The Evolution of the Brain
The human brain is a collection of some 30 billion neurons.
As animals have become more complex, in order to express an increasingly complex mind with more vrttis, the brain has developed in three main stages. The earliest part is the brain stem, at the top of the spin, and is present in reptiles. The second stage, which appears in mammals is the limbic system. The third layer, which has developed mainly in humans is the cortex.
The physical brain is made up of three gross parts which have developed sequentially, one on top of the other. The oldest is the "reptilian brain" which is the brain stem, and evolved more than 500 million years ago. The brain stem manages the basic biological stability of the body and the basic life support systems, e.g. breathing, the heart, sensing of other animals (prey or predator). These functions were necessary in the oceans. On land several new factors had to be dealt with, e.g. gravity, temperature changes, and the uncertain availability of food and water. Some 200 to 300 million years ago the limbic system developed in the center of the brain, on top of the brain stem. The limbic system is mainly responsible for the stability of the basic conditions of the body, e.g. heart rate, temperature, blood pressure, blood sugar level, etc. In mammals it is also involved with the basic emotions (hypothalamus). About 50 million years ago the cerebral cortex developed. This thin folded layer is where decisions are made, models of the external and internal worlds are formed, memories are accessed, language is produced, and sight and sound are appreciated. [HB]
It is pointed out in The Healing Brain that the primary function of the brain is to keep the body out of trouble, to manage and tend to its needs, keeping it free from injury or disease. Most of the brain is taken up with these processes. The thinking and "rational" functions are a very recent development and involve a relatively small portion of the physical volume of the brain. Even the higher functions, such as speech and communication have the primary goal of keeping the body safe, healthy, and happy. It creates both external and internal models against which new sensory data is constantly compared, and which are adjusted as conditions and experience changes. The brain therefore is the vehicle for adapting to change. There is also a prioritizing system that ranks which aspects of the world to deal with or to respond to first. The physical and psychological needs are ranked, with the most basic generally the strongest. These are all balanced by the brain.[HB]
The brain is said to be many small brains combined into one, each with its own functions and preferences. This is part of the reason that we may have mixed feeling, emotions etc. It can also happen that one will suddenly override another, or come to the fore due to an external trigger. In its more extreme forms we may do things we hadn't intended, or apparently change personalities quickly, as a different component comes to the fore. This is not a signal that we are possessed by beings.In general not all sub-systems are active at the same time, but turn on an off as necessary. The number of these units that are involved with conscious awareness at any one time is even smaller.[HB]
It seems probable that these regions develop as the brain of the infant and child becomes more complexly interconnected in its early years. [AHM, evidence?] I.e. the mind creates a brain that will carry out certain functions.
The brain is directly sensitive to light (at least the pineal gland is). Many people suffer a cycle of depression in the fall and winter, which switches to an almost manic state in the spring. [HB]
Baba says that cerebral nerve cells are necessary for the experience of pleasure and pain.
The oldest part of the brain is the brain stem which
sits at the top of the spinal column, or the base of the
brain. The brain stem manages the basic biological stability
of the body and the basic life
support systems.
The stimulation of the portions of the brain stem
around the cerebral ventricles results in the production of
large numbers of endorphins.
The regions with the most opiate receptors also produced
the most endorphins when stimulated. This is part of the
body's natural pain control system. [HB]
A portion of the brain stem, the Reticular Activating
System (RAS) helps to filter the incoming sensory impressions.
This filtering is different in each of
us and can change over time even within the individual. This means
that we all experience our own individual reality. This is a
feedback loop, the more individual we are, the more also is our
experience.
This filtering system can be qualitatively different, but
also quantitatively, i.e. the RAS of different people may
pass more or less of the incoming stimuli. Example of
someone like Van Gogh who probably was relatively flooded
with input, particularly visual. This effect is also found
under the influence of some psychotropic drugs which may
reduce the filtering, leading to `heightened sensory
awareness. An interesting question is what the other extreme
is, are there people who have overly strong filters?
