I. Introduction. 2. The brain functions as a communication
system. 3. The brain functions as a gland, with neurotransmitters
and neuropeptides. 4. The brain functions as a system of adaptation. 5.
The brain controls emotions. Mood related to patho-physiology. 6.
The brain controls activity and behavior. Hypo-activity and
hyper-activity. 7. The nervous system is built on stimulus-response
mechanisms. 8. Biofeedback as a treatment modality in
neuropsychiatry. 9. Biofeedback as a treatment modality in
restorative neurology.
1. INTRODUCTION People commonly ask
the questions : "Why?", "How does a thing work?" and "How can I fix
it?". I do not attempt to answer "Why?" because it is a metaphysical
question. Much of this article answers the question of "How can I fix
it?". I shall mainly describe "How does the brain work?" which I
freely acknowledge is an immodest goal. The nervous system
is built upon a living network of feedback, constantly adapting to the
environment, both the internal and the external. The prefix"bio" in
biofeedback is semantically unnecessary since we are dealing with
systems during life. However, because of the historical use of
"biofeedback" as a treatment modality the term can be accepted.
Biofeedback is an important technique in the wide spectrum of
behavioral medicine. Behavior is the motor output of the nervous system
which depends upon the conscious and unconscious reception and
acceptance of stimuli by an individual. It is the response to a
continuous stream of stimuli in the waking and the sleeping state.
Biofeedback professionals learn the art of encouraging self-awareness
both of themselves and of their patients, in order for perception of
stimuli to be changed if desired. Therefore we need to become
more self-aware of the physiology that generates our behavior. We need
to harness our feedback forces, and to use the inherent physiological
mechanisms of feedback to the best advantage of ourselves and of those
whom we contact. Behavioral responses can be modified by the
way the individual perceives these incoming stimuli. Similar stimuli
are experienced differently by different people, and they also vary
according to the actual psycho-physiological state of the individual,
including their age and experiences. A.R. Luria in his
classic book "Higher Cortical Function in Man" analysed "the reflex
mechanisms by means of which the organism maintains its equilibrium with
the environment" and "the problem of the cerebral mechanisms of mental
activity". Replace the word "reflex" by "biofeedback" and we see how
we are perpetually studying these mechanisms. For an
excellent review of the central autonomic network (CAN), with its
functional organization and dysfunction, the reader is referred to the
article by Eduardo Benarroch (1993), (see Fig 1).
2. THE BRAIN
AS A COMMUNICATION SYSTEM The brain functions as a system for
communication over the entire body. The nervous system consists of a
CENTRAL part (the brain and the spinal cord) and a PERIPHERAL part
which comprises the nerves that arises from the brain and spinal cord.
These nerves supply the special senses, the musculature and the
sensation of the trunk and the four limbs. This chapter
deals with the central nervous system (CNS). It is a bilateral and in
many ways symmetrical group of structures consisting of 6 parts: (1)
the Spinal cord; (2) the Brain stem subdivided into 3 regions, the
midbrain, the pons and the medulla; (3) the Cerebellum, important for
modulating and co-ordinating motor movement together with (4) the Basal
ganglia, (the caudate nucleus, putamen and globus pallidus); (5) the
Diencephalon (the thalamus, hypothalamus, subthalamus, and epithalamus)
and (6) the Cerebral Hemispheres capped by the cerebral cortex or rind
with higher perceptual cognitive and motor functions, (Kandel). (see fig
2). The brain weighs 3 lbs. The spinal cord is like a tail arising
from the base of the brain and its thickness averages that of a human
finger. Broadly speaking the tasks of the brain can be
divided into three categories: (1) the RECEPTION OF STIMULI (this is
the sensory system); (2) the association of stimuli and the analysis
or PERCEPTION OF INCOMING STIMULI; and ( 3) the MOTOR RESPONSE to
those stimuli. These motor responses summate so as to constitute the
behavior of the individual. At the cellular level, sensory signals are
transformed into motor acts.
