Nervous System - Part 2 - The Cerebellum
Muscle Spindles:
   Input to the pilot human being within a human being comes largely from proprioceptive sensory organs which
include the neuromuscular spindles distributed throughout the skeletal muscles of the body. The focus here will
be on input from these spindles that feedback information on the relative position of the body's parts with
respect to the environment. They are generally small in relation to the muscle group they monitor and simulate.
They consist of a nuclear bag element and a nuclear chain element in parallel, as shown below. Because of
their dual structure they can be activated by gamma motor neurons independently of the parent muscles and
they can therefore simulate an anticipated action sequence prior to the parent muscles carrying it out. It is via
proprioceptive sensory feedback from muscle spindle simulations that we get a feel for doing an action before
we do it, often just an instant before.
 Since they are attached to the parent muscles the spindles also monitor the relative degree of flex or
relaxation during each action sequence in both the T5E and T5R physical action terms in Steps 2 and 4
respectively of each System 4 Cycle. In Step 3 of each Cycle there is a muscle spindle simulation. Part 1 shows
how they work in accord with System 4 at the spinal level and some further comments are relevant.  
 The nuclear chain element feeds back the amount of change in the related muscle and the nuclear bag feeds
back the rate of change. The nuclear bag element also receives motor input from a collateral branch of the
alpha motor neuron that activates the parent muscle, which keeps the spindle in adjustment with the parent
muscle. But it also receives two other gamma motor inputs which project to these proprioceptive organs from
the ventral horns of the spinal cord. (Some 30% of the motor neurons in the ventral horns of the cord are
gamma motor neurons.)
Diagram of Muscle Spindle redrawn from Cunningham's Textbook of Anatomy.  It does not distinguish between nuclear bag
and nucear chain fibers, nor between modes of motor innervation.
Diagram of Muscle Spindle redrawn from Ganong, W. F., Review of Medical Physiology. Typical nuclear bag and chain fibers
are shown, together with modes of innervation. The enclosing sheath is omitted.
Simulation:
  The motor simulation can originate in the brain stem or at various spinal levels via the reticular system. The
reticular system of the brain stem is a complex nerve net that is associated among other things with conscious
arousal and thus with the recall process. It is interconnected with both ascending and descending reticular
tracts that are multi-synaptic throughout the length of the spinal column. Since reticular tracts are
multi-synaptic and also closely associated with the hypothalamus, they can regulate autonomic energy
patterns at various spinal levels to adjust emotional energies that fuel modified action sequences at various
spinal levels accordingly.
 Since muscles spindles have two independent gamma motor supplies in addition to the alpha motor supply
to the parent muscles they can activate muscle spindles independently of the parent muscle. In general the
static gamma motor supply determines the amount of movement, and the dynamic gamma motor supply
determines the rate of movement. This duel organization allows for simulation since monitoring parent muscle
movement and maintaining muscle tone could be accomplished with a simpler arrangement.
 The parallel processes of the nervous system that synchronously mesh together precisely in accord with the
way that System 4 works are very complex. Before we begin a simplified review of the synchronous System 4
transformations is in order, since they are quite complex as well.

Review of System 4 Transformations as Outlined in Part 1:
  As illustrated in Part 1, in System 4 there are three Particular Sets of active energy interfaces that transform
through a Six Step Sequence of different Terms, each set transforming through the same Term sequence
one Step apart. Particular Terms also have Expressive and Regenerative Modes that interact in the
synchronous matrix of transformations that is regulated and integrated by two Universal Sets in recurrent four
step Cycles. There are thus 12 Steps needed to complete both an expressive and a regenerative sequence.

Chart Summary of Twelve Step Sequence:
  The following chart from Part 1 is reproduced here for easier reference. Expressive and regenerative
particular terms, as well as universal terms, are shown for each sequential Step. Regenerative Terms are
shown in bold. For an explanation of how the Universal Terms work see Part 1.

Keep in mind that in general each System 4 Step corresponds to a synapse in the nervous system.

Step        Set 1        Set 2        Set 3        Set U1       Set U2        Cycle
1             T8E          T7R          T4E          T9             T3               #1
2             T5E          T1R          T2E          T9             T6
3             T7E          T4R          T8E          T8R           T6
4             T1E          T2R          T5R          T8R           T2E
5             T4E          T8E          T7R          T9             T3               #2
6             T2E          T5E          T1R          T9             T6
7             T8E          T7E          T4R          T8R           T6
8             T5R          T1E          T2R          T8R           T2E
9             T7R          T4E          T8E          T9             T3               #3
10           T1R          T2E          T5E          T9             T6
11           T4R          T8E          T7E          T8R           T6
12           T2R          T5R          T1E          T8R           T2E
Gross Anatomy of the Cerebellum:
  The hemispheres of the cerebellar cortex evolved in three major steps, analogous to the way the cerebral
hemispheres evolved. The most ancient is the vestibular cortex that appeared with fish and amphibians. The
spino-cerebellum developed mainly with the reptiles, and the neo-cerebellum expanded bilaterally into the
cerebellar hemispheres, mainly with the mammals.
 There are two homunculi topologically represented in the cerebellum, one being inverted upside down to the
other. One of them is represented in two halves, one for each half of the body. Their most central portions,
concerned with trunk movements, are represented in the middle portion, part of the spino-cerebellum. The
limbs of the homunculi extend bilaterally laterally through the intermediate zones into the cerebro-cerebellum.
This is especially important for the control of fine movements of the hands and fingers.
There are lateral ridges called folia that transverse the whole cortex, and their internal structure is similar
throughout. See the illustrations of the Cerebellum Cortex below. The cerebellum receives widespread input
from throughout the central nervous system. Inputs from different sources project preferentially to specific
areas of the cortex, with lesser projections to more widespread areas in some cases
General Cerebellar Inputs and Outputs(See Diagram of Cerebellar Cortex below):
  There are two general types of input to the cerebellar cortex, either by mossy fibers or climbing fibers. Mossy
fiber inputs arise from throughout the body and cerebral hemispheres. They have many collateral branches
that project to widely distributed areas of the cerebellar cortex. They always synapse with Granule cells first,
which synapse in turn with Purkinje cells which are the sole output from the Cerebellar Cortex.
 Climbing fibers originate only in the inferior olive, a major brain stem structure, and they have a very specific
pattern of projection directly to Purkinje cells. All Purkinje cells have an inhibitory output and they project back
either to four deep nuclei in the cerebellum or, in the case of the vestibular areas of the cerebellar cortex, to
four corresponding vestibular nuclei.
 The inferior Olive receives inputs from the cerebral cortex (via the red nucleus), nerves of the face,
proprioceptive sensory input from throughout the spinal cord, vestibular input from the vestibular nuclei and
inputs from various other sources. The inferior olive is a fairly complex structure in itself and climbing fibers
project in a highly specific way. Each climbing fiber projects to no more than 10 Purkinje cells in the cerebellar
cortex, and each Purkinje cell receives input from only one climbing fiber, albeit with a great many synapses.
 Apart from sparse and diffuse inputs from two other minor sources ALL other projections to the cerebellum
arrive via widely branched mossy fibers. There are major projections from the Cerebral Cortex that are also
relayed via one synapse, in Pontine nuclei of the brain-stem, to the cerebellar cortex via mossy fibers.
In general, both mossy and climbing fiber projections to the cortex of the cerebellum have collateral
projections to the deep cerebellar nuclei, or in the case of the vestibular system to the vestibular nuclei.

