Brain
For other uses, see Brain (disambiguation).
Human brain
In animals, the brain is the control center of the central nervous system, responsible for behavior.
In mammals, the brain is located in the head, protected by the skull and close to the primary
sensory apparatus of vision, hearing, equilibrioception (balance), sense of taste, and olfaction
(smell).
While all vertebrates have a brain, most invertebrates have either a centralized brain or collections
of individual ganglia. Some animals such as cnidarians and echinoderms do not have a centralized
brain, and instead have a decentralized nervous system, while animals such as sponges lack both
a brain and nervous system entirely.
Brains can be extremely complex. For example, the human brain contains roughly 100 billion
neurons, linked with up to 10,000 connections each.
Contents
[hide]

1 History

2 Mind and brain

3 Comparative anatomy

o
3.1 Insects
o
3.2 Cephalopods
o
3.3 Mammals and other vertebrates

3.3.1 Vertebrate brain regions

3.3.2 Humans
4 Neurobiology
o
4.1 Structure
o
4.2 Function

4.2.1 Neurotransmitter systems
o
4.3 Pressure on the Brain
o
4.4 Origin
o

4.5 Pathology
5 Study of the brain
o
5.1 Fields of study
o
5.2 Methods of observation
o

5.2.1 Electrophysiology

5.2.2 EEG

5.2.3 MEG

5.2.4 fMRI and PET

5.2.5 Behavioral

5.2.6 Anatomical
5.3 Other studies

6 Brain energy consumption

7 As food

8 See also

9 References

10 Further reading

11 External links
History
Main article: History of the brain
Early views on the function of the brain regarded it as little more than cranial stuffing. In Ancient
Egypt, from the late Middle Kingdom onwards, in preparation for mummification, the brain was
regularly removed, for it was the heart that was assumed to be the seat of intelligence. According
to Herodotus, during the first step of mummification, "The most perfect practice is to extract as
much of the brain as possible with an iron hook, and what the hook cannot reach is mixed with
drugs." Over the next five-thousand years, this view came to be reversed; the brain is now known
to be seat of intelligence, although idiomatic variations of the former remain, as in "memorizing
something by heart".[1]
The first thoughts on the field of psychology came from ancient philosophers, such as Aristotle.
As thinkers became more in tune with biomedical research over time, as was the case with
medieval psychologists such as Alhazen and Avicenna for example, the concepts of experimental
psychology and clinical psychology began emerging. From that point, different branches of
psychology emerged with different individuals creating new ideas, with modern psychologists
such as Freud and Jung contributing to the field.
Mind and brain
This section does not cite any references or sources.
Please help improve this section by adding citations to reliable sources. Unverifiable material
may be challenged and removed. (June 2008)
Mind and Brain portal
The mind-body problem is one of the central problems in the history of philosophy. The brain is
the physical and biological matter contained within the skull, responsible for electrochemical
neuronal processes. The mind, in contrast, consists in mental attributes, such as beliefs, desires,
perceptions, and so on. There are scientifically demonstrable correlations between mental events
and neuronal events; the philosophical question is whether these phenomena are identical, at
least partially distinct, or related in some unknown way.
Philosophical positions on the mind-body problem fall into two main categories. The first
category is dualism, according to which the mind exists independently of the brain. Dualist
theories are further divided into substance dualism and property dualism. René Descartes is
perhaps the most prominent substance dualist, while property dualism is more popular among
contemporary dualists like David Chalmers. Dualism requires admitting non-physical substances or
properties into ontology, which is in apparent conflict with the scientific world view. The second
category is materialism, according to which mental phenomena are identical to neuronal
phenomena. A third category of view, idealism, claims that only mental substances and
phenomena exist. This view, most prominently held by 18th century Irish philosopher Bishop
George Berkeley, has few contemporary adherents.
Comparative anatomy
A mouse brain.
Three groups of animals have notably complex brains: the arthropods (insects, crustaceans,
arachnids, and others), the cephalopods (octopuses, squids, and similar mollusks), and the
craniates (vertebrates and hagfish).[2] The brain of arthropods and cephalopods arises from twin
parallel nerve cords that extend through the body of the animal. Arthropods have a central brain
with three divisions and large optical lobes behind each eye for visual processing.[2]
