Capturing shared fNIRS responses to visual affective stimuli in young healthy women

Functional near-infrared spectroscopy (fNIRS) studies focusing on prefrontal cortex (PFC) have shown mixed results in relating hemodynamic changes to emotional processing, posing a challenge for clinical practice. Concerns related to instrumentation, recruited sample, task design, signal processing, and data analysis have been highlighted. To minimize some biasing factors, we proposed an experimental approach based on: (1) a homogeneous recruited sample, (2) an identical sequence of content-grouped affective pictures for emotion induction, (3) multi-distance forehead fNIRS recordings to separate cerebral from extra-cerebral components, and (4) a model-free frequency-based analysis to capture shared response patterns across individuals. We piloted a study to assess the feasibility of the approach in a sample of 20 young healthy women during an emotional task with affective pictures of neutral, sexual and violence content. We found coherent fNIRS responses to sexual and violence content located in slow fluctuations (0-0.019 Hz), characterized by positive and negative oxygenation patterns of extra-cerebral and cerebral origin, respectively. Additionally, we corroborated the strong interference of surface hemodynamics. This study proves the feasibility of our approach to identify frequency-specific fNIRS response patterns to affective visual stimuli, which holds promise for exploring functional biomarkers of healthy and altered emotional processing.