Cerebellum Cortex:
  The cortex of the cerebellum has an unusual organization. It has only three 3 layers containing 5 cell types,
and four of them are inhibitory, including output from Purkinje cells, which is the only output from the
cerebellar cortex. This strange situation has suggested to neural biologists that the cerebellum sculpts out a
result, rather than producing it directly by excitation, but it is not known how it works as a whole in a
meaningful way. In the diagram below note the following:
  • There are only five cell types organized in three cortical layers.
  • Spinal sensory and proprioceptive inputs come via widely branched Mossy fibers.
  • Sensory and motor centers of the brain also input via Mossy fibers through a relay in Pontine nuclei.
  • Vestibular inputs come via Mossy fibers.
  • There are also spinal, cerebral and vestibular inputs to the inferior olive.
  • Mossy fibers terminate in large endings that synapse with a number of Granule cells.
  • Granule cells have very long axons that run parallel through the Folia ridges of the cortex.
  • Granule cells synapse with hundreds of Purkinje cells.
  • Purkinje cells are inhibitory and are the sole output of the cerebellum cortex.
  • Climbing fibers originate in the inferior olive and project to no more than ten Purkinje cells.
  • Each Purkinje cell receives input from only one climbing fiber.
  • All cerebellar cortical cells are inhibitory except Granule cells.
  • Granule cells are the most populous in the human body (some 100 billion).

Note: Since the only possible output from the cerebellum is inhibitory it can not be considered as a System 4
Step. It either sculpts away from the pattern of collateral inputs to the vestibular and deep nuclei, modifying
their outputs in this way, or it remains neutral and does nothing. We shall see that this is very important.
 The cerebellar cortical output projects via Purkinje cells back to four deep nuclei within the cerebellum.
Inputs to the cerebellar cortex also send collateral branches to the deep nuclei so that the cortex itself is
bridged by inputs and outputs. The inputs are excitatory, and the outputs are inhibitory, so processes in the
cortex sculpt away conflicting input to the deep nuclei. They are very active centers that reconcile inputs from
parallel particular sets of System 4, Step by Step and synapse by synapse. But first let us review the actions
of each of the five cell types in the cerebellar cortex.

Purkinje Cells:
  Purkinje cells have huge dendritic trees that accommodate hundreds of thousands of synaptic inputs and yet
they have a single inhibitory output to targets in one of the four deep nuclei inside the cerebellum or to
corresponding vestibular nuclei. They also have collateral outputs to Golgi cells that inhibit Granule cells.
 Purkinje cell bodies are located in the middle layer of the cerebellar cortex and the dendritic tree of each is
arranged in a two dimensional plane that extends into the outer Molecular Layer of the cortex. The dendritic
trees are thus stacked like plates in rows. The only direct input they receive from outside the cortex comes via
climbing fibers from the inferior olive. All other synaptic inputs to the Purkinje cells require two synapses within
the cerebellar cortex, the first being mossy fiber projections to Granule cells. Except for Granule cells, all
synapses to Purkinje cells are inhibitory and so is there output.

Granule Cells:
  The most inner layer of the cortex is called the Granular Layer. Granule cells are the most populous in the
human body. The granular layer contains some 100 billion of them, about as many as the rest of the cells in
the entire brain. They are activated by a number of mossy fiber pathways which branch widely to many
Granule cells, even in adjacent folia.
 Granule cells have excitatory outputs that project to the outermost Molecular Layer of the cortex, where their
axons divide into parallel fibers running longitudinally in both directions for long distances across the stacked
rows of dendritic trees of the Purkinje cells. In this way one Granule cell can synapse with hundreds of
Purkinje cells. Also the parallel fibers from Granule cells overlap so one Purkinje cell can receive synapses
from as many as a couple hundred thousand parallel Granule axons. The axons of Granule cells project
longitudinally along the folia of the cerebellum, that is, along the folds that run laterally across the cerebellum.
Since the Purkinje cells are stacked like rows of two dimensional plates across the longitudinal axis of each
folia, this simple arrangement can accommodate an incredible wealth of diverse inputs.   

Stellate, and Basket Cells:
  The remaining three kinds of inter-neurons are all inhibitory, and they all receive inputs from Granule cells.
Stellate cells synapse on the dendrites of Purkinje cells. Basket cells synapse on the cell bodies of Purkinje
cells and thus have a stronger inhibitory influence on this the only cell that produces an output from the
cerebellar cortex. Since their inhibitory action occurs one Step after that of the Granule cell that results in an
inhibitory Purkinje cell output, the Purkinje cell tends to be neutralized in the following Step.