The RAS then passes its output to the Thalamus, which is the
secretary or answering service of the brain. This center routes
the various signals to the different regions of the cortex
which interpret them, or bring them into consciousness. When
the thalamus is damaged or destroyed the person loses sensory
awareness, and enters a vegetative state. The thalamus is the
physical aspect of the Manas Chakra, which is in the center
of the brain and controls the indryas (the sense organs).
It is a group of neural structures that form a border (limbe)
deep in the brain. It is widely connected through out the brain
and is involved in maintaining (along with the
hypothalamus) the stability of the physical parameters of the
body, e.g. heartbeat, respiration, temperature etc. It is also
involved in the emotions (particularly
their physical manifestation) through communication with the
hypothalamus. [SFF]
The frontal lobe limbic system is the center of the emotional
"selfish" brain, which is primarily responsible for the integrity
of the body. While this center can be overridden, it tends to be
the most powerful director of action, when it feels the need to
act. There is an emotional interpretation that is overlaid on all
sensory perception, which is a
primary means for judging the
appropriate reaction. While it is impossible to pinpoint the seat
of the "self" in the brain, many of the functions that are
involved in defining and
maintaining the "self" are located in the frontal lobes.[HB]
Destruction of parts of the limbic system in monkeys lead
them to become tame, lacking in fear or anger, but hypersensitive
to sensory input, sexually overactive and to place all objects
into their mouths. In people it is involved in the emotions and
Although the hypothalamus is mainly a neural structure it
produces various controlling hormones, and may serve as a key
juncture between the neural and neurotransmitter communications
systems. Its control over the pituitary
allows it to switch the body on and off, disconnecting it from
conscious awareness for meditation
and sleep.[Bp] Note the use of the hypothalamus in exactly this
way in some psychic meditations [AHM].
There are specific temperature cells in the hypothalamus
which change their rate of firing when the body temperature
(the blood through the brain) deviates more that 1 C from the
nominal value. This changed rate of firing activates mechanisms
to either heat or cool the body. The mechanism for regulating
body fluids is more complex, beginning with sensitive pressure
sensors in the blood vessels which react to a rise in pressure
due to the release os cellular water into the blood, itself a
reaction to increased salt content in the blood stream.
Communications via the sympathetic
nervous system to the kidneys, results in the release of renin.
This reacts with a blood protein to form a "thirst substance" which
activates certain receptors in the hypothalamus and the rest of
the limbic system. At night a hormone (ADH) feedback system is
used to signal the kidneys to remove water from the urine and
dump it into the blood stream. [HB]
The regulation of hunger is even more complex, and is that
only one of the three that is prone to serious imbalances, (absent
physical damage to the hypothalamus). It involves external cues
as well as internal ones. Absence of the lateral hypothalamus
causes a complete loss of appetite, and of the ventromedial nuclei
(VMN) a tendency to overeat, but only preferred foods. These regions
of the brain have an established "set point" for body weight,
which they tend to maintain quite closely, irrespective of the
actual intake of food. The number of fat cells in the body is
determined in the first two years of life. Once formed they do
not go away, they can only be emptied out, but remain waiting
to be filled. These help to fix the set point, and changing that
can be very hard, however exercise does help in this way, by
raising the rate at which calories are burned throughout the
day, not just during the exercise. [HB]
The hypothalamus apparently is necessary for proper immune system functioning, probably
through its control of the thymus
gland. Information is also received here from the immune system,
as shown by increased activity when antigens are present. The
greater the immune response the greater the activity.
Sensory signals from the eyes and ears come first to the thalamus.
They are then routed to the amygdala
and the neo-cortex.
This region is a key player in the
emotions.
A pair of almond shaped clusters of interconnected structures,
perched above the brainstem, near the bottom of the
limbic ring, one on either side of
the brain. Along with the hippocampus
it formed the primate "nose brain" that evolved into the
cortex and neo-cortex. Main seat for
emotional memory, significance, and personal meaning. Plays a key
role in all passions, emotions, sense of social structures, etc.
