fNIRS + Eye Tracking: Mapping Gaze to Hemodynamic Brain Responses

The integration of functional Near-Infrared Spectroscopy (fNIRS) and Eye Tracking is a powerful multimodal approach for studying human behavior in naturalistic environments. By combining the "where" of visual attention (eye tracking) with the "how" of cortical metabolic demand (fNIRS), researchers can decode the neural drivers behind visual exploration and decision-making. Hardware Synergy and Wearability:. Integrated Headgear: NIRx offers specialized caps and spacers that allow eye-tracking glasses (such as Tobii or Pupil Labs) to be worn comfortably alongside fNIRS optodes., Ultra-Portable Setup: Using the NIRSport2 platform, the entire system is wearable and battery-powered, allowing for data collection during walking, shopping, or social navigation., Zero Signal Interference: Because fNIRS uses near-infrared light and eye trackers typically use infrared illumination, NIRx systems include specialized filters to ensure that the two modalities do not interfere with each other's data quality. Technical Synchronization:. Shared Triggering: Precise synchronization is achieved through TTL pulses or software-based triggers (LSL - Lab Streaming Layer), ensuring that every gaze fixation is time-locked to a specific hemodynamic response., Real-Time Visualization: Researchers can monitor both the pupil position and the cortical oxygenation levels simultaneously during the experiment to ensure high data integrity. Key Research Applications:. Neuroergonomics: Assessing mental workload while a participant navigates a complex interface or cockpit., Developmental Psychology: Studying how infants or children process social cues (faces/eyes) and the corresponding activation in the prefrontal cortex., Marketing & Consumer Neuroscience: Understanding which visual elements of a product trigger the highest metabolic engagement in the reward centers of the brain., Navigation & Wayfinding: Analyzing brain activity during real-world spatial navigation where gaze is used to identify landmarks.