(1) The RECEPTION OF STIMULI by the
brain occurs via the AFFERENT PATHWAYS FOR SENSATION. (The
term"afferent" indicates travelling towards the brain, and "efferent"
travelling away from the brain.) The pathways for light touch,
(tickle), pain, pressure, heat, cold and vibration from the periphery to
the cerebral cortex are well-known and they do not vary significantly.
It is the conscious PERCEPTION by the individual of these stimuli
(when they reach the appropriate area of the cerebral cortex) which
varies constantly throughout life. In order to prevent
overloading of the individual by a continous stream of stimuli, the
nervous system has developed a variety of methods of INHIBITION.
Inhibition is an important neurological concept for biofeedback
professionals since learning how to inhibit sensations, thoughts or
behavior is basic in biofeedback training. Inhibition as applied to
synaptic transmission refers to an active process by which excitatory
transmission is prevented. Inhibition occurs in the CNS both before and
after the synapse ("pre-synaptic" and "post-synaptic"). A major
pre-synaptic neurotransmitter, which is inhibitory in many processes, is
gamma-amino-butyric-acid (GABA). In the thalamus (its nucleus is the
main way-station for sensation) there is both pre- and post-synaptic
inhibition. At higher levels in the brain, both in the cerebellum and in
the cerebral cortex, inhibition is mainly post-synaptic.
Inhibition can be directed from the cerebral cortex. Efferent pathways
from the sensori-motor cortex excite thalamo-cortical relay cells. By
exerting inhibition the cerebral cortex is able to block the synapses
and thus to protect itself from being stimulated by cutaneous stimuli;
it can neglect these stimuli. This happens for example when one is deep
in thought, preoccupied with an experience or intensely involved in
carrying out an action. Counter-irritation to relieve pain acts in this
way. Discharges from the cerebral cortex down the pyramidal tracts and
other pathways may exert an inhibitory blockage at the relays in the
spino-cortical pathways. This can inhibit unwanted motor movements.
INHIBITORY
FUNCTIONS OF THE CEREBELLUM. The cerebellum is the great
"smoother" of all motor activities. The Purkinje cells are large nerve
cells in the cerebellar cortex. The unique feature of the cerebellar
cortex is that its output is expressed entirely by the inhibitory
Purkinje cells. Nowhere else in the brain is inhibition so dominant.
How can information be conveyed effectively in this negative manner?
Because this inhibitory action is exerted on nuclear cells that have a
strong background discharge. Eccles gives the analogy of the
sculpture of stone. A sculptor has a block and achieves form by "taking
away" stone through chiselling. Similarly the Purkinje cells of the
cerebellum achieve form in the nuclear cell discharge by taking away
from the background discharges through the process of inhibition.
(2)
The association of stimuli and the analysis or PERCEPTION OF INCOMING
STIMULI is carried out in the cerebral hemispheres. Here memory,
judgement, thought association, verbal and non-verbal communication, the
emotional coloring of stimuli all combine to create the personal
interpretation of on-going stimuli. This is the meeting-ground which
regulates the psycho-physiology of the individual.
(3) THE MOTOR
RESPONSE TO THE STIMULI. This is the output of the brain, the efferent
system, via the pyramidal, extra-pyramidal and non-pyramidal pathways. These
responses require exquisite MOTOR COORDINATION. The CEREBELLUM is
concerned with the reliable and regulated control of movement. The
cerebellum is the part of the brain which through the process of
evolution has come to function as a special computer by handling all the
complex inputs from receptors or from other parts of the brain. The
articulation of speech is subserved by cerebellar mechanisms.
Let us visualize the neural events in the cerebro-cerebellar circuits
during a skilled action, such as running a machine at work or playing
the piano. There will be initially a motor command with a preprogramming
of the movements by circuits in the association cortex, cerebellum,
basal ganglia and thalamic nuclei. The learned skills are mobilized and
the discharge leads on to the action impulses in the pyramidal tract,
with the consequent report of the discharge to the part of the
cerebellar cortex receiving and projecting both to the cerebrum and the
spinal cord. Cerebral"willing" of a muscle movement sets in train
neural events that lead to the discharge of pyramidal cells.
