Broca's area

Broca's area
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Brain: Broca's area

Broca's area is a section of the human brain that is involved in language processing, speech or sign[1] production, and comprehension. Broca's area is named after the 19th-century physician Paul Broca. The concept of Broca's Area was originally produced with the intent to explain how speech production was inhibited in the learning of communication by the deaf; however, it is currently used to describe many anatomical aspects of psychological processing mechanisms.
Contents[hide]
1 Description
1.1 Parts
2 Aphasia
3 Evolution of human language[9]
4 See also
5 References

[edit] Description
Broca's area is located in the opercular and triangular sections of the inferior frontal gyrus of the frontal lobe of the cortex. Broca's and Wernicke's areas are found unilaterally in the brain (dominant hemisphere, usually left hemisphere). It is supplied by the superior division of the Left Middle Cerebral Artery.
Broca's area comprises Brodmann area 44[2] and (according to some authorities) Brodmann area 45.[3][4][5] Broca's Area is connected to Wernicke's area by a neural pathway called the arcuate fasciculus. The corresponding area in macaque monkeys is responsible for high-level control over orofacial actions.[6]

[edit] Parts
Broca's area has two main parts, which express different roles during language comprehension and production:
Pars triangularis (anterior), which is thought to support the interpretation of various 'modes' of stimuli (plurimodal association) and the programming of verbal conducts
Pars opercularis (posterior), which is thought to support the management of only one kind of stimulus (unimodal association) and the coordination of the speech organs for the actual production of language, given its favorable position close to motor-related areas

[edit] Aphasia
People suffering from damage to this area may show a condition called Broca's aphasia (sometimes known as expressive aphasia, motor aphasia, or nonfluent aphasia), which makes them unable to create grammatically-complex sentences: It's often described as telegraphic speech and contains little but content words. Patients are usually aware that they cannot speak properly. Comprehension in Broca's aphasia is relatively normal, although many studies have demonstrated that Broca's aphasics have trouble understanding certain kinds of syntactically-complex sentences.[7]
For example, in the following passage, a Broca's aphasic patient is trying to explain how he came to the hospital for dental surgery:
"Yes... ah... Monday... er... Dad and Peter H...and Dad.... er... hospital... and ah... Wednesday... Wednesday, nine o'clock... and oh... Thursday... ten o'clock, ah doctors... two... an' doctors... and er... teeth... yah."[8]
This type of aphasia can be contrasted with Wernicke's aphasia, named for Carl Wernicke, which is characterized by damage to more posterior regions of the left hemisphere in the superior temporal lobe. Wernicke's aphasia manifests as a more pronounced impairment in comprehension. Because speech production retains a natural-sounding rhythm, and remains relatively normal grammatically, it is nonetheless often roundabout, vague, or meaningless. It is therefore also known as receptive aphasia.
Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have found decreases in activity in the Broca's area in stuttering. There is greater activation of the right hemisphere homologue of the Broca's area (area of Ross), which is believed to be a compensatory response to the hypoactivity in the Broca's area proper. Volumetric magnetic resonance imaging (VMRI) has shown that the pars triangularis is smaller in people that stutter.

[edit] Evolution of human language[9]
Broca's area is considered a marker for the development of language in the evolution of humans. The paleontological record of species leading to modern humans, Homo sapiens, finds that this part of the neural structure of the brain is present in fossils of Homo sapiens, and of Homo habilis, whereas the presumed precursors of these early humanoids, australopiths, lacked this area of the brain (note that this information depends on the analysis of skulls where the presence of Broca's area can be determined).
Whereas Broca's area is unique in its linguistic role to humans, it is present in animals, although it performs other similar roles that were adapted to language in humans.
The fossil record cannot, of course, give firm data about the beginning of language, which is one of the critical factors contributing to the evolution of Homo sapiens into the species that we have become. However, the association of Broca's area with language in modern man may guide further analysis of this evolution.

[edit] See also
arcuate fasciculus
cortex
expressive aphasia
human brain
language
pars opercularis
pars triangularis
Wernicke's area

