The frontal lobe is the largest of the four major lobes of the brain in mammals, is located at the front of each hemisphere. It is separated from the parietal lobe by a groove between tissues called the central sulcus, from the temporal lobe by a deeper groove called the lateral sulcus; the most anterior rounded part of the frontal lobe is known as the frontal pole, one of the three poles of the cerebrum. The frontal lobe is covered by the frontal cortex; the frontal cortex includes the premotor cortex, the primary motor cortex – cortical parts of the motor cortex. The front part of the frontal lobe is covered by the prefrontal cortex. There are four principal gyri in the frontal lobe; the precentral gyrus, is directly anterior to the central sulcus, running parallel to it and contains the primary motor cortex, which controls voluntary movements of specific body parts. Three horizontally arranged subsections of the frontal gyrus are the superior frontal gyrus, the middle frontal gyrus, the inferior frontal gyrus.
The inferior frontal gyrus is divided into three parts – the orbital part, the triangular part, the opercular part. The frontal lobe contains most of the dopamine neurons in the cerebral cortex; the dopaminergic pathways are associated with reward, short-term memory tasks and motivation. Dopamine tends to select sensory information arriving from the thalamus to the forebrain; the frontal lobe is the largest lobe of the brain and makes up about a third of the surface area of each hemisphere. On the lateral surface of each hemisphere, the central sulcus separates the frontal lobe from the parietal lobe; the lateral sulcus separates the frontal lobe from the temporal lobe. The frontal lobe can be divided into a lateral, polar and medial part; each of these parts consists of a particular gyrus: Lateral part: lateral part of the superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus. Polar part: Transverse frontopolar gyri, frontomarginal gyrus. Orbital part: Lateral orbital gyrus, anterior orbital gyrus, posterior orbital gyrus, medial orbital gyrus, gyrus rectus.
Medial part: Medial part of the superior frontal gyrus, cingulate gyrus. The gyri are separated by sulci. E.g. the precentral gyrus is in front of the central sulcus, behind the precentral sulcus. The superior and middle frontal gyri are divided by the superior frontal sulcus; the middle and inferior frontal gyri are divided by the inferior frontal sulcus. In humans, the frontal lobe reaches full maturity around the late 20s, marking the cognitive maturity associated with adulthood. A small amount of atrophy, however, is normal in the aging person’s frontal lobe. Fjell, in 2009, studied atrophy of the brain in people aged 60–91 years; the 142 healthy participants were scanned using MRI. Their results were compared to those of 122 participants with Alzheimer's disease. A follow-up one year showed there to have been a marked volumetric decline in those with Alzheimer's and a much smaller decline in the healthy group; these findings corroborate those of Coffey, who in 1992 indicated that the frontal lobe decreases in volume 0.5%–1% per year.
The frontal lobe plays a large role in voluntary movement. It houses the primary motor cortex; the function of the frontal lobe involves the ability to project future consequences resulting from current actions. Frontal lobe functions include override and suppression of unacceptable response as well as differentiation tasks; the frontal lobe plays an important part in integrating longer non-task based memories stored across the brain. These are memories associated with emotions derived from input from the brain's limbic system; the frontal lobe modifies those emotions to fit acceptable norms. Psychological tests that measure frontal lobe function include finger tapping, the Wisconsin Card Sorting Test, measures of language and numeracy skills. Damage to the frontal lobe can result in many different consequences. Transient ischemic attacks known as mini-strokes, strokes are common causes of frontal lobe damage in older adults; these strokes and mini-strokes can occur due to the blockage of blood flow to the brain or as a result of the rupturing of an aneurysm in a cerebral artery.
Other ways in which injury can occur include head injuries such as traumatic brain injuries incurred following accidents, diagnoses such as Alzheimer's disease or Parkinson's disease, frontal lobe epilepsy. Common effects of damage to the frontal lobe are varied. Patients who have experienced frontal lobe trauma may know the appropriate response to a situation but display inappropriate responses to those same situations in "real life". Emotions that are felt may not be expressed in the face or voice. For example, someone, feeling happy would not smile, the voice would be devoid of emotion. Along the same lines, the person may exhibit excessive, unwarranted displays of emotion. Depression is common in stroke patients. Common is a loss of or decrease in motivation. Someone might not want to carry out normal daily activities and would not feel "up to it"; those who are close to the person who has experienced the damage may notice changes in behavior. This personality change is characteristic of damage to the frontal lobe and was exemplified in the case of Phineas Gage.