The brain of craniates develops from the anterior section of a single dorsal nerve cord, which later
becomes the spinal cord.[3] In craniates, the brain is protected by the bones of the skull.
Mammals have a six-layered neocortex (or homotypic cortex, neopallium), in addition to having
some parts of the brain that are allocortex.[3] In mammals, increasing convolutions of the brain are
characteristic of animals with more advanced brains. These convolutions provide a larger surface
area for a greater number of neurons while keeping the volume of the brain compact enough to
fit inside the skull. The folding allows more grey matter to fit into a smaller volume. The folds are
called sulci, while the spaces between the folds are called gyri.
In birds, the part of the brain that functionally corresponds to the neocortex is called nidopallium
and derives from a different part of the brain. Some birds (like corvids and parrots), are thought
by some to have high intelligence, but even in these, the brain region that forms the mammalian
neocortex is in fact almost entirely absent.
All vertebrates have a similar general histology of the brain, but may have differing structural
anatomy. Apart from the gross embryological divisions of the brain, the location of specific gyri
and sulci, primary sensory regions, and other structures differs between species.
Insects
In insects, the brain has four parts, the optic lobes, the protocerebrum, the deutocerebrum, and
the tritocerebrum. The optic lobes are behind each eye and process visual stimuli. [2] The
protocerebrum contains the mushroom bodies, which respond to smell, and the central body
complex. In some species such as bees, the mushroom body receives input from the visual
pathway as well. The deutocerebrum includes the antennal lobes, which are similar to the
mammalian olfactory bulb, and the mechanosensory neuropils which receive information from
touch receptors on the head and antennae. The antennal lobes of flies and moths are quite
complex.
Cephalopods
In cephalopods, the brain has two regions: the supraesophageal mass and the subesophageal
mass,[2] separated by the esophagus. The supra- and subesophageal masses are connected to
each other on either side of the esophagus by the basal lobes and the dorsal magnocellular
lobes.[2] The large optic lobes are sometimes not considered to be part of the brain, as they are
anatomically separate and are joined to the brain by the optic stalks. However, the optic lobes
perform much visual processing, and so functionally are part of the brain.
Mammals and other vertebrates
The telencephalon (cerebrum) is the largest region of the mammalian brain. This is the structure
that is most easily visible in brain specimens, and is what most people associate with the "brain".
In humans and several other animals, the fissures (sulci) and convolutions (gyri) give the brain a
wrinkled appearance. In non-mammalian vertebrates with no cerebrum, the metencephalon is the
highest center in the brain. Because humans walk upright, there is a flexure, or bend, in the brain
between the brain stem and the cerebrum. Other vertebrates do not have this flexure. Generally,
comparing the locations of certain brain structures between humans and other vertebrates often
reveals a number of differences.
Behind (or in humans, below) the cerebrum is the cerebellum. The cerebellum is known to be
involved in the control of movement, [3] and is connected by thick white matter fibers (cerebellar
peduncles) to the pons.[4] The cerebrum has two cerebral hemispheres. The cerebellum also has
hemispheres. The telencephalic hemispheres are connected by the corpus callosum, another large
white matter tract. An outgrowth of the telencephalon called the olfactory bulb is a major
structure in many animals, but in humans and other primates it is relatively small.
Vertebrate nervous systems are distinguished by bilaterally symmetrical encephalization.
Encephalization refers to the tendency for more complex organisms to gain larger brains through
evolutionary time. Larger vertebrates develop a complex, layered and interconnected neuronal
circuitry. In modern species most closely related to the first vertebrates, brains are covered with
gray matter that has a three-layer structure (allocortex). Their brains also contain deep brain
nuclei and fiber tracts forming the white matter. Most regions of the human cerebral cortex have
six layers of neurons (neocortex).[4]
Vertebrate brain regions
(See related article at List of regions in the human brain)
Diagram depicting the main subdivisions of the embryonic vertebrate brain. These regions will
later differentiate into forebrain, midbrain and hindbrain structures.
According to the hierarchy based on embryonic and evolutionary development, chordate brains
are composed of the three regions that later develop into five total divisions:

