Understanding speech generation and speech comprehension depends on the fundamental process of speech processing. Correct recognition of fundamental speech elements requires precise timing and sound acquisition throughout speech production. The human brain contains specific spatial locations for analyzing phonemes, which are the smallest speech units, and these locations include the superior temporal gyrus (STG) and superior temporal sulcus (STS).
These brain regions serve as exploratory centers to detect different individual speech elements, including vowels and articulation. Sustainable communication depends on five essential components, which include phonemes, prosody, rhythm, pitch, loudness, and vowel quality. Prosody serves as an essential tool for the speaker to share their intended meaning through statements versus questions, word emphasis, and topic-switch notification. While extensive research has investigated phonetic patterns in speech processing, studies on tonal patterns as key contributors to speech effectiveness remain limited. STG and STS operate as fundamental brain areas that process speech and language, while separate portions on the lateral side of the STG are responsible for understanding phonological characteristics.
Research shows that speech processing involves an auditory thalamo-STG pathway, which skips the basic sound processing area within the primary auditory cortex. Researchers need to conduct additional studies to completely understand how the brain processes pitch information in natural speech. This study used extremely detailed intracerebral recordings from human subjects to understand brain processing mechanisms of intonation.
The application of stereoelectroencephalography enabled scientists to study Heschl’s gyrus (HG), the supratemporal plane, and other deep structures inside the brain. These brain regions processed intonation categories with their alternating high and low pitches as the main subjects of investigation.
A total of 11 participants (female = 2) were included in this study. All participants were between 9 and 24 years old, and 2 out of 11 were left-handed. This study utilized human intracerebral recordings to study brain mechanisms of intonation processing and their precise spatial and temporal aspects. The researchers applied stereoelectroencephalography (sEEG) as the research method instead of electrocorticography because it allows brain structure investigations of Heschl’s gyrus (HG) and the supratemporal plane (STP). The research investigated how the brain stores the different intonation categories formed by high and low-pitch alternations within these brain regions.
Research data verified the vital function of the HG in interpreting pitch accents, as these intonations serve critical roles in distinguishing speech patterns and speaker intent interpretation. The research shows that the HG processes pitch accents more extensively than previously recognized by scientific models. Initial sound processing occurs in the brain region, where distinct representations for pitch accent categories are created during encoding.
The neural representation of pitch accents differs from how pitch or intensity affects basic acoustic signals. Brain areas within the medial and anterolateral HG, along with the planum temporale (PT), together form what researchers have called the “pitch center.” The study confirms the HG functions as a vital area for speech pitch accent processing because it demonstrates neural regions that specifically detect periodicity signatures, relative pitch variations, and amplitude envelope patterns.
Furthermore, the research demonstrated that pitch accents were not distinct from the HG, while the STG was not free of this finding. The HG exhibited pitch accent separability across its total extent, which indicates that it specializes in combining various indications to detect pitch accents. This suggests that the HG functions as a complex neural network that can solve computations beyond basic spectrotemporal processing and simple phase-locking to periodicity.
Overall, this study enhances the scientific understanding of brain processes related to pitch accent interpretation. Pitch accent encoding takes place mainly in the HG to differentiate meaningful tonal speech patterns necessary for understanding the semantic and motivational aspects of human communication; by examining how the brain processes speech, the research reveals advanced neural computing operations that contribute to a deeper understanding of pitch systems in language comprehension.
References: Gnanateja GN, Rupp K, Llanos F, et al. Cortical processing of discrete prosodic patterns in continuous speech. Nat Commun. 2025;16:1947. doi:10.1038/s41467-025-56779-w
