Showing posts with label Energy. Show all posts
Showing posts with label Energy. Show all posts

Sunday, September 28, 2014

Shamanism and Transmuting Energy (work in progress: reference material)

  Shamanism: Healing of Individuals and the Planet   
by Sandra Ingerman 


                                               

 Image by: http://eclecticshaman.com/blog/wp-content/uploads/2013/06/blue_energy_by_koalacid-d5ss736.jpg

http://www.sandraingerman.com/abstractonshamanism.html
Shamanism: A Brief Overview
   Shamanism is the most ancient spiritual practice known to humankind. We know from the archaeological evidence the practice dates back at least 40,000 years. Some anthropologists believe that the practice dates back over 100,000 years.

   The word “shaman” comes from the Tungus tribe in Siberia and it means spiritual healer or one who sees in the dark. Shamanism has been practiced in Siberia, Asia, Europe, Africa, Australia, Greenland, and native North and South America.

   A shaman is a man or woman who uses the ability to see “with the strong eye” or “with the heart” to travel into hidden realms. The shaman interacts directly with the spirits to address the spiritual aspect of illness and perform soul retrievals, retrieve lost power, as well as remove spiritual blockages.  The shaman also divines information for the community. Shamans have and still act as healers, doctors, priests and priestesses, psychotherapists, mystics, and storytellers.

   Shamanism teaches us that everything that exists is alive and has a spirit. Shamans speak of a web of life that connects all of life and the spirit that lives in all things. Everything on earth is interconnected and any belief that we are separate from other life forms including the earth, stars, wind, etc is purely an illusion. And it is the shaman’s role in the community to keep harmony and balance between humankind and the forces of nature.

   There are a variety of ceremonies that shamans perform. They lead ceremonies to welcome children into the world, perform marriages, and help people transition to a good place at the time of death. They lead ceremonies to mourn the death of loved ones. There are important initiation ceremonies performed to mark certain transitions in a person’s life such as from moving from childhood into being an adult.

   One of the major ceremonies a shaman performs is called a shamanic journey. A shaman is a man or woman who goes into an altered state of consciousness and travels outside of time into the hidden realms that many term non-ordinary. I see non-ordinary reality as a parallel universe to ours. The Australian aborigines call non-ordinary the Dreamtime. It is also referred to as the Other World in Celtic traditions.

   In these hidden realities there are helping spirits, compassionate spirits who offer their guidance and also their healing help in behalf of all life on earth.

   Typically shamans use some form of percussion, especially drumming or rattling, to go into an altered state that allows the free soul of the shaman to journey into the invisible worlds.  In Australia you also see shamans use the didgeridoo and/or click sticks. Some traditions use sticks or bells.  The Sami people of Lapland and Norway also use monotonous chanting called “joiking”.

   When one looks at shamanic traditions around the world there are three common levels that are spoken about and also depicted through different paintings and other forms of artwork. The hidden worlds that the shaman travels to are known as the Under World or Lower World, the Middle World, and the Upper World. There are numerous levels in both the Lower World and also in the Upper World and they are outside of time.

   We live in an unlimited universe. Although descriptions of non-ordinary reality are subject to mental limitations I will describe some of the more common shamanic experiences of these worlds.

   Shamanism is a system of direct revelation. All shamans might describe experiences differently. And how the different experiences are interpreted and seen by others is how beautiful they all are.

   The Lower World is reached by journeying through a tunnel that leads into the earth. This world seems very earthy and tangible to the shaman and is characterized by caves, seas, dense jungles, forests, and deserts. The beings inhabiting the Lower World are the spirits of animals, trees, plants, and rocks as well as human spirits that are connected with the mysteries of the earth.

   T
he Upper World is experienced as more ethereal than the Lower World. The lighting is bright and can go from pastels, to gray, to complete darkness.  In the Upper World I might know I am standing on something but what is holding me might seem vague.  The landscape here is also very varied. There are crystal cities and cities of clouds. This level also inhabits a variety of spirits.
   The Middle World is the hidden reality of the world we live in. In the Middle World the shaman can travel back and forth in time. It 
is also a place where the shaman can journey in looking for lost and stolen objects.

   As I already mentioned to the shaman everything is alive. The Middle World is one place where the shaman can speak to the spirit of the rocks, trees, plants, wind, water, fire, earth, etc. The shaman can speak to the spirit that lives in all things here.

   The Middle World is also inhabited by a variety of spirits such as “the hidden folk”. The hidden folk are the fairies, elves, dwarves, trolls, and forest guardians that are present in so many myths and stories. The hidden folk remind us of a magical time in our lives before, through cultural conditioning, we closed the veils between the worlds.

   In the Lower World and Upper Worlds there are a variety of helping spirits that can help the shaman with healing individuals, the community, and the planet.

   The two most common types of spirits who work in partnership with the shaman are power animals also called guardian spirits as well as there are teachers in human form.

   Shamanic cultures believe that when we are born the spirit of at least two power animals volunteer to remain with us to keep us healthy emotionally and physically and also protect us from harm. These animals are akin to the Christian belief in guardian angels.

   The other form of helping spirit that shamans work with is a teacher in human form. These typically were the gods and goddesses of the culture, religious figures, and ancestors who wished to help.

   These helping spirits work with the shaman to bring healing to individuals, the community, and the environment. The helping spirits are also consulted with when information is needed.

S
oul Retrieval: How Shamans Heal Trauma
   Shamans look at the spiritual form of illness which might manifest on an emotional or physical level. When I was doing the research for my book Soul Retrieval: Mending the Fragmented Self, I found that most shamanic cultures around the world believe that illness is due to the loss of the soul.