Rhombencephalon (hindbrain)
o
Myelencephalon
o
Metencephalon

Mesencephalon (midbrain)

Prosencephalon (forebrain)
o
Diencephalon
o
Telencephalon
The brain can also be classified according to function, including divisions such as:

Limbic system

Sensory systems
o
Visual system
o
Olfactory system
o
Gustatory system
o
Auditory system
o
Somatosensory system

Motor system

Associative areas
In recent years it was realized that certain birds have developed high intelligence entirely
convergently from mammals such as humans. Hence, the functional areas of the avian brain have
been redefined by the Avian Brain Nomenclature Consortium. See also Bird intelligence.
Humans
This section does not cite any references or sources.
Please help improve this section by adding citations to reliable sources. Unverifiable material
may be challenged and removed. (June 2008)
Human brain with color coded lobes
Main article: Human brain
The structure of the human brain differs from that of other animals in several important ways.
These differences allow for many abilities over and above those of other animals, such as
advanced cognitive skills. Human encephalization is especially pronounced in the neocortex, the
most complex part of the cerebral cortex. The proportion of the human brain that is devoted to
the neocortex—especially to the prefrontal cortex—is larger than in all other mammals (indeed
larger than in all animals, although only in mammals has the neocortex evolved to fulfill this kind
of function).
Humans have unique neural capacities, but much of their brain structure is similar to that of other
mammals. Basic systems that alert the nervous system to stimulus, that sense events in the
environment, and monitor the condition of the body are similar to those of even non-mammalian
vertebrates. The neural circuitry underlying human consciousness includes both the advanced
neocortex and prototypical structures of the brain stem. The human brain also has a massive
number of synaptic connections allowing for a great deal of parallel processing.
Neurobiology
The brain is composed of two broad classes of cells, neurons and glia, both of which contain
several different cell types which perform different functions. Interconnected neurons form neural
networks (or neural ensembles). These networks are similar to man-made electrical circuits in that
they contain circuit elements (neurons) connected by biological wires (nerve fibers). These do not
form simple one-to-one electrical circuits like many man-made circuits, however. Typically neurons
connect to at least a thousand other neurons. [5] These highly specialized circuits make up systems
which are the basis of perception, different types of action, and higher cognitive function.
Structure
Structure of a typical neuron
Neuron
Dendrite
Soma
Axon
Nucleus
Node of
Ranvier
Axon Terminal
Schwann cell
Myelin sheath
Neurons are the cells that convey information to other cells; these constitute the essential class of
brain cells.
In addition to neurons, the brain contains glial cells in a roughly 10:1 proportion to neurons. Glial
cells ("glia" is Greek for “glue”) form a support system for neurons. They create the insulating
myelin, provide structure to the neuronal network, manage waste, and clean up neurotransmitters.
Most types of glia in the brain are present in the entire nervous system. Exceptions include the
oligodendrocytes which myelinate neural axons (a role performed by Schwann cells in the
peripheral nervous system). The myelin in the oligodendrocytes insulates the axons of some
neurons. White matter in the brain is myelinated neurons, while gray matter contains mostly cell
soma, dendrites, and unmyelinated portions of axons and glia. The space between neurons is
filled with dendrites as well as unmyelinated segments of axons; this area is referred to as the
neuropil.
In mammals, the brain is surrounded by connective tissues called the meninges, a system of
membranes that separate the skull from the brain. This three-layered covering is composed of
(from the outside in) the dura mater, arachnoid mater, and pia mater. The arachnoid and pia are
physically connected and thus often considered as a single layer, the pia-arachnoid. Below the
arachnoid is the subarachnoid space which contains cerebrospinal fluid, a substance that protects
the nervous system. Blood vessels enter the central nervous system through the perivascular
space above the pia mater. The cells in the blood vessel walls are joined tightly, forming the
blood-brain barrier which protects the brain from toxins that might enter through the blood.
The brain is bathed in cerebrospinal fluid (CSF), which circulates between layers of the meninges
and through cavities in the brain called ventricles. It is important both chemically for metabolism
and mechanically for shock-prevention. For example, the human brain weighs about 1-1.5 kg or
about 2-3 lb. The mass and density of the brain are such that it will begin to collapse under its
own weight if unsupported by the CSF. The CSF allows the brain to float, easing the physical
stress caused by the brain’s mass.
Function
Vertebrate brains receive signals through nerves arriving from the sensors of the organism. These
signals are then processed throughout the central nervous system; reactions are formulated based
upon reflex and learned experiences. A similarly extensive nerve network delivers signals from a
brain to control important muscles throughout the body. Anatomically, the majority of afferent
and efferent nerves (with the exception of the cranial nerves) are connected to the spinal cord,
which then transfers the signals to and from the brain.
Sensory input is processed by the brain to recognize danger, find food, identify potential mates,
and perform more sophisticated functions. Visual, touch, and auditory sensory pathways of
vertebrates are routed to specific nuclei of the thalamus and then to regions of the cerebral
cortex that are specific to each sensory system, the visual system, the auditory system, and the
somatosensory system. Olfactory pathways are routed to the olfactory bulb, then to various parts
of the olfactory system. Taste is routed through the brainstem and then to other portions of the
gustatory system.
To control movement the brain has several parallel systems of muscle control. The motor system
controls voluntary muscle movement, aided by the motor cortex, cerebellum, and the basal
ganglia. The system eventually projects to the spinal cord and then out to the muscle effectors.
Nuclei in the brain stem control many involuntary muscle functions such as heart rate and
breathing. In addition, many automatic acts (simple reflexes, locomotion) can be controlled by the
spinal cord alone.
Brains also produce a portion of the body's hormones that can influence organs and glands
elsewhere in a body—conversely, brains also react to hormones produced elsewhere in the body.
In mammals, the hormones that regulate hormone production throughout the body are produced
in the brain by the structure called the pituitary gland.
Evidence strongly suggests that developed brains derive consciousness from the complex
interactions between the numerous systems within the brain. Cognitive processing in mammals
occurs in the cerebral cortex but relies on midbrain and limbic functions as well. Among
"younger" (in an evolutionary sense) vertebrates, advanced processing involves progressively
rostral (forward) regions of the brain.
Hormones, incoming sensory information, and cognitive processing performed by the brain
determine the brain state. Stimulus from any source can trigger a general arousal process that
focuses cortical operations to processing of the new information. This focusing of cognition is
known as attention. Cognitive priorities are constantly shifted by a variety of factors such as
hunger, fatigue, belief, unfamiliar information, or threat. The simplest dichotomy related to the
processing of threats is the fight-or-flight response mediated by the amygdala and other limbic
structures.
Neurotransmitter systems
Main article: Neurotransmitter systems
Neurons expressing certain types of neurotransmitters sometimes form distinct systems, where
activation of the system causes effects in large volumes of the brain, called volume transmission.
The major neurotransmitter systems are the noradrenaline (norepinephrine) system, the dopamine
system, the serotonin system and the cholinergic system.
Drugs targeting the neurotransmitter of such systems affects the whole system, which explains the
mode of action of many drugs;

