Improving interference control without conflict exposure: prefrontal fNIRS-decoded neurofeedback training

Traditional exposure therapy or cognitive training requires repeated presentation of unwanted stimuli, whereas localizationist neuromodulation overlooks individual variation. We propose a closed-loop neuromodulation approach termed functional near-infrared spectroscopy-decoded neurofeedback training, designed to modify prefrontal hemoglobin dynamics and neural activity patterns.

We aim to enhance interference control without interfering stimuli using a data-driven, individualized, time-resolved decoded neurofeedback, potentially offering a balanced compromise and an alternative to traditional approaches.

We employed a randomized, double-blind, between-group design. Both the decoded neurofeedback group (DecNef, $n=20$ ) and the Sham group (Sham, $n=25$ ) developed individualized decoders with a 1-s temporal resolution following the color-word Stroop task (CWST) before training. Both groups received decoded neurofeedback training sessions lasting 25 min daily for three consecutive days, but there was a gap in their decoding accuracy due to differences in sample size. Interference control was assessed via CWST at three timepoints: pre-training (pre-test), post-training (post-test), and 1-week follow-up.

There was no significant difference in feedback scores between groups, but the Stroop effect of reaction time (RT) in the DecNef group showed a significant reduction compared with the Sham group, both at post-test ( $t=3.056$ , $p=0.004$ ) and follow-up test ( $t=2.180$ , $p=0.035$ ). The difference wave amplitude (incongruent minus congruent trials) for hemodynamic response functions significantly decreased at post-test in the DecNef group (within a continuous period of 7 to 12 s, $p<0.05$ ), but not in the Sham group. Multivariate pattern analysis (MVPA) revealed significantly higher classification accuracy in the DecNef group compared with the Sham group ( $t=2.370$ , $p=0.024$ ); furthermore, this classification accuracy showed a significant negative correlation with changes in the RT Stroop effect ( $r=-0.36$ , $p=0.015$ ).

We proposed a closed-loop neuromodulation approach designed to modify prefrontal neural dynamics, with its core innovation lying in time-resolved individualized decoding. This method can significantly improve cognitive function such as interference control while avoiding exposure to unwanted stimuli and has potential for cognitive enhancement and the treatment of psychological disorders such as phobias and post-traumatic stress disorder.