The goal of this study is to learn if a new brain training method, called combined electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) neurofeedback, can improve thinking, emotions, and social functioning in children with autism spectrum disorder (ASD). It will also learn if this training is practical and safe to use with children in Hong Kong.

The main questions this study aims to answer are:

• Does combined EEG-fNIRS neurofeedback improve attention, emotion regulation, and social skills in children with ASD?
• Is this type of neurofeedback training feasible and well-tolerated by children? Researchers will compare the new combined EEG-fNIRS training with single EEG or fNIRS training to see if it provides additional benefits.

Participants will:

.Receive sessions of EEG-fNIRS neurofeedback training. .Complete assessments of thinking skills, emotional regulation, and social functioning before and after training.

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental condition characterized by difficulties in social communication and interaction, often accompanied by cognitive and emotional regulation challenges. In Hong Kong and many other countries, ASD is increasingly prevalent. Despite this, the brain health of autistic individuals has been relatively neglected in both healthcare systems and public policies. There is also a lack of approaches and technologies that directly intervene with brain function. Since many autistic children experience poor vocational and health outcomes in adulthood, there is a strong need to develop effective and accessible neuroscience-based treatments.

This project aims to apply cutting-edge neuroscientific methods to develop an innovative closed-loop brain training intervention for children with ASD. The intervention will combine electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) in a unified neurofeedback training system. Neurofeedback training teaches individuals to self-regulate brain activity by providing real-time feedback. In the traditional neurofeedback study, EEG has been used to guide neurofeedback by monitoring electrical activity in the brain, while more recently fNIRS has been used to track hemodynamic activity. However, no existing neurofeedback system has integrated these two modalities. Combining EEG and fNIRS provides an opportunity to enhance neurovascular coupling, the relationship between neural activity and blood flow, which is often altered in neuropsychiatric conditions such as autism.

The proposed neurofeedback application will include multiple training modules designed to address cognitive, emotional, and social difficulties common in autism. The cognitive training module will target brain activity patterns associated with attention and executive function. The affective training module will focus on modulating frontal brain activity linked to emotional regulation. The social training module will aim to enhance neural and hemodynamic activity associated with social cognition and communication. By integrating both EEG and fNIRS indices, the system will encourage children to regulate electrical and hemodynamic activity simultaneously, which cannot be achieved using either modality alone.

To maximize engagement, the application will incorporate ecologically valid feedback stimuli and reward-based learning principles. Instead of relying solely on abstract indicators such as bars or tones, the feedback will involve intrinsically rewarding stimuli, such as videos or positive visual cues, to increase motivation and adherence. The training difficulty will be adjusted progressively based on individual performance to ensure sustained engagement and improvement.

In addition, the system will be developed as a cross-device application using open-source lab streaming layer (LSL) software, ensuring compatibility with a wide range of EEG and fNIRS devices. The hardware and software will be optimized to ensure high-quality signals, including the use of shielded wet electrodes for EEG to reduce noise and short-separation channels in fNIRS to minimize extracerebral signal contamination. These features will allow neurofeedback training to be conducted with minimal environmental interference, enhancing both reliability and clinical applicability.

Through this proof-of-concept project, this project aims to establish the feasibility of combined EEG-fNIRS neurofeedback as a novel form of brain training for autistic children. If successful, this approach has the potential to offer a comprehensive, technology-based neurorehabilitation solution that can improve functional outcomes, reduce healthcare burdens, and foster innovation in neurotechnology in Hong Kong.

Inclusion Criteria:

• Children aged 8 to 12 years
• Previous diagnosis of autism spectrum disorder (ASD) or Asperger's syndrome
• No intellectual impairment or studying in mainstream schools
• Right-handedness
• Normal or corrected-to-normal vision

Exclusion Criteria:

- Not meeting any of the above inclusion criteria

All data related to this study will be kept strictly confidential and will be accessible only to the research team for research purposes. Study findings may be published in academic journals or presented at conferences; however, the names of participants and their families will remain confidential. All assessment instruments will be identified by coded numbers rather than names, and all personal information will be stored in a locked filing cabinet until the fifth year following the dissemination of study results. The Confidentiality and Privacy Ordinance of The Educational University Of Hong Kong shall protect and keep all medical data.

During each training session, a cap adjusted to the participant's head size will be used to mount the EEG and fNIRS sensors. The hardware setup will be the same for all groups to ensure that both the participant and experimenter are blinded to the training group. Besides, all participants will be identified by numbers, which are randomly assigned to one of three conditions by the Principal Investigator, who does not involve in either the assessment or training session.