The Efficacy of an IADL-based Non-immersive Virtual Reality Training Program to Enhance ADL Performance and Cognitive Function for Persons at Risk of Dementia

The goal of this clinical trial is to learn if a touchscreen-based virtual reality (VR) training program that simulates everyday life tasks works to improve daily living skills and thinking abilities in adults aged 50 and older, including those at risk of dementia (individuals with Subjective Cognitive Decline or Mild Cognitive Impairment). It will also explore what personal factors influence the training results. The main questions it aims to answer are: * Does the daily life VR training program improve participants' ability to perform complex everyday activities and adapt flexibly to daily life challenges? * Does the training improve overall thinking skills (such as memory, attention, and problem-solving), brain activity, and mood (depression and anxiety)? Researchers will compare the daily-life VR training program (IADL-VR) to a non-situational game VR program (Game-VR) and a traditional in-person tabletop cognitive training program (Cog-Entity) to see if realistic daily-life VR simulation works better to enhance everyday functioning and brain health. Participants will: * Be randomly assigned to one of the three training groups (daily-life VR tasks, digital brain-training mini-games, or traditional tabletop board games). * Attend a 2-hour group session once a week for 12 weeks, which includes 1 hour of assigned cognitive training and 1 hour of physical fitness exercise. * Complete assessments of their daily living skills, thinking abilities, mood, and brain activity (using functional magnetic resonance imaging, or fMRI) within 2 weeks before and after the 12-week program.

Inclusion Criteria: General Inclusion Criteria (Applicable to All Participants): * Aged 50 years or older. * Completed at least elementary school education (6 or more years of formal education) and able to read and write in Chinese. Group-Specific Inclusion Criteria: 1. Cognitively Healthy Middle-Aged and Older Adults Group: * Taiwanese version of the Montreal Cognitive Assessment (MoCA) score \> 26. * Does not meet the diagnostic criteria for Subjective Cognitive Decline (SCD), Mild Cognitive Impairment (MCI), or dementia. 2. Subjective Cognitive Decline (SCD) Group: * Taiwanese version of the Montreal Cognitive Assessment (MoCA) score \> 23. * Subjective Cognitive Decline Questionnaire (SCD-Q) score \> 7 (out of a total score of 24). * Answers "Yes" to both of the following questions: "Do you feel that you have memory problems compared to your previous normal state?" and "Have your family members or close friends noticed that you have memory problems compared to your previous state?" * Normal performance on standardized neuropsychological tests (Color Trails Test and memory-related tests), defined as scoring higher than 1.5 standard deviations below the age- and education-adjusted normative mean. * Does not meet the diagnostic criteria for Mild Cognitive Impairment (MCI) or dementia. 3. Mild Cognitive Impairment (MCI) Group: * Taiwanese version of the Montreal Cognitive Assessment (MoCA) score \> 21. * Diagnosed with Mild Cognitive Impairment (MCI) by a neurologist or psychiatrist. * Does not meet the diagnostic criteria for dementia. Exclusion Criteria (Applicable to All Participants): * Meets the clinical diagnostic criteria for dementia. * Geriatric Depression Scale Short-Form (GDS-S) score \>= 8, or cognitive changes caused by other psychiatric disorders, neurological diseases, or substance abuse with unstable medical conditions and interfering symptoms. * Severe visual or hearing impairments that prevent the completion of cognitive function assessments. * Physical illnesses or conditions that prevent participation in the cognitive and physical training interventions.