaju, varira od slučaja do slučaja. Mada ozbiljnih istraživanja akrotomofilije nije bilo mnogo, dosadašnja istraživanja su pokazala da akrotomofili ne ispoljavaju psihopatološke osobine u većoj meri od proseka populacije a pokazalo se da su obrazovni nivo i inteligencija akrotomofila iznad proseka populacije. Verovatno je zato sve veći broj stručnjaka sklon da na akrotomofiliju ne gleda kao na seksualni poremećaj, perverziju ili bolest, već kao na normalan varijetet koji ne treba lečiti nego pravilno usmeriti ka seksualnoj i bračnoj vezi sa odgovarajućom osobom.
U praksi se, izgleda, ovaj savet stručnjaka ipak veoma teško realizuje. Jedan od razloga je to što žene koje su doživele amputaciju nekog uda s razlogom taj događaj doživljavaju kao ličnu tragediju, kao ekstremno traumatičan, bolan i frustrirajući, a deo tela gde im je izvršena amputacija vide kao nešto ružno, nakazno i neprivlačno. Zbog toga većina žena-amputirki ne želi da ulazi ni u kakve veze sa muškarcima kojima je privlačno ono što one doživljavaju kao svoju najveću nesreću.

Naravno, ima i amputirki koje to što su za neke muškarce izuzetno privlačne doživljavaju ne samo kao nešto sasvim prihvatljivo, već kao svojevrsnu prednost. Takve žene su činjenicu da su im neki udovi amputirani sasvim prihvatile kao deo sopstvenog identiteta i ne osećaju se više "oštećenim" amputacijom koliko "promenjenim". Takve žene ne samo da rado ulaze u seksualne veze sa akrotomofilima i sklapaju sa njima brakove, već su mnogo više zainteresovane da budu u vezi sa akrotomofilima nego sa "normalnim" muškarcima, jer se samo u vezi sa akrotomofilima osećaju celovitim i do kraja prihvaćenim takvima kakve jesu. Ali ovakav stav, izgleda, nije dominantan kod žena-amputirki, možda i zato što je većini amputirki ipak izuzetno teško da se do kraja pomire sa svojom amputacijom.
Drugi razlog zbog koga je akrotomofilima teško da zasnuju normalnu vezu je to što je broj žena sa amputiranom rukom ili nogom mali. Dok "normalan" muškarac svakodnevno sreće stotine žena koje bi potencijalno mogle da mu budu seksualni partneri, akrotomofil je "srećan" ako jednom u pola godine negde na ulici sretne neku ženu bez noge. Amputirke odgovarajućih godina sreće još ređe, da o onima koje poseduju ostale psihofizičke osobine neophodne za stvaranje uspešne veze i ne govorimo.
Neki akrotomofili zbog toga ulaze u veze sa ženama-amputirkama koje im po svojim ostalim psihofizičkim osobinama ne odgovaraju. Takve veze, naravno, ne mogu da budu uspešne i to sve izaziva još veće frustracije.



To što se amputirke retko sreću dovodi i do toga da neki akrotomofili ispoljavaju sasvim neprihvatljivo ponašanje kada negde sretnu ženu bez noge ili bez ruke: prate je, krišom fotografišu ili snimaju kamerom, pokušavaju da otkriju gde stanuje... Mada je ovakvo ponašanje donekle razumljivo, ne samo da je takva praksa u većini zemalja kažnjiva, nego ona s razlogom amputirke plaši, frustrira i uznemiruje. Ovakvo ponašanje samo još više doprinosi da amputirke ne žele da imaju ništa sa akrotomofilima.
Istine radi, treba reći da ipak ima mnogo veoma uspešnih, srećnih i dugotrajnih veza između amputirki i akrotomofila. Zato, kao i u svim ostalim ljudskim stvarima, verovatno je potrebno više otvorenosti, više razumevanja i više spontanosti s obe strane. To znači da bi amputirke treba da na svakog čoveka, bio on akrotomofil ili ne, da gledaju kao na posebnu i jedinstvenu ličnost i da ne polaze od predrasuda odbacujući unapred svaku pomisao da uđu u vezu sa nekim muškarcem koji oseća privlačnost prema amputirkama. Niko ne može garantovati da će eventualna veza neke amputirke sa akrotomofilom biti uspešna, ali isto tako niko ne može unapred tvrditi da ona neće biti pun pogodak. Predrasude i apriorno negativni stavovi, kao i obično, ni ovde nisu dobar savetodavac.
Akrotomofili pak treba, isto tako, da amputirku gledaju pre svega kao posebnu i jedinstvenu ličnost, da je tretiraju kao celovitu osobu i da umesto neprihvatljivih postupaka poput praćenja i tajnog fotografisanja pristupe amputirki koju sretnu onako kako bi muškarac pristupio svakoj drugoj ženi koja mu je privlačna.