Golgi Cells:
  Golgi inter-neuron cells can receive synaptic input from three sources: (1) from collateral branches of mossy
fibers that project to Granule cells, (2) from collateral branches of Granule cells themselves, and (3) from
collateral outputs from Purkinje cells that synapse on their cell bodies.
 All Golgi cells project to inhibit Granule cells. Their dendrites branch tree-like to occupy a volume of the outer
Molecular Layer of the Cerebellar cortex where they receive input from many Granule parallel fibers. Their
axons also project tree-like into the Granular layer where they can synapse to inhibit  a volume of Granule
cells. Their axons do not synapse with the same pattern of Granule cells as their dendrites however, since the
parallel axon fibers of the Granule cells travel long distances as compared with their dendrites.
 Synapses on Golgi cells can have differently patterned effects, depending upon the source from which they
are activated or inhibited. When they are activated by mossy fibers in parallel with Granule cells, they
feedback most quickly to inhibit a volume of Granule cells, one System 4 Step later. Affected Granule cells in
this case get a chance to fire during only one System 4 synchronous Step, being inhibited in the next Step.
 This can have a synchronous reinforcing effect with basket and stellate inhibition of Purkinje cells as
described above. There will be overlap here in the pattern of Purkinje cells affected but the patterns will not be
identical. Since the stelate and basket cells are activated by parallel granule fibers their input can come from
broad areas on the cortex, whereas Golgi cell activation in this case comes directly from mossy fiber input,
which will be more specific for specific Golgi cells.    
 For example, if we are considering an initial mossy fiber input that originates from spinal proprioceptive
feedback that input may result in an inhibitory output from a Purkinje cell two Steps later. But in the following
Step, which may originate from a cerebral projection via the pontine nuclei the same spinal proprioceptive
input can feed forward, via synapses on Golgi cells, to inhibit the Granule cells involved in the Cerebral
System 4 sequence that follows one Step later. This feed forward from the spinal input will tend to prevent an
inhibitory output from the same or different Purkinje cells in the Cerebral System 4 sequence. This may or may
not reinforce the pattern of activity originating from the cerebral motor cortex, but it does contribute to
reconciliation between Spinal and Cerebral inputs in those areas of the cerebellar cortex where they overlap.
 When Golgi cells are activated by a volume of parallel fibers from Granule cells they feed back from broad
areas of the cortex to inhibit a related but smaller patterned volume of Granule cells one System 4 Step later.
(Because their dendritic trees synapse with parallel Granule fibers and their axon trees project to a more
limited volume of Granule cells.) In some affected Granule cells this can also have a synchronous reinforcing
effect with stellate and basket cells as above, but there can be mutual overlaps and exclusions in the pattern
of projections from different Golgi cells back to different Granule cells. These overlaps and exclusions can
further facilitate the mutual reconciliation of divergent inputs originating from the  Cerebral Hemispheres and
from sensory and proprioceptive spinal feedback. This feedback also functions as a feed forward mechanism,
since a Cerebral pattern of Granule cell activity can influence a Spinal pattern that follows one Step later, and
vice-versa.
 When Golgi cells receive a strong collateral inhibitory projection from Purkinje cells on their cell bodies, they
are strongly inhibited from acting, and the volume of Granule cells they synapse with are thus not inhibited for
that Step which is either one or two Steps after the initial pattern of synapses in the cerebellar cortex
depending whether that input came via mossy or climbing fibers. This inhibitory influence on Golgi cells is
more selective, since Purkinje output is more selective. This can fine tune the reconciliation between inputs
from the cerebral hemispheres with those from the spinal column and vestibular system both by mossy and
climbing fiber inputs.
 With these introductory formalities dispensed with we will proceed to the meat of the business.
Mossy Fiber Inputs:
(Adapted from Nieuwenhuys.Voogd.van Huijzen The Human Central Nervous System, Springer Verlag 1990)
Illustration adapted from J. H Martin, Neuroanatomy, Elsevier 1991.
Adapted from R.M. Berne, M.N. Levy, Physiology, Mosby-Year Book Inc., 1993.
(Adapted from Nieuwenhuys.Voogd.van Huijzen The Human Central Nervous System, Springer Verlag 1990)
INTRODUCTION:
  The cerebellum is widely interconnected with the central nervous system and is primarily concerned with the
interconnections of these various pathways have been diligently mapped to a good degree, an understanding
interconnections of these various pathways have been diligently mapped to a good degree, an understanding
of how they work together as an integrated whole has remained elusive. The pieces of the jigsaw puzzle are all
laid out on the table but without the picture on the cover of the box one hardly knows where to begin to put
them together. In what follows it will be shown that System 4 can provide an overall picture as to how they fit. It
can offer a solution to this vexing and complex challenge.
can offer a solution to this vexing and complex challenge.

 First we will review from Part 1 some observations on how the proprioceptive nervous system works at the
spinal level via input from muscle spindles, since this is very relevant. Next we will explore the structure of the
cerebellum with some general observations on how it works within itself. Then we will explore the main pathways
to and from the cerebellum. In Part 1 it was shown how System 4 works at the spinal level. Here in Part 2 we will
see how spinal, vestibular and cerebral processes are mutually reconciled by the cerebellum.
 The cerebellum can be regarded as something of a pilot that navigates the immensely complex jungle of  
interconnected neural pathways within us according to our over-riding instructions from the control tower.

Note: A review of System 4 Terms will be very helpful in what follows.
The Human Nervous System - Part 2 - The Cerebellum
By Robert Campbell 2006
General Meanings of Each Term:
  For simplicity the Universal Terms will not be considered below. There are Cycles within Cycles and the
descriptions in Part 1 should be sufficient to give an overall idea. Note that meanings must be interpreted in
context. They are listed here as they apply to sensory and motor relationships at the spinal level. In their
projections to brain stem, cerebellar and cerebral levels they continue to represent these direct spinal
characteristics but obviously the representations do not relate directly to the environment. The
representations become neural abstractions of spinal processes. See Part 1 for more information on how
these meanings are generated by System 4.
    T1 - Perception of need in relation to response capacity.
    T4 - Ordered sensory input alternately from the environment and simulated.
    T2 - Creation of idea as a potential action response or creative concept.
    T8 - Balanced response to sensory input stimuli as a motor output to muscles.
    T5 - Action sequence of muscular activity with proprioceptive feedback.
    T7 - Sequence encoded as a unit memory simultaneous with recall to T1 and another sequence.
 With this background knowledge of System 4 clearly in mind, it is possible to follow through the neural
circuitry involved in the integration of behavior synapse by synapse. The main focus here is on how the
cerebellum works to reconcile spinal behavior with vestibular input and conscious cerebral intention. With
sufficient patient study the meaningful operation of the nervous system is rendered transparent. The
illustrations of neural anatomy are essential to understanding the text.
MAIN PATHWAYS TO AND FROM THE CEREBELLUM:

  The main pathways to and from the cerebellum will be explored in three main sections as listed below. The
first area to investigate is the vestibular system which can function directly via parallel routes that do not involve
the cerebellum, so we will investigate this first then proceed to routes that do involve the cerebellum.

  • The Vestibular System:
    We will begin with the vestibular system essential to balance which also implicates the visual sense and
    proprioceptive spinal input. We will consider it via the various pathways involved in the following:
  1.  Vestibular integration with eye, head and body movement.
  2.  Vestibular projections to the cerebral hemispheres.
  3.  Vestibular integration via the cerebellum.
  1. Direct projection by-passing the vestibular nuclei
  2. Projection via the vestibular nuclei.

