Arcuate Fasciculus

The arcuate fasciculus is a bundle of axons that forms a significant part of the brain's connective white matter. Its primary role lies in connecting two crucial areas of the cerebrum: Wernicke's area in the superior temporal gyrus and Broca's area in the inferior frontal gyrus^[1]. These areas, located in the dominant cerebral hemisphere (which is the left hemisphere in about 95% of right-handed individuals and 70% of left-handed individuals), are vital for language comprehension and speech production, respectively^[2].

Historically, the arcuate fasciculus was thought to be the primary and direct pathway between these two areas, based on the classic Wernicke-Lichtheim-Geschwind model of language^[4]. According to this model, auditory information is processed in Wernicke's area, transmitted to Broca's area via the arcuate fasciculus, and then utilized for the motor planning and execution of speech^[5]. This model further posited that a lesion in the arcuate fasciculus results in conduction aphasia, a rare speech disorder characterized by fluent speech, intact comprehension, but impaired speech repetition^[6].

However, modern neuroimaging methods such as diffusion tensor imaging (DTI) have provided a more nuanced view of the cortical language network and the role of the arcuate fasciculus^[7]. The current understanding is that the arcuate fasciculus is one component of a larger dorsal stream of language processing, which is involved in the mapping of acoustic speech signals to frontal lobe articulatory networks^[8]. Meanwhile, the ventral stream, which includes the extreme capsule fiber system, is thought to be involved in mapping acoustic speech signals to meaning^[9].

The actual role of the arcuate fasciculus in language and its relationship with conduction aphasia remains a topic of ongoing research^[10]. In addition to language, the arcuate fasciculus is also thought to be involved in other cognitive functions, including working memory and music perception^[11].