Brain Localization and the Integrated Systems Hypothesis: Evidence from Broca’s Region

Abstract

The human brain is a fascinatingly complex organ with specialized structures associated with distinct functions. Classical and recent studies on brain localization propose that Broca’s area underpin expressive language and this has been generalized to explain brain functional organization. However, recent neuroimaging studies have shown that the Broca’s area is an extended network that not only participate in its primary function-expressive language processing but in secondary functions-processing non-linguistic/nonverbal tasks as well. Also, there is hierarchical connectivity and interaction of Broca’s region and different brain areas in underlying related primary functions. For this review, I start with revisiting the classical description of brain localization. I then discuss the neuroanatomy of language production and the role of Broca’s region in language processing. I then highlight the participation of the Broca’s area in non-linguistic tasks and non-primary linguistic tasks. Ultimately, I propose a novel hypothesis called integrated systems hypothesis. The integrated systems hypothesis is useful for guiding research on the multimodal role of specific localized integrated systems of the brain especially the role of the Broca’s region in integrating linguistic and non-linguistic processing and how this facilitate language production.