  • Pathways to the Cerebellum via the Inferior Olive:
  1. Pathways originating in the spinal levels.
  2. Pathways originating in the vestibular system.

  • Cerebral pathways to and from the Cerebellum

THE VESTIBULAR SYSTEM

Primary Sensory Organs:
  There are two types of hair cells in the semi-circular canals of the ear that have active membrane potentials.
They discharge in the same way as a neuron but in response to fluid motion in the semi-circular canals. The
two types are similar in structure to the two types of cochlear hair cells involved in hearing. In these vestibular
sensory organs most of the output comes from Type 1 cells with intermittent output from Type 2 cells. Both
types of cells discharge across a synapse to primary neurons that project to the four vestibular nuclei with
collateral branches that project directly to the ancient vestibular areas of the cerebellum.
 The collateral branches of the primary neurons synapse directly with Granule cells in the vestibular areas of
the Cerebellar Cortex called the nodulus and flocculous. They also project to the Fastigial Nucleus of the
cerebellum and to the Nucleus Cuneatus. The latter nucleus relays spinal proprioceptive sensory feedback for
the upper body via a synapse in the thalamus to the Primary Sensory Cerebral Cortex, so direct vestibular
input can influence this. (Vestibular primary neurons correspond to spinal secondary neurons. Hair cells work the same as neurons.)  
  Both types of hair cells receive efferent projections via the eighth cranial nerve that arise in the reticular
formation. In Type 1 cells the efferent axons synapse with the primary afferent nerve endings that engulf the
body of each hair cell like a cup. In Type 2 cells the afferent nerve endings via the cranial nerve synapse
directly on the body of the hair cells and activate them directly. This direct activation indicates relative
movement of some kind that is more than an automatic reaction to fluid motion in the semicircular canals.
 The relative function of the two types of hair cells is not well understood and this structure suggests that
together they have a regenerative and an expressive role. There is evidence that efferent projections to the
afferent endings on Type 1 hair cells stalls  their activation while the opposite is true on Type 2 hair cells. This
can facilitate alternate expressive and regenerative sequences of System 4. We know from personal
experience, for example, that when we struggle to correct for sensations of vertigo or imbalance that there is an
anticipated, although tentative, sensation of proper balance that guides our efforts at corrective action. This
anticipated sense of balance is evidence of a regenerative input. Without it the body is left victim to blind
reactionary forces. (See the diagrams below:)
In both types of hair cells when the stereocilia are bent
towards the kinocilium the hair cell is depolarized and the
fiber is excited. When the stereocilia are bent away from
the kinocilium the hair cell is hyper-polarized and the
discharge slows or stops. These structures together with
the structure of the kinocilium below suggest that the
kinocilium of the Type 2 hair cells can move with respect
to the stereocilia independently of fluid motion in the
semi-circular canals to simulate a regenerative sensory
afferent output designated as T4R.
Illustrations adapted from R.M. Berne, M.N. Levy,
Physiology, Mosby-Year Book Inc., 1993.
The kinocilium:
  Vestibular hair cells differ from auditory hair cells in that each one has one kinocilium in addition to a number
of stereocilia. The kinocilium is a true cilium made up of nine sets of two microtubues arranged in a circle, with
an additional pair in the center. Whether or not the hair cell depolarizes and fires depends upon the relative
position between the stereocilia and the kinocilium. The kinocilium is similar in structure to the motile cilia that
mobilize protists. It is thus reasonable to expect that it can move independently of the stereorcilia to regulate
expressive and regenerative modes of firing. It should further be noted that System 4 subsumes System 5,
which consists of two sets of nine terms, one regenerative and one expressive, with two primary universal terms
regulating the alternations between them. (For example the two divisions of the autonomic nervous system
correspond to an expressive sympathetic mode and a regenerative parasympathetic mode, each with
expressive and regenerative sequences reciprocating within them, consistent with System 5. System 5
elaborates on System 4.)
The above diagram illustrates the structure of a cilium. They occur widely in many applications from clearing
the lungs of inhaled debris to propelling single celled protists. Note that in this diagram of a cilium that propels
a one-celled animal the cilium corresponds to a System 5 structure while the basal body corresponds to the
three cycles of System 4 which subsume System 5. The basal body is similar in structure to the centrioles that
regulate cell division in eukaryotic cells.
Adapted from Life:The Science of Biology, W.K. Purves et al, Sinauer Associates,
W.H Freeman, 1998
The Regenerative & Expressive Sequences of System 4:
  Projections to the hair cells initiate in the reticular formation that is concerned among other things with
conscious arousal. Arousal in this context can be synonymous either with the regenerative recall term T7R or
the expressive recall term T7E. The efferent regenerative projection in the following System 4 Step is T1R
which represents a pattern of motor simulation which projects to the hair cells. Type 1 cells may be
synchronously stalled by this projection while the synapse to Type 2 cells initiates a simulation of corrective
balance in a T4R term (analogous to the regenerative simulations in muscle spindles). The relationship
between the two hair cell projections represents the regenerative corrective balance. The efferent expressive
projection to hair cells T1E assesses the tonus and membrane potentials for a conditioned pattern of T4E
sensory input that follows. We thus have a situation where T4E terms alternate with T4R Terms in the
relationship between the two hair cell types, consistent with how System 4 works.
The Four Vestibular Nuclei:
 The four nuclei are called superior, lateral, medial and inferior. The nuclei receive sensory and proprioceptive
feedback from all spinal levels in addition to primary input from hair cells and feedback from the cerebellum. The
input from hair cells projects most densely to the superior, medial, and inferior nuclei, which are reciprocally related
by interneurons and also with their counterparts on the other side of the body.
 The lateral nucleus gives rise to the uncrossed lateral vestibular spinal tract that influences body movement at all
spinal levels. The lateral, medial and superior nuclei initiate the main projections via the thalamus to the primary
sensory cortex of the cerebrum to provide a conscious sensation of balance. The superior, medial and inferior
nuclei project bilaterally via the Medial Longitudinal Fasciculus (MLF) to the nerve centers that control eye
movement and the muscles of the neck and upper back. The muscles of the neck and upper back are also
supplied by the lateral vestibular spinal tract so there are inputs from two vestibular nuclei sources. The muscles of
the neck are also richly represented with muscle spindles for proprioceptive feedback to the vestibular nuclei.
 The vestibular nuclei also project directly to the cerebellum as well as via a collateral synapse in the inferior olive
to the cerebellum.  

Three Main Vestibular Outputs:
The vestibular nuclei project to three main destinations:
    A.   The spinal cord for influencing body, head, and eye movement.
    B.   The sensory cerebral cortex via the thalamus.
    C.   The cerebellum, both directly and via the inferior olive.

