Real-Time EEG Neurofeedback Using a Subject-Independent Classifier in Women With Depressive Symptoms

A Randomized, Double-blind Feasibility Study of a Subject-independent Classifier-based EEG Neurofeedback in Women With Depressive Symptoms

This completed feasibility study examined whether right-handed women aged 18-35 years with mild-to-moderate depressive symptoms could use real-time electroencephalography (EEG) neurofeedback based on a subject-independent classifier to regulate brain activity toward a classifier-defined reference pattern. Participants were randomly assigned to receive either classifier-contingent visual feedback with performance-contingent monetary rewards or noncontingent sham visual feedback with yoked monetary rewards. All participants completed five training sessions over approximately 3 weeks. The primary purpose was to determine whether overall classifier accuracy during training exceeded the theoretical 50% chance level. Changes in clinician-rated and self-reported depressive symptoms, associations between classifier performance and symptom change, EEG spatial patterns, and procedural tolerability were exploratory.

The subject-independent classifier had been developed from EEG recordings obtained from an independent reference sample of healthy right-handed women during positive autobiographical memory recall and motor imagery. It used a Filter Bank Common Spatial Pattern feature-extraction pipeline and a linear support vector machine to classify the two mental states from 28 EEG channels.

After eligibility and baseline assessments, participants were randomly assigned in a 1:1 ratio to an experimental or control arm using a sequence generated before the intervention. Participants and the clinical psychologists administering the Hamilton Depression Rating Scale were masked to allocation. The experimental arm was implemented before the control arm because the control rewards were yoked to a reward sequence generated in the experimental arm; this operational sequence did not determine assignment.

Each participant completed five EEG neurofeedback sessions on separate days over approximately 3 weeks. Each session contained four 300-second runs. In each run, participants completed positive autobiographical memory recall and motor imagery blocks while viewing a thermometer-like display. In the experimental arm, the display was updated approximately once per second according to the classifier output and monetary rewards depended on run-level classifier accuracy. In the control arm, display movements were random and independent of EEG activity, and rewards were yoked to the run-by-run reward sequence of the experimental participant with the highest total reward.

This record was created retrospectively after study completion. The protocol information reflects the completed study procedures and the outcome hierarchy reported in the final manuscript; exploratory analyses have not been promoted to primary outcomes.

Inclusion Criteria:

• Self-identification as a woman.
• Female sex assigned at birth, reported during the intake interview
• Self-reported right-handedness
• Age 18-35 years
• Beck Depression Inventory-II score of 14-29
• Hamilton Depression Rating Scale score below 24
• Score below 2 on the suicide-related item of both the Beck Depression
• Inventory-II and Hamilton Depression Rating Scale

Exclusion Criteria:

• Current psychotherapy
• Self-reported history of bipolar disorder or schizophrenia
• Prior suicide attempt
• Self-reported history of post-traumatic stress disorder, obsessive-compulsive disorder, substance use disorder, or anorexia nervosa
• Neurological disorder, including dementia, brain tumor, or epilepsy
• Intellectual disability
• Regular or intermittent use of benzodiazepines, anticonvulsants, or psychostimulants
• Use of another psychotropic medication unless the medication and dose had remained unchanged for at least 3 months before enrollment