There is a sequence of neuronal events, a chain reaction, such that one
part is called into operation (in the temporal or time sense) and this
leads other parts to go into action which generates further activity .
Since, however, all areas of the brain are constantly (and therefore
concurrently) active, many elements are carrying out their own intrinsic
activities (cross-talks between the cells) which are not apparent to an
outside observer; these do not impinge on the consciousness of the
individual concerned. It is clear, therefore, that a good deal of
cerebral activity goes unheeded by the originator and all observers.
Biofeedback treatment is based on learning. How does the brain as the
organ of communication bring about learning? The process of
learning consists of excluding from consciousness all stimuli except the
one which the individual chooses to focus upon, and to which his
attention is directed. The acquisition of new data thus involves a
process of selective listening and consists mainly of rejection or
ignoring of stimuli which are nonrelevant at that time.
Biofeedback consists of acquiring a technique for selective "listening"
to a particular set of stimuli, which may come from the external
environment or from inside the individual's own body (internal
environment) . The purpose of the technique is for the student to have
the ability to regulate psycho-physical function himself. In order to
acquire and to teach this technique, we have to know, first, the
GEOGRAPHY OF SPECIALIZED FUNCTIONING, meaning the localization within
the brain of neurons with specialized function. These neurons in
different parts of the brain vary greatly one from another. For example
they vary in size as a petunia varies from an oak tree, (Stevens).
Second, we have to understand the interconnections (neural connections)
or microstructural changes in SYNAPSES, linkages or pathways of the
brain, because this gives a basis of the HOW of behavior, both of the
patient and of ourselves. Third, we have to understand the concept of
EXCITATION and INHIBITION. The neurons are either excitatory or
inhibitory and/or secretory. When two parts of the brain (two neuronal
populations) interact, they may each exert an excitatory or an
inhibitory effect. A neuronal impulse may release a
neurotransmitter which excites or inhibits. If one part fails to act,
there is uncontrolled or deafferented functioning of neurones, because
they are lacking their accustomed stimulation or input.
NEURONAL
FUNCTION. Neurons have four main functions: (1) they respond
to specific neurotransmitters by altering membrane permeability to
common ions (sodium, chloride, potassium, calcium); (2) they conduct
electrical impulses; (3) they secrete transmitters (see below in
"Neurotransmitter"); (4) they communicate with other post-synaptic
cells by the process of synaptic transmission. Neurons are
able to respond and act as "receptors"; this is because their intrinsic
membranes (coverings) contain proteins which can receive messages and
are therefore called receptors. The membranes of different neurons
contain different receptors.. These receptors are protein-complexes
bound in the intrinsic membrane of the neuron.
3.
THE BRAIN AS A GLAND When we add together the concepts of
the brain as the organ for communication and the brain as a gland,
secreting chemicals, we see that the sensory messages that arrive at the
brain from the periphery are being continuously changed, altered,
modified, censored, embellished, intensified or inhibited by
NEUROTRANSMITTERS. A transmitter is a chemical substance that is
released synaptically by one neuron and that affects another cell
(neuron or effector organ) in a specific manner. However, a given
transmitter does not always open the same ionic gates or bring about
the same biochemical change in the postsynaptic neuron; the receptor
determines whether the synapse will be excitatory or inhibitory.
These transmitters act at the neuro-muscular junctions, the
interneuronal junctions and the sensory way-stations, and they are
either repressed or further attended to and analysed according to the
state of the "receiving" cortex. The incoming sensations are matched
with previous experiences. The brain can discard anything "foreign" in
the same way that foreign substances like grafts, bacteria or other
non-self substances are rejected by the tissues which represent the
"self". Some nerve cell receptors have been found to be isomers of
immune cell receptors.
SYNAPTIC TRANSMISSION. There are four
biochemical steps in synaptic transmission: (1) synthesis of the
neurotransmitter substance; (2) release of transmitter into the
synaptic cleft; (3) binding of transmitter to the postsynaptic
receptor, and (4) removal or destruction of the transmitter substance,
(Schwartz). There are eight substances which are the
original classical neurotransmitters: Acetylcholine, the 4 biogenic
amines: Dopamine, Histamine, Nor-epinephrine (the locus caeruleus is
rich in nor-epinephrine), and Serotonin (5-hydroxy-tryptamine) ; and 3
amino-acids: Gamma-amino-butyric acid (GABA), Glycine and Glutamate.
