The cerebrum (: cerebra), telencephalon or endbrain is the largest part of the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

, containing the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...

(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 hemispheres ...

s) as well as several subcortical structures, including the

hippocampus The hippocampus (: hippocampi; via Latin from Ancient Greek, Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the ...

basal ganglia The basal ganglia (BG) or basal nuclei are a group of subcortical Nucleus (neuroanatomy), nuclei found in the brains of vertebrates. In humans and other primates, differences exist, primarily in the division of the globus pallidus into externa ...

, and

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...

. In the

human brain The human brain is the central organ (anatomy), organ of the nervous system, and with the spinal cord, comprises the central nervous system. It consists of the cerebrum, the brainstem and the cerebellum. The brain controls most of the activi ...

, the cerebrum is the uppermost region of the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

. The cerebrum develops prenatally from the

forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions. Ve ...

(prosencephalon). In mammals, the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

telencephalon, or pallium, develops into the cerebral cortex, and the ventral telencephalon, or subpallium, becomes the

. The cerebrum is also divided into approximately symmetric left and right cerebral hemispheres. With the assistance of the

cerebellum The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or eve ...

, the cerebrum controls all voluntary actions in the human body.

Structure

The cerebrum is the largest part of the

. Depending upon the position of the animal, it lies either in front or on top of the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

. 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), and the underlying regions of

white matter White matter refers to areas of the central nervous system that are mainly made up of myelinated axons, also called Nerve tract, tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distr ...

. 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

, 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 (: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulcus (neuroanatomy), sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the brain in huma ...

(ridges) and sulci (furrows) which increase the

surface area The surface area (symbol ''A'') 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 d ...

. The cerebral cortex is generally classified into four lobes: the frontal, parietal, occipital and temporal lobes. The lobes are classified based on their overlying neurocranial bones. A smaller lobe is the insular lobe, a part of the cerebral cortex folded deep within the lateral sulcus that separates the temporal lobe from the parietal and frontal lobes, is located within each hemisphere of the mammalian brain.

Cerebral hemispheres

The cerebrum is divided by the medial longitudinal fissure into two

s, the right and the left. The cerebrum is contralaterally organized, i.e., the right hemisphere controls and processes signals (predominantly) from the left side of the body, while the left hemisphere controls and processes signals (predominantly) from the right side of the body. According to current knowledge, this is due to an axial twist that occurs in the early embryo. There is a strong but not complete

bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symme ...

between the hemispheres, while lateralization tends to increase with increasing brain size. The

lateralization of brain function The lateralization of brain function (or hemispheric dominance/ lateralization) is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates ...

looks at the known and possible differences between the two.

Development

In the developing vertebrate

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

, the

neural tube In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, ...

is subdivided into four unseparated sections which then develop further into distinct regions of the

; these are the prosencephalon (

), the mesencephalon (

midbrain The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

) the rhombencephalon ( hindbrain) and the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

. The prosencephalon develops further into the

telencephalon The cerebrum (: cerebra), 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 olf ...

and the diencephalon. The dorsal telencephalon gives rise to the pallium (cerebral cortex in mammals and reptiles) and the ventral telencephalon generates the

. The diencephalon develops into the

thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...

and

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

, including the optic vesicles (future

retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

). 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 the cerebrum is a gross division with many subdivisions and sub-regions, it is important to state that this section lists only functions that the cerebrum ''as a whole'' serves. (See main articles on cerebral cortex and

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, and it functions as the center of sensory perception, memory, thoughts and judgement; the cerebrum also functions as the center of voluntary motor activities.

Motor functions

Upper motor neurons in the primary motor cortex send their

axons An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...

to the brainstem and spinal cord to

synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

on the lower motor neurons, which innervate the muscles. Damage to motor areas of the 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 Paralysis (: paralyses; also known as plegia) is a loss of Motor skill, motor function in one or more Skeletal muscle, muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory d ...

Sensory processing

The primary sensory areas of the cerebral cortex receive and process visual, auditory, somatosensory, gustatory, and olfactory information. Together with association cortical areas, these brain regions synthesize sensory information into our perceptions of the world.

Olfaction

The

, 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

first. Olfaction is also the only sense that is represented by the ipsilateral side of the brain. Damage to the olfactory bulb results in a loss of olfaction (the sense of smell).

Language and communication

Speech Speech is the use of the human voice as a medium for language. Spoken language combines vowel and consonant sounds to form units of meaning like words, which belong to a language's lexicon. There are many different intentional speech acts, suc ...

and language are mainly attributed to parts of the cerebral cortex. Motor portions of language are attributed to

Broca's area Broca's area, or the Broca area (, also , ), is a region in the frontal lobe of the dominant Cerebral hemisphere, hemisphere, usually the left, of the Human brain, brain with functions linked to speech production. Language processing in the brai ...

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

tract, the arcuate fasciculus. Damage to the Broca's area results in

expressive aphasia Expressive aphasia (also known as Broca's aphasia) is a type of aphasia characterized by partial loss of the ability to produce language (Spoken language, spoken, Sign language, manual, or Written language, written), although comprehension genera ...

(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

and associated regions of the medial temporal lobe. This association was originally described after a patient known as HM had both his left and right hippocampus surgically removed to treat chronic emporal 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 into adulthoo ...

, as well as the hippocampus.

Other animals

In the most primitive vertebrates, the

hagfish Hagfish, of the Class (biology), class Myxini (also known as Hyperotreti) and Order (biology), order Myxiniformes , are eel-shaped Agnatha, jawless fish (occasionally called slime eels). Hagfish are the only known living Animal, animals that h ...

es and

lamprey Lampreys (sometimes inaccurately called lamprey eels) are a group of Agnatha, jawless fish comprising the order (biology), order Petromyzontiformes , sole order in the Class (biology), class Petromyzontida. The adult lamprey is characterize ...

s, the cerebrum is a relatively simple structure receiving nerve impulses from the

. In cartilaginous and lobe-finned fishes and also in

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

s, 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

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

s. In

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

es, 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

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

s. 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 brain ...

. In the amniotes, the cerebrum becomes increasingly large and complex. In

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s, 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

, but in some reptiles, it spreads out to the surface to form a primitive cortex, especially in the anterior part of the brain. In

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s, this development proceeds further, so that the cortex covers almost the whole of the cerebral hemispheres, especially in more developed species, such as the

primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

s. 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

. In placental mammals, a

corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental ...

also develops, further connecting the two hemispheres. The complex convolutions of the cerebral surface (see

gyrus In neuroanatomy, a gyrus (: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the brain in humans and other mammals. ...

gyrification Gyrification is the process of forming the characteristic folds of the cerebral cortex. The peak of such a fold is called a ''gyrus'' (pl. ''gyri''), and its trough is called a ''Sulcus (neuroanatomy), sulcus'' (pl. ''sulci''). The neurons of the ...

) are also found only in higher mammals. Although some large mammals (such as elephants) have particularly large cerebra,

dolphins A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

are the only species (other than humans) to have cerebra accounting for as much as 2 percent of their body weight. The cerebra of

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s are similarly enlarged to those of mammals, by comparison with reptiles. The increased size of bird brains was classically attributed to enlarged

, with the other areas remaining primitive, but this view has been largely abandoned. Birds appear to have undergone an alternate process of encephalization, 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.

References

External links

NIF Search - Cerebrum
via the

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