EPILOG
Prvo si Njetočki napisao da je portret s/završen (Barthes itd). Riječ doista ima semantičku vrijednost u oba slučaja, hehe. Potom, ovo s njezinim fantomskim udom, daš joj dijagnozu kod Kizze, nađeš prikladnu sliku i još podastreš cijelu elaboraciju i više... Fenomenalno! Razvio si čitavu jednu priču (ne u fikcionalnom smislu) iz jednog njezinog komentara.
Iako, tema je morbidna je pa nisam mogla odjedno pročitati nego u navratima (jednom sam pala u nesvijest gledajući film Harry and Maud - film o tipu koji voli posjećivati sprovode i svako mao inscenira samoubojstvo).

Hvala! Veseli me da zapažaš ove detalje koji mi zapravo znače koliko i slikarima što u nekoj renesansnoj masovnoj sceni naslikaju diskretnu gemmu oko vrata dame na vjenčanju mletačkoga dužda. Čudno je to što je zaista krenulo od opaske o muškobanjastosti (aluzija na mogući skriveni Kozzin alter ego!?), a završilo s tom blagom viješću da je portret s/završen! Ali, tu ima i skrivenih aliteracija: recimo, spot banda "The Shins" nosi naziv "Phantom Limb"! Sve su ilustracije posvećene tom motivu, a jedna (slika) izrijekom nosi taj naziv! "Boxing Helena", gospođice Lynch, zastupa filmsku umjetnost, varirajući isti motiv! Onda, tu je sretno mada morbidno nadošla i tema ove akrotomofilije; morbidezza ima eho u Witkinovim fotografijama.
Jay Rosenblatt je autor filma Phantom Limb! Objašnjavajući sintagmu 'phantom limb' kao SAVRŠENU METAFORU GUBITKA VOLJENE OSOBE, izriče punch-line cijelog projekta! Onda, tu je znanstveni, psihijatrijsko-medicinski diskurs, historijat, dijagnostika te kurativa koja završava nevjerojatnom rečenicom: virtual reality has been used to combat the discomfort caused by phantom limb syndrome, dakle - ti bi rekla - autoreferencijalnošću, jer tu dolazimo do svijesti o vlastitom mediju (virtual reality) kao oruđu borbe protiv tegoba uzorkovanih sindromom fantomskoga uda (ujedno i ironijski odmak od Njetočkinog portreta, ili nje same). Granice su tu kao politička dimenzija fenomena. Crvolika gospođa, donedavna je supruga Sir Paula, Heather Mills, i sama invalid! Retroaktivno, nakon cijelog gornjeg posta, koji je sljedio prvotni portret, sama naslovna ilustracija poprima viši smisao, tj. biva resemantizirana: fantomski je ud falus MUMIJE/FANTOMA koji je zaklonjen peruškom od koje smo portret započeli! Baš kao što je namjerno u gornjem tekstu, koji je tek fus-nota na tekst o Njet točki - odatle asteriks - uvrštena Witkinova ilustracija žene s falusom: iako je u cijelom tekstu riječ o tome da nešto nedostaje, ovdje imamo posla sa suviškom; to je lacanistički motiv onoga manjka koji je suvišak. O motivu sobarice kao romansirane autostilizacije i fantazmi naše Njet točke, koji dovodi do priče o fetišu, ne treba trošiti riječi: uživao sam u slaganju ovih cipelica, spomenu Oza, potrazi za Garcijinim balerinkama - ima ih moja prijateljica, kupila ih je za Božić u Njemačkoj - uglavnom u izvršavanju ove nijansirane dijalektike želje i zapovijedi, kao što sam obećao Njet točki. Pa i sama ta igra je sretno ispala: kao, ona nije ovo što pokazujemo, nego nešto drugo! Znam da je sve ovo sumanuto, ali zaista mislim na sve te stvari kad kolažiram recentne postove.
Zato me je zaista razveselilo kad sam shvatio da si vidjela što radim.
Nemoj nikome kazati!
Danke Dojčland!



p.s.