   It is believed that whenever we suffer an emotional or physical trauma a piece of our soul flees the body in order to survive the experience. The definition of soul that I am using is soul is our essence, life force, the part of our vitality that keeps us alive and thriving.

   The types of trauma that could cause soul loss in our culture would be any kind of abuse: sexual, physical, or emotional. Other causes could be an accident, being in a war, being a victim of a terrorist act, acting against our morals, being in a natural disaster (a fire, hurricane, earthquake, tornado, etc.), surgery, addictions, divorce, or death of a loved one. Any event that causes shock could cause soul loss. And what might cause soul loss in one person might not cause soul loss in another. Shamans believe that alarm clocks can cause soul loss. I think we all know what they mean.

   It is important to understand that soul loss is a good thing that happens to us. It is how we survive pain. If I were going to be in a head-on car collision the last place I would want to be at the point of impact is in my body. My psyche could not endure that kind of pain. So our psyches have this brilliant self protect mechanism where a part of our essence or soul leaves the body so that we do not feel the full impact of the pain.

   In psychology we talk about this as dissociation. But in psychology we don’t talk about what disassociates and where that part goes. In shamanism we know that a piece of the soul leaves the body and goes to a territory in what shamans call non ordinary reality where it waits until someone intervenes in the spiritual realms and facilitates its return.

   Although soul loss is a survival mechanism the problem from a shamanic point of view is that the soul part that left usually does not come back on its own. The soul might be lost, or stolen by another person, or doesn’t know the trauma has passed and it is safe to return.

   It has always been the role of the shaman to go into an altered state of consciousness and track down where the soul fled to in the alternate realities and return it to the body of the client.

   There are many common symptoms of soul loss. Some of the more common ones would be dissociation where a person does not feel fully in his or her body, alive and fully engaged in life. Other symptoms include chronic depression, suicidal tendencies, post traumatic stress syndrome, immune deficiency problems, and grief that just does not heal. Addictions are also a sign of soul loss as we seek external sources to fill up the empty spaces inside of us whether through substances, food, relationships, work, or buying material objects. Anytime someone says” I have never been the same since” a certain event and they don’t mean this in a good way, soul loss has probably occurred.

   You can really see how much soul loss there is today as we put money over life. Anytime someone says that we have to kill other life forms for material gain that person must be suffering from soul loss. Anytime someone feels that buying one more car or that gathering material objects will bring happiness that person is suffering from the loss of soul. As you can see we are looking at a great deal of planetary soul loss today as you watch how we behave towards each other and the rest of life.

   Coma is also soul loss. But in coma there is more of the soul out of body than in the body. Coma is very complicated to work with today for many reasons. It takes skill on behalf of the shaman to find out which way the soul is trying to go. Does the soul want to re-enter the body? Or does it need help moving on which would lead to the death of the patient? There is a lot to say about this topic and it beyond the scope of this article.

   Today there has been a resurgence in the interest of the practice of shamanism. We now have many hundreds of wonderful shamanic practitioners reintroducing the practice of soul retrievals into our culture.

   It is interesting to note that as soul loss was so understood in shamanic cultures people who suffered traumas were given a soul retrieval within three days after a trauma occurred. Today as we have not been practicing soul retrieval, modern day practitioners are going back ten, twenty, thirty, or forty years or even more looking for lost soul parts.

   Also in a shamanic culture the individuals knew what was out of balance in their lives that might have caused an illness or issue to occur.

   In our culture we are unaware of what is out of spiritual harmony that is creating illness. And because often our soul loss happened so young we are unaware of the unconscious patterns we are living out due to our first soul loss. We are always trying to retrieve our soul. And how we do this is by repeating the same trauma over and over again. The names might change of the people involved in our life story, but the story is often the same.

   The effects of having a soul retrieval vary from person to person. Some people feel that they are more grounded in their body and feel more solid. Some people feel lighter and a joyful way of being returns to them. For some memories of the past traumas might be triggered bringing up a variety of feelings that must be worked through. And for some people the effects are too subtle to notice a change until further work to integrate the soul is done.

   As people feel more present in their bodies and in the world, they become more conscious of behavior that might be out of balance and disharmonious. When we are numb we might be aware that things in the world are not right but we can easily distract ourselves from feeling a need to change. When we are fully “inspirited” there is no place to retreat to and we are more inspired to change our lives.

   I believe that once a person has his or her soul brought back the client now has to do some work. If the person has done a lot of personal work the soul retrieval might be the end of the work. If not the soul retrieval would be the beginning of the work.

   Now it is up to the client to look at how to create a healthy life style and attract healthy relationships that will support wholeness and a life filled with healing. How do we want to use the energy that was returned from the soul retrieval and our returned vitality to create a positive present and future for ourselves? And how do we bring passion and meaning back into our lives again so that we thrive instead of just survive? All these issues I call “life after healing” and are crucial to create long term healing after a soul retrieval.

   I write about spiritual practices we can bring into our lives to create a positive present and future in my books Welcome Home: Following Your Soul’s Journey Home and 
Medicine for the Earth: How to Transform Personal and Environmental Toxins.

   This is vital work for the times we live in. The earth wants her children home and she wants them home now. It is time to come back home again and take our rightful place on the earth. It is our birthright to fully express our souls and create the world we want to live in. And it is our birthright to shine as brightly as the stars above us. It is time to share our light again in the world.

Medicine for the Earth: Healing Our Planet

   I started practicing shamanism in 1980 and my own personal practice led me to explore with the spirits the issue of reversing environmental pollution.  One of the most important messages I was to receive over my twenty years of journeying on this was it is who we become that changes the world and our environment not what we do.  Harmony within will create harmony without.  So the true work is learning how to change our thoughts, attitudes and belief systems.  We actually have to work with “ the alchemy of the soul” to really be able to change our inner environment as our inner state of being will be reflected in the outer world. The literal definition of alchemy is “working within and through the dense darkness inside.” This is big work and involves committing to spiritual practices that we must engage in daily and throughout the day.