       Some primary neurons excited by hair cells project directly to the vestibular areas of the cerebellum. These
mossy fiber inputs to the cerebellar cortex have collateral branches to the Fastigial nucleus, one of four deep
nuclei in the cerebellum that are analogous to the four vestibular nuclei. Two synapses later Purkinje cells in the
cortex project a pattern of inhibition back to the Fastigial nucleus. Vestibular inputs to the cerebellum thus bridge
the cerebellar cortex as do inputs from other sources.
 Purkinje cells of the vestibular cerebellum and vermal spinocerebellum project to the lateral vestibular nucleus.
They also project to the Fastigial nucleus which in turn projects to the lateral vestibular nucleus as well as to the
pontine reticular formation. These outputs thus influence axial and proximal limb muscles by way of the lateral
vestibulospinal and pontine reticulospinal tracts of the medial motor projection system.
Adapted from Life:The Science of Biology, W.K. Purves et al, Sinauer Associates, W.H Freeman, 1998
C-2.) Vestibular Projections via the Vestibular Nuclei:
  Consistent with comments above, for the sake of simplicity, for the time being let us assume that the primary
projections to the vestibular nuclei are an expressive mode of System 4 that alternates with the regenerative
mode in 3a) above. If there is a parallel regenerative projection to the vestibular nuclei it is easy enough to
follow by simply substituting the vestibular nuclei for the Fastigial nucleus in the description above. We will
come back to this later. As mentioned the general pattern is analogous to the way the expressive and
regenerative modes work via muscle spindles at the spinal level. Later we shall see that there are
complementary pathways via the inferior olive.
 Allowing alternating sequences in hair cells as well as for one synapse in the vestibular nuclei, this means that
there is an expressive sequence via the vestibular nuclei alternating with a direct regenerative sequence
projecting to the cerebellum every two Steps. Since the projection via granule cells to inhibitory Purkinje
feedback to the Fastigial nucleus takes two Steps this facilitates the reconciliation of the expressive and
regenerative modes. Purkinje inhibition from an expressive sequence modifies a regenerative pattern and vice
versa. It moderates the transitions between modes into smooth patterns of motor projection. In the case of a
parallel regenerative sequence via the vestibular nuclei it works in an identical way except that the Purkinje
projection is back to the vestibular nuclei rather than to the Fastigial nucleus.
 The vestibular nuclei play a similar role to the Fastigial nucleus in this expressive sequence as compared with
the regenerative sequence. There are various alternatives possible in some portions of the vestibular system
as opposed to other portions, affecting some motor projections in different ways than others, although they all
conform to the way System 4 works. This can direct experimental work to investigate the possible expressive
and regenerative alternatives. For now we will focus only on the expressive mode through the vestibular nuclei
as follows:    

  • T7E – Patterns of expressive recall T7E arouse in the reticular formation. (Step 3 of a Cycle)
  • T1E – Preparedness of cells to respond to needs by efferent projections to hair cells in Step 4.
  • T4E – Expressive sensory input from hair cells synapse with primary neurons in Step 1.
  • T2E – Primary neurons project mostly to the superior, medial and inferior vestibular nuclei, but also to
    the lateral nucleus in Step 2. The lateral nucleus also receives spinal T2 proprioceptive sensory inputs
    from the spinal dorsal horns.
  • T8E – Motor outputs from the lateral nucleus project via the lateral vestibulospinal tract to the motor
    areas at all spinal levels. The superior, medial and inferior nuclei project via the medial longitudinal
    fasciculus (MLF) to eye and neck motor nuclei. Motor outputs project to the inferior olive and also via
    mossy fibers to the cerebellar cortex. Both of these latter projections to the cerebellum result in a pattern
    of Purkinje inhibitory feedback two steps later. This reconciles expressive and regenerative motor
    projections from the vestibular nuclei,since they alternate every two System 4 Steps.
  • T5R – The motor projections T8E via the lateral vestibulospinal tract synapse in the spinal motor horns
    throughout the cord. As before the T8E reticulated motor pattern projections coincide with T2
    interneuron inputs to the motor cells in the ventral horns. These motor cells must reconcile these inputs
    from different sources  that project as T8E Terms in the final spinal motor projection to the skeletal
    muscles. This is the same as with the descending cerebral motor projection T8E described for the
    regenerative sequence above, but it follows two Steps later. Direct Motor projections from the Primary
    Motor Cortex of the cerebral hemispheres also project to the ventral horns as T8E Terms. Both have
    priority over the T2 spinal interneuron projection from the dorsal horn as pointed out above. We may
    stumble when walking but vestibular balance will tend to prevail over the next automated step and
    conscious intension quickly follows in a later sequence.  
  • T7R – The vestibular and cerebellar sequence Steps are recorded in memory both in the Void and as
    protein synthesis in the dendrite and axon connections of related sequence cells, as a regenerative
    sequence follows as outlined above. Learning through experience elaborates on synaptic connections
    that reflect our remembered ability to perform in specific patterns.

 The pattern of inhibitory output of Purkinje cells back to the vestibular nuclei is thus similar to the regenerative
sequence where they project back to the Fastigial nucleus. The inhibitory Purkinje output likewise carves away
from the T2E projections originating from hair cells and muscle spindles alike to the vestibular nuclei in the
expressive sequence Steps just as it does in the regenerative sequence Steps to the Fastigial nucleus.
Purkinje cells in part of the Vermis area of the cerebellum project back to the lateral vestibular nucleus that
gives rise to the lateral vestibulospinal motor tract that projects as a T8E Term to all spinal levels. Purkinje cells
in the nodulus and floccuus areas of the cerebellar cortex project to back to the superior, medial and inferior
vestibular nuclei. Together these nuclei project as T8E terms to both the ascending and descending medial
longitudinal tracts (MLF) as outlined in Section A above.
THE INFERIOR OLIVE - CEREBELLUM CONNECTIONS:

Projections to the Inferior Olive:
The inferior olive is a major structure in the brain stem that receives inputs from the following two main sources:
  1. Collaterals of spinal somatic and proprioceptive sensory input from all levels. These all initiate in the PNS
    as T4 sensory input Terms of System 4 and project as T2 idea Terms to the inferior olive via a single
    synapse.
  2. Collaterals from the superior, medial and inferior vestibular nuclei arise as T4 sensory Terms from hair
    cells that project as T2 idea Terms to vestibular nuclei. They then project as T8E motor terms to the
    inferior olive.