Luce
DEVOTEE (mn. devotees) - Osoba koju seksualno privlače osobe sa amputacijom, tj. osobe bez noge ili bez ruke. Koriste se i izrazi admirer, akrotomofil, akrotomofiličar.
Riječ devotee također se može prevesti kao štovalac, sljedbenik, poklonik, isto kao i riječ admirer.
Zbog toga, evolucijski netaknuta ostaje činjenica da kurac, kao takav, nije trebao biti smješten u pičci, iz jednostavnog razloga : ne bi ga bilo moguće štovati kao fantomskog, što obara pojam štovanja po defaultu; štovanje uda kojeg osjećaš i kad fizički nisi spojen za njega osnovni je lajt-motiv proze i poezije žena trećeg milenija i upravo ih nepostojanje evolucijske greške drži pet centimetara iznad vode, to jest pet centimetara od prelaska tanke granice između devotte-a i akromotofila. Muškarci s udom najstrasniji su fetiš (može li fetiš biti nestrastan?) žena akromotofiličarki, u tom paradoksu glavna je činjenica da tuđi ud štuješ kao svoj otkinuti.
Po domaće, kurac štujem upravo zato jer je izvan mene i tako dugo dok postoji opasnost da ću ga opet morati pustiti van.
Upravo zbog toga je Glenn Close skuhala zeca ljubimca Douglasu za večeru.
Isti taj zec bio je fantomsko produženje Douglasove vječite težnje za neodrastanjem, u kojoj ga je beštija okrutno zaustavila, dajući tako sebi mogućnost za štovanje fiktivnog mladosnog batrljka, Duglasovog, ne zečevog.
27.01.2007. (12:49) - #

Nemanja
U pičku materinu, nisam znao da si tako pametna! Sad sam još potaknuo i tebe na mudroslovlje, što neće dobro završiti, već vidim (overlook). Anyhow, da bi se razumjela tvoja upadica, moram čitateljstvo izvjestiti o prethodnoj debati i erotologijskom obaranju evolucionizma; prenosim krtku raspravu s Lucilijinog bloga u cjeloći:
EVO LUCIJA
heidegger
Drsko bih predložio da na tragu poetskog preseljenja organa napraviš anatomski atlas. Bila bi to svojevrsna pjesnička mapa koja bi potakla i slikare i poete da kroz umjetnički izraz razmišljaju o ljudskoj prirodi. Da je evolucija znala možda bi i sama, kad je bilo vrijeme, smjestila srce uz samu pičku. Glazba bi sigurno imala druge putove. Treba također razraditi solucije kamo s kurcem. On je sada trenutno vani ali kod presađivanja mogla bi mu dati neko zahvalnije mjesto. Slikari kao Dimitrije Popović zacijelo bi oduševljeno ilustrirali tvoj anatomski atlas. Mogla bi slikarska naiva poslije zamora opet snažno krenuti naprijed. Nemoj domovini uskratiti da s tvojim sintetičkim proizvodom obogati svjetsko tržište.
26.01.2007. (11:36) - #
Slave
evolucija bi trebala kurac premjestiti na čelo
26.01.2007. (20:25) - #
Nemanja
@Slave: kolone.
(...kurac premjestiti na čelo kolone. Inače bi padala jaja na oko. Pola šest. To bi zbog otegotnosti okolbe nemogućilo zrenje i kretitbu. Govoritelj o gladosti ima neku hladnost i nejasninu, kao kad kuhiraš praznoću ili prostranoću, bez potrebne punosti i radoće.
Slušaonik tada, kao običan službalac, postaje trčatelj ka staroći. Staroća mu pak odnosi vedroću visokosti. Za tili čas.)
Čista poezija.
27.01.2007. (11:44) - #
Nemanja
Evolucija je trebala kurac smjestiti u pičku.
Upravo ste pročitali osnovni antievolucionistički argument. Obrazložimo to ukratko(sic!):
Eva-Lucija, u najširem smislu te riječi, proces je u kojem nizom promjena ili razvojnih stupnjeva živi organizam ili skupina organizama stječe karakteristične morfološke i fiziološke značajke; teorija po kojoj različiti tipovi životinja i biljaka potječu od drugih preegzistentnih tipova. Ta teorija, prema kojoj se viši oblici života izvode iz nižih, temelji se na opsežnim promatranjima.
Budući da sam se ja u životu najebao, na temelju opsežnih promatranja, zapažanja, beleženja, usporedaba i zaključivanja, došao sam do nepozive spoznaje da je evolucionistička teorija, najblaže rečeno, zakurac (i sada ide osnovni antievolucionistički argument): da evolucija ima ikakvoga smisla, dakle da je Život smisleno svrhovito kretanje od manje očitog do nedvosmislenog oblika jednog te istog, kurac bi zaista bio vazda smješten u pičci, a ljudi bi, konzekventno i nasmešeno, živjeli u stanju permanentnog orgazma kao realiziranog eshatona ukupne prirodne i humane povijesti (praksis kao mimezis fizisa). Budući da tome tako nije, evolucija ne postoji, a ako postoji, besmislene je i nesvrhovita! Mislim da sam bio jasan.
Evo je dakle erotologičko obaranje evolucionističke teorije. Na pathos.


