Introduction: During the late 19th and early 20th century, a 'brain language area' was proposed corresponding to the peri-Sylvian region of the left hemisphere as concluded by clinical observations. This point of view has continued up today. Aim: Departing from contemporary neuroimaging studies, to re-analyze the location and extension the brain language area with regard to the different Brodmann areas. Materials and methods: Using the method known as metaanalytic connectivity modeling seven meta-analytic studies of fMRI activity during the performance of different language tasks are analyzed. Conclusions: Contemporary neuroimaging studies suggest that the brain language are is notoriously more extended than it was assumed one century ago based on clinical observations.
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This paper additionally proposes that the insula BA13 plays a certain coordinating role in interconnecting these two brain language systems. During that historical moment the second half of the 19th century , it was supposed that language was associated with the activity of three areas in the left hemisphere: the posterior frontal lobe, the upper segment of the temporal lobe, and the insula.
Although he suggested that the insula BA13 may also participate in language, he did not explicitly include it within the brain language area. As a result, the interest in the potential participation of the insula in language virtually disappeared until the end of the 20th century.
Dronkers demonstrated that the insula is a critical brain region for the coordination of complex articulatory movements speech praxis. Further articles were published emphasizing the participation of the insula in language during the following years e. During the last decades of the 20th century, the aphasia model was generally used to illustrate the brain organization of language e.
That is, brain organization of language was explained departing from language pathology. Different types of language disorders were reported in cases with brain damage, depending upon the specific location of the damage. Consequently, it was proposed that specific brain areas are involved in processing particular aspects of language. Two major aphasia models were generally used during the middle and late 20th century: Geschwind and associates' model and Luria's model.
During the early 21st century, Ardila further developed the idea concerning the two fundamental dimensions in language impairments. He proposed—following Jakobson linguistic analysis—that there are only two fundamental forms of aphasia which are linked to impairments in the lexical-semantic paradigmatic axes and grammatical syntagmatic axes systems of language, namely Wernicke-type aphasia and Broca-type aphasia, respectively Ardila, , He further suggested that grammar correlates with the ability to internally represent actions verbs , depending on the functioning of what is known as Broca's area BA44 and BA45 and its related brain circuits; it is also associated with the ability to quickly carry out the sequencing of articulatory movements required for speaking speech praxis.
He argued that lexical-semantic and grammatical systems not only depend on different brain circuitries but also on different types of memory and learning declarative and procedural. These systems tend to appear at different moments during language development in the child and language evolution in humankind.
Ardila emphasized that other aphasic syndromes do not impair language knowledge per se , but rather peripheral mechanisms required to produce language in conduction aphasia and the aphasia of the supplementary motor area , or the executive control of language in extra-Sylvian, transcortical motor, or dynamic aphasia.
Geschwind and associates' model so-called Wernicke—Geschwind model of language Benson, ; Geschwind, , ; Kertesz, represents an extension of the Wernicke—Lichtheim model Lichtheim, In this model, seven different types of aphasia, each one related with the pathology of a specific brain area, are distinguished: motor, sensory, conduction, transcortical motor, subcortical motor, transcortical sensory, and subcortical sensory. Minor variations to the basic classification, proposed by Wernicke, were sometimes used e.
According to the Wernicke—Geschwind model, three major dimensions of language can be impaired in cases of aphasia: fluency in cases of pre-rolandic aphasias , comprehension in temporal lobe aphasias , and repetition in perisylvian aphasias. Luria's model , , According to Luria's aphasia interpretation, seven different forms of aphasia can be recognized: efferent motor or kinetic, dynamic, afferent motor or kinesthetic, semantic, acoustic-agnosic, acoustic-amnesic, and amnesic.
Each one suggests a specific level factor of language processing impairment. Some aphasias can be due to a paradigmatic disorder i. In pre-rolandic aphasias motor kinetic and dynamic , the syntagmatic dimension of language is impaired sequencing words in a sentence in the first one; sequencing sentences in language discourse in the second one ; whereas the retro-rolandic aphasias are due to a defect in the selection process selecting phonemes in acoustic-agnosic; selecting words in acoustic-amnesic; selecting the word meanings in amnesic; and selecting the meaning of word spatial relations in semantic aphasia paradigmatic axes of language.
The introduction of contemporary neuroimaging techniques, especially positron emission tomography and functional magnetic resonance imaging fMRI , significantly advanced the understanding of the brain organization of language.
These contemporary techniques have allowed the localization of language processing areas in the brain to be re-analyzed. Attempts have been made to pinpoint the language-comprehensive area in the temporal lobe BA22, BA21 e.
For instance, DeWitt and Rauschecker suggested two different systems can be distinguished in Wernicke's area: dorsal and ventral. There is a significantly large body of research today based on functional neuroimaging techniques.
Now is the time to put these significant amounts of information collected during these last decades together, develop more meta-analytic studies to integrate and reinterpret the available fragmented pieces of information, and ultimately reach a clearer understanding of the brain organization of language.
These studies aimed to analyze the specific contribution of different BAs to the language system. A meta-analytic approach integrating a significant amount of recent neuroimaging studies potentially allows an overall perspective of the different circuits and areas involved in language processing.
Some areas potentially involved in language reception and understanding lexical-semantic system as well as areas involved in language production grammatical system were analyzed. Two frontal areas BA44 and BA46 were selected. BA44 is regarded as the core Broca's area and BA46 is considered a major frontal lobe executive functioning area. Because the angular gyrus BA39 is at times included within the Wernicke's area e. Finally, the insula BA13 was notably analyzed, considering its unclear, but perhaps crucial involvement in language processes.
Brain areas co-activated when performing a particular task suggest that they belong to a common specific network or brain circuit related to the function selected as filter criterion e.