   Stories that come from the Bible, from the Kabbalah, and from various Taoist, Hindu, yogic, alchemical, Egyptian, and shamanic works show that miracles were once an everyday occurrence.  I researched different spiritual traditions to give me clues to how miracles were performed by ancient cultures, mystics, and saints.  As I read about miracles a formula of elements that seem to be part of all miracles started to form.  The formula that came to me is a hologram.  The elements cannot be taken separately but combined with each other create transmutation.  The definition of transmutation I am using is the ability to change the nature of a substance.  The work of effecting environmental change is how to change toxic substances into neutral substances.

   The formula I arrived at is intention + union + love + focus + concentration + harmony +imagination = transmutation. Although we cannot use these elements as separate entities I would like to explain them separately.

   For all miracles to happen we must hold a strong intention of what we want to see happen. Intention creates action.  This involves concentration.  We know that a key to the success of spiritual practice is the ability to concentrate.  We must also be able to maintain a focus on our short term and long term goals.

   All miracles involve union with a divine force.  In the bible when Jesus says to heal in my name the true Aramaic translation of this is to know God and heal as God does.  This means having union with the creative force of life is essential for true healing to take place.  Sai Baba, a guru in India, is known for his miraculous acts and healing abilities. He says: “The only difference between me and you is I know who I am and you don’t” (meaning he knows he is divine).   These are just a couple of examples of what different mystics say about union.

   Love is an essential ingredient in all miracles as it is only love that heals.  Techniques don’t heal.  Where there is an open heart there is the energy to bring through miraculous and magical energy.  Love is the great transformer.

   I have already mentioned harmony as it is known in the practice of alchemy that harmony within will create harmony without.  Disharmony creates disease; harmony creates beauty and health.

   Imagination is another key in performing the miracle of transmutation in that we must be able to envision an environment that is pure and clean and which supports all of life.  Caroline Casey, an American astrologer, says:  “Imagination lays the tracks for the reality train to drive down.”  With our imagination we have to ability to sculpt our world.

   To add to this formula there are more principles to remember.  As we change our perception we change our reality.  To change our perception to create a reality of a clean environment we must be able to see the beauty in all things.  To see the beauty in all things, we must live in a state of appreciation and gratefulness.

   There are two phases of the work. One phase of the work is to learn how to recognize that we are more than a body, our thoughts, and our past experiences. We are spiritual light and we are divine at all times.

   We are not separate rather we are connected to one source and to a web of life. Imagine a hand where one of the fingers drops to the floor and thinks it can have an independent life without being connected to the body. That is what is happening today. Humankind is acting like separate fingers that have forgotten the connection to the original source of life.

   In our egoic states we perceive ourselves as separate from each other and the rest of life. Life circumstances and our relationships with others trigger negative thoughts and feelings. As human beings it is important to acknowledge our thoughts and feelings. It is also important to acknowledge that there is energy behind our thoughts and feelings that we can send out to others and into the environment. In shamanic cultures it is understood that there is a difference between expressing anger and sending anger.

   It is healthy to have a range of thoughts and emotions. The work we must do is to learn how to transmute or transform the energy behind our thoughts and emotions into love and light. In this way we can feel the depth of our feelings but not create any harm by doing so.

   We must again recognize as all ancient cultures did that words are vibration. And when we speak out loud we send a vibration out into the universe that will manifest back down on others and us.

   You might remember when you were a child saying the phrase abracadabra. This is actually an Aramaic phrase “abraq ad habra” and it literally translates to “I will create as I speak”.

   I write about how to transmute the energy of our negative thoughts into an energy embracing love and light and how to work with the power of words in my book How to Heal Toxic Thoughts: Simple Tools for Personal Transformation.

   The second phase of the work is gathering together in community to do ceremonies to reverse the pollution that we have created.

   My book, Medicine for the Earth: How to Transform Personal and Environmental Toxins goes into detail about this material.  After I wrote the book I started some scientific experiments to check out if the practices I wrote about will truly transmute toxins.  I have been working with intentionally polluting de-ionized water (pure water with no minerals in it) with ammonium hydroxide, a common and dangerous pollutant in our environment. As ammonium hydroxide is a strong base it is easy to check its presence with the use of pH strips.  I have worked with many groups of students at this point.  With every group I have worked with using the principles I wrote about, the water has changed a pH of 1-3 points toward neutral. We have prepared for days but once we begin the ceremony work it has only taken approximately 15-20 minutes before the water changes.  From a scientific point of view this would be seen as impossible.

   Since these initial experiments I started using a gas discharge visualization camera which is based on the Kirlian effect. We can now take pictures of the change in energy of the substances present in our circle. Besides water we have put in the circle a peach, some soil from a road that has a lot of cars driving on it, and some cheddar cheese crackers. To see some of the pictures we have gotten you can visit www.medicinefortheearth.com and click on “Results”.

   It is important to note that in our ceremonies we have not tried to manipulate the environment. We have not focused on the substances on the altar of our circle. We change ourselves with the understanding that our outer world will reflect back to us the inner changes that we make. This way of perception goes back to the ancient and esoteric principle of “as above, so below; as within, so without”.

   Alchemists did not actually change lead into gold.  The practice of alchemy was about changing lead consciousness into gold light consciousness.  As we begin to change our consciousness and get in touch with the light inside of us we can effect great changes in our outer world.  It is who we become that changes the world not what we do. The world changes by how we change.

