The cerebrum, telencephalon or endbrain is the largest part of the
brain
A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
containing the
cerebral cortex (of the two
cerebral hemisphere
The vertebrate cerebrum ( brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemisphere ...
s), as well as several subcortical structures, including the
hippocampus
The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...
,
basal ganglia, and
olfactory bulb. In the
human brain
The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of ...
, the cerebrum is the uppermost region of the
central nervous system. The cerebrum
develops prenatally from the
forebrain (prosencephalon). In mammals, the
dorsal telencephalon, or
pallium, develops into the cerebral cortex, and the
ventral telencephalon, or
subpallium, becomes the
basal ganglia. The cerebrum is also divided into approximately symmetric
left and right cerebral hemispheres.
With the assistance of the
cerebellum, the cerebrum controls all voluntary actions in the human body.
Structure
The cerebrum is the largest part of the
brain
A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
. Depending upon the position of the animal it lies either in front or on top of the
brainstem. In humans, the cerebrum is the largest and best-developed of the five major divisions of the brain.
The cerebrum is made up of the two cerebral hemispheres and their
cerebral cortices (the outer layers of
grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil ( dendrites and unmyelinated axons), glial cells ( astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is ...
), and the underlying regions of
white matter
White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribu ...
.
Its subcortical structures include the hippocampus, basal ganglia and olfactory bulb. The cerebrum consists of two C-shaped cerebral hemispheres, separated from each other by a deep fissure called the
longitudinal fissure.
Cerebral cortex
The
cerebral cortex, the outer layer of grey matter of the cerebrum, is found only in mammals. In larger mammals, including humans, the surface of the cerebral cortex folds to create
gyri
In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the brain in humans and other ...
(ridges) and
sulci (furrows) which increase the
surface area
The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of ...
.
The cerebral cortex is generally classified into four
lobes: the
frontal
Front may refer to:
Arts, entertainment, and media Films
* ''The Front'' (1943 film), a 1943 Soviet drama film
* ''The Front'', 1976 film
Music
*The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...
,
parietal,
occipital and
temporal lobes. The lobes are classified based on their overlying
neurocranial bones.
Cerebral hemispheres
The cerebrum is divided by the
medial longitudinal fissure into two
cerebral hemisphere
The vertebrate cerebrum ( brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemisphere ...
s, the right and the left. The
cerebrum is contralaterally organized, i.e., the right hemisphere controls and processes signals from the left side of the body, while the left hemisphere controls and processes signals from the right side of the body.
There is a strong but not complete
bilateral symmetry between the hemispheres. The
lateralization of brain function looks at the known and possible differences between the two.
Development
In the developing vertebrate
embryo, the
neural tube is subdivided into four unseparated sections which then develop further into distinct regions of the central nervous system; these are the
prosencephalon (
forebrain), the
mesencephalon (
midbrain) the
rhombencephalon (
hindbrain) and the
spinal cord. The prosencephalon develops further into the
telencephalon
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. ...
and the
diencephalon. The dorsal telencephalon gives rise to the pallium (cerebral cortex in mammals and reptiles) and the ventral telencephalon generates the
basal ganglia. The diencephalon develops into the
thalamus and
hypothalamus, including the
optic vesicles (future
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
). The dorsal telencephalon then forms two lateral telencephalic vesicles, separated by the midline, which develop into the left and right cerebral hemispheres. Birds and fish have a dorsal telencephalon, like all vertebrates, but it is generally unlayered and therefore not considered a cerebral cortex. Only a layered cytoarchitecture can be considered a cortex.
Functions
Note: As cerebrum is a gross division with many subdivisions and sub-regions, it is important to state that this section lists functions that cerebrum ''as a whole'' serves. See main articles on cerebral cortex and
basal ganglia for more information. The cerebrum is a major part of the brain, controlling emotions, hearing, vision, personality and much more. It controls all precision of voluntary actions.
Upper motor neurons
Upper motor neurons (UMNs) is a term introduced by William Gowers in 1886. They are found in the cerebral cortex and brainstem and carry information down to activate interneurons and lower motor neurons, which in turn directly signal muscles t ...
in the primary motor cortex send their
axons to the brainstem and spinal cord to
synapse on the
lower motor neurons, which innervate the muscles. Damage to motor areas by chance of cortex can lead to certain types of
motor neuron disease. This kind of damage results in loss of muscular power and precision rather than total
paralysis.
It functions as the center of sensory perception, memory, thoughts and judgement; the cerebrum also functions as the center of voluntary motor activities.
Sensory processing
The primary sensory areas of the cerebral cortex receive and process
visual
The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight ...
,
auditory,
somatosensory
In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position ( proprioception), and pain. It ...
,
gustatory, and
olfactory information. Together with association cortical areas, these brain regions synthesize sensory information into our perceptions of the world.
