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Speech sequencing in the human precentral gyrus

Nature Human Behaviour volume 9, pages 2327–2344 (2025)Cite this article

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Abstract

Fluent speech production is mediated by serially ordering and preparing motor plans corresponding to target speech sounds, a process known as speech-motor sequencing. Here we used high-density direct cortical recordings while 14 participants spoke utterances with varying phonemic and syllabic sequence complexity after reading a target sequence and a delay period. Phasic activations corresponding to speech production and auditory feedback were observed, but also sustained neural activity that persisted throughout all task phases including the target presentation, the delay period and production of the sequence. Furthermore, sustained activity in a specific area, the middle precentral gyrus (mPrCG), was both modulated by sequence complexity and predicted reaction time, suggesting a role in speech-motor sequencing. Electrocortical stimulation of the mPrCG caused speech disfluencies resembling those seen in apraxia of speech. These results suggest that speech-motor sequencing is mediated by a distributed cortical network in which the mPrCG plays a central role.

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Fig. 1: Sustained cortical activation from encoding to planning and production of syllable sequences.
Fig. 2: Sustained cortical activity differentiates task phases during speech planning and production.
Fig. 3: Sequence and articulatory complexity modulate sustained neural activity for planning syllable sequences.
Fig. 4: mPrCG pre-speech activity predicts behavioural reaction time.
Fig. 5: Direct cortical stimulation of the mPrCG results in speech-motor sequencing errors.

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Data availability

Data that support the main conclusions of the paper are available via Zenodo at https://doi.org/10.5281/zenodo.15346719 (ref. 78). Source data are provided with this paper. Specific statistical data is also provided in the Supplementary Data.

Code availability

Code for relevant analyses and figure creation is available via GitHub at https://github.com/ChangLabUcsf/Liu2025_Sequencing.

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Acknowledgements

We thank all the participants who generously donated their time and effort to the collection of these data. We also thank the Chang Lab for helpful feedback and clinical support, in particular M. K. Leonard, D. F. Levy, A. B. Silva, Q. Greicius, C. Wang and M. P. Seaton, as well as R. C. Knowlton and J. K. Kleen. J.R.L. was supported by the National Institutes of Health grant no. U01 DC018671-01A1. L.Z. was supported by the National Institute on Deafness and Other Communication Disorders grant no. K99 DC020235. P.W.H. was supported by the National Center for Advancing Translational Sciences grant no. 5TL1TR001871-05.

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Author notes

  1. These authors contributed equally: Jessie R. Liu, Lingyun Zhao.

Authors and Affiliations

  1. Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA

    Jessie R. Liu, Lingyun Zhao, Patrick W. Hullett & Edward F. Chang

  2. Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, USA

    Jessie R. Liu, Lingyun Zhao, Patrick W. Hullett & Edward F. Chang

  3. University of California, Berkeley—University of California, San Francisco Graduate Program in Bioengineering, Berkeley, CA, USA

    Jessie R. Liu & Edward F. Chang

  4. Department of Neurology, University of California, San Francisco, San Francisco, CA, USA

    Patrick W. Hullett

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Contributions

J.R.L. and E.F.C. conceptualized the research and designed the experiments. J.R.L., L.Z. and others collected the ECoG data. P.W.H. and J.R.L. collected the stimulation data. J.R.L. and L.Z. analysed the data. J.R.L., L.Z. and E.F.C. wrote the paper with input from all authors. E.F.C. supervised the project.

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Correspondence to Edward F. Chang.

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Competing interests

J.R.L. and E.F.C. are inventors of pending provisional University of California, San Francisco patent applications relevant to neural decoding approaches. EFC is co-founder of Echo Neurotechnologies, LLC.

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Nature Human Behaviour thanks Anaïs Llorens, Nick Ramsey and Stephanie Ries for their contribution to the peer review of this work.

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Supplementary Methods, Figs. 1–23 and Tables 1–8.

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Statistical source data for Supplementary Figs. 1 and 2, and summary electrode ROI counts.

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Statistical source data for Figs. 2c, 3b, 3c, 5d and 5e.

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Liu, J.R., Zhao, L., Hullett, P.W. et al. Speech sequencing in the human precentral gyrus. Nat Hum Behav 9, 2327–2344 (2025). https://doi.org/10.1038/s41562-025-02250-1

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