[edit] References
^ Horwitz B, Amunts K, Bhattacharyya R, Patkin D, Jeffries K, Zilles K, Braun AR. "Activation of Broca's area during the production of spoken and signed language: a combined cytoarchitectonic mapping and PET analysis," Neuropsychologia. 2003; 41(14): 1868-76.
^ Mohr JP in Studies in Neurolinguistics (eds. Witaker H & Witaker NA) 201–235 (Academic, New York, 1976)
^ Penfield W & Roberts L Speech and Brain Mechanisms (Princeton Univ Press, Princeton, 1959)
^ Ojemann GA, Ojemann JG, Lettich E, Berger MS (1989). "Cortical language localization in left, dominant hemisphere. An electical stimulation mapping investigation in 117 patients". J Neurosurg 71: 316–26. doi:10.1038/nature03628.
^ Duffau H et al. (2003). "The role of dominant premotor cortex in language: a study uding intraoperative functional mapping in awake patients". Neuroimage 20: 1903–14. doi:10.1016/S1053-8119(03)00203-9.
^ Petrides M, Cadoret G, Mackey S (2005). "Orofacial somatomotor responses in the macaque monkey homologue of Broca's area". Nature 435: 1235–38. doi:10.1038/nature03628.
^ Caramazza A & Zurif E (1976). "Dissociation of algorithmic and heuristic processes in language comprehension: evidence from aphasia". Brain and Language 3: 572–82. doi:10.1016/0093-934X(76)90048-1.
^ Goodglass H & Geschwind N. Language disorders. In E. Carterette and M.P. Friedman (eds.) Handbook of Perception: Language and Speech. Vol II (New York, Academic Press, 1976)
^ Watson, Peter "Ideas: A History of Thought and Invention from Fire to Freud", Harper, New York 2006 [ISBN]0-06-093564-2], Chapter 2

LBT 443-446

Language has been thought of as being the expression of man’s reason, the result of onomatopoeia, invented as a means of communication, considered basic to the formation of society, or simply a gift of God. Each of these definitions of language has been used in the construction of a multitude of language theories[1]. We shall not be concerned with the development of these theories, but limit ourselves to a discussion of the recurrent emergence of the thoughts on the biological basis of language.
語言被認為是人類理性的一種表達方式，也被認為是一種為了社會形成而去溝通所發明出擬聲詞的結果。或是被認為是神的禮物與恩賜。各種語言的定義被使用來形成了多種的語言理論。 我們不應只關心這些理論的發展過程，而限制了我們去討論經常出現的關於生物基礎語言方面的想法。

The idea that language is one of man’s inherent characteristics, like vision or hearing, is found in some myths on the creation of man[2]. In these myths, language is given to man in conjunction with his senses, so that apparently it was considered one of them, and not part of man’s cultural or social functions ( which are also described as given or taught by the gods). By no means can these assertions of a divine origin be considered antithetical to a natural origin of language; on the contrary, everything natural to man was God’s gift to him.

語言是人類與生俱有的特色的想法，就像是視覺或是聽覺。都被發現是有關一些人類起源的神話。在這些神話,語言是跟感官一起給予人類的,所以,語言被認為是感官之一，而非人類文化或社會作用的一部份。(也被認為語言是由神給予或教導的)。這些有關神的起源的主張並不被認為是與語言自然的起源是對立的，相反的，每種人類的天賦都可以說是神的禮物。

Between the realm of mythology and science stands the experiment of the Egyptian King Psammetichos of the seventh century B.C. and related by Herodotus ( fifth century B.C.). Psammetichos suppossedly tried to have two children raised by shepherds who never spoke to them in order to see what language they would develop [3]. This experiment is relevant to our discussion in so far as its design implies the belief that children left to themselves will develop language. Psammetichos thought he would be able to demonstrate which language was the oldest, but apparently did not doubt that even untutored children would speak.

在神話和科學的領域之間存在著西元七世紀前的埃及的國王Psammetichos的實驗，Psammetichos的實驗也和希羅多德有關(西元前五世紀)。 Psammetichos 試著觀察由牧羊人飼養的兩個小孩，在牧羊人不曾跟他們說話的情況下，他們的語言會如何發展。這項實驗跟我們到目前為止的討論有關,到目前為止,他的信仰意味著認為兒童將自己會發展語言。Psammetichos認為他能証明哪一種語言是最古老的,但也顯然堅信即使沒受過教育的兒童仍會說話。

Language first became the subject of discussion by the presocratic philosophers in the latter part of the sixth century B.C. The setting up of antitheses, typical for Greek philosophy, was also applied to the problems which language posed. But discussions of language were limited to a mere consideration of naming and were purely secondary outgrowths of the philosopher’s search for general truths. In order to understand the statements on language made by the Greek philosophers, it is essential to give an idea of the context in which they were made and briefly describe the evolution of the meaning of the two everrecurring terms nomos and physis in which language was to be discussed. Nomos was later replaced by theses and was often wrongly translated as convention while physis has been incorrectly equated with nature.

