The relationship between language ability and brain activity across language processes and modalities

Abstract

Existing neuroimaging studies on the relationship between language ability and brain activity have found contradictory evidence: On the one hand, increased activity with higher language ability has been interpreted as deeper or more adaptive language processing. On the other hand, decreased activity with higher language ability has been interpreted as more efficient language processing. In contrast to previous studies, the current study investigated the relationship between language ability and neural activity across different language processes and modalities while keeping non-linguistic cognitive task demands to a minimum. fMRI data were collected from 22 healthy adults performing a sentence listening task, a sentence reading task and a phonological production task. Outside the MRI scanner, language ability was assessed with the verbal scale of the Wechsler Abbreviated Scale of Intelligence (WASI-II) and a verbal fluency task. As expected, sentence comprehension activated the left anterior temporal lobe while phonological processing activated the left inferior frontal gyrus. Higher language ability was associated with increased activity in the left temporal lobe during auditory sentence processing and with increased activity in the left frontal lobe during phonological processing, reflected in both, higher intensity and greater extent of activations. Evidence for decreased activity with higher language ability was less consistent and restricted to verbal fluency. Together, the results predominantly support the hypothesis of deeper language processing in individuals with higher language ability. The consistency of results across language processes, modalities, and brain regions suggests a general positive link between language abilities and brain activity within the core language network. However, a negative relationship seems to exist for non-linguistic cognitive functions located outside the language network.