<P> Area 45 receives more afferent connections from 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 . </P> <P> 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 . </P> <P> 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, it has recently been found in functional magnetic resonance imaging (fMRI) experiments involving 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 . </P> <P> 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: </P>

Which region of the brain is responsible for motor aspects of speech