With the cingulate gyrus controls tears.[EI]
The amygdala scans incoming sensory signals, coming over a
single synapse from the thalamus,
for survival level patterns. If these are recognized it sends out
alarm signals to every part of the brain. The body and brain are
alerted, placed in emergency modes, and focused on the source of
the alarm. This state of emotional emergency will override the
cortex and any rational, conscious processes, which are processed
by the neo-cortex producing a more
refined, but slower (by a factor of roughly 2) response. This
is the main brain system for non-mammals. [EI]
Emotional responses can be learned completely subconsciously
via the direct link from the thalamus to the amygdala, as well as
via the conscious analysis of the cortex. It is possible for the
unconscious and conscious emotional reactions to be different.
Thus there is a storehouse of unconscious emotional memories and
opinions in the amygdala. The emotional (hormonal) state of the
body and brain affects the strength
forming memories via the amygdala.[EI]
The amygdala's processing of inputs is associative, and often
somewhat sloppily so. This is partly due to the limited signal that
is passed by the thalamus, while the full sensory input goes only
to the neo-cortex. This memory center is fully functional early in
life, before the hippocampus and
neo-cortex are fully on line.[EI]
When circuits between the amygdala and the
neo-cortex are damaged people have difficulty making good decisions,
or sometimes in making any decision at all. Access to emotional
memory and learning appears to be an important contribution to
reasoned decision making. [EI]
Timidity and general fearfulness, including major traumatic
reactions (post traumatic syndrome), is correlated with over
activity in the amygdala and the locus ceruleus, which regulates
the secretion of adrenaline and
noradrenaline. In PSTD Vietnam veterans there were fewer
receptors for stopping these hormones. The
hippocampus, hypothalamus, and
cortex are all linked in the circuitry
that regulate these hormones. Changes also appear in the nerves
linking the limbic brain with the
pituitarygland which controls the release of CRF (the major
stress hormone). [EI]
Curved ridges on the floor of the lateral ventricles. This
is part of the limbic system? It is certainly associated with
it.
It is involved in regulating heartbeat, digestion, and
respiration. Also appears to be essential to the processes
involved in short and long term memory. [SFF] In one
case it seems that the destruction of the hippocampus impacted
the ability to form new long term memories, but not short term
memories. It also did not affect memory related to music,
geometry, physical procedures, etc. [AM]
Along with the amygdala
it formed the primate "nose brain" that evolved into the
cortex and neo-cortex.
A main seat for learning and memory. It appears to play
its main role in providing contextual memory, recognizing
patterns that provide a context (is the tiger in a cage
or not), while the amygdala handles the emotional aspects.
Provides recognition, remembers sensory detail. [EI]
This is located deep below the cortex. It is involved in the
production of memories. It is also involved in the basic basic desires for sleep, food, and
sex. When it is not functioning a person tends to respond only
to presented external stimulus, the internally generated impulse
is lacking. [AM]
This is the region that processes smell.[AM]
The cortex is the seat of sensory organs of the brain, the
indryas and corresponds to the
kamamaya kosa. This is the third and latest part of the
brain to develop. It is mainly present in human beings. It is
also the center for decision making, memory, and model building
(functions of the manomaya
kosa).
The cortex is divided into lobes, the frontal, temporal,
parietal, and occipital, though the divisions of functions occur
on a smaller scale.
The cells of the cortex are arranged in columns, which have
specialized functions, such as recognizing edges or corners in
images. They are hardwired (surely after birth) as modules that
preform specific analysis tasks, and which can be combined for
more complex tasks. The different senses and body abilities
(such as balance or coordination) each have their own area for
analysis and processing. The development of these areas varies
from person to person, as does the talent that depends on them.
[HB]
The cortex receives sensory signals from the
thalamus, compares them to prior experience (memory), makes decisions,
and sends signals for action to the muscles, glands, etc. From the cortex
signals are sent to the amigdula and the limbic
brain, the seat of feelings. From here the signals to the motor organs
are sent out. There are cases in which the cortex is by-passed, a backdoor
nervous path that allows direct reaction to
perceived danger, before the input has time to come into consciousness.
In processing the input from the
eyes, the signals apparently go first to the "blobs" of V1 cells,
which interpret intensity, and then via the "stripes" of V2 cells are
passed to the V4 cells which seem to help form the sensation of color.
The V4 cells are then widely connected throughout the brain, sending
their output on to all the areas the interpret and give meaning and emotion to the images in the limbic system and the amygdala.