在西元前六世紀後期，語言已經變成前蘇格拉底哲學家所討論的主題。這種典型的希臘哲學對立的命題也運用到討論語言方面的問題。但有關語言的討論大多侷限於命名的討論，其次哲學家才是在尋找真理。為了瞭解希臘哲學家對語言所做出的陳述，對於去了解他們針對語言所討論到兩個重複出現的術語nomos and physis的意義是很重要的。Nomos也可以說是theses但通常被錯譯為convention，physis也並完全不等於nature.
For Herakleitos (ca. 500 B.C.), nomos was the order regulating the life of society and the individual, but he did not see it as a product of society[4].The nomos of society was valid, but not absolute. Similarly names were valid as they reflected some aspect of the object they named. (Apparently, he did not consider them physis as had been thought)[5]. Physis would have implied that names are an adequate expression of reality or of the true nature of things, an idea to which Herakleitos did not subscribe.
對Herakleitos而言，nomos是由社會與個人所規範的秩序，但他並不了解它也是社會的產物。社會的nomos是正確的但不是絕對的。相似的，名字也是反映出它所命名的物體。(明顯的，他沒有考慮到physis這方面。)Physis可以說是事物的事實或是真實的本質的一種適當的表達方式。這個觀念是Herakleitos不贊成的。

相關連結

Socrates' Logic of Language

LB Chapter 2 p056-060 威鈴

LB Chapter 2 p56-60

The most painstaking histological investigations of Broca’s area were carried out by Kreht (1936), who followed the tradition of the Vogts with their careful description of every detail and variation in cell density and size. Von Bonin’s and Bailey’s observations were essentially the same as Kreht’s, but the latter also occasionally found larger cells in layer VI. The fourth layer in all cortices examined was noticeably sparsely populated with cells. Kreht observed that Broca’s area always tended to be different from surrounding areas, but that the cytoarchitecture itself in this region varied greatly from brain to brain. Kreht also investigated homologous areas in brains of a few apes and monkeys and found that the cortices of these animals had areas with similar cytoarchitecture as that found in Broca’s area. Thus the microscopic anatomical detail does not contribute to our search for histological correlates of speech and language.

Behavioral Maps. The mapping of speech areas is based on observations of behavioral derangement in the presence of (α) internal brain disease; (β) of penetrating head injuries (trauma); (γ) surgical excision; and (δ) observations of behavior during electrical stimulation of the exposed cortex during surgery.

(α). From a heuristic point of view, the first type of observation ids the most unsatisfactory one because of many cases in which the exact location of the lesion is only a matter o speculation, and even if these brains should become available for postmodern examination the patient may have died of more widespread disease and destruction in the brain than the lesion which first caused aphasia.

Nevertheless, the vast majority of aphasia patients owe their speech disturbance to internal brain disease, particularly cerebro-vascular accidents, commonly known as strokes. Tissue is destroyed or function is temporarily interrupted because of insufficient blood supply caused by a clot in or rupture of a vessel. The artery most often implicated is the left middle cerebral artery, which runs along the sylvian fissure and sends out branches through the entire lateral face of the hemisphere, as shown in Fig. 2.21. It is precisely because of the vast territorial extent of this artery that behavioral derangement resulting from interference with it gives us the least specific information concerning the localization of the speech and language function. Even when the vascular insufficiency is demonstrated by x-rays of the vascular tree, the exact location of the actual dysfunction remains largely a matter of speculation.

(β). Inferences from traumatic lesions have been drawn repeatedly (Goldstein, 1942, Luria, 1947, Conrad, 1954, Russell and Espir, 1961), resulting in various maps. The extent of the lesion can be determined more accurately in these cases than in internal brain disease, but the fact is frequently overlooked that trauma also causes secondary pathology (particularly hemorrhage and edema) which may have deleterious effects on tissue far beyond the visibility destroyed areas. In Fig. 2.22 the centers of penetrating head injuries to the left hemisphere are shown with indications of those injuries which caused lasting aphasia and which did not. The subjects were veterans of Word War II. To make Russel’s and Espir’s material comparable to Conrad’s, the diagrams had to be redrawn, and in this process some distortions are inevitable because neither the original drawings nor the present mode of representation can be read unequivocally. The distortions, however, occur primarily around the outer margins of these diagrams and are due to the shortened perspective of the curved surfaces. Nevertheless, it is clear that the resulting maps are not identical although correspondences exit.

In Conrad’s material, motor-speech deficits predominate on both margins of the central sulcus and extend frontally; linguistic sensory and amnestic deficits predominate in the parieto-occipital areas, but there are few cases which do not conform to this distribution. Russel and Espir do not indicate the nature of the language deficit in their original data. In both cases we cannot fail to be impressed with the random-appearing scatter of lesions and with the overlap between aphasia-producting and aphasia-free lesions. The most striking findings of these recent studies are that there seems to be no more than a statistical relationship between Broca’s area and the resultant deficit.