Thus, it is assumed that if two or more areas are activated within the same task they are functionally connected and consequently participate in a single network. Currently, there are several techniques that potentially demonstrate brain circuitries or networks. MACM is based on automatic meta-analysis done by pooling co-activation patterns. The technique takes advantage of Brainmap. Sleuth provides a list of foci, in Talairach or MNI coordinates, each one representing the center of mass for a cluster of activation.
The method takes the region of interest for instance, BA44 , makes it the independent variable, and interrogates the database for studies showing activation of the chosen target. The query is easily filtered by different conditions such as age, normal vs. By pooling the data with these conditions, this tool provides a universe of co-activations that can be statistically analyzed for significant commonality.
As mentioned, this methodology assumes coactivation of brain areas within the same task to indicate interconnectivity between activated areas and their participation in a common network. In the papers included in the current review, meta-analyses of seven discrete BAs were performed. The following common criteria were used: first, studies reporting activation of a specific BA i.
The final condition was used because today a significant amount of fMRI research utilizes Chinese language; including a distant language from the English phonology, lexicon, and grammar could introduce a potential uncontrolled confounding variable. The other seven conditions were used in an attempt to have a relatively homogenous normal population, studied using a single technical procedure i.
Meta-analyses of three types of brain areas were developed: first, areas involved in language reception and understanding lexical-semantic system BA20, BA37, BA38, and BA39 ; second, areas involved in language production grammatical system BA44 and BA46 ; and third, the insula BA13 , a brain area potentially involved in language control and coordination. Activation foci associated to each specific area search criteria were obtained automatically from the Sleuth software.
This automatic report lists a number of clusters defined by the center of mass in MNI coordinates , volume in cubic millimeter, maxima intensity peak , and neighboring BA's-peaks within 5 mm of the maxima plus and minus with respect the orthogonal coordinates.
Clusters are labeled accordingly with location of maxima. Statistical significance of clusters found on the pooled-data was then analyzed utilizing the ALE method Eickhoff et al. ALE treats reported peaks of activation as spatial probability distributions centered at the given coordinates. ALE computes the union of activation probabilities for each voxel, allowing differentiation between true convergence of activation foci from random clustering noise.
ALE scores obtained from thousands of random iterations are used to assign p -values to the observed clusters of activation. Only clusters of or more cubic millimeter were accepted as valid clusters. A mosaic of transversal-cut insets of fusioned images was obtained utilizing the same tool. Eleven papers, corresponding to 12 experimental conditions, and participants were used in this analysis. Our results demonstrated seven clusters of activation: The first cluster Cluster 1 included the left temporal lobe, BA20 and BA21, whereas Cluster 2 was located at the left insula BA13 and left prefrontal BA Cluster 3 involved the left inferior frontal lobe BA47 and Cluster 4 was situated in the left inferior temporal lobe BA Cluster 5 was again situated in the left prefrontal cortex BA9.
All seven clusters were located in the left hemisphere. BA37 inferior temporal gyrus, fusiform gyrus Ardila et al. Twenty papers, with 28 suitable experiments, and participants were obtained.
Twelve different clusters were found, six related to the left and six to the right hemisphere. Significantly higher connectivity values, as represented by higher ALE scores, were located in the left hemisphere. It was concluded that left BA37 is a common node of two distinct networks: visual recognition perception and semantic language functions.
It is well known that BA37 is involved in lexico-semantic associations i. Clinical observations demonstrate that damage in the left BA37 is associated with significant word-finding difficulties anomia e. Eleven papers, corresponding to 12 experimental conditions, and participants were selected Ardila et al. The last two clusters involved were the right parietal BA7 and temporal BA21 lobes.
Seemingly, this area has two major connection pathways: one within the left hemisphere language and the other involving the right hemisphere plausibly participating in visuospatial and integrative audiovisual functions. Eight papers, corresponding to 13 experimental conditions, and participants were selected Rosselli et al. Sixteen activation clusters made a network that included the activation of the two angular gyri BA39 , the superior right parietal lobe BA7 and right supramarginal gyri BA40 , the left middle temporal lobe BA21 , and the frontal lobe bilateral premotor—BA6—and left prefrontal—BA46—.
Some connectivity with the limbic cortex cingulate gyrus was also observed. In addition, clusters of activations were observed with right superior BA7 and inferior parietal lobe BA40 and the right insula BA One of the clusters indicated an activation of the right precuneus BA Considering these studies, it can be concluded that BA20, BA37, BA38, and BA39 have a partial participation in language, specifically associating language with other types of information.
Fifty-seven papers, 84 experiments, and participants were selected Bernal et al. A network consisting of 16 clusters of activation were obtained. There were also clusters in subcortical structures including the left thalamus, left putamen, and right cerebellum see Fig. The main cluster encompasses left BA44 and its abutting areas. The involvement of the right anterior cingulate gyrus could be real, or most likely, an effect of the post-processing utilized to remove pixelation and aliasing of the cluster borders.
This effect could explain the aspect of activation of the neighbor contralateral homologue anterior cingulate gyrus. The third cluster is located in the left superior and inferior parietal lobule, an area shared by BA7, BA39, and BA The fourth cluster involves some mirror areas of the left Broca right BA44, right anterior insula, and right BA9 , plus one subcortical structure, namely the putamen.
The fifth cluster refers to the left fusiform gyrus. The sixth cluster represents the core of the receptive language area or Wernicke's area left BA The next cluster in importance is located in the left thalamus. Brain connectivity of BA44 and BA Left panel, left lateral view; right panel, mesial view. The networks are color coded.
BA44 is represented by black and gray blue and purple in the online version ; BA46 is represented by darker gray and gray red and purple in the online version.
[The Language Area of the Brain: A Functional Reassessment]