Which left hemisphere brain regions are commonly associated with apraxia of speech?

• A. Occipital lobe.
• B. Cerebellum.
• C. Inferior frontal gyrus (including Broca's area), insula, and supplementary motor area.
• D. Brainstem.

Answer: (C)

Apraxia of speech arises from a disruption in planning and programming the precise sequences of movements needed for articulation. In the left hemisphere, a key frontal-lobe network handles this planning. The inferior frontal gyrus, which includes Broca’s area, is central to formulating the motor plan for speech and organizing the sequence of articulatory movements. The insula supports integrating timing and coordination of the speech articulators, helping to fine-tune how sounds are produced. The supplementary motor area (SMA) is involved in initiating and sequencing complex motor actions, including speech.

Damage to this left frontal network intercepts the conversion of linguistic plans into accurate articulatory movements, leading to the hallmark features of apraxia of speech such as effortful, distorted, and hesitating speech with inconsistent errors, while language comprehension and automatic speech may be relatively preserved.

Other regions like the occipital lobe are mainly for vision, and the brainstem is crucial for basic motor commands, but apraxia of speech specifically points to the left frontal regions—inferior frontal gyrus (Broca’s area), insula, and supplementary motor area—as the most commonly implicated sites. The cerebellum can influence timing and coordination, but the classic association with AOS centers on this left frontal network.