They also go the hippocampus which is involved
in memory.[AM]
Other areas of the cortex involved in primary visual processing
are the M system, which handles motion and depth perception, and
the P-interblob system which may probably produces fine-scale form
perception. Including the regions that add
meaning, or create a stable visual world for us, roughly half
the cortex is involved with sight. [AM]
These are a crossroads in the brain, being at the intersection
of the nerve paths from the emotional
limbic system carrying information about the state of the
body, and the parietal areas which contain information about
other people and external conditions. They also contribute to
basic functions like the heart rate. They are very closely
connected to the limbic system (and are sometimes classified as
a part of it). [HB]
The frontal lobe limbic system is the center of the emotional
"selfish" brain, which is primarily responsible for the integrity
of the body. While this center can be overridden, it tends to be
the most powerful director of action, when it feels the need to
act. There is an emotional interpretation that is overlaid on all
sensory perception, which is a
primary means for judging the
appropriate reaction. While it is impossible to pinpoint the seat
of the "self" in the brain, many of the functions that are
involved in defining and
maintaining the "self" are located in the frontal lobes.[HB]
Decision making, memory, and model building are controlled
by the frontal lobes. These are involved in the construction of
all higher level concepts, including
ego formation, language, judgement, imagination, and emotion. These are highly developed
in humans (only reaching full development around age seven),
much less so in other primates and hardly at all in other
mammals. These are also responsible for conscience and the
sense of duty, from which we need an occasional break. [AM]
The prefrontal lobes, behind the forehead, appear to play a
role in shutting down immediate emotional responses from the
amygdala. These secondary responses
are more calculated and are generally based on more accurate
information. They serve to amend or correct limbic responses.
In the normal course most sensory input goes here first and
after analysis responses are sent out, including emotional
responses, to the amygdala.[EI]
Strong emotional signals from the
amygdala to the neocortex can interfere with rational thought
and "working memory" which is another
prefrontal function. On the other hand, positive emotions can
enhance thinking and provide a boost to concentration. [EI]
Removal of one or the other lobe has drastic effects on personality.
Inter and intra-personal intellegences. Loss of the left lobes
produces anti-social and uncontrolled behavior dominated by fear
and aggression (e.g. Phineas Gage). Loss of the right lobes produces
eternally happy emotional states, no responsibility. In experiments
where shock therapy rendered one side temporarily inoperative there
were similar results. When the left side was shocked the patients
where very unhappy, while the shocking of the right side made them
very happy [HB]. This is compared to the two petals of the ajina chakra, the right controlling
mundane and the left spiritual vrttis in
the lower chakras. When the left lobes are gone only the mundane
vrttis remain and visa versa?[DAM]
There is a strong correlation between which lobe is generally
more active in a person and that persons overall mood. If the left
lobe dominates they tend to be cheerful and up beat. If the right
lobe dominates they tend to be more gloomy and fearful. [EI]
When both lobes are damaged, there is a general lack of control,
a disintegration of the coherence
of the ego, a lack of "psychological distance" between the person
and his or her environment. Most incoming stimuli are treated
equally, without judgement or
weight. [AM]
In serial killers, there is no measurable frontal lobe
activity. I.e. no emotional
connection.
The prefrontal lobes, behind the forehead, appear to play a
role in shutting down immediate emotional responses from the
amygdala. These secondary responses
are more calculated and are generally based on more accurate
information. They serve to amend or correct limbic responses. [EI]
The medial temporal lobes are necessary for conscious (explicit)
learning, long term memory. [AM]
The brain is nearly completely divided down the middle into a
left and a right side, which physically are roughly mirror images.
They are connected through the corpus collasum, a thick bundle of
nerve fibers in the middle of the head. Starting with observations
of people suffering traumatic brain injuries and more recently those
who have had their corpus collapsum severed to prevent epileptic
fits, it has been determined that some mental functions are normally
performed on one side if the brain or the other.
It is important to note that work by Japanese surgeons has
indicated that the allocation of functions to the right and left
brains depends on the first language spoken by an infant. While
most languages produce a structure similar to English, a handful
of others including Japanese ... produce a different structure.
