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Brodmann area 8 is one of Brodmann's cytologically defined regions of the brain. It is involved in planning complex movements.
File:Brodmann area 8 animation small.gif, Animation.
File:Brodmann area 8 frontal.jpg, front view.
File:Brodmann area 8 lateral.jpg, Lateral view.
File:Brodmann area 8 medial.jpg, Medial view.
Brodmann area 8 is one of Brodmann's cytologically defined regions of the brain. It is involved in planning complex movements.
Human
Brodmann area 8, or BA8, is part of the frontalcortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
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 ...
. Situated just anterior to the premotor cortex ( BA6), it includes the frontal eye fields
The frontal eye fields (FEF) are a region located in the frontal cortex, more specifically in Brodmann area 8 or BA8, of the primate brain. In humans, it can be more accurately said to lie in a region around the intersection of the middle frontal ...
(so-named because they are believed to play an important role in the control of eye movements). Damage to this area, by stroke, trauma or infection, causes tonic deviation of the eyes towards the side of the injury. This finding occurs during the first few hours of an acute event such as cerebrovascular infarct (stroke) or hemorrhage (bleeding).
Guenon
The term Brodmann area 8 refers to a cytoarchitecturally defined portion of the frontal lobe of theguenon
The guenons (, ) are Old World monkeys of the genus ''Cercopithecus'' (). Not all members of this genus have the word "guenon" in their common names; also, because of changes in scientific classification, some monkeys in other genera may have co ...
. Located rostral to the arcuate sulcus, it was not considered by Brodmann-1909 to be topographically homologous to the intermediate frontal area 8 of the human.
Distinctive features (Brodmann-1905): compared to Brodmann area 6
Brodmann area 6 (BA6) is part of the frontal cortex in the human brain. Situated just anterior to the primary motor cortex ( BA4), it is composed of the premotor cortex and, medially, the supplementary motor area (SMA). This large area of the fr ...
-1909, area 8 has a diffuse but clearly present internal granular layer (IV); sublayer 3b of the external pyramidal layer (III) has densely distributed medium-sized pyramidal cell
Pyramidal cells, or pyramidal neurons, are a type of multipolar neuron found in areas of the brain including the cerebral cortex, the hippocampus, and the amygdala. Pyramidal cells are the primary excitation units of the mammalian prefrontal cort ...
s; the internal pyramidal layer (V) has larger ganglion cells
Introduction
In neurophysiology, a ganglion cell is a cell found in a ganglion (a cluster of neurons in the peripheral nervous system). Depending on their location and function, ganglion cells can be categorized into several major groups:
* ...
densely distributed with some granule cell
The name granule cell has been used for a number of different types of neurons whose only common feature is that they all have very small cell bodies. Granule cells are found within the granular layer of the cerebellum, the dentate gyrus of t ...
s interspersed; the external granular layer (II) is denser and broader; cell layers are more distinct; the abundance of cells is somewhat greater.
Functions
The area is involved ineye movements
Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of i ...
and possibly in the management of uncertainty. A functional magnetic resonance imaging
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...
study demonstrated that Brodmann area 8 activation occurs when test subjects experience uncertainty, and that with increasing uncertainty there is increasing activation.
An alternative interpretation is that this activation in the frontal cortex encodes hope, a higher-order expectation positively correlated with uncertainty.
Image
See also
*Brodmann area
A Brodmann area is a region of the cerebral cortex, in the human or other primate brain, defined by its cytoarchitecture, or histological structure and organization of cells. The concept was first introduced by the German anatomist Korbinian B ...
* List of regions in the human brain
The human brain anatomical regions are ordered following standard neuroanatomy hierarchies. Functional, connective, and developmental regions are listed in parentheses where appropriate.
Hindbrain (rhombencephalon)
Myelencephalon
* M ...
References