   All life is made of light.  We are all light.  Everything is light.  In remembering this we can transmute everything in our outer environment and what we take in to pure healing light.

   All spiritual traditions teach that everything manifests on a spiritual level before manifesting on the physical. Where we have power right now to create change on the planet is by incorporating spiritual practices into our lives.

Proprioception (work in progress: reference material)

Proprioception

(current work in progress: data to be researched and added to N.Hill's 10 Stimulus of Transmutation)

Elizabeth O. Johnson, Ph.D.
Department of Anatomy, Histology & Embryology
University of Aathens, School of Medicine
Athens, Greece
Email: elizabethojohnson@gmail.gr
Panayotis N. Soucacos, MD, FACS
Department of Orthopaedic Surgery
University of Athens, School of Medicine,
Athens, Greece
psoukakos@ath.forthnet.gr

Abstract

The term proprioception is used to describe the sensory information that contributes to the sense of position of self and movement. Body position is perceived both at the conscious and unconscious levels. The information of conscious proprioception is utilized to facilitate complex motor activity, while unconscious proprioception is important to coordinate basic posturing during sitting, standing and simple gait activities. Proprioception is based on a multi-component sensory system. There are various peripheral receptors that detect specific signals and major sensory afferent pathways which carry the information from the spinal cord up to the cortex. There are parallel pathways, some of which serve conscious proprioception, and others that serve subconscious proprioception. Conscious proprioception is relayed mostly by the dorsal column, and in part by the spinocervical tract. The goal here is to outline our current understanding of these complex neural pathways, starting from the peripheral receptors and working up towards the center of perception, the brain.

Definition of Proprioception

The term proprioception is used to describe the sensory information that contributes to the sense of position of self and movement. Sir Charles Bell named the "sixth sense" as the sense of the positions and actions of the limbs (McCloskey 1978). Sherrington (1906) first used the term proprioception to define the sense of body position. Body position is perceived both at the conscious and unconscious levels. The information of conscious proprioception is utilized to facilitate complex motor activity, while unconscious proprioception is important to coordinate basic posturing during sitting, standing and simple gait activities. Defects in the conscious proprioception system manifest as stumbling, although gait and posture may be normal. Defects anywhere along the unconscious proprioceptive pathways may be manifest as postural deficits or ataxia.
There is a long history of studies aimed at understanding the neural mechanisms of position sense perception. Today, it is believed that proprioception refers to 2 kinds of sensations: that of static limb position and of kinesthesia. Static position reflects the conscious recognition of the orientation of the different body parts, while kinesthesia is the conscious recognition of rates of movement. In general, impulses from receptors in the joints and surrounding tissues are synthesized into a picture of the body's position. The brain then functions to perceive this information. Unfortunately, however, the system for proprioception is not quite that simple. Rather, proprioception is based on a multi-component sensory system which includes: various types of peripheral receptors which detect specific signals and major sensory afferent pathways which carry the information from the spinal cord up to the cortex. (Johnson et al. 2008)

Receptors of Proprioception

It is well recognized that joint movements activate receptors in the joint, skin and muscle. In turn, any of these receptors may play a role in the perception and control of limb movement and joint angle. Position sense has been associated with a distinct class of sensory receptors; particularly those found in the muscles and related deep tissues (Jami 1992). Kinesthesis has been associated with receptors located in joints and cutaneous tissue (Burgess et al. 1982).
A sensory unit is comprised of a stem fiber (a nerve fiber which forms the same kind of nerve ending at all of its terminals) and its family of endings. The territory from which a sensory unit can e excited is its receptive field.
Position sense is elicited by mechanical disturbances in the joints and surrounding tissues. These disturbances are first detected by mechanoreceptors and then, a given sensation, is signalled either by changes in the receptor's activity or by the number of receptors activated. Today, it is clear, that sensory information from several different types of receptors is used. These include extensive sensory endings, specific receptors, as well as muscle spindles. Free nerve endings are found throughout the substance of the ligaments and in the synovial covering. These transmit information on both joint position and movement. Of the Ruffini endings, the most abundant is this multi-branched encapsulated ending which is important for signalling the joint's limit of motion. Golgi-tendon like receptors are common around the knee joint. These encapsulated receptors signal information on tension. Pacinian corpuscles are usually dispersed in the surrounding tissues. They are easily recognized by their capsule, which surrounds a central nerve fiber. They detect rate of motion, and are stimulated by very minute and rapid movement.
Finally, two types of muscle spindles signal changes in muscle length. The flower spray ending relays static position information, and the annulospiral ending transmits mostly information regarding movement. It was believed that for the most part, kinesthesia sensations are detected by Pacinian corpuscles and Ruffini endings. However, it is now clear that muscle spindles, once thought to encode exclusively individual muscle lengths, are also major contributors to the kinesthetic sense of position and movement (Clark et al.1985). Static limb position is mostly detected by flower spray muscle spindles and Golgi tendon organs.

Figure 1: Principal cutaneous receptors for position sense

Figure 1
An explanation of figure 1 is available.
Cutaneous receptors contribute to position and movement sense of the hand (Edin and Abbs 1991). In general, there are four types of mechanoreceptors of the glabrous hand, each with a different sensory function, which are responsible for proprioception of the hand. Slow adapting Type I receptors are essential for transmitting information regarding form and texture, while cutaneous rapid adapting receptors are important in grip control. The Pacinian system is related to the detection of distant events by vibrations through objects in the hand. Finally, the slow adapting type II receptor system relays information regarding hand conformation and perception of forces acting on the hand.

Sensory Innervation of Skin

Meissner's Corpuscles

The capsule of the Meissner corpuscle is comprised of an outer coat of connective tissue, a middle coat of perineural epithelium and an inner coat of modified Schwann cells (teloglia). Several axons zigzag among the stacks of teloglial lamellae in these ovoid-shaped receptors. As all encapsulated nerve endings it is a mechanoreceptor, which detects and transmits mechanical stimuli. Meissner's corpuscles are numerous in the finger pads. They respond to delicate tactile stimuli.

Pacinian corpuscles

The capsule of the Pacinian corpuscle is similar to that of the Meissner's corpuscle. Inside a thin connective sheath they show onion like layers of perineural epithelium which also contains a few capillaries. The innermost layer is comprised of several teloglial lamellae surrounding a single central axon that lacks a myelin sheath. The Pacinian corpuscle is about the size of rice grains, with about 300 in the hand. These subcutaneous receptors lie close to the underlying periosteum and along the sides of fingers, as well as in the palm. They are rapidly adapting mechanoreceptors and are particularly sensitive to vibration.

Ruffini endings

These encapsulated nerve endings are found in both hairy and glabrous skin. Their morphology is similar to that of Golgi tendon organs with a collagenous core and several axons branching out. These mechanoreceptors respond to shearing stress and are slowly adapting.

Merkel Disks

Merkel disks consist of expanded nerve terminals (tactile menisci) in the basal epithelium of epidermal pegs and ridges. These are slowly adapting receptors, which discharge continuously in response to sustained pressure.

Free nerve endings

Free nerve endings branch out in a subepidermal network. The sensory fiber at this point has lost its perineural sheath and myelin sheath (if any). The Schwann cell sheaths have opened to allow naked axons to terminate between collagen bundles or within the epidermis. Some sensory units are thermoreceptors, supplying either warm or cold spots. In addition, there are two types of nociceptors for pain transmission. The finely myelinaed A-delta parent fiber responds to severe mechanical deformation of the skin, while the C-fiber parent fibers are polymododal nociceptors that respond to mechanical deformation, intense heat and chemical irritants.

Follicular nerve endings

These are naked terminals that lie along the outer root sheath epithelium of the hair follicles just below the level of the sebaceous gland. Each follicular unit supplies several follicles.

Sensory Innervation of Skeletal Muscle

Neuromusclular spindles

These are found in skeletal muscle and are most abundant towards the tendinous attachment of the muscle. Each spindle is surrounded by a fusiform capsule of connective tissue, with slender intrafusal muscle fibers inside. There are two types of sensory innervation of muscle spindles: the annulospiral and the flower spray. The former are situated at the equator of the intrafusal fibers, where the unmyelinated axon winds spirally around the intrafusal fiber. The flower spray endings are found towards the ends of the spinal. In these nerve endings, the unmyelinated axon branches out terminally. Stretching of the intrafusal fibers results in stimulation of both the annulosprial and flower spray endings.

Golgi tendon organs (Neurotendinous spindles)

These are located in tendons and near the junctions of tendons with muscle. The spindle consists of a fibrous capsule that surrounds a small bundle of loosely arranged collagen fibers. A single I-beta nerve fiber forms complex sprays that intertwine with tendon fiber bundles.

The Peripheral Nerve - Mediators of Proprioception

Neurons are specialized cells that receive and send signals to other cells through their numerous extensions, axons and dendrites. Most neurons give rise to a single axon and many dendrites. Dendrites receive and transmit incoming synaptic information to the nerve cell body, whereas axons convey impulses from the neuron to its synpatic terminal (Johnsonet al. 2005, Johnson et al. 2006). A peripheral nerve contains both dendrites and axons; fibers which conduct information to (afferent) or from (efferent) the CNS, respectively. Efferent fibers, for the most part axons, relay impulses related to motor function from the brain and spinal cord to muscles, glands, etc. in the periphery. On the other hand, afferent fibers, mostly dendrites, usually convey sensory stimuli to the CNS via their nerve cell bodies in the spinal ganglia.

Table 1: Sensory fibers and receptors

FiberDiameter (nm)ReceptorFunction
A-alpha10-20nuclear bag intrafusal fibersChanges in length & velocity muscle stretch
Golgi tendon organMuscle & ligament tension
A-beta4-12nuclear bag chain fibersChanges in length muscle stretch
Meissner's corpuscleVibration & discriminative touch
Pacinian corpuscleVibration & discriminative touch
Merkel diskPressure on skin
Ruffini's endingSkin stretch
Ruffini joint receptorRange of motion (extremes)
Pacinian joint receptorJoint range of motion
A-delta1-5Free nerve endingsCrude touch, pain temperature
C<1Free nerve endingsPain temperature
Spinal nerve contains both somatic and visceral fibers. The somatic component consists of efferent and afferent fibers. Efferent fibers innervate the skeletal muscles and are comprised mostly of axons of &#945;, &#946;, & &#947; neurons in the anterior grey column of the spinal cord. Afferent fibers, on the other hand, convey impulses to the CNS from various peripheral receptors and comprise the peripheral processes from unipolar cells in spinal ganglia. The visceral component of spinal nerves is also comprised of afferent and efferent fibers; these belong to the autonomic nervous system and include sympathetic and parasympathetic fibers at different spinal levels (Johnson et al. 2005, Johnson et al. 2006).
Spinal nerves are formed by the union of ventral and dorsal spinal nerve roots as they emerge through the intervertebral foramina. The ventral root contains axons from the cells of the anterior and lateral grey columns of the spinal cord. Each root emerges as a series of 2 to 8 rootlets arranged in 2 or 3 irregular rows over a distance of about 3 m.m. on the anterolateral aspect of the spinal cord. The ventral roots which constitute the motor outflow tracts from the spinal cord are comprised of large-diameter alpha motor neuron axons for the extrafusal striated muscle fibers; smaller gamma motor neuron axons that supply the intrafusal muscle of the muscle spindles; and a few small diameter axons (Johnson et al.2006).
The dorsal root contains axons of cells in the spinal ganglia, and are fibers from cutaneous and deep structures. The largest fibers (I&#945;) come from muscle spindles and participate in spinal cord reflexes; the medium sized fibers (A&#946;) convey impulse from mechanoreceptors in the skin and joints. Most of the axons in the dorsal nerve roots are small (C, nonmyelinated; A-delta, myelinated). Each root consists of 2 fascicles, medial and lateral, and diverges into rootlets that enter the cord along the posterolateral sulcus (Johnson et al. 2006).
The spinal ganglia are a collection of nerve cells on the dorsal root. Normally they are located within the intervertebral foramina, immediately lateral to the site where the nerve roots perforate the dura mater. Immediately beyond the spinal ganglia, the ventral and dorsal roots unite to form a spinal nerve and emerge through the intervertebral foramen. The spinal nerve gives off recurrent meningeal branches and then divides immediately into a dorsal and ventral ramus. At or immediately distal to its origin the ventral ramus of each spinal nerve is joined by a grey ramus communicans from the corresponding ganglion of the sympathetic trunk (Johnson et al. 2005).

The Transitional Zone Between the Peripheral – Central Nervous System

The sections of axons that comprise a nerve root are enclosed within a short glial segment that lies close to the surface of the spinal cord or brainstem when crossing the transitional zone between the central and peripheral nervous system. The transitional zone is that length of rootlet containing both central and peripheral nervous tissue. In man, this zone lays more peripherally in sensory nerves than in motor nerves.
The apex of the transitional region has been described as the glial dome with its convexity directed toward the periphery (Johnson et al. 2006). Electron microscopy has shown that the center of the dome consists of fibers showing typical central organization surrounded by an outer mantle of astrocytes (corresponding to the external glial limiting membrane). From this mantle, numerous process, the glial fringe, project into the endoneurial compartment of the peripheral nerve and interdigitate with the Schwann cells. Astrocytes form a loose meshwork through which the axons pass. It is not clear as to whether the basement membrane that surrounds the astrocytes is capable of preventing central Schwann cell migration.
In general, peripheral myelinated fibres cross the transitional zone at a node of Ranvier, termed a PNS-CNS compound node by Carlstedt and Berhold (Carlstedt and Berhold 1977). On the peripheral side of the node, the axon has a corona of Schwann cell microvilli and mitochondria-laden paranodal Schwann cell cytoplasm. The central side is characterized by a few astrocyte processes that typically make specialized contacts with the axolemma. Considerable rearrangement of axons occurs in the rootlets, and many of the largest non-myelinated peripheral axons become invested with a thin myelin sheath as they pass through this transitional region.

Sensory and Motor Connections with the Brain.

Multiple tracts connect many parts of the nervous system. Multiple ascending and descending tracts connect the PNS and lower spinal centers with the brain. This reflects that the nervous system is able to extract different pieces of sensory information from its surroundings and encode them separately, and that it is able to control specific aspect of motor behavior using different sets of neurons. The multiplicity of tracts endows the nervous system with a degree of redundancy. Thus, with partial destruction of nervous tissue, only some functions will be lost.
The nervous system is constructed with bilateral symmetry and with crossed representation. Although there are occasional exceptions to the pattern of crossed innervation, for the most part somatosensensory information (touch, temperature, joint position sense) from the body's right side is processed in the somatosensory cortex in the left cerebral hemisphere. Similarly, the motor cortex of the left cerebral hemisphere controls body movements of the right side of the body. Of course there is one major exception to the rule of crossed motor control. Each cerebellar hemisphere controls coordination and muscle tone on the ipsilateral side of the body.
Examination of the major sensory or motor pathways reveals a highly and tightly organized nervous system. In particular, at each of many levels, we see fairly exact maps of the world within the brain. For example, sensory axons with within its ascending pathway are arranged in a very orderly manner, with fibers from specific anatomic locations (e.g. digits, hand, forearm, and so on) preserving very specific topographical locations with in the dorsal column, thalamus, internal capsule and sensory cortex.

Sensory Afferent Pathway of Proprioception

In general, impulses from peripheral receptors in the skin, muscles and joints are synthesized into a picture of the body's position, condition, etc. The brain then functions to perceive this information. Sensory perception is based on a multi-component sensory system that includes: various types of peripheral receptors which detect specific signals and major sensory afferent pathways which carry the information from the spinal cord up to the cortex. For the most part, conscious proprioceptive information is transmitted up the spinal cord in the dorsal colums and medial lemnisci to the cerebral cortex. This is not the only pathway system, however. There are also subconscious pathways with endpoints at the spinal cord, the cerebellum, as well as others in the cerebral cortex. In the conscious pathway, sensory information from receptors in the limbs and trunk is carried by peripheral nerves then the spinal cord via the fasciculus cuneatus and fasciculus gracillus to the brainstem where it crosses over to the contralateral cerebral cortex. The cortex then perceives and organizes precise information regarding the position and orientation of the limbs. In the unconscious proprioceptive pathway, sensory information from receptors in the limbs and trunk are transmitted via peripheral nerves to the spinocerebellar tracts where they information terminates on the ipsilateral cerebellum.

Figure 2: Primary somatosensory pathway that conveys fine discriminative touch, pressure, vibratory sensation, and conscious joint position sense

Figure 2
An explanation of figure 2 is available.
Sensory perception is elicited by disturbances in the skin, muscles, joints and surrounding tissues. These disturbances are first detected by mechanorecptors, pain receptor, temperature receptors, touch receptors etc. and then, a given sensation, is signaled either by changes in the receptor's activity or by the number of receptors activated. Today, it is clear, that sensory information from several different types of receptors is used. Sensory fibers arise from pain, thermal, tactile and stretch receptors; the cell bodies for these fibers are located within the dorsal root ganglia and their axons entering the posterolateral sulcus of the cord by way of several rootlets. For the most part, somatosensory information is transmitted up the spinal cord in the dorsal columns and medial lemnisci to the cerebral cortex. These tracts convey well-localized sensations of fine touch, vibration, two-point discrimination and proprioception from the skin and joints. This is not the only pathway system, however. There are also subconscious pathways with endpoints at the spinal cord, the cerebellum, as well as others in the cerebral cortex. (Johnson et al. 2008).
On entering the spinal cord from the dorsal root, the fibers immediately divide to form a medial and lateral branch. The medial branch turns upward in the dorsal column and proceeds to the brain. The lateral branch divides in the same segment giving off terminals to the cord gray matter. These terminals serve 3 purposes: some give rise to the spinocervical tract that later joins the dorsal column, others give rise to tracts for the cerebellum, and others elicit local spinal reflexes.
At spinal cord entry, there is an anatomically distinct separation of modalities in specific regions of each spinal cord lamina. The dorsal column is the main afferent system. The dorsal column is formed by the medial branch that does not terminate in the spine. It transmits information regarding both movement and static position from Pacinian corpuscles. The spinocervical tract, on the other hand, is derived from those fibers that terminate in layer IV. This tract relays proprioceptive information regarding static position coming mostly from Ruffini endings, and this tract joins the dorsal column later on. Fibers conveying joint or position sense and some tactile fibers turn cephalad in the dorsal columns and do not synapse before reaching the gracile and cuneate nuclei at the cervicomedullary junction. Pain and temperature fibers synapse in the substantia gelatinosa and cross to ascend in the dorsal spinothalamic tract. Tactile fibers enter, synapse and cross to ascend in the ventral spinothalamic tract.
Somatosensory fibers ascend without crossing in the dorsal white column of the spinal cord to the lower brain stem. Immediately after entry into the spinal cord, the fibers of the dorsal column enter one of two white bundles. Fibers from the upper limb enter the fasciculus cuneatus, which lies between the fasciculs gracilis (which carries input from the lower half of the body) and the dorsal gray column. It is important to note that they ascend in the column, maintaining a distinct spatial orientation with respect to the body parts they were derived from. Fibers from the thoracic segments are more medial than the higher cervical fibers. Thus, one dorsal column contains fibers from all segments of the ipsilateral half of the body arranged in an orderly somatotopic fashion from medial to lateral. In the lower medulla, fibers from the upper extremity synapse with neurons of the cuneate nuclei. The new fibers from these neurons crossover immediately (lemniscal decussation) and then go on to form new afferent bundles, the medial lemnisci. The lemnisci ascend through the brainstem. By the time they reach the midbrain, the gracile portion that carries information regarding lower limb, has moved posterolateral to the cuneate.
All of these fibers synapse with the ventral posterolateral nucleus of the thalamus. This is a large cell mass that serves all somatic sensory modalities. The distinct spatial orientation is maintained in the thalamus, with the upper limb being represented by the most medial portion. However, because of the crossing over of fibers, the left side of the body is represented on the right side of the thalamus.
For all sensory systems, the thalamus acts as a crucial way station, much like a "check point Charlie". That is, it intercepts all messages going to the cerebral cortex. Thus, the thalamus appears to "translate the information" before final processing by the cortex. New fibers from the thalamus enter the cerebral cortex via the posterior limb of the internal capsule. There the fibers synapse on the post-central gyrus of the parietal lobe (Luth et al. 1980, Mehler and Nauta 1974).
In the sensory cortex there is a point for point localization of peripheral areas. The size of the cortical receiving areas is porportionate to the number of receptors coming from that particular part of the body. This is represented by the sensory homunculus, a cartoon, which overlies a coronal section through the sensory gyrus. The proportions of the homuculus are distorted to correspond to the size of the cortical receiving area. The lower limb is located near the longitudinal fissure (Druschky et al. 2002, Sato et al. 2002).
Functionally, the neurons in the most anterior portion of the post-central gyrus respond to proprioceptive information. This indicates that this area is the cortical end-point for conscious proprioception. It is important to note the close anatomical relationship between the proprioceptive and motor cortex; the motor cortex which lies immediately anterior to the proprioceptive center.

Central Perception of Position Sense: What Does that Brain See?