Cocaine, for example, blocks the reuptake of dopamine, leaving these neurotransmitters in
the synaptic gap longer.

Prozac is a selective serotonin reuptake inhibitor (SSRI), hence potentiating the effect of
naturally released serotonin.

AMPT prevents the conversion of tyrosine to L-DOPA, the precursor to dopamine;
reserpine prevents dopamine storage within vesicles; and deprenyl inhibits monoamine
oxidase (MAO)-B and thus increases dopamine levels.
Diseases may affect specific neurotransmitter systems. For example, Parkinson's disease is at least
in part related to failure of dopaminergic cells in deep-brain nuclei, for example the substantia
nigra. Treatments potentiating the effect of dopamine precursors have been proposed and
effected, with moderate success.
A brief comparison of the major neurotransmitter systems follows:
Neurotransmitter systems
System
Origin
Effects[6]
Noradrenaline
locus coeruleus

arousal
system
lateral tegmental field

reward
dopamine pathways:

mesocortical pathway
Dopamine

mesolimbic pathway
motor system, reward, cognition, endocrine,
system

nigrostriatal pathway
nausea

tuberoinfundibular
pathway
Serotonin
system
caudal dorsal raphe nucleus
rostral dorsal raphe nucleus
pontomesencephalotegmental
Cholinergic
system
Increase introversion, mood, satiety, body
temperature and sleep, while decreasing
nociception.

