discovery suggests that broca's area may be included in some aspect of verbalization or articulation; however, this does not address its part in sentence comprehension. still, broca's area frequently emerges in functional imaging studies of sentence processing. however, it also becomes activated in word-level tasks. this suggests that broca's area is not dedicated to sentence processing alone, but supports a function common to both. in fact, broca's area can show activation in such non-linguistic tasks as imagery of motion. considering the hypothesis that broca's area may be most involved in articulation, its activation in all of these tasks may be due to subjects' covert articulation while formulating a response. despite this caveat, a consensus seems to be forming that whatever role broca's area may play, it may relate to known working memory functions of the frontal areas. (there is a wide distribution of talairach coordinates reported in the functional imaging literature that are referred to as part of broca's area.) the processing of a passive voice sentence, for example, may require working memory to assist in the temporary retention of information while other relevant parts of the sentence are being manipulated (i.e. to resolve the assignment of thematic roles to arguments). miyake, carpenter, and just have proposed that sentence processing relies on such general verbal working memory mechanisms, while caplan and waters consider broca's area to be involved in working memory specifically for syntactic processing. friederici (2002) breaks broca's area into its component regions and suggests that brodmann's area 44 is involved in working memory for both phonological and syntactic structure. this area becomes active first for phonology and later for syntax as the time course for the comprehension process unfolds. brodmann's area 45 and brodmann's area 47 are viewed as being specifically involved in working memory for semantic features and thematic structure where processes of syntactic reanalysis and repair are required. these areas come online after brodmann's area 44 has finished its processing role and are active when comprehension of complex sentences must rely on general memory resources. all of these theories indicate a move towards a view that syntactic comprehension problems arise from a computational rather than a conceptual deficit. newer theories take a more dynamic view of how the brain integrates different linguistic and cognitive components and are examining the time course of these operations. neurocognitive studies have already implicated frontal areas adjacent to broca's area as important for working memory in non-linguistic as well as linguistic tasks. cabeza and nyberg's analysis of imaging studies of working memory supports the view that ba45/47 is recruited for selecting or comparing information, while ba9/46 might be more involved in the manipulation of information in working memory. since large lesions are typically required to produce a broca's aphasia, it is likely that these regions may also become compromised in some patients and may contribute to their comprehension deficits for complex morphosyntactic structures. broca's area as a key center in the linking of phonemic sequences broca's area has been previously associated with a variety of processes, including phonological segmentation, syntactic processing, and unification, all of which involve segmenting and linking different types of linguistic information. although repeating and reading single words does not engage semantic and syntactic processing, it does require an operation linking phonemic sequences with motor gestures. findings indicate that this linkage is coordinated by broca's area through reciprocal interactions with temporal and frontal cortices responsible for phonemic and articulatory representations, respectively, including interactions with the motor cortex before the actual act of speech. based on these unique findings, it has been proposed that broca's area is not the seat of articulation, but rather is a key node in manipulating and forwarding neural information across large-scale cortical networks responsible for key components of speech production. history in a study published in 2007, the preserved brains of both leborgne and lelong (patients of broca) were reinspected using high-resolution volumetric mri. the purpose of this study was to scan the brains in three dimensions and to identify the extent of both cortical and subcortical lesions in more detail. the study also sought to locate the exact site of the lesion in the frontal lobe in relation to what is now called broca's area with the extent of subcortical involvement. louis victor leborgne (tan) leborgne was a patient of broca's. at 30 years old, he was almost completely unable to produce any words or phrases. he was able to repetitively produce only the word tan. after his death, a neurosyphilitic lesion was discovered on the surface of his left frontal lobe. lelong lelong was another patient of broca's. he also exhibited reduced productive speech. he could only say five words, 'yes', 'no', 'three', 'always', and 'lelo' (a mispronunciation of his own name). a lesion within the lateral frontal lobe was discovered during lelong's autopsy. broca's previous patient, leborgne, had this lesion in the same area of his frontal lobe. these two cases led broca to believe that speech was localized to this particular area. mri findings examination of the brains of broca's two historic patients with high-resolution mri has produced several interesting findings. first, the mri findings suggest that other areas besides broca's area may also have contributed to the patients' reduced productive speech. this finding is significant because it has been found that, though lesions to broca's area alone can possibly cause temporary speech disruption, they do not result in severe speech arrest. therefore, there is a possibility that the aphasia denoted by broca as an absence of productive speech also could have been influenced by the lesions in the other region. another finding is that the region, which was once considered to be critical for speech by broca, is not precisely the same region as what is now known as broca's area. this study provides further evidence to support the claim that language and cognition are far more complicated than once thought and involve various networks of brain regions. evolution of language the pursuit of a satisfying theory that addresses the origin of language in humans has led to the consideration of a number of evolutionary "models". these models attempt to show how modern language might have evolved, and a common feature of many of these theories is the idea that vocal communication was initially used to complement a far more dominant mode of communication through gesture. human language might have evolved as the "evolutionary refinement of an implicit communication system already present in lower primates, based on a set of hand/mouth goal-directed action representations." "hand/mouth goal-directed action representations" is another way of saying "gestural communication", "gestural language", or "communication through body language". the recent finding that broca's area is active when people are observing others engaged in meaningful action is evidence in support of this idea. it was hypothesized that a precursor to the modern broca's area was involved in translating gestures into abstract ideas by interpreting the movements of others as meaningful action with an intelligent purpose. it is argued that over time the ability to predict the intended outcome and purpose of a set of movements eventually gave this area the capability to deal with truly abstract ideas, and therefore (eventually) became capable of associating sounds (words) with abstract meanings. the observation that frontal language areas are activated when people observe hand shadows is further evidence that human language may have evolved from existing neural substrates that evolved for the purpose of gesture recognition. the study, therefore, claims that broca's area is the "motor center for speech", which assembles and decodes speech sounds in the same way it interprets body language and gestures. consistent with this idea is that the neural substrate that regulated motor control in the common ancestor of apes and humans was most likely modified to enhance cognitive and linguistic ability. studies of speakers of american sign language and english suggest that the human brain recruited systems that had evolved to perform more basic functions much earlier; these various brain circuits, according to the authors, were tapped to work together in creating language. another recent finding has showed significant areas of activation in subcortical and neocortical areas during the production of communicative manual gestures and vocal signals in chimpanzees. further, the data indicating that chimpanzees intentionally produce manual gestures as well as vocal signals to communicate with humans suggests that the precursors to human language are present at both the behavioral and neuronanatomical levels. more recently, the neocortical distribution of activity-dependent gene expression in marmosets provided direct evidence that the ventrolateral prefrontal cortex, which comprises broca's area in humans and has been associated with auditory processing of species-specific vocalizations and orofacial control in macaques, is engaged during vocal output in a new world monkey. these findings putatively set the origin of vocalization-related neocortical circuits to at least 35 million years ago, when the old and new world monkey lineages split. additional images broca's area (shown in red). animation. approximate location of broca's area highlighted in gray. arcuate fasciculus connects broca's area and wernicke's area. sagittal sections of broca's area coronal sections of broca's area transversal sections of broca's area