The frontal lobe is the same part of the brain, responsible for executive functions
Brodmann area 4
Brodmann area 4 refers to the primary motor cortex of the human brain. It is located in the posterior portion of the frontal lobe. Brodmann area 4 is part of the precentral gyrus; the borders of this area are: the precentral sulcus in front, the medial longitudinal fissure at the top, the central sulcus in back, the lateral sulcus along the bottom. 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. 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: the cortex is unusually thick. Brodmann area List of regions in the human brain List of Brodmann areas
Brodmann area 7
Brodmann area 7 is one of Brodmann's cytologically defined regions of the brain. It is involved in locating objects in space, it serves as a point of convergence between vision and proprioception to determine where objects are in relation to parts of the body. Brodmann area 7, is part of the parietal cortex in the human brain. Situated posterior to the primary somatosensory cortex, superior to the occipital lobe, this region is believed to play a role in visuo-motor coordination. In addition, area 7 along with area 5 has been linked to a wide variety of high-level processing tasks, including activation in association with language use; this function in language has been theorized to stem from how these two regions play a vital role in generating conscious constructs of objects in the world. Brodmann area 7 spans both the lateral walls of the parietal cortex. Medially, the area corresponding to Brodmann area 7 is called precuneus. Laterally, it is called the superior parietal lobule. At the base of the SPL is the intraparietal sulcus, below, the inferior parietal lobule, which in turn divides into Brodmann areas 39 and 40.
Brodmann area 7 is a subdivision of the cytoarchitecturally defined parietal region of cerebral cortex in Guenon primates. It occupies most of the parietal lobe excluding superior parietal lobule; this layer is distinguished by a lack of large ganglion cells in cortical layer V larger layer III pyramidal cells, a multiform layer VI, bounded by white matter tracts. Brodmann area Korbinian Brodmann List of regions in the human brain Precuneus ancil-67 at NeuroNames
Brodmann area 18
Brodmann area 18, or BA18, is part of the occipital cortex in the human brain. It accounts for the bulk of the volume of the occipital lobe, it is known as a "Visual Association Area" and is responsible for the interpretation of images. This area is known as parastriate area 18, it is a subdivision of the cytoarchitecturally defined occipital region of cerebral cortex. In the human it is located in parts of the cuneus, the lingual gyrus and the lateral occipital gyrus of the occipital lobe, it is bounded on one side by the Brodmann area 17, from which it is distinguished by absence of a band of Gennari, on the other by the peristriate area 19. Brodmann area 18 is a subdivision of the cerebral cortex of the guenon defined on the basis of cytoarchitecture, it is cytoarchitecturally homologous to parastriate area 18 of the human. Distinctive features: a wide, dense internal granular cell layer. Like area 17 of Brodmann-1905, area 18 is thin, with the three deep layers thin relative to the three outer layers, has distinct boundaries between layers, abundance of granule cells, narrow layer VI, sharp boundary between cortex and subcortical white matter.
Brodmann area List of regions in the human brain For Neuroanatomy of the parastriate area 18 visit BrainInfo For Neuroanatomy of Brodmann area 18 visit BrainInfo
Brodmann area 19
Brodmann area 19, or BA 19, is part of the occipital lobe cortex in the human brain. Along with area 18, it comprises the extrastriate cortex. In humans with normal sight, extrastriate cortex is a visual association area, with feature-extracting, shape recognition and multimodal integrating functions; this area is known as peristriate area 19, it refers to a subdivision of the cytoarchitecturally defined occipital region of cerebral cortex. In the human it is located in parts of the lingual gyrus, the cuneus, the lateral occipital gyrus and the superior occipital gyrus of the occipital lobe where it is bounded by the parieto-occipital sulcus, it is bounded on one side by the parastriate area 18. It is bounded rostrally by the angular area 39 and the occipitotemporal area 37. Brodmann area 19-1909 is a subdivision of the cerebral cortex of the guenon defined on the basis of cytoarchitecture, it is cytoarchitecturally homologous to the peristriate area 19 of the human. Distinctive features: Compared to Brodmann area 18-1909, the pyramidal cells of sublayer 3b of the external pyramidal layer are not as densely distributed, the layer is not as narrow, its boundary with the internal granular layer is not as distinct.
