Hearing and saying

TLDR

Prior neuropsychological and neuroimaging studies implicate Wernicke’s and Broca’s areas in language processing, with consistent activation of Wernicke’s but variable involvement of Broca’s. The study investigates the neural systems underlying hearing and repeating single words using PET. PET experiments were conducted to map neural activity during hearing and repetition tasks. Broca’s area is activated during both hearing and repeating single words, with greater activation during repetition and at slower rates, and its peak frontal activation for hearing is anterior to that for repetition (BA45 vs BA44/precentral sulcus); the activation is subtle and design‑dependent, and the auditory association cortex responds similarly to own and other voices during repetition.

Abstract

SummaryThe neural systems involved in hearing and repeating single words were investigated in a series of experiments using PET. Neuropsychological and psycholinguistic studies implicate the involvement of posterior and anterior left perisylvian regions (Wernicke's and Broca's areas). Although previous functional neuroimaging studies have consistently shown activation of Wernicke's area, there has been only variable implication of Broca's area. This study demonstrates that Broca's area is involved in both auditory word perception and repetition but activation is dependent on task (greater during repetition than hearing) and stimulus presentation (greater when hearing words at a slow rate). The peak of frontal activation in response to hearing words is anterior to that associated with repeating words; the former is probably located in Brodmann's area 45, the latter in Brodmann's area 44 and the adjacent precentral sulcus. As Broca's area activation is more subtle and complex than that in Wernicke's area during these tasks, the likelihood of observing it is influenced by both the study design and the image analysis technique employed. As a secondary outcome from the study, the response of bilateral auditory association cortex to 'own voice' during repetition was shown to be the same as when listening to 'other voice' from a prerecorded tape.