Climbing Fiber Projections from Inferior Olive to Purkinje Cells & Deep Nuclei:
  The inferior olive projects via climbing fibers directly to Purkinje cells in nearly all areas of the cerebellar cortex
with collateral projections to all four deep cerebellar nuclei. However it projects preferentially from specific olive
nuclei to the Vermis cortex, the Intermediate cortex, and the Cerebrocerebellar cortex. The respective collateral
branches project to the Fastigial nucleus, the Globus & Emboliform nuclei, and the Dentate nucleus. Since
Purkinje cells project back to these nuclei the cortex is bridged in a single Step as compared to two Steps via
mossy fibers.

1. Spinal System 4 Steps via Inferior Olive:
  Sensory input from the spinal level comes once in each System 4 Step of each Cycle from one of the three
Particular Sets. (See Chart above or Part 1.). Sensory input from the head does not use the spinal nerves but it
follows analogous pathways. In Step 1 of each Cycle it is always Somatic sensory input associated with touch,
pain, temperature. Proprioceptive feedback from muscle spindles comes in Steps 2, 3, & 4 of each spinal Cycle
and the nature of its origin is determined only by which Step it is in. For example proprioceptive simulation of an
action sequence always takes place in Step 3 of each Cycle. In Step 2 input from muscle spindles is generated
by an expressive muscle action sequence and in Step 4 by a regenerative muscle action sequence, but it still
comes from the same muscle spindles. These latter two are also sensory inputs and so far as higher centers are
concerned they are represented by T4 Terms, whereas at the spinal level they are represented by a specific
Relation Whole in the T5 Term providing direct sensory feedback that monitors muscle action in this spinal
context. (See Part 1) Although the specific expressive or regenerative nature of the proprioceptive sensory inputs
to the inferior olive may not seem very significant, in a later section we shall see that they are. In this section, it is
very significant with respect to the Fastigial nucleus as pointed out below. With these observations in mind the
sensory inputs to the inferior olive corresponds to the following system 4 sequence Steps.

  • T1 – Restoration of action potentials T1E occurs in Step 4 of each Cycle in readiness for a new sequence
    pattern at the beginning of the next Cycle. This is synchronous in both the spinal and vestibular pathways.
    In Step 2 of each Cycle in one Particular Set there is a Gamma T1R motor simulation projecting to muscles
    spindles (See Part 1). In the same Step there is also an efferent motor simulation projecting to hair cells.
    Both simulations arise as a pattern of spontaneous recall in the reticular system. We will look at the
    vestibular-olive projections in Section 2 below.   
  • T4 – In Step 1 of each Cycle primary somatic input from the PNS synapses in the CNS. In Steps 2, 3, & 4,
    proprioceptive sensory neurons project from muscle spindles in the PNS to a synapse in the CNS.
  • T2 – Collaterals of all secondary sensory neurons from the first CNS synapse, project to the inferior olive in
    each Step of each Cycle. Note that secondary neurons from spinal levels also project via mossy fibers
    directly to the cerebellar cortex with collaterals to the deep nuclei in each Step, but one Step ahead of
    projections to the cerebellar cortex via the Olive route. This is very significant, since Purkinje inhibitory
    feedback is very specific and comes in one Step via the climbing fiber route and in two Steps via the mossy
    fiber route which is more widely dispersed. This means that the respective patterns of Purkinje cell
    inhibition back to the deep nuclei are synchronous between mossy and climbing fibers. They arrive back at
    the deep nuclei together to simultaneously influence the patterns of projection from them.
  • T8E – The Inferior Olive projects to Purkinje cells in a highly specific manner with collateral projections to
    the deep cerebellar nuclei. Purkinje cells project via this route back to the deep nuclei in one Step. They
    inhibit to carve a pattern of motor projections from the affected nuclei one Step later. Although mossy fiber
    projections get to the cortex one Step ahead of Inferior Olive projections, it takes two Steps to generate a
    more widely dispersed pattern of Purkinje cell inhibition back to the deep nuclei. The mossy fiber
    projections integrate more diverse areas of the body in more general ways. Note that the collateral T8E
    projection to the Fastigial nucleus in Step 3 originates from an expressive somatic sensory input sequence
    and it is synchronous with a direct T2R vestibular-Fastigial input from hair cells as outlined in C-1 above.
    They must find reconciliation in the pattern of projection from the Fastigial nucleus. This is essential
    because otherwise a conditioned pattern of expressive spinal responses would unilaterally prevail. This is
    strong evidence that the direct vestibular projection to the cerebellum that bypasses the vestibular nuclei is
    regenerative in this Step. The reverse is true in the following T8E Term two Steps later, because this spinal
    sequence originates in a pattern of regenerative muscle spindle simulations. This strongly indicates that
    the direct projection from vestibular hair cells is expressive in this Step. It also indicates that hair cell
    projections alternate between expressive and regenerative sequences in the pathway via the vestibular
    nuclei as well as via the pathway that bypasses them and projects directly to the Fastigial nucleus and
    cerebellum. This is very important.
  • T5 – All four deep nuclei project modified motor patterns ascending to motor, pre-motor and parietal areas
    of the cerebral cortex as well as to basal ganglia via one synapse in the thalamus. The thalamus is the final
    ascending T5 terminal in all these sequences.  Descending motor patterns project from the Fastigial
    nucleus to the reticular formation. It is reticulated via this multi-synaptic pathway to the motor areas of the
    entire spinal cord where it influences the final motor projection to skeletal muscles as before. This
    influence is delayed via the reticulation as compared with more direct routes via the vestibular nuclei. The
    reticulation can also influence the recall pattern of regenerative sequences in the next Step at various
    spinal levels.
  • T7 – The memory sequence is stored via protein synthesis elaborating on axon and dendrite
    interconnections between the cell processes involved in the whole sequence as well as in the Void as
    always. In the same Step appropriate related memories are recalled. In the expressive sequence the recall
    relates to the pattern of cells required in a conditioned response. In the regenerative sequence it relates to
    the pattern of cells needed in a motor simulation. This alternating pattern as it projects up to the cerebral
    hemispheres will be governed largely by the return path from earlier input to the cerebral cortex via direct
    mossy fiber input to the cerebellum to be described below.
  • T1 –  In the expressive mode the restoration of the action potentials in the spinal pattern of nerve and
    muscle cells needed is reflected as an ability to respond. The response capacity may be affected by their
    exhaustion, in extreme cases exhausting the whole person. In other cases the response capacity may be
    hyper-sensitized to conditioned patterns of recall depending upon general circumstances, as in facing
    threatening or pleasing events. In the regenerative sequence motor simulations are initiated from the
    reticular system. They project via efferent neurons to hair cells and also via gamma motor neurons to
    muscle spindles.
Climbing Fiber Interconnections via the Inferior Olive:
2. Vestibular System 4 Steps via the Inferior Olive:
  Projections from the vestibular nuclei with expressive and regenerative sequences arrive in the inferior olive as
T8E Terms in Steps 2 and 4 of each Cycle. For simplicity we will deal with them together here. The same terms
project as collaterals to the Fastigial nucleus which is closely associated with the vestibular system.  

