broca's area broca's area broca's area, or the broca area (/ˈbroʊkə/, also uk: /ˈbrɒkə/, us: /ˈbroʊkɑː/), is a region in the frontal lobe of the dominant hemisphere, usually the left, of the brain with functions linked to speech production. broca's areabroca's area is made up of brodmann areas 44 (pars opercularis) and 45 (pars triangularis).broca's area (shown in red)detailspart offrontal lobearterymiddle cerebralveinsuperior sagittal sinusidentifiersmeshd065711neuronames2062fma242176anatomical terms of neuroanatomy language processing has been linked to broca's area since pierre paul broca reported impairments in two patients. they had lost the ability to speak after injury to the posterior inferior frontal gyrus (pars triangularis) (ba45) of the brain. since then, the approximate region he identified has become known as broca's area, and the deficit in language production as broca's aphasia, also called expressive aphasia. broca's area is now typically defined in terms of the pars opercularis and pars triangularis of the inferior frontal gyrus, represented in brodmann's cytoarchitectonic map as brodmann area 44 and brodmann area 45 of the dominant hemisphere. functional magnetic resonance imaging (fmri) has shown language processing to also involve the third part of the inferior frontal gyrus the pars orbitalis, as well as the ventral part of ba6 and these are now often included in a larger area called broca's region. studies of chronic aphasia have implicated an essential role of broca's area in various speech and language functions. further, fmri studies have also identified activation patterns in broca's area associated with various language tasks. however, slow destruction of broca's area by brain tumors can leave speech relatively intact, suggesting its functions can shift to nearby areas in the brain. structure brodmann area 44 brodmann area 45 broca's area is often identified by visual inspection of the topography of the brain either by macrostructural landmarks such as sulci or by the specification of coordinates in a particular reference space. the currently used talairach and tournoux atlas projects brodmann's cytoarchitectonic map onto a template brain. because brodmann's parcelation was based on subjective visual inspection of cytoarchitectonic borders and also brodmann analyzed only one hemisphere of one brain, the result is imprecise. further, because of considerable variability across brains in terms of shape, size, and position relative to sulcal and gyral structure, a resulting localization precision is limited. nevertheless, broca's area in the left hemisphere and its homologue in the right hemisphere are designations usually used to refer to the triangular part of inferior frontal gyrus (ptr) and the opercular part of inferior frontal gyrus (pop). the ptr and pop are defined by structural landmarks that only probabilistically divide the inferior frontal gyrus into anterior and posterior cytoarchitectonic areas of 45 and 44, respectively, by brodmann's classification scheme. area 45 receives more afferent connections from the prefrontal cortex, the superior temporal gyrus, and the superior temporal sulcus, compared to area 44, which tends to receive more afferent connections from motor, somatosensory, and inferior parietal regions. the differences between area 45 and 44 in cytoarchitecture and in connectivity suggest that these areas might perform different functions. indeed, recent neuroimaging studies have shown that the ptr and pop, corresponding to areas 45 and 44, respectively, play different functional roles in the human with respect to language comprehension and action recognition/understanding. the broca's area is about 20% larger in women than in men. functions language comprehension for a long time, it was assumed that the role of broca's area was more devoted to language production than language comprehension. however, there is evidence to demonstrate that broca's area also plays a significant role in language comprehension. patients with lesions in broca's area who exhibit agrammatical speech production also show inability to use syntactic information to determine the meaning of sentences. also, a number of neuroimaging studies have implicated an involvement of broca's area, particularly of the pars opercularis of the left inferior frontal gyrus, during the processing of complex sentences. further, functional magnetic resonance imaging (fmri) experiments have shown that highly ambiguous sentences result in a more activated inferior frontal gyrus. therefore, the activity level in the inferior frontal gyrus and the level of lexical ambiguity are directly proportional to each other, because of the increased retrieval demands associated with highly ambiguous content. there is also specialisation for particular aspects of comprehension within broca's area. work by devlin et al. (2003) showed in a repetitive transcranial magnetic stimulation (rtms) study that there was an increase in reaction times when performing a semantic task under rtms aimed at the pars triangularis (situated in the anterior part of broca's area). the increase in reaction times is indicative that that particular area is responsible for processing that cognitive function. disrupting these areas via tms disrupts computations performed in the areas leading to an increase in time needed to perform the computations (reflected in reaction times). later work by nixon et al. (2004) showed that when the pars opercularis (situated in the posterior part of broca's area) was stimulated under rtms there was an increase in reaction times in a phonological task. gough et al. (2005) performed an experiment combining elements of these previous works in which both phonological and semantic tasks were performed with rtms stimulation directed at either the anterior or the posterior part of broca's area. the results from this experiment conclusively distinguished anatomical specialisation within broca's area for different components of language comprehension. here the results showed that under rtms stimulation: semantic tasks only showed a decrease in reaction times when stimulation was aimed at the anterior part of broca's area (where a decrease of 10% (50 ms) was seen compared to a no-tms control group) phonological tasks showed a decrease in reaction times when stimulation was aimed at the posterior part of broca's area (where a decrease of 6% (30 ms) was seen compared to control) to summarise, the work above shows anatomical specialisation in broca's area for language comprehension, with the anterior part of broca's area responsible for understanding the meaning of words (semantics) and the posterior part of broca's area responsible for understanding how words sound (phonology). action recognition and production recent experiments have indicated that broca's area is involved in