Olfaction
The
olfactory bulb, responsible for the sense of smell, takes up a large area of the cerebrum in most vertebrates. However, in humans, this part of the brain is much smaller and lies underneath the frontal lobe. The olfactory sensory system is unique since the neurons in the olfactory bulb send their axons directly to the
olfactory cortex, rather than to the
thalamus first. Damage to the olfactory bulb results in a loss of olfaction (the sense of smell).
Language and communication
Speech and language are mainly attributed to the parts of the cerebral cortex. Motor portions of language are attributed to
Broca's area within the frontal lobe. Speech comprehension is attributed to
Wernicke's area, at the temporal-parietal lobe junction. These two regions are interconnected by a large
white matter
White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribu ...
tract, the
arcuate fasciculus
The arcuate fasciculus (AF) is a bundle of axons that generally connects the Broca's area and the Wernicke's area in the brain. It is an association fiber tract connecting caudal temporal cortex and inferior frontal lobe. ''Fasciculus arcuatus' ...
. Damage to the Broca's area results in
expressive aphasia (non-fluent aphasia) while damage to Wernicke's area results in
receptive aphasia (also called fluent aphasia).
Learning and memory
Explicit or declarative (factual) memory formation is attributed to the
hippocampus
The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...
and associated regions of the
medial temporal lobe
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The temporal lobe is involved in p ...
. This association was originally described after a patient known as
HM had both his left and right hippocampus surgically removed to treat chronic
temporal lobe epilepsy. After surgery, HM had
anterograde amnesia, or the inability to form new memories.
Implicit or procedural memory, such as complex motor behaviors, involves the basal ganglia.
Short-term or working memory involves association areas of the cortex, especially the
dorsolateral prefrontal cortex
The dorsolateral prefrontal cortex (DLPFC or DL-PFC) is an area in the prefrontal cortex of the primate brain. It is one of the most recently derived parts of the human brain. It undergoes a prolonged period of maturation which lasts until adult ...
, as well as the hippocampus.
Other animals
In the most primitive vertebrates, the
hagfishes and
lampreys, the cerebrum is a relatively simple structure receiving
nerve impulses
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ca ...
from the
olfactory bulb. In
cartilaginous and
lobe-finned fishes and also in
amphibians, a more complex structure is present, with the cerebrum being divided into three distinct regions. The lowermost (or ventral) region forms the
basal nuclei, and contains fibres connecting the rest of the cerebrum to the thalamus. Above this, and forming the lateral part of the cerebrum, is the ''paleopallium'', while the uppermost (or dorsal) part is referred to as the ''archipallium''. The cerebrum remains largely devoted to olfactory sensation in these animals, in contrast to its much wider range of functions in
amniotes.
In
ray-finned fishes the structure is somewhat different. The inner surfaces of the lateral and ventral regions of the cerebrum bulge up into the
ventricles; these include both the basal nuclei and the various parts of the pallium and may be complex in structure, especially in
teleosts. The dorsal surface of the cerebrum is membranous, and does not contain any
nervous tissue
Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the bra ...
.
In the amniotes, the cerebrum becomes increasingly large and complex. In
reptiles, the paleopallium is much larger than in amphibians and its growth has pushed the basal nuclei into the central regions of the cerebrum. As in the lower vertebrates, the grey matter is generally located beneath the
white matter
White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribu ...
, but in some reptiles, it spreads out to the surface to form a primitive cortex, especially in the anterior part of the brain.
In
mammals, this development proceeds further, so that the cortex covers almost the whole of the cerebral hemispheres, especially in more developed species, such as the
primates. The paleopallium is pushed to the ventral surface of the brain, where it becomes the olfactory lobes, while the archipallium becomes rolled over at the medial dorsal edge to form the
hippocampus
The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...
. In
placental mammals, a
corpus callosum also develops, further connecting the two hemispheres. The complex convolutions of the cerebral surface (see
gyrus,
gyrification) are also found only in higher mammals.
Although some large mammals (such as elephants) have particularly large cerebra,
dolphins are the only species (other than humans) to have cerebra accounting for as much as 2 percent of their body weight.
The cerebra of
birds are similarly enlarged to those of mammals, by comparison with reptiles. The increased size of bird brains was classically attributed to enlarged
basal ganglia, with the other areas remaining primitive, but this view has been largely abandoned.
Birds appear to have undergone an alternate process of
encephalization
Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed to predicted brain mass for an animal of a given size, based on nonlinear regress ...
,
as they diverged from the other
archosaurs, with few clear parallels to that experienced by mammals and their
therapsid ancestors.
Additional images
File:Slide2KLI.JPG, Cerebrum. Lateral face. Deep dissection.
File:Slide4KLI.JPG, Cerebrum. Medial face. Deep dissection.
See also
*
List of regions in the human brain
Notes
References
External links
NIF Search - Cerebrumvia the
Neuroscience Information Framework
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