  • T1 -  In Step 2 of each Cycle there is motor simulation projected to the hair cells that initiates a patterned
    simulation in the hair cells. In Step 4 of each Cycle the pattern of efferent projections to hair cells readies
    the next action sequence.  
  • T4 -  In Step 1 of each cycle the hair cells respond in the expressive sequence. Motion of the head produces
    a pattern of sensory input T4E to the vestibular nuclei that makes conditioned synapses there. In Step 3 the
    Type 2 hair cells simulate a corrective T4R response with respect to the Type 1 hair cells. The resulting
    pattern of synapses is not automatically conditioned but anticipates a better response pattern.
  • T2 - In Step 2 a conditioned pattern of response is projected to the vestibular nuclei as an expressive idea
    T2E. In Step 4 the T2R projection is a regenerative idea.
  • T8E - In the Particular Sequences the T8 Terms are always expressive since they all result in motor
    patterns. (Only the Primary Universal Set has a T8R Term. See Part 1) Projected motor patterns have either
    an expressive or a regenerative history however. They project to the inferior olive with a collateral projection
    to the Fastigial nucleus. We saw in the section above how the direct route bypassing the vestibular nuclei to
    the Fastigial nucleus synchronized in Steps 1 and 3 as expressive and regenerative inputs with alternate
    T2R and T2E projections from the spinal levels. Now, with one synapse in the vestibular nuclei, we find that
    this T8E projection has alternate expressive and regenerative histories. This complements proprioceptive
    sensory feedback to the Fastigial nucleus from muscle action terms having alternate expressive and
    regenerative histories and that input the Fastigial nucleus as T2R and T2E Terms respectively in Steps 2
    and 4.  Again we have a situation where expressive and regenerative modes must be mutually reconciled to
    result in smooth performance.
  • T5 -  From the synapse in the inferior olive there is a climbing fiber projection directly to the Purkinje cells in
    the vestibular areas of the cerebellar cortex. This is not a System 4 Step however since there is either no
    feedback from the Purkinje cell or inhibitory feedback, as mentioned previously. This feedback may be
    either to the Fastigial nucleus or to the vestibular nuclei depending on inputs. As feedback to the lateral
    vestibular nucleus it influences a modified pattern of motor projection that must find reconciliation with the
    T2 spinal inputs and T2 hair cell inputs to that nucleus that result in the T8E projections to the spinal nuclei
    via the lateral vestibular-spinal tract. This over-riding influence comes in a later sequence of projections
    than the initial inputs to the lateral nucleus however. Nevertheless the expressive or regenerative history of
    the T5 Term will require reconciliation with the alternate T2R and T2E Terms that project to the lateral
    nucleus from spinal muscle spindles as well as from hair cells. Terms 1, 2 and 5 always occur together and
    T2 and T5 are aways tensionally coupled.
  • T7 -  As usual the System 4 expressive and regenerative sequences contribute synaptic interconnections
    via protein synthesis associated with memory storage, as well as via the Void. A new but associated pattern
    of recall will be initiated via reticular system arousal. The pattern will be appropriate to new sensory input
    since Terms 8, 7 & 4 always occur together and T7 and T4 are tensionally coupled.   
Cerebellum Outputs:
(Adapted from Nieuwenhuys.Voogd.van Huijzen The Human Central Nervous System, Springer Verlag 1990)

CEREBRAL PATHWAYS TO AND FROM THE CEREBELLUM:

Return Pathways to the Cerebellum:
  The largest contingent of mossy fiber projections to the cerebellum comes from the Pontine nuclei which receive
somato-topically organized projections from the whole Cerebral Cortex. The densest projections come from the
following areas: the pre-motor area, the primary and secondary motor areas, the primary and secondary sensory
areas, and the sensory association areas. The pre-motor area integrates input to the topological motor areas, in a
similar way that the sensory association area integrates input to the topological sensory areas.
 They project to most areas of the cerebellum with the possible exception of the nodulus and they send collateral
fibers to the deep nuclei, especially the dentate nucleus. The somato-topical projections overlap with those from
spinal levels in the homunculi which extend into the lateral hemispheres of the cerebro-cerebellum. The dentate,
globose and emboliform nuclei project back via the thalamus to the cerebral cortex in a similar pattern to which
they arose. There are a total of six synapses involved in the return journey which correspond to the six sequential
Steps of System 4. The return feedback is thus positioned to influence integrated motor outputs from the cerebral
cortex one sequence later. Again this means that the expressive and regenerative modes must find reconciliation.

Cerebral Sensory Return Pathway:
  For example, output from the Primary Sensory Cortex represents either an expressive or regenerative T2 Idea
term following the assimilation of T4 sensory input to it from many sources via the parietal lobe. It projects to
synapse with the Primary Motor Cortex resulting in a descending motor pattern T8E. The parallel projection to the
Pontine nuclei also results in a pattern of T8E projection to the deep cerebellar nuclei with a collateral projection to
the granule cells of its cortex. Two Steps later a pattern of Purkinje inhibition projects back from the cortex to the
deep nuclei which now have received the next T8E projection from the Primary Sensory Cortex. This pattern of
inhibition modifies the latter input to the deep nuclei which project back as alternating T5R and T5E Terms to the
thalamus. The two Step inhibitory pathway means that alternating expressive and regenerative sequences must be
reconciled in the deep nuclei. The T5 projection to the thalamus results in a T7 Term, with the sequence stored as
protein synthesis as well as in the Void as described before. The pattern of recall at this point will be tensionally
coupled to the assimilation of sensory input T4 in the parietal sensory association area which supplies the Primary
Sensory Cortex. This pattern of spontaneous recall results in T1 projection from the thalamus back to the Primary
Sensory Cortex. Expressive and regenerative modes of T1 will alternate in this projection to synapse as either T2E
or T2R Terms back with the alternate mode of the T2 Term currently being formulated in the Primary Sensory
Cortex. In other words the regenerative and expressive modes find mutual reconciliation spanning one complete six
Step sequence. The anticipated idea pattern of regenerative action is thus reconciled smoothly with the
conditioned expressive idea pattern of action.