NEUROPEPTIDES. Some neurotransmitters are, chemically, neuropeptides.
Neuroactive peptides or neuropeptides have been found to be
localized in neurons. More than 50 neuropeptides have now been isolated
and arranged in a chemical sequence. They range is size from small
peptides (two amino acids joined by a single peptide bond) to a large
molecule such as corticotropin-releasing-factor (CRF) which is comprised
of 41 amino acids.(Nemeroff). The amino acids arranged in chains
include Glycine, Alanine, Leucine, Aspartine and Arginine.
These neuropeptides act as hormones in some tissues, (a hormone is a
chemical messenger, a substance released at considerable distance from
its intended site of action); and in other tissues these peptides act
as neurotransmitters ( a neurotransmitter is released directly onto
the site of the intended action). Neuropeptides are
important in the field of biofeedback because their action is closely
related to the psycho-physical state of the individual.
Certain neuropeptides are involved in the perception of pain, pleasure,
fear, depression and other emotions. Others are involved in the
control of blood pressure, reproduction, and the mobilizing of energy.
Some can be termed neuromodulators because they are substances that
modulate the action of classical neurotransmitters, (the first 25 or so
neurotransmitters to be isolated), but the field is increasing so
rapidly that terms change their exact meaning. The brain,
functioning as a gland secreting chemicals, regulates our
psycho-physical state through many systems, including the
gastro-intestinal, the cardio-vascular and the immune systems. Many
brain areas are particularly involved, including the hypothalamus. the
pituitary, and the amygdala. We shall discuss these biochemical factors
as they relate to mood and behavior. First we review the brain
areas identified as specially important.
The HYPOTHALAMUS. The
hypothalamus is a minute collection of nuclei situated just below the
thalamus. These nuclei are distinguished microscopically, and they
include the median eminence, the peri-and para-ventricular nuclei, the
preoptic nuclei, the arcuate nucleus and many others.
HYPOTHALAMIC-RELEASING
HORMONES include Thyrotropin-releasing hormone (TRH), Luteinizing
hormone (LH), and somatostatin (growth hormone release-inhibiting
factor, SRIF).
The PITUITARY. The pituitary is the pea-like body
sitting in the pituitary fossa at the base of the skull. PITUITARY
PEPTIDES include Adrenocorticotropin (ACTH), Beta-Endorphin,
Vasopressin and Oxytocin. The hypothalamic-pituitary-adrenal axis is
central to many aspects of the stress response.
The AMYGDALA.
(plural for amygdalum). The amygdalum is a nucleus the shape of an
almond situated deep in each temporal lobe. The two nuclei constitute
the amygdala and are part of the limbic system, the so-called affective
brain, associated with emotionally-based behavior. The amygdala within
the limbic system connects to the cerebral cortex, to the thalamus and
hypothalamus, and to the brainstem and spinal cord. The amygala is
important for the mediation of normal responses to fear-evoking or
anxiety-producing stimuli. Epileptic seizures where the abnormal
neuronal discharge involves the amygdalum can be manifested by severe
sensations of fear and memories of events full of fear. Autonomic
changes can accompany this fear with increases in heart rate and blood
pressure, dialation of the pupils and pallor. "A majority of the
peptides that have been localised with neurons of the brain are found
within either neuronal cells bodies or terminals of the amygdala"
(Gray). These include cortocotropin-releasing factor (CRF), neurotensin,
Enkephalin, Somatostatin and Substance P.
Next we review the
systems where neuropeptides are particularly involved.
Dr. Fischer-Williams received her M.D. in Edinburgh, Scotland, and practiced Neurology in Oxford England, and at the London Hospital, London, England. She was Assistant Professor of Neurology at Wayne State Univ., Detroit, MI; Research Associate and (more...)
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Mariella Fischer-Williams, MD, FRCP Social Media Pages: