Brodmann area 4
Encyclopedia
Brodmann area 4 comprises the primary motor cortex
of the human brain
. It is located in the posterior portion of the frontal lobe
.
Brodmann area 4 is about the same as the precentral gyrus. The borders of this area are: the precentral sulcus
in front (anteriorly), the medial longitudinal fissure
at the top (medial
ly), the central sulcus
in back (posteriorly), and the lateral sulcus
along the bottom (laterally).
This area of cortex, as shown by Wilder Penfield
and others, has the pattern of a homunculus
. That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the area shown here; and the face is near the bottom of the figure. Because Brodmann area 4 is in the same general location as primary motor cortex
, the homunculus
here is called the motor homunculus.
The term area 4 of Brodmann-1909 refers to a cytoarchitecturally defined portion of the frontal lobe
of the guenon
. It is located predominantly in the precentral gyrus. Brodmann
-1909 regarded it as topographically and cytoarchitecturally homologous to the human gigantopyramidal area 4 and noted that it occupies a much greater fraction of the frontal lobe in the monkey than in the human. Distinctive features (Brodmann-1905): the cortex is unusually thick; the layers are not distinct; the cells are relatively sparsely distributed; giant pyramidal (Betz) cell
s are present in the internal pyramidal layer (V); lack of an internal granular layer
(IV) such that the boundary between the external pyramidal layer (III) and the internal pyramidal layer (V) is indistinct; lack of a distinct external granular layer (II); a gradual transition from the multiform layer (VI) to the subcortical white matter
.
Primary motor cortex
The primary motor cortex is a brain region that in humans is located in the posterior portion of the frontal lobe. Itworks in association with pre-motor areas to plan and execute movements. M1 contains large neurons known as Betz cells, which send long axons down the spinal cord to synapse onto...
of the human brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. It is located in the posterior portion of the frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...
.
Brodmann area 4 is about the same as the precentral gyrus. The borders of this area are: the precentral sulcus
Precentral sulcus
The precentral sulcus lies parallel to, and in front of, the central sulcus....
in front (anteriorly), the medial longitudinal fissure
Medial longitudinal fissure
The great longitudinal fissure is the deep groove which separates the two hemispheres of the vertebrate brain....
at the top (medial
Medial
- Medial magmas :In abstract algebra, a medial magma is a set with a binary operation which satisfies the identity \cdot = \cdot , or more simply, xy\cdot uv = xu\cdot yv...
ly), the central sulcus
Central sulcus
-External links:* via the Neuroscience Information Framework...
in back (posteriorly), and the lateral sulcus
Lateral sulcus
-External links:* * * http://www.uams.edu/radiology/education/residency/diagnostic/pdf/sylvian_cistern_RSNA2003.pdf...
along the bottom (laterally).
This area of cortex, as shown by Wilder Penfield
Wilder Penfield
Wilder Graves Penfield, OM, CC, CMG, FRS was an American born Canadian neurosurgeon. During his life he was called "the greatest living Canadian"...
and others, has the pattern of a homunculus
Homunculus
Homunculus is a term used, generally, in various fields of study to refer to any representation of a human being. Historically, it referred specifically to the concept of a miniature though fully formed human body, for example, in the studies of alchemy and preformationism...
. That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the area shown here; and the face is near the bottom of the figure. Because Brodmann area 4 is in the same general location as primary motor cortex
Primary motor cortex
The primary motor cortex is a brain region that in humans is located in the posterior portion of the frontal lobe. Itworks in association with pre-motor areas to plan and execute movements. M1 contains large neurons known as Betz cells, which send long axons down the spinal cord to synapse onto...
, the homunculus
Homunculus
Homunculus is a term used, generally, in various fields of study to refer to any representation of a human being. Historically, it referred specifically to the concept of a miniature though fully formed human body, for example, in the studies of alchemy and preformationism...
here is called the motor homunculus.
The term area 4 of Brodmann-1909 refers to a cytoarchitecturally defined portion of the frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...
of the guenon
Guenon
The guenons are the genus Cercopithecus of Old World monkeys. Not all the members of this genus have the word "guenon" in their common names, and because of changes in scientific classification, some monkeys in other genera may have common names that do include the word "guenon"...
. It is located predominantly in the precentral gyrus. Brodmann
Brodmann
Brodmann may refer to:* Korbinian Brodmann, German neurologist* Brodmann area, a region in the brain cortex...
-1909 regarded it as topographically and cytoarchitecturally homologous to the human gigantopyramidal area 4 and noted that it occupies a much greater fraction of the frontal lobe in the monkey than in the human. Distinctive features (Brodmann-1905): the cortex is unusually thick; the layers are not distinct; the cells are relatively sparsely distributed; giant pyramidal (Betz) cell
Pyramidal cell
Pyramidal neurons are a type of neuron found in areas of the brain including cerebral cortex, the hippocampus, and in the amygdala. Pyramidal neurons are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract. Pyramidal neurons were first discovered and...
s are present in the internal pyramidal layer (V); lack of an internal granular layer
Granular layer
The term granular layer may refer to:*the granular layer of Tomes, seen in dentin of the teeth. When dry section of the root dentin of teeth are visualized under transmitted light, a granular layer is seen adjacent to cementum.It is believed to be caused by coalescing & looping of terminal portion...
(IV) such that the boundary between the external pyramidal layer (III) and the internal pyramidal layer (V) is indistinct; lack of a distinct external granular layer (II); a gradual transition from the multiform layer (VI) to the subcortical white matter
White matter
White matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...
.