Area 19 is a histologically delineated band anterolaterally abutting visual area 18. Single-cell electrophysiological recordings from area 19 in the cat suggest sensitivity to motion-delineated forms. In humans, this band is reputed to contain regions of the visual areas designated V3, V4, V5, V6 in the primate. Functional magnetic resonance imaging shows the existence of various retinotopic maps within area 19. In general, the diverse fields that comprise area 19 have reciprocal connections with areas 17 and 18, as well as posterior parietal and inferior temporal association areas. Area 19 has been noted to receive inputs from the retina via the superior colliculus and pulvinar, may contribute to the phenomenon of blindsight. In patients blind from a young age, the area has been found to be activated by somatosensory stimuli; because of these findings, it is thought that area 19 is the differentiation point of the two visual streams, of the'what' and'where' visual pathways. The dorsal region may contain motion-sensitive neurons, ventral areas may be specialised for object recognition.
Brodmann area List of regions in the human brain Hyvarinen, J. Carlson, Y. and Hyvarinen, L. Early visual deprivation alters modality of neuronal responses in area 19 of monkey cortex, Neurosci. Lett. 26, 239–243 Theories of visual cortex organization in primates: areas of the third level, Prog Brain Res. 1996.
Humans are the only extant members of the subtribe Hominina. Together with chimpanzees and orangutans, they are part of the family Hominidae. A terrestrial animal, humans are characterized by their erect bipedal locomotion. Early hominins—particularly the australopithecines, whose brains and anatomy are in many ways more similar to ancestral non-human apes—are less referred to as "human" than hominins of the genus Homo. Several of these hominins used fire, occupied much of Eurasia, gave rise to anatomically modern Homo sapiens in Africa about 315,000 years ago. Humans began to exhibit evidence of behavioral modernity around 50,000 years ago, in several waves of migration, they ventured out of Africa and populated most of the world; the spread of the large and increasing population of humans has profoundly affected much of the biosphere and millions of species worldwide. Advantages that explain this evolutionary success include a larger brain with a well-developed neocortex, prefrontal cortex and temporal lobes, which enable advanced abstract reasoning, problem solving and culture through social learning.
Humans use tools better than any other animal. Humans uniquely use such systems of symbolic communication as language and art to express themselves and exchange ideas, organize themselves into purposeful groups. Humans create complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established an wide variety of values, social norms, rituals, which together undergird human society. Curiosity and the human desire to understand and influence the environment and to explain and manipulate phenomena have motivated humanity's development of science, mythology, religion and numerous other fields of knowledge. Though most of human existence has been sustained by hunting and gathering in band societies many human societies transitioned to sedentary agriculture some 10,000 years ago, domesticating plants and animals, thus enabling the growth of civilization; these human societies subsequently expanded, establishing various forms of government and culture around the world, unifying people within regions to form states and empires.
The rapid advancement of scientific and medical understanding in the 19th and 20th centuries permitted the development of fuel-driven technologies and increased lifespans, causing the human population to rise exponentially. The global human population was estimated to be near 7.7 billion in 2015. In common usage, the word "human" refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of "hominid" and "hominin" have changed during the recent decades with advances in the discovery and study of the fossil ancestors of modern humans; the clear boundary between humans and apes has blurred, resulting in now acknowledging the hominids as encompassing multiple species, Homo and close relatives since the split from chimpanzees as the only hominins. There is a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species; the English adjective human is a Middle English loanword from Old French humain from Latin hūmānus, the adjective form of homō "man."
The word's use as a noun dates to the 16th century. The native English term man can refer to the species as well as to human males, or individuals of either sex; the species binomial "Homo sapiens" was coined by Carl Linnaeus in his 18th-century work Systema Naturae. The generic name "Homo" is a learned 18th-century derivation from Latin homō "man," "earthly being"; the species-name "sapiens" means "wise" or "sapient". Note that the Latin word homo refers to humans of either gender, that "sapiens" is the singular form; the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. Modern humans, defined as the species Homo sapiens or to the single extant subspecies Homo sapiens sapiens, proceeded to colonize all the continents and larger islands, arriving in Eurasia 125,000–60,000 years ago, Australia around 40,000 years ago, the Americas around 15,000 years ago, remote islands such as Hawaii, Easter Island and New Zealand between the years 300 and 1280.
