Non-specific increase in alpha power during a neurofeedback session targeting its downregulation

Electroencephalographic neurofeedback is often assumed to provide volitional control over neural oscillations, with the alpha rhythm regarded as a particularly accessible target. Yet, evidence supporting single-session alpha modulation remains controversial, largely because of insufficient controls for non-specific influences such as time-on-task effects. This study examined whether individuals can downregulate alpha parietal-scalp power during a single neurofeedback session while controlling for feedback veracity and targeted modulation direction. Healthy individuals completed three training blocks in which the size of a visual stimulus reflected either their real-time alpha power (Alpha-Down group), alpha power in the opposite direction (Alpha-Up group), or prerecorded trajectories (Sham group), followed by a transfer block without feedback. The frequency of feedback update was varied across training blocks (1, 5, or 10 Hz). Results showed robust within-session increases in alpha power across all groups, independent of targeted direction, feedback veracity, or update frequency. Theta and sensorimotor rhythm bands also demonstrated an independent increase, while beta remained stable. These findings indicate that apparent alpha modulation in single-session protocols reflects spontaneous, non-specific increases in oscillatory activity rather than genuine volitional control. The results generalise previous evidence on alpha upregulation to its attempted downregulation, reinforcing that time-dependent dynamics such as arousal, fatigue, or mind wandering may dominate single-session outcomes. This work highlights the need for stringent methodological controls when evaluating the specificity of neurofeedback interventions.