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Brodmann area 10

Brodmann area 10

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Brodmann area 10, or BA10 is the frontopolar part of the frontal
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...

 cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

 in the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

. BA10 was originally defined in terms of cytoarchitectonic traits in autopsy brains; modern functional imaging
Functional imaging
Functional imaging , is a method of detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorption....

 research cannot directly identify these boundaries and the terms anterior prefrontal, rostral prefrontal cortex and frontopolar prefrontal cortex are used to refer to the area in the most anterior part of the frontal cortex that approximates to or principally covers BA10.

BA10 is the largest cytoarchitectonic area in the human brain. It has been described as "one of the least well understood regions of the human brain". Present research suggests that it is involved in strategic processes in memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

 retrieval and executive function. During human evolution
Human evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...

, the functions in this area resulted in its expansion relative to the rest of the brain.

Size


The volume of the human area 10 is 14 cm3 and 1.2% of brain volume. This is twice what would be expected in a hominoid with a human sized brain. For comparison the volume of bonobo
Bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...

 area 10 is 2.8 cm3 and makes up only 0.74% of its brain. In each hemisphere, area 10 contains an estimated 250 million neurons.

Location


This area is a subdivision of the cytoarchitecturally defined frontal region of cerebral cortex. It occupies the most rostral portions of the superior frontal gyrus
Superior frontal gyrus
The superior frontal gyrus makes up about one-third of the frontal lobe of the human brain. It is bounded laterally by the superior frontal sulcus....

 and the middle frontal gyrus
Middle frontal gyrus
The middle frontal gyrus makes up about one-third of the frontal lobe of the human brain....

. In humans, on the medial aspect of the hemisphere it is bounded ventrally by the superior rostral sulcus. It does not extend as far as the cingulate sulcus
Cingulate sulcus
The cingulate sulcus is a sulcus on the medial wall of the cerebral cortex. The frontal and parietal lobes are separated by the cingulate sulcus from the cingulate gyrus.-External links:* via the Neuroscience Information Framework...

. Cytoarchitecturally it is bounded dorsally by the granular frontal area 9, caudally by the middle frontal area 46, and ventrally by the orbital area 47 and by the rostral area 12 or, in an early version of Brodmann's cortical map (Brodmann-1909), the prefrontal Brodmann area 11
Brodmann area 11
Brodmann area 11 is one of Brodmann's cytologically defined regions of the brain. It is involved in planning, reasoning, and decision making.-Human:Brodmann area 11, or BA11, is part of the frontal cortex in the human brain...

-1909.

Area 10 lies underneath a bony air sinus which has limited Electrophysiology
Electrophysiology
Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...

 research upon it.

Relation to frontal pole


In humans the frontal pole area of the prefrontal cortex includes not only area 10 but part of BA 9. BA 10 also extends beyond the pole area into its ventromedial side. In 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"...

 monkeys, the pole area is filled by BA 12 (and its BA 10 is found in the orbital prefrontal region).

Cytoarchitecture


In humans the six cortical layers of area 10 have been described as having a "remarkably homogeneous appearance". All of them are readily identified. Relative to each other, layer I is thin to medium in width making up 11% of the depth of area 10. Layer II is thin and contains small granular and pyramidal medium to dark staining cells (in terms of Nissl staining) which colors RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 and DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

. The widest layer is III. Its pyramidal neurons are smaller nearer the above layer II than the below layer IV. Like layer II its cells are medium to dark. Layers II and III make up 43% of the cortex depth. Layer IV has clear borders with layers III above and V below and it thin. Its cells are pale to medium in staining. Layer V is wide and contains two distinct sublayers, Va and Vb. The density of cells Va is greater than in Vb and have darker staining. Layers IV and V make up 40% of cortical thickness. Layer VI below layer V and above the white matter contains dark pyramidal and fusiform neurons. It contributes 6% of area 10 thickness.

Area 10 differs from the adjasant Brodmann 9 in that the latter has a more distinct layer Vb and more prominent layer II. Neighbouring Brodmann area 11 compared to area 10 has a thinner layer IV with more prominent layers Va, Vb and II.

Area 10 in humans has the lowest neuron density among primate brains. It is also unusual in that its neurons have particularly extensive dendritic arborization and are highly dense with dendritic spines. This situation has been suggested to enable integration of inputs from multiple areas.