(γ). Surgical excision of limited cortical tissue is a fairly common occurrence in clinical neurology. Pefield and Roberts (1959) have described the outcome of such operations performed on 273 patients who had suffered from focal cerebral seizures caused by earlier injuries, infection, or anoxia of the brain. Over the years, examples of ablations on every part of the cortex have been accumulated, although Broca’s area was only excised once and this happened to be a patient with an atypical early history. In all of this material from which tumor cases are excluded, there are few cases in which the removal of cortical tissue resulted in more than a temporary dysphasic condition, with language function restored within a matter of days or weeks. Many operations in the critical areas had no language disturbance. This is puzzling in view of the consequences of traumatic lesions and cerebro-vascular accidents. We might have expected that in many more cases permanent aphasia had resulted. The explanation must be due to some important differences between the surgical cases and others. First, patients who come to surgery have had histories of years of abnormally functioning brains manifested by recurrent and uncontrollable seizures. we cannot be sure of the effect that this might have had on localization (using the world here in its loosest terminology). Penfield and Roberts believe that the epileptogenic focus is not the location of the lesion but is adjacent to it. The lesion itself constitutes an irritant which induces abnormal function in structurally healthy tissue. Thus, there may be a systematic “bias” in the localization of function in these brains. The tissue that is surgically removed probably had not been participating in speech function for some years. However, this explanation begs the basic question: why does sudden destruvtion of tissue interfere irrevocably with language in adult patients, whereas language often remains essentially unaffected in cases where similar destructions were preceded by years (sometimes a lifetime) of sporadic, short, physiological interferences?

The surgical cases do not differ only from traumatic and vascular lesions in terms of abnormal function. The surgical lesion is always different from the other lesions; it is usually shallower, there is no uncontrolled bleeding, it does not follow the distribution of the vascular tree, and the healing process is histologically and morphologically different from the events that follow the cerebro-vascular accidents and trauma. With this many differences between the surgical cases and other cases, it is fair to say that surgical lesions are not commensurable, and the difference in effects cannot yet be interpreted. However, there is one lesson we may learn from cortical excisions. The narrow localization theory which holds that engrams for words or syntactic rules are stored in certain aggregates of cells cannot be in accord with the clinical facts.

(δ) Electrical stimulation of the exposed cortex during neurosurgery is another source of evidence for cortical function-maps. It is again Penfield and Roberts who have systematized their findings. For instance, they have published (1959) a cortical map showing points of stimulation affecting motor speech. From this map it is difficult to discern any sharply circumscribed area of functional representation. Roughly, the stimulation map corroborates the impression gained from the maps of Fig. 2.22 although it does seem as if there were at least statistical discrepancies between the two types of source-material for such maps.

Chapter 3 VI Summary 119-120 威鈴 Translation

VI. SUMMARY
Language as any other type of behavior, is seen as a manifestation of intricate physiological processes. In higher mammals the processes have many common denominators, but they have also undergone modifications in accordance with specializaion in behavior. Respiration, which is in many ways identical in a wide variety of species, shows particularly well forms of adaptations to species-specific behavior patterns. Some such adaptations have been described for the execution of speech and vocalization.
語言可以當作是任何其他類型的行為,被視為一種十分複雜的生理過程。根據行為上的特別化，較高的哺乳動物的心理過程中有許多共同點,但他們在過程中也有些微的調整與不同。呼吸，這是各種各樣的物種大多相似的部分,顯示出適應良好的物種之間的行為模式。一些這類調整已被描述為進行講話和發聲。
From examination of speech production, the following points emerged:
(1) The neuromuscular correlates of speech sounds are muscular contraction patterns among one and the same set of muscles.
(2) In most instances, physiological events precede the acoustic events of speech sounds.
(3) For individual speech sounds, the duration of physiological events may be twice as long as the duration of acoustic events.
從檢視口說產生的過程中,我們可以發現以下各點:(1)語音與神經的關聯是肌肉收縮的形式以及使用的是同一套肌肉。(2)在大多數情況下,生理活動發生在語音的聽覺之前。(3)從個別語音來看,這一時期的生理活動可能聽覺時間的兩倍長。

(4) Hence, the sequential arrangemetns of muscular events require preplanning with anticipation of later events; therefore, the occurrence of some events is contingent upon other events yet to come, which may be adduced as proof that sequencing on a neuromuscular level is not accomplished by an associative mechanism.
(5) The interdigitation of muscular correlates of phones is mirrored also on higher levles of segmentation. Thus ordering-phenomena on all levels of speech and language appear to be related and to exhibit striking formal similarites.

(4)因此,按順序去安排肌肉活動讓我們邊期待之後會發生的事同時也做預先規劃,因此,一些事件的發生是緊接著其他活動尚未發生的事件。這可能會是証明神經水平的順序是不能由一個聯合機制所決定的証據。 (5) 語音的肌肉關聯和interdigitation反射出分割的更高層次。 因此所有層次上的講話和語言的順序現象似乎彼此相關並且展現出十分正式的相似性。