learning

short-term memory
basal optic nucleus of Meynert

arousal
medial septal nucleus

reward
complex
Pressure on the Brain
The Castaricial valve controls the force in which the Castaonic liquid is kept in place around the
brain. A recent discovery due to the investigation of deformation of this valve is due to a recent
death which the post mortem revealed extreme expansion of the brain. The results proved that
the Casta valve uses some of its pressure producing muscles to assist the eye closing muscles if
they are also deformed or generally unable to perform their jobs. In the extremely rare
circumstances that both these glands fail to operate the leaking of casta liquid escapes as the
casta valve doesn’t seal the arteries and veins allowing the liquid to swell the veins and apply
pressure onto the brain. The swelling is a result of long periods of the upper eye lateral retug
muscle being extended straining the cata valve and allowing extreme pressure to be apllied to the
brain.
Origin
Since even unicellular organisms can have, at least, photosensitive eyespots and react to tactile
stimuli, it is hypothesized that sensory organs developed before the brain did.[7] The brain is an
information-processing organ and its evolution is dependent on the presence of information
accessed into sensory organs, sensory input, and the need to process this information and
transmit it.
Pathology
A human brain showing frontotemporal lobar degeneration causing frontotemporal dementia.
Clinically, death is defined as an absence of brain activity as measured by EEG. Injuries to the
brain tend to affect large areas of the organ, sometimes causing major deficits in intelligence,
memory, and movement. Head trauma caused, for example, by vehicle or industrial accidents, is a
leading cause of death in youth and middle age. In many cases, more damage is caused by
resultant edema than by the impact itself. Stroke, caused by the blockage or rupturing of blood
vessels in the brain, is another major cause of death from brain damage.
Other problems in the brain can be more accurately classified as diseases rather than injuries.
Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, motor neurone
disease, and Huntington's disease are caused by the gradual death of individual neurons, leading
to decrements in movement control, memory, and cognition. Currently only the symptoms of
these diseases can be treated. Mental illnesses, such as clinical depression, schizophrenia, bipolar
disorder, and post-traumatic stress disorder are brain disorders that impact personality and,
typically, other aspects of mental and somatic function. These disorders may be treated by
psychiatric therapy, pharmaceutical intervention, or through a combination of treatments;
therapeutic effectiveness varies significantly among individuals.
Some infectious diseases affecting the brain are caused by viruses and bacteria. Infection of the
meninges, the membrane that covers the brain, can lead to meningitis. Bovine spongiform
encephalopathy (also known as mad cow disease), is deadly in cattle and humans and is linked to
prions. Kuru is a similar prion-borne degenerative brain disease affecting humans. Both are linked
to the ingestion of neural tissue, and may explain the tendency in some species to avoid
cannibalism. Viral or bacterial causes have been reported in multiple sclerosis and Parkinson's
disease, and are established causes of encephalopathy, and encephalomyelitis.
Many brain disorders are congenital. Tay-Sachs disease, Fragile X syndrome, and Down syndrome
are all linked to genetic and chromosomal errors. Many other syndromes, such as the intrinsic
circadian rhythm disorders, are suspected to be congenital as well. Malfunctions in the embryonic
development of the brain can be caused by genetic factors, drug use, nutritional deficiencies, and
infectious diseases during pregnancy.
Certain brain disorders are treated by brain neurosurgeons while others are treated by
neurologists and psychiatrists.
Study of the brain
Fields of study
Neuroscience seeks to understand the nervous system, including the brain, from a biological and
computational perspective. Psychology seeks to understand behavior and the brain. Neurology
refers to the medical applications of neuroscience. The brain is also one of the most important
organs studied in psychiatry, the branch of medicine which exists to study, prevent, and treat
mental disorders.[8][9][10] Cognitive science seeks to unify neuroscience and psychology with other
fields that concern themselves with the brain, such as computer science (artificial intelligence and
similar fields) and philosophy.
Methods of observation
Main article: neuroimaging
Each method for observing activity in the brain has its advantages and drawbacks.
Electrophysiology
Electrophysiology allows scientists to record the electrical activity of individual neurons or groups
of neurons.
EEG
By placing electrodes on the scalp one can record the summed electrical activity of the cortex in a
technique known as electroencephalography (EEG). EEG measures the mass changes in electrical
current from the cerebral cortex, but can only detect changes over large areas of the brain with
very little sub-cortical activity.
MEG
Apart from measuring the electric field around the skull it is possible to measure the magnetic
field directly in a technique known as magnetoencephalography (MEG). This technique has the
same temporal resolution as EEG but much better spatial resolution, although admittedly not as
good as fMRI. The main advantage over fMRI is a direct relationship between neural activation
and measurement.
fMRI and PET
A scan of the brain using fMRI
Functional magnetic resonance imaging (fMRI) measures changes in blood flow in the brain, but
the activity of neurons is not directly measured, nor can it be distinguished whether this activity is
