Chinese-Specific Speech Imagery Coding Using High-Density ECoG

Investigation of Chinese-Specific Speech Imagery Encoding and Decoding Using High-Density Electrocorticography

The goal of this study is to investigate whether high-density electrocorticography (ECoG) signals recorded from the surface of the brain can be used to decode neural representations of Mandarin Chinese speech features, including lexical tone, without requiring overt speech movements. The study focuses on the development and evaluation of decoding algorithms based on neural activity recorded during clinically indicated neurosurgical procedures.

The main questions it aims to answer are:

Can high-density ECoG signals be decoded to reconstruct neural representations of Mandarin Chinese speech features, particularly lexical tone?

Can neural activity recorded during silent auditory speech imagery be decoded to reconstruct tone-specific speech representations without actual articulation?

The study includes two groups of adult patients with neurological conditions who require cortical electrode placement as part of clinically indicated care:

A intraoperative high-density ECoG temporary coverage group, enrolling approximately 50 patients with functional-area glioma or drug-resistant epilepsy who undergo awake neurosurgery with temporary high-density ECoG coverage for clinical functional mapping.

A permanent high-density ECoG implantation group, enrolling approximately 10 patients with severe speech or language impairment caused by neurological conditions such as stroke, brain tumors, amyotrophic lateral sclerosis (ALS), or locked-in syndrome, who receive permanent high-density cortical electrode implantation for long-term monitoring.

Participants will:

Complete preoperative clinical assessments as part of standard medical care, including brain imaging, language function evaluation, and routine neurological assessments

Undergo clinically indicated awake neurosurgical procedures during which high-density ECoG electrodes are placed on the cortical surface for clinical functional localization

Perform language-related tasks, such as listening to speech, imagining speech, and limited spoken responses, while brain electrical activity is recorded for approximately 20-30 minutes during surgery, without altering standard surgical procedures

For participants in the permanent implantation group, participate in long-term follow-up visits approximately every 2 weeks or monthly for up to 12 months after surgery, including evaluation of signal quality and research-related analysis and optimization of decoding algorithms

All surgical procedures involving temporary or permanent electrode placement are performed for clinical indications and have been approved through institutional ethical and scientific review. Participation in this study does not alter standard clinical care for the temporary recording group and does not require additional clinical procedures beyond routine treatment.

This research aims to support the long-term development of silent brain-to-speech communication technologies for individuals with severe speech or motor impairments and to improve understanding of how frontal, parietal, and temporal brain regions represent imagined speech in tonal languages such as Mandarin Chinese.

Inclusion Criteria:

• Age between 20 and 80 years.
• Ability and willingness to provide informed consent and comply with study procedures.
• No severe preoperative emotional or consciousness disorders that would preclude participation in experimental tasks.
• For patients undergoing intraoperative temporary high-density ECoG coverage: Patients with cerebral eloquent-area gliomas or refractory epilepsy undergoing awake craniotomy as part of standard clinical management.
• For patients undergoing intraoperative temporary high-density ECoG coverage: Lesions involving or adjacent to eloquent brain areas including language, motor, or memory-related regions.
• For patients undergoing intraoperative temporary high-density ECoG coverage: Mild mass effect without severe intracranial hypertension.
• For patients undergoing intraoperative temporary high-density ECoG coverage: Preoperative language function largely preserved, with naming, reading, and language comprehension ≥80% of normal performance.
• For patients undergoing permanent high-density ECoG implantation: Severe speech or language dysfunction caused by stroke, brain tumors, amyotrophic lateral sclerosis (ALS), or locked-in syndrome.
• For patients undergoing permanent high-density ECoG implantation: No substantial improvement after 3-6 months of adequate rehabilitation and disease duration >12 months.
• For patients undergoing permanent high-density ECoG implantation: Structural integrity of speech imagery-related cortices (ventral central lobule, supramarginal gyrus, superior temporal gyrus, middle temporal gyrus, middle frontal gyrus, and inferior frontal gyrus).
• For patients undergoing permanent high-density ECoG implantation: Diagnosis of severe dysarthria or severe motor aphasia, with spontaneous speech score <5/20 on the Aphasia Battery of Chinese (ABC) and auditory comprehension ≥80% of normal levels.

Exclusion Criteria:

• Significant mass effect with severe intracranial hypertension precluding awake craniotomy or electrode implantation.
• Severe neurological dysfunction that would prevent participation in study procedures (except for speech or language impairment in the permanent implantation cohort).
• Contraindications to MRI scanning or awake craniotomy, including incompatible implanted medical devices, severe claustrophobia, or obstructive sleep apnea syndrome.
• Severe psychiatric disorders or cognitive impairment preventing participation in treatment or follow-up assessments (Mini-Mental State Examination score <24).
• Severe systemic medical comorbidities.
• Pregnancy or lactation.
• Refusal or inability to provide informed consent.