Chatbot Intervention Effects on Resting-State Brain Function in Anhedonia

Anhedonia represents a core characteristic of depression and is characterized by reduced experience of pleasure. It is closely related to decreased motivation, altered reward processing, and alterations in intrinsic brain network function. Resting-state fMRI provides a way to examine intrinsic brain activity and functional connectivity without requiring participants to perform a specific task. This is important because changes associated with anhedonia may not only appear during reward-related tasks, but may also be reflected in spontaneous brain network organization.

Inclusion criteria

• 18-40 years
• Right-handed
• Normal or corrected normal visual acuity
• Participants must show elevated anhedonia and depressive symptoms at screening, defined as a total score of 22 or higher on the Snaith-Hamilton Pleasure Scale and a score of 14 or higher on the Beck Depression Inventory

Exclusion criteria

• History of major central nervous system disorders, such as epilepsy, traumatic brain injury, stroke, or brain tumors.
• History of severe mental illness, including schizophrenia spectrum disorders, bipolar disorder, or other psychotic disorders.
• History of substance or alcohol use disorder or substance or alcohol misuse within the past 12 months that may affect study participation or outcome assessment.
• Individuals currently at high risk of suicide, severe self-harm, or experiencing an acute psychiatric crisis.
• Individuals who are currently using psychiatric medications or have undergone psychotherapy within the past 4 weeks that may significantly affect mood, motivation, or reward processing.
• Severe vision or hearing impairments that cannot be corrected and would interfere with task performance.
• Contraindications to MRI scanning, including metallic implants, pacemakers, severe claustrophobia, or other conditions incompatible with MRI.
• Pregnancy or breastfeeding.