inhibitory or excitatory. fMRI is a noninvasive, indirect method for measuring neural activity that is
based on BOLD; Blood Oxygen Level Dependent changes. The changes in blood flow that occur
in capillary beds in specific regions of the brain are thought to represent various neuronal
activities (metabolism of synaptic reuptake). Similarly, a positron emission tomography (PET), is
able to monitor glucose and oxygen metabolism as well as neurotransmitter activity in different
areas within the brain which can be correlated to the level of activity in that region.
Behavioral
Behavioral tests can measure symptoms of disease and mental performance, but can only provide
indirect measurements of brain function and may not be practical in all animals. In humans
however, a neurological exam can be done to determine the location of any trauma, lesion, or
tumor within the brain, brain stem, or spinal cord.
Anatomical
Autopsy analysis of the brain allows for the study of anatomy and protein expression patterns, but
is only possible after the human or animal is dead. Magnetic resonance imaging (MRI) can be
used to study the anatomy of a living creature and is widely used in both research and medicine.
Other studies
Computer scientists have produced simulated "artificial neural networks" loosely based on the
structure of neuron connections in the brain. Some artificial intelligence research seeks to replicate
brain function—although not necessarily brain mechanisms—but as yet has been met with limited
success.
Creating algorithms to mimic a biological brain is very difficult because the brain is not a static
arrangement of circuits, but a network of vastly interconnected neurons that are constantly
changing their connectivity and sensitivity. More recent work in both neuroscience and artificial
intelligence models the brain using the mathematical tools of chaos theory and dynamical
systems. Current research has also focused on recreating the neural structure of the brain with the
aim of producing human-like cognition and artificial intelligence.
[edit] Brain energy consumption
PET Image of the human brain showing energy consumption
Although the brain represents only 2% of the body weight, it receives 15% of the cardiac output,
20% of total body oxygen consumption, and 25% of total body glucose utilization. The energy
consumption for the brain to simply survive is 0.1 Calories per minute, while this value can be as
high as 1.5 Calories per minute (100W) during crossword puzzle-solving.[11] The demands of the
brain limit its size in many species. Molossid bats and the Vespertilionid Nyctalus spp. have brains
that have been reduced from the ancestral form to invest in wing-size for the sake of
maneuverability. This contrasts with fruit bats, which require more advanced neural structures and
do not pursue their prey.[12]
The brain most utilizes glucose for energy, but certain areas can use fatty acids. Although supply
of glucose to the brain is generally plentiful, as the brain focuses on a specific task, it uses up the
glucose in that particular area and makes the task harder to do. Studies have shown that glucose
stores are available to a particular area of the brain for approximately 20 minutes. Deprivation of
glucose to the brain, as can happen in hypoglycemia, can result in loss of consciousness. About
half of the brain's energy is used up in cell-to-cell signalling, which represents about 10% of the
body's entire energy supply.
As food
Like most other internal organs, the brain can serve as nourishment. For example, in the Southern
United States canned pork brain in gravy can be purchased for consumption as food. This form of
brain is often fried with scrambled eggs to produce the famous "Eggs n' Brains".[13] The brain of
animals also features in French cuisine such as in the dish tête de veau, or head of calf. Although
it sometimes consists only of the outer meat of the skull and jaw, the full meal includes the brain,
tongue, and glands.
Similar delicacies from around the world include Mexican tacos de sesos made with cattle brain as
well as squirrel brain in the US South.[14] The Anyang tribe of Cameroon practiced a tradition in
which a new tribal chief would consume the brain of a hunted gorilla while another senior
member of the tribe would eat the heart.[15] Indonesian cuisine specialty in Minangkabau cuisine
also served beef brain in a gravy coconut milk named gulai otak (beef brain curry). Roasted or
fried goat brain is eaten in the south of India and some parts of northern India.
Consuming the brain and other nerve tissue of animals is not without risks. The first problem is
that the makeup of the brain is 60% fat due to large quantities of myelin (which itself is 70% fat)
insulating the axons of neurons.[16] As an example, a 140 g can of "pork brains in milk gravy", a
single serving, contains 3500 milligrams of cholesterol, 1170% of our recommended daily intake. [17]
Brain consumption can result in contracting fatal transmissible spongiform encephalopathies such
as Variant Creutzfeldt-Jakob disease and other prion diseases in humans and mad cow disease in
cattle.[18] Another prion disease called kuru has been traced to a funerary ritual among the Fore
people of Papua New Guinea in which those close to the dead would eat the brain of the
deceased to create a sense of immortality.[19] Some archaeological evidence suggests that the
mourning rituals of European Neanderthals also involved the consumption of the brain. [20]
Because of the risk of being infected by prions one should always wear gloves when handling
brains.
It is also well-known in the hunting community that the brain of wild animals should not be
consumed, due to the risk of chronic wasting disease. The brain is still useful to hunters, in that
most animals have enough brain matter for use in the tanning of their own hides.
See also

