The goal of this clinical trial is to compare the user experience of Augmented Reality (AR) and Virtual Reality (VR) applications during music therapy interventions in individuals with Cerebral Palsy aged 15 to 35 years with Gross Motor Function Classification System (GMFCS) level I-V.

The main questions it aims to answer are:

Does AR or VR result in lower levels of cybersickness as measured by the Simulator Sickness Questionnaire (SSQ)? Does AR or VR provide better usability, preference, and perceived ease of interaction?

Researchers will compare AR and VR conditions to determine which technology results in lower cybersickness levels, higher usability scores, and greater user preference.

Participants will:

complete a pre-intervention SSQ assessment; engage in AR and VR sessions in a counterbalanced order using the Meta Quest 3 headset; explore each virtual environment for 5 minutes; perform motor tasks involving reaching and interacting with virtual musical objects (musical cubes representing musical notes: C-D-E-F-G-A-B); perform cognitive tasks involving identification and reproduction of musical note sequences guided by a therapist; perform percussion activities by following rhythmic patterns played by a therapist using virtual instruments; complete post-condition assessments after each session, including SSQ, System Usability Scale (SUS), preference, and reported difficulties.

This study investigates the use of immersive technologies in music therapy for individuals with Cerebral Palsy, focusing on the comparative effects of Augmented Reality (AR) and Virtual Reality (VR) on user experience and interaction.

Individuals classified at Gross Motor Function Classification System (GMFCS) level I-V often present severe motor impairments that limit their ability to engage in conventional therapeutic activities. Music therapy has been shown to support cognitive and emotional engagement; however, traditional approaches may require adaptations to accommodate motor limitations. Immersive technologies such as AR and VR offer alternative interaction modalities that may enhance accessibility, engagement, and autonomy.

The study adopts a within-subject crossover design in which all participants are exposed to both AR and VR conditions in a counterbalanced order to minimize sequence effects. The experimental sessions are conducted on separate days, with one condition (AR or VR) performed first and the alternate condition performed approximately one week later to minimize carryover effects.

The intervention is delivered using the Meta Quest 3 headset, which supports hand-tracking interaction. A custom application, named GenVirtual, was developed in the Unity 3D environment to provide accessible and adaptive interaction for individuals with severe motor impairments. The system leverages hand-tracking to enable interaction without the need for physical controllers, reducing barriers related to fine motor control.

Each experimental session is structured into three phases: (1) initial familiarization with the immersive environment, (2) interaction with musical cubes representing musical notes, and (3) rhythmic interaction using virtual percussion instruments. The musical cubes are visually differentiated by color and correspond to the seven musical notes (C-D-E-F-G-A-B), allowing participants to perform structured tasks involving sequencing and auditory discrimination. In the percussion phase, participants reproduce rhythmic patterns demonstrated by a therapist, promoting synchronization, attention, and sensorimotor coordination.

The applications were designed to support both motor and cognitive engagement by integrating multimodal feedback (visual and auditory cues) and minimizing the need for precise fine motor control. The therapist provides guidance throughout the session, ensuring task comprehension and adapting the pace as needed based on participant performance.

Data collection focuses on subjective measures of user experience, including perceived usability, cybersickness symptoms, and interaction-related difficulties. The crossover design allows for direct comparison between AR and VR conditions within the same participants, reducing inter-subject variability and increasing sensitivity to detect differences between technologies.

Inclusion Criteria:

• Individuals with a confirmed diagnosis of Cerebral Palsy
• Aged between 15 and 35 years
• Participants of any sex
• Cognitive ability compatible with participation in the study, determined by a minimum Intelligence Quotient (IQ) score established through the Wechsler Intelligence Scale for Children (WISC) or Wechsler Adult Intelligence Scale (WAIS)
• Ability to participate in immersive music therapy activities using hand-tracking interaction with the Meta Quest 3 headset

Exclusion Criteria:

• Failure to attend the second experimental session
• Withdrawal or interruption of participation in the study for any reason before completion of all study procedures
• Insufficient corrected visual acuity to adequately interact with the immersive system, verified through a simple visual screening assessment
• Failure to achieve the minimum Intelligence Quotient (IQ) score required for understanding the proposed tasks, as determined by the Wechsler Intelligence Scale for Children (WISC) or Wechsler Adult Intelligence Scale (WAIS) assessments