Beyond Broca: neural architecture and evolution of a dual motor speech coordination system.

The article focuses on a proposed dual speech coordination model that challenges classical views attributing speech motor coordination solely to Broca's area. It presents evidence for two parallel but interacting neural systems in the lateral precentral gyrus: a dorsal precentral speech area (dPCSA) involved in pitch-related vocalization (prosody and song) coordinated via the dorsal laryngeal motor cortex, and a ventral precentral speech area (vPCSA) responsible for phonetic and syllabic articulation coordinated via the ventral laryngeal motor cortex. The authors argue these systems have distinct evolutionary origins, with the dorsal system evolving from a premotor goal-directed orienting network sensitive to auditory pitch cues, and the ventral system deriving from ventral orofacial motor circuits involved in lip smacking and mastication. This dual architecture has implications for understanding speech production, language evolution, and clinical speech disorders such as apraxia of speech and stuttering.