Broca’s area, responsible for speech production, is regulated by lung function

For more than 150 years, Broca's area-specifically, the pars opercularis and pars triangularis in the left inferior frontal gyrus-has been recognized as crucial for human speech production. However, it remains unknown why this region is recruited for speaking. Speech production involves not only conceptualization and motor planning but also respiration to provide the necessary airflow for creating sounds. Thus, the role of Broca's area in speech may be shaped by the functionality and related brain regions of the lungs. To test this hypothesis, we recruited patients with chronic obstructive pulmonary disease and asked them to read words aloud while their brains were scanned using functional magnetic resonance imaging, with quantitative magnetic resonance imaging acquired separately. The chronic obstructive pulmonary disease patients exhibited altered cortical responses in the left inferior prefrontal cortex and other regions during speech tasks, and also had abnormal activation in cortical sites associated with breathing. In addition, using quantitative magnetic resonance imaging to generate longitudinal relaxation time (T 1 ) maps as an index of brain microstructural changes, including dendritic maturation and myelination, we observed significantly longer longitudinal relaxation times in Broca's area in the chronic obstructive pulmonary disease group than in the control group, suggesting reduced myelination and impaired microstructural integrity. Crucially, our data indicated that more severe dyspnea was associated with less well-developed microstructure in Broca's area and weaker activation of this region. The present study indicates for the first time that the lungs may function to shape Broca's area as the speaking center, providing novel evidence that pulmonary dysfunction can influence both the functional and structural properties of cortical language regions. These findings highlight the mechanistic role of the lung-brain axis in speech production and suggest potential targets for interventions to enhance speech performance.