The closest living relatives of humans are gorillas. With the sequencing of the human and chimpanzee genomes, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. By using the technique called a molecular clock which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated; the gibbons and orangutans were the first groups to split from the line leading to the h
The guenons are the genus Cercopithecus of Old World monkeys. Not all members of this genus have the word "guenon" in their common names. Nonetheless, the use of the term guenon for monkeys of this genus is accepted. All members of the genus are endemic to sub-Saharan Africa, most are forest monkeys. Many of the species are quite local in their ranges, some have more local subspecies. Many are endangered because of habitat loss; the species placed in the genus Chlorocebus, such as vervet monkeys and green monkeys, were considered as a single species in this genus, Cercopithecus aethiops. In the English language, the word "guenon" is of French origin. In French, guenon was the common name for all species and individuals, both males and females, from the genus Cercopithecus. In all other monkey and apes species, the French word guenon only designates the females. Genus Cercopithecus C. dryas group Dryas monkey or Salongo monkey, Cercopithecus dryas C. diana group Diana monkey, Cercopithecus diana Roloway monkey, Cercopithecus roloway C. mitis group Greater spot-nosed monkey, Cercopithecus nictitans Cercopithecus nictitans nictitans Bioko putty-nosed guenon, Cercopithecus nictitans martini Blue monkey, Cercopithecus mitis Pluto monkey, Cercopithecus mitis mitis Silver monkey, Cercopithecus doggetti Golden monkey, Cercopithecus kandti Sykes' monkey, Cercopithecus albogularis Zanzibar Sykes' monkey, Cercopithecus albogularis albogularis Pousargues' Sykes' monkey, Cercopithecus albogularis albotorquatus Cercopithecus albogularis erythrarchus Cercopithecus albogularis francescae Cercopithecus albogularis kibonotensis Cercopithecus albogularis kolbi White-lipped monkey, Cercopithecus albogularis labiatus Cercopithecus albogularis moloneyi Cercopithecus albogularis monoides Cercopithecus albogularis phylax Cercopithecus albogularis schwarzi Zammarano's white-throated guenon, Cercopithecus albogularis zammaranoi C. mona group Mona monkey, Cercopithecus mona Campbell's mona monkey, Cercopithecus campbelli Lowe's mona monkey, Cercopithecus lowei Crested mona monkey, Cercopithecus pogonias Cercopithecus pogonias pogonias Cercopithecus pogonias nigripes Cercopithecus pogonias grayi Cercopithecus pogonias schwarzianus Wolf's mona monkey, Cercopithecus wolfi Cercopithecus wolfi wolfi Cercopithecus wolfi elegans Dent's mona monkey, Cercopithecus denti C. cephus group Lesser spot-nosed monkey, Cercopithecus petaurista Cercopithecus petaurista petaurista Cercopithecus petaurista buettikoferi White-throated guenon, Cercopithecus erythrogaster Red-eared guenon, Cercopithecus erythrotis Bioko red-eared guenon, Cercopithecus erythrotis erythrotis Cercopithecus erythrotis camerunensis Moustached guenon, Cercopithecus cephus Cercopithecus cephus cephus Cercopithecus cephus cephodes Ngotto guenon, Cercopithecus cephus ngottoensis Red-tailed monkey, Cercopithecus ascanius Cercopithecus ascanius ascanius Cercopithecus ascanius atrinasus Cercopithecus ascanius whitesidei Cercopithecus ascanius katangae Schmidt's guenon, Cercopithecus ascanius schmidti Sclater's guenon, Cercopithecus sclateri C. lhoesti group L'Hoest's monkey, Cercopithecus lhoesti Preuss's monkey, Cercopithecus preussi Sun-tailed monkey, Cercopithecus solatus C. hamlyni group Hamlyn's monkey, Cercopithecus hamlyni Owl-faced guenon, Cercopithecus hamlyni hamlyni Kahuzi owl-faced guenon, Cercopithecus hamlyni kahuziensis Lesula, Cercopithecus lomamiensis C. neglectus group De Brazza's monkey, Cercopithecus neglectus The red-tailed monkey is known to hybridize with the blue monkey in several locations in the wild in Africa.
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