Subareas


BA 10 is divided into three sub-areas, 10p, 10m and 10r. 10p
occupies the frontal pole while the other two cover the ventromedial part of the prefrontal cortex. Area 10m has thin layers II and IV and a more prominent layer V. In contrast, area 10r has a prominent layer II and a thicker layer IV. Large pyramidal cells are also present in 10r layer III and even more so in area 10p. But it is noted that the, "differences between the three
areas are gradual, however, and it is difficult to draw sharp boundaries between them".

Connections


Research upon primates suggests that area 10 has inputs and output connections with other higher-order association cortex areas particularly in the prefrontal cortex while having few with primary sensory or motor areas. Its connections through the extreme capsule
Extreme capsule
The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between such areas as the claustrum and the insular cortex, and the inferior frontal gyrus and the middle-posterior portion of the superior temporal gyrus...

 link it to the auditory and multisensory areas of the superior temporal sulcus
Superior temporal sulcus
The superior temporal sulcus is the sulcus separating the superior temporal gyrus from the middle temporal gyrus in the temporal lobe of the brain. The superior temporal sulcus is the first sulcus inferior to the lateral fissure....

. They also continue in the medial longitudinal fasciculus
Medial longitudinal fasciculus
The medial longitudinal fasciculus is a pair of crossed fiber tracts , one on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem and are composed of both ascending and descending fibers that arise from a number of sources and terminate in different...

 in the white matter of the superior temporal gyrus areas on the superior temporal gyrus (areas TAa, TS2, and TS3) and nearby multisensory areas on the upper bank of the superior temporal sulcus (TPO). Another area connected through the extreme capsule is the ventral region of the insula
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...

. Connections through the cingulate fasciculus link area 10 to the anterior
Anterior cingulate cortex
The anterior cingulate cortex is the frontal part of the cingulate cortex, that resembles a "collar" form around the corpus callosum, the fibrous bundle that relays neural signals between the right and left cerebral hemispheres of the brain...

, posterior cingulate cortex, and retrosplenial cortex. The uncinate fasciculus
Uncinate fasciculus
The uncinate fasciculus is a white matter tract in the human brain that connects parts of the limbic system such as the hippocampus and amygdala in the temporal lobe with frontal ones such as the orbitofrontal cortex. Its function is unknown though it is affected in several psychiatric conditions...

 connects it with the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...

, temporopolar proisocortex
Proisocortex
Proisocortex is an area in the cerebral cortex. It is a transitional area between the isocortex and periallocortex.It is found in cingulate cortex , insula and parahippocampal gyrus.- External links :* , BrainInfo....

 and anterior most part of the superior temporal gyrus. There are no connections to the parietal cortex, occipital cortex nor inferotemporal cortex

Its connections have been summarized as "it seems not to be interconnected with ‘downstream’ areas in the way that other prefrontal areas are. .. it is the only prefrontal region that is predominantly (and possibly exclusively) interconnected with supramodal cortex in the PFC, anterior temporal cortex and cingulate cortex." It has been proposed that due to this connectivity that it can "play a major role in the highest level of integration of information coming from visual, auditory, and somatic sensory systems to achieve amodal, abstract, conceptual interpretation of the environment .. and may be the anatomical basis for the suggested role of the rostral prefrontal cortex in influencing abstract information processing and the integration of the outcomes of multiple cognitive operations".

Evolution


Katerina Semendeferi and colleagues has suggested that "During hominid evolution, area 10 underwent a couple of .. changes: one involves a considerable increase in overall size, and the other involves a specific increase in connectivity, especially with other higher-order association areas."

Cranial endocast
Endocast
An endocast is the internal cast of a hollow object, often specifically used for an endocasts of the cranial vault. Endocasts can be man-made for examining the properties of a hollow, inaccessible space, or occur naturally through fossilisation....

s taken from the inside of the skull of Homo floresiensis
Homo floresiensis
Homo floresiensis is a possible species, now extinct, in the genus Homo. The remains were discovered in 2003 on the island of Flores in Indonesia. Partial skeletons of nine individuals have been recovered, including one complete cranium...

show an expansion in the frontal polar region suggesting enlargement in its Brodmann's area 10.

Function


Although this region is extensive in humans, its function is poorly understood. Koechlin & Hyafil have proposed that processing of 'cognitive branching' is the core function of the frontopolar cortex. Cognitive branching enables a previously running task to be maintained in a pending state for subsequent retrieval and execution upon completion of the ongoing one. Many of our complex behaviors and mental activities require simultaneous engagement of multiple tasks, and they suggest the anterior prefrontal cortex may perform a domain-general function in these scheduling operations. However, other hypotheses have also been proffered, such as those by Burgess et al..

External links

- "frontopolar area 10" - "Brodmann area 10"