[Omni??..circa 1978?]
In left-handed persons, the distribution of functions may be
reversed from the normal (see below), or a mixture. [HB]
The right brain controls the left side of the physical body.
The mental functions that it supports are primarily integrative,
and have to do with spatial relationships and imagery. It is often
spoken of as the artistic and creative side. Subjects generally
associate the right brain (left side of the body) with the femine
and other yin aspects.
The right frontal lobe is more involved
with emotions like anger and sadness, and recognizes them faster
in faces. The right side appears to have more to do with large
scale muscle control, e.g. running, hitting etc. [is this just
the frontal lobe]?[HB]
How does this relate to the dominance of
aparavrtti or paravrtti as indicated
by the breath coming through the
right and left nostril respectively?
The left brain controls the right side of the physical body.
The mental functions that it supports are primarily analytical,
and have to do with linear logic, mathematics, and language. It
deals with cause and effect and temporal sequencing. It is often
spoken of as the intellectual side. Subjects generally associate
the left brain (right side of the body) with the masculine and
other yang aspects.
The left frontal lobe is more involved
with emotions like joy and happiness, and recognizes them faster
in faces. The left side appears to have more to do with fine
scale muscle control and coordination, e.g. various sensitive uses
of the hands, stroking or petting, or rummaging for a favorite food
[is this just the frontal lobe]?[HB]
There is some evidence that the left cortical hemisphere is
related to the immune system. This
may be due to the impact of the "hostile" emotions that are
associated with the right hemisphere.
The symbolism of body right and left (brain left and right)
representing male and female, or yang and yin in general is
common to nearly all cultures and ages.
This occurs in the visual cortex and the associative cortex
in preparation for perceiving a familiar
sight, or object. Thousands of cells generate high frequency
gamma waves by synchronizing their
firing. The rate of firing appears to be a separate parameter,
and has more to do with the incoming sensation, while the
synchronization is related to the actual perception. If the perception
is followed up by an action, the waves shift to the motor cortex
and to other parts of the associative cortex.
The brain likes an optimum throughput of new information. Too
much information or change is stressful, but so is too little. The
quality of the change is also important (i.e. good vrs bad stress).
The brain, from that of an infant, balances increased access to
information with simplification and organization of information.
The older we get the more familiar things become and the more we
have to expand or explore to find something new. When sensory input is reduced, or prevented
we become disorganized, lose intellectual ability, concentration,
and coordination. Eventually we may hallucinate, associated with
feelings of boredom, anxiety, irritability, paranoia etc. [In
mediation this is the rise of
normally unconscious material after practice of sense withdrawal]. It is important to note
that while stress may lead to disease, it actually does in only
some people. Others get sick without much objective stress, while
some with a great deal remain healthy. It is more how one reacts
to stress than the stress itself which is important.[HB]
Concentrations of negative or positive ions in the air affect
our brain chemistry. Negative ions increase
serotonin, which brings a more positive mood, while positive ions
adversely affect our mood, energy level, and health. Closed buildings,
air pollution, and hot winds produce a balance of positive ions, while
water falls and the ocean produce negative ones. In rats, those raised
in a negative ion environment developed larger
cortices. [HB]
See also these articles notes.
The Reptilian Brain: the Brain Stem
The RAS
The Mammalian Brain and the Limbic System
The Hypothalamus
The Hypothalamus controls the
basic physical desires, hunger, thrist, sleep, and sex,
and is involved in many of the basic
emotions. It also regulates temperature, blood pressure,
the heart and the lungs, etc. This operation is via a feed back
mechanism, in which sensory input from the body, via the nervous
system and from the organs via hormones
in the blood, is used to determine adjustments that will keep
the parameters within desired bounds. It also balances hormone
levels through chemical and electrical control of the pituitary gland, which in turn controls
all the other endocrine glands . [HB]
The Thalamus
The Amygdala
The Hippocampus
The Diencephalon, or Forebrain
The Rhinencephalon
The Human Brain and the Cortex
The Frontal Lobes
The Temporal Lobes
Right and Left Brains
Neural Synchronization
Change and Stress
Atmospheric Ions