Cerebral Motor Return Pathway:
  We can follow input from the Primary Motor Cortex in the same way. It generates a T8E Term with either an
expressive or regenerative history which projects to the motor areas of the ventral spinal cord. The parallel
projection to the Pontine nuclei is also a T8E Term. This results, after the synapse, in a T5 Term projection to the
deep cerebellar nuclei and to the granule cells of its cortex. With the synapse in the deep nuclei the motor
sequence is recorded in memory as above, along with the spontaneous recall, T7, of a new pattern that is also
tensionally coupled to the T4 sensory association area of the parietal lobe. (The latter has intimate dense
projections to the pre-motor area which in turn projects as a T2 Term to the Primary Mortor Cortex resulting in the
initial T8E projections.)  The pattern of recall in the deep nuclei is thus very relevant to the assimilation of idea in
the Primary Sensory Cortex. It activates a pattern of T1 projection back to the thalamus. This can be either
expressive, preparing a conditioned pattern of related cells, or a regenerative simulation that more creatively
designates an original pattern. However the two Step pattern of Purkinje cell inhibition requires that the expressive
and regenerative sequences again be reconciled in the deep nuclei. The modified T1 pattern of projection to the
thalamus alternates between expressive and regenerative modes and it results in corresponding T2E and T2R
alternating projections back to the Primary Motor Cortex where they synapse to produce descending T8E motor
Terms to the spinal ventral horns, as well as another parallel sequence back to the cerebellum. In this way the
return input from the cerebellum to the Primary Motor Cortex complements the reconciled input from the Primary
Sensory Cortex and alternating T2E and T2R inputs to the Primary Motor Cortex.

Feed Forward and Feed Back Cerebellar Cortical Processes:
  The projections from the Primary Sensory Cortex come to the deep nuclei one sequence Step earlier and later
than those from the Primary Motor Nuclei, and vice versa. So the deep nuclei are only involved with one or the
other at the same time. In examining the cell structure of the cerebellar cortex above, we have seen that there are
feed back and feed forward processes at work within the cerebellar cortex. These processes can thus serve to
facilitate the sensory assimilation of an integrated idea with the motor execution of the plan.
 This has synchronous implications with inputs from other sources. For example spinal sensory input T4 arrives
after one CNS synapse as a T2 Term at the deep nuclei which results in a T8 motor projection back to spinal
levels. But projections from the Primary Sensory cortex to the deep nuclei arrive as T8 Terms, that is, one System
4 Step later that the T2 Term input from spinal levels. The feed back and/or feed forward synaptic processes within
the cortex can thus serve to reconcile spinal sensory inputs with those that have been integrated from prior
sequences in the Cerebral Hemispheres. This further facilitates smooth transitions from one action sequence to
the next, spanning sequential spatial orientation and increments of time.

Bilateral Integration:
  Cortical processes in the cerebellum can also facilitate the smooth bilateral integration of motor patterns as they
relate to the two sides of the body. This works in conjunction with interneuron connections between the vestibular
nuclei on the left and right sides of the body and likewise with the deep cerebellar nuclei on one side as opposed
to the other. Inputs to the cerebellum can be bilateral, contralateral or ipsilateral depending upon their source. But
in general the motor pattern on one side generally acts as a referent to the motor pattern on the other just as one
foot step takes the other foot as a point of departure in walking. The feedback and/or feed forward cortical
processes may be employed in this bi-lateral integration of behavior.
 Once one is familiar with the correspondence between System 4 and the way the nervous system has been
structured to function synapse by synapse, anyone with the patience can explore these and other pathways at
their leisure.

SUMMARY:
  The cerebral hemispheres invest us with conscious experience. It invests us with conscious knowledge of our
intuitive, rational and emotional experience. This general triadic organization corresponds with the right
hemisphere of the neo-cortex, the left hemisphere of the neo-cortex, and the ancient limbic cortex respectively.
There are commissures that connect the hemispheres of the neo-cortex and separate commissures that connect
the two hemispheres of the limbic cortex. (See Inside our Three Brains) Within each hemisphere there are both
primary and secondary sensory and motor areas that accommodate a self-similar arrangement of conscious
intuitive, rational and emotional experience within each hemisphere but subsumed within the over-riding context
each of these three focal points as they apply to the whole cortex.
 For example we can have socially oriented intuitions confined to the left brain that relate to rationalizations
employing language and that may result in explicit behavior. We can also seek holistic right brain intuitive insight
into the workings of the cerebral hemispheres that can find left brain expression as science. The former is confined
to the left brain, while the latter involves the integrated workings of the whole cortex. The main point here is that
the cerebral cortex is an instrument that allows us to consciously simulate experience in thought. This allows us to
span and integrate space-time events from practicing our golf swing to understanding our own historical evolution.
There has traditionally been a strong emphasis on dominant left brain social thinking as opposed to right brain
intuitive insight. The System however provides a paradigm as to how we can relate more constructively to our
social, spiritual and natural environments.  
 As we have seen the cerebellum reconciles cerebral processes with spinal and vestibular inputs, depending upon
our level of physical activity. There are also other primary sensory inputs to the process, including vision, hearing,
taste, and smell. System 4 can in some measure be applied to these sensory systems piecemeal synapse by
synapse although the higher systems are also involved, such as in generating virtual images in the vision process.
The autonomic nervous system also has sensory and motor neurons and System 4 can be applied to it piecemeal
as well. Its integration with the somatic nervous system involves System 5 at the limbic level, however. System 5
has twenty terms and is considerably more complex in the way it works as an elaboration of System 4. Virtual
images, whether visual, conceptual, intuitive or emotional, first appear in System 5.
 It should be mentioned that there are other variants to System 4 that we have not explored. The expressive and
regenerative variants involve Centers 1 and 2 changing places in the Particular Terms. There are expressive and
regenerative  involutionary variants also where Centers 3 and 4 change places in the Particular Terms. Values
become inverted. Processes of disease and decay are related to involutionary variants, but they are essential to
metabolism also. Other variants are possible but they have no conscious meaning. They can be related to sleep
and dream states.  
 The above should be sufficient to demonstrate the System as a new paradigm that can prove of great value in its
practical application to science.


Note: A few minor corrections were made on May 1, 2009.
Nervous System - Part 1 - Spinal Cord
System 4
System 4 Terms
Inside Our Three Brains
Nervous System - Part 1 - Spinal Cord
System 4
System 4 Terms
Inside Our Three Brains