various cognitive and perceptual tasks. one important contribution of brodmann's area 44 is also found in the motor-related processes. observation of meaningful hand shadows resembling moving animals activates frontal language area, demonstrating that broca's area indeed plays a role in interpreting action of others. an activation of ba 44 was also reported during execution of grasping and manipulation. speech-associated gestures it has been speculated that because speech-associated gestures could possibly reduce lexical or sentential ambiguity, comprehension should improve in the presence of speech-associated gestures. as a result of improved comprehension, the involvement of broca's area should be reduced. many neuroimaging studies have also shown activation of broca's area when representing meaningful arm gestures. a recent study has shown evidence that word and gesture are related at the level of translation of particular gesture aspects such as its motor goal and intention. this finding helps explain why, when this area is defective, those who use sign language also have language deficits.: 494–7 this finding, that aspects of gestures are translated in words within broca's area, also explains language development in terms of evolution. indeed, many authors have proposed that speech evolved from a primitive communication that arose from gestures. (see below.) speaking without broca's area damage to broca's area is commonly associated with telegraphic speech made up of content vocabulary. for example, a person with broca's aphasia may say something like, "drive, store. mom." meaning to say, "my mom drove me to the store today." therefore, the content of the information is correct, but the grammar and fluidity of the sentence is missing. the essential role of the broca's area in speech production has been questioned since it can be destroyed while leaving language nearly intact. in one case of a computer engineer, a slow-growing glioma tumor was removed. the tumor and the surgery destroyed the left inferior and middle frontal gyrus, the head of the caudate nucleus, the anterior limb of the internal capsule, and the anterior insula. however, there were minimal language problems three months after removal and the individual returned to his professional work. these minor problems include the inability to create syntactically complex sentences including more than two subjects, multiple causal conjunctions, or reported speech. these were explained by researchers as due to working memory problems. they also attributed his lack of problems to extensive compensatory mechanisms enabled by neural plasticity in the nearby cerebral cortex and a shift of some functions to the homologous area in the right hemisphere. clinical significance stuttering a speech disorder known as stuttering is seen to be associated with underactivity in broca's area. aphasia aphasia is an acquired language disorder affecting all modalities such as writing, reading, speaking, and listening and results from brain damage. it is often a chronic condition that creates changes in all areas of one's life. expressive aphasia vs. other aphasias patients with expressive aphasia, also known as broca's aphasia, are individuals who know "what they want to say, they just cannot get it out". they are typically able to comprehend words, and sentences with a simple syntactic structure (see above), but are more or less unable to generate fluent speech. other symptoms that may be present include problems with fluency, articulation, word-finding, word repetition, and producing and comprehending complex grammatical sentences, both orally and in writing. this specific group of symptoms distinguishes those who have expressive aphasia from individuals with other types of aphasia. there are several distinct "types" of aphasia, and each type is characterized by a different set of language deficits. although those who have expressive aphasia tend to retain good spoken language comprehension, other types of aphasia can render patients completely unable to understand any language at all, unable to understand any spoken language (auditory verbal agnosia), whereas still other types preserve language comprehension, but with deficits. people with expressive aphasia may struggle less with reading and writing (see alexia) than those with other types of aphasia.: 480–500 although individuals with expressive aphasia tend to have a good ability to self-monitor their language output (they "hear what they say" and make corrections), other types of aphasics can seem entirely unaware of their language deficits. in the classical sense, expressive aphasia is the result of injury to broca's area; it is often the case that lesions in specific brain areas cause specific, dissociable symptoms, although case studies show there is not always a one-to-one mapping between lesion location and aphasic symptoms. the correlation between damage to certain specific brain areas (usually in the left hemisphere) and the development of specific types of aphasia makes it possible to deduce (albeit very roughly) the location of a suspected brain lesion based only on the presence (and severity) of a certain type of aphasia, though this is complicated by the possibility that a patient may have damage to a number of brain areas and may exhibit symptoms of more than one type of aphasia. the examination of lesion data in order to deduce which brain areas are essential in the normal functioning of certain aspects of cognition is called the deficit-lesion method; this method is especially important in the branch of neuroscience known as aphasiology. cognitive science – to be specific, cognitive neuropsychology – are branches of neuroscience that also make extensive use of the deficit-lesion method. major characteristics of different types of acute aphasia type of aphasia speech repetition naming auditory comprehension fluency expressive aphasia moderate–severe moderate–severe mild difficulty non-fluent, effortful, slow receptive aphasia mild–severe mild–severe defective fluent paraphasic conduction aphasia poor poor relatively good fluent mixed transcortical aphasia moderate poor poor non-fluent transcortical motor aphasia good mild–severe mild non-fluent transcortical sensory aphasia good moderate–severe poor fluent global aphasia poor poor poor non-fluent anomic aphasia mild moderate–severe mild fluent newer implications related to lesions in broca's area since studies carried out in the late 1970s it has been understood that the relationship between broca's area and broca's aphasia is not as consistent as once thought. lesions to broca's area alone do not result in broca's aphasia, nor do broca's aphasic patients necessarily have lesions in broca's area. lesions to broca's area alone are known to produce a transient mutism that resolves within 3–6 weeks. this