Traumatic brain injury
References
1.
^ Hendrickson, Robert (April 2000). The Facts on File Encyclopedia of Word and Phrase
Origins. New York: Facts on File. “The ancient Greeks believed that the heart, the most
noticeable internal organ, was the seat of intelligence and memory as well as emotion.
This belief was passed on down the ages and became the basis for the English expression
'learn by heart,' which is used by Chaucer (1374) and must have been proverbial long
before that. 'To record' reminds us again of this ancient belief in the heart as the seat of
the mind. When writing wasn't a simple act, things had to be memorized; thus we have
the word 'record,' formed from the Latin 're,' 'again,' and 'cor,' 'heart,' which means exactly
the same as 'learn by heart.'”
2.
^
a b c d e
Butler, Ann B. (2000). "Chordate Evolution and the Origin of Craniates: An Old
Brain in a New Head". The Anatomical Record 261: 111–125. doi:10.1002/10970185(20000615)261:3<111::AID-AR6>3.0.CO;2-F.
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^
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Kandel, ER; Schwartz JH, Jessell TM (2000). Principles of Neural Science, 4th ed.,
New York: McGraw-Hill. ISBN 0-8385-7701-6.
4.
^
a b
Martin, John H. (1996). Neuroanatomy: Text and Atlas, Second Edition, New York:
McGraw-Hill. ISBN 0-07-138183-X.
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^ Junqueira, L.C.; J. Carneiro. Basic Histology: Text and Atlas, 10th ed.. (Statistic from page
161)
6.
^ Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone, page 474 for
noradrenaline system, page 476 for dopamine system, page 480 for serotonin system and
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