The human brain has multiple body representations and basically, two body maps. One is the body schema, which codes the orientations of one's body parts in space and time. The second is the body structural description, which codes the position of each body segment. Sense of position of body parts is a result of three inputs on the dorsal premotor cortex. These a three secondary inputs related to proprioceptive information which initially was transmited to the somatosensory cortex, visual information which was initially transmitted to the occipital cortex, and the combination of the vestibular system input from the bony labyrinth of the inner ear and tactile information from the somatosensory cortex. These pieces of information converge to the dorsal premotor cortex that ultimately is recognized as the primary site where sense of limb position contributes to controlled movement.
Most amputees experience phantom limb sensations and/or phantom limb pain that for the most part are resistant to management (Hunter et al. 2005). Phantom limbs provide valuable information and insight into the proprioreceptive pathways underlying body position awareness. In general, phantom phenomena include spontaneous perceptions that usually generated by activation of thermoreceptors that signally warmth or coolness, deep or proprioceptive receptors which signal limb position, size, volume or movement and tingling sensations (Fraser et al. 2001)
Various factors are related to the functional results following nerve repair, including: axonal growth, atrophy of targets, misdirection of regenerating axons, death of nerve cell bodies at dorsal root or spinal cord level, and functional reorganization of somatosensory cortex. Children show better results following nerve repair with no major differences in axonal regeneration. It is hypothesized that this may be related to superior brain plasticity in children. Today, the weight of the available evidence suggests that the organization of the sensorimotor cortex is not fixed, even in the adult brain, and that organizational changes in cortical regions can be produced.
Normally the hand is represented in areas 3b and 1 of the somatosensory cortex with the individual fingers being represented in well-defined bands (Sato et al. 2002). A recent magnetoencephalography study provided evidence for a sequential topographical arrangement of not only the ventral, but also the dorsal surface representations of the individual digits in the human somatosensory cortex (Druschky et al. 2002). Information regarding a topographic (homuncular) representation of the dorsal finger surfaces, and the sequential rostrocaudal array of the ventral finger aspects in the cortical area of 3b, might allow us to better understand cortical reorganization of the a subtly differentiated cortical map of the hand after peripheral nerve injury.
Recent evidence suggests that the organization of the sensorimotor cortex is not fixed and that organizational changes can be produced within these regions with external manipulations (Stefan et al. 2000). A key factor in producing these organizational changes appears to be stereotyped afferent inputs. Motor cortex mapping has been used to study organizational changes in the motor cortex associated with peripheral sensory stimulation (Hamdy et al. 1998), limb amputation and ischaemic nerve block (Cohen et al. 1991, Brasil-Neto et al. 1992) and motor learning (Pascual-Leone et al. 1995). Moreover, a period of peripheral stimulation can induce striking organizational changes with the motor cortex (Ridding et al. 2000, Ridding and Rothwell 1995).
PET (Positron emission tomography) has shown functional plasticity by showing an increase in projections in sensory and motor cortex with new uses of the fingers. Pascual-Leone and colleague (Pascual-Leone et al. 1995) showed this in blind people learning to read Braile with increased projection of the reading finger.
Following medial nerve transection, the hand is partly denervated. However, we forget that the sensory cortex is also denervated, in part, due to the absence of sensory input. Primate studies have shown that after transection, a black hole in the sensory cortex develops corresponding to the sensory territory of the nerve. Soon following the transection (or repair) this area becomes occupied by substitute tactile input from adjacent hand areas that remain innervated by other nerves (cortical reorganization)(Lemon et al. 2004, Nakajima et al. 2000). When regenerating axons make peripheral connections, again there is a functional cortical reorganization. Sometimes this entails a total functional reorganization of the somatosensory cortex. This implies that the hand "speaks" a new language to the brain.

Assessment of Proprioception

Proprioception includes two components, the sense of stationary position of the limbs (limb position sense) and the sense of limb movement (kinaesthesia). Each component can be clinically tested individually, and give important information regarding specific cutaneous sensory receptors, peripheral nerves, dorsal roots, and central nervous system pathways. (Gilman 2002)
A thorough patient history often provides the clinician clues of the type of sensory disturbance. Pain, paraesthesias, tingling, numbness are often related to pain and temperature sensations involving smaller diameter fibers, and not fibers related to position sense or vibration sense. On the other hand, stumbling, difficulty standing straight when eyes are closed, uncoordinated use of the upper limb and hands, pseudoathetosis (involuntary movements of limbs when eyes are closed) suggest abnormalities of position sense or vibration sense. The clinician should use both static and dynamic stimuli to assess joint position sense. Joint position sense is evaluated by having the individul experience a specific joint position (angle) and then reproduce the position actively or react during passive movement. The joint position test measures the accuracy of position replication and can be conducted actively or passively in both open and closed kinetic chain positions. Joint kinaesthesia is determined by establishing a threshold at which motion is detected during various velocities and ranges of movement. Kinesthesia testing can be conducted by using the criterion of threshold to detection of passive motion direction, where the test assesses one's ability to not only detect motion, but also detect the direction the motion is occurring.
Several testing techniques and instrumentation have been used to assess the conscious submodalities of proprioception (joint position sense, kinaesthesia and sense of tension). Among the growing variety of equipment include commercial isokinetic dynamometers, electromagnetic tracking devices and custom-made jigs, for measuring conscious appreciation of proprioception.
Current evidence suggests that aging results in diverse declines in the morphology and physiological function of various sensory structures, preferential loss of distal large myelinated sensory fibers and receptors and impaired distal lower-extremity proprioception, vibration and discriminative touch and balance. (Shaffer and Harrison 2007) This suggests the need of refining sensory measures (vibration, 2-point discrimination and proprioception testing) in order to accurately assess the functin of large myelinated fibers in older patients.

Conclusion

Proprioception is the sense of body position that is perceived both at the conscious and unconscious levels. Typically, it refers to 2 kinds of sensations: that of static limb position and of kinesthesia. Static position reflects the recognition of the orientation of the different body parts, while kinesthesia is the recognition of rates of movement. Proprioception is based on a multi-component sensory system. There are various peripheral receptors, which detect specific signals and major sensory afferent pathways which carry the information from the spinal cord up to the cortex. There are parallel pathways, some of which serve conscious proprioception, and others that serve subconscious proprioception. Conscious proprioception is relayed mostly by the dorsal column, and in part by the spinocervical tract. Finally, the organ of perception for position sense is the sensory cortex of the brain.

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Johnson EO, Soucacos PN. 2010. Proprioception. In: JH Stone, M Blouin, editors. International Encyclopedia of Rehabilitation. Available online: http://cirrie.buffalo.edu/encyclopedia/en/article/337/

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