Nemanja, ti si Bog! Informatički i globano.
Kako si samo stigao u tili čas ovjekovječiti i učiniti on-line dostupnom moju ekstazu koju si postigao opaskom o muškobanjanosti.?
Molim te samo da me ubuduće upozoriš da me fotkaš, tako da usne izgorjele od želje napućim u položaj kao da izvikujem tvoje ime! (Luce 27.01.2007. 13:44)

Draga Lucija, pokušat ću ti odgovoriti suvislo i nekim redom, iako mi se jebe. Pa sam dekoncentriran.
Ja još uvijek nisam Bog. Nekoć sam bio umišljen, misleći da jesam; danas više nisam, umišljen, pa bi se moglo kazati da sam - savršen. To je zapravo, vidiš i sama, velik teološki problem. Circulus vitiosulus maximus/m rerum novarum. (kitica cvijeća za Baku)
Informatički gledano, danas nije teško biti upućen u rumorenje globalnoga sela, kad je local colour globalna zavjera: čitatelj je per definitionem paranoik, jer misli da svaka riječ i svaki redak, pa i ono između redaka, ima smisao, te je tako senzibiliziranoj osobi vrlo lako pronaći ne samo željenu, već nažalost i neželjenu informaciju o daljnjem svome (trač, to je ljubav za daljnjeg svoga; vlastito otkriće). Tajna ove fotografije, koja je objavljena još vruća, tj. hot-line a ne samo on-line, upravo je u ekstazi: biti u ekstazi, znači biti van sebe, napraviti u sebi mjesta Njemu - fantomskom udu, recimo, Falus, das Ding. Dok si bila van sebe, kao lopov, krišom, čak u potaji, ušao sam u tebe otkrivši tvoje skrovište/utočište. A bila si van sebe, jer sam bio u tebi. Da, možda ja ipak jesam bog, kad ovako djelujem, naizgled samo uzročno, he, he. Što se tiče izgaranja i ekspiroze, već sam ti, u poglavlju o SaMSari - koje začudo otada više nema! - razgovjetno kazao:
"Lucija, ti jesi moja poetesa, ali, tvoji stihovi:

"Prije nego izvadiš kurac, oralno zadovolji moje rečenice,
jer ni ja ni one ne padamo na jebački pedigre,
preskoči smoking i lizing i peting,
porječkaj se sa mnom
umjesto predigre."

samo su noćni lahor u hramu sudbine spram riječi koje suše usne kao mrtvi jezici:

"....više poetičnosti ipak ima u gutanju i sisanju, nego u pisanju."

Devojke, uklešite ove reči kao epitaf u svoja kamena srca!
Samsara, devojčice, nemam reči.
I ja sam tih.
Kao Don.
King."

Eto, odatle valjda tvoje usne izgorjele od želje kao da uzvikuju moje ime!
Po trgovima drevnih gradova. (Nemanja 27.01.2007. 14:00)

Svaka čast, svaka čast. Odoh. Koncentrirati se.
Širiti legendu oralnom predajom. Po trgovima drevnih gradova. (Luce 27.01.2007. 14:06)

Evo Luce, što piše devojčica: "Sjajno je to, fantom limb kao falus. I cijelo to poigravanje nesvjesnim. To je takvo prezahvalno područje, možeš se izgubiti u njemu. Tvoj post me podsjetio na Borgesa, njegov stil općenito, ali posebno na priču Kenningar u kojoj baš zajebava čitatelja, stalno ga tjerajući na višu ili dublju razinu razumijevanja, i istovremeno traži od njega veći angažman - i još, i još... - dubina je, dakako, beskonačna.

Mrrrrrrrr..."
A? To su reči koje pale usne, a ne porječkaj se sa mnom...devojka sve razume i prozire jednim pogledom: fantomski Ud i beskrajno ludičko područje poigravanja s njime, mogućnost gubljenja u ekstazi spoznaje koja je pravi hermeneutički rollercoaster što tera dublje ili više istovremeno tražeći i još i još, do u beskonačnost vrtložne dubine, kao u pesmi Vaska Pope 'Pre igre':