Ipsilateral stimulation shows somatotopy of thumb and shoulder auricular points on the left primary somatosensory cortex using high-density fNIRS

Abstract Significance Auriculotherapy is a technique based on stimulation applied to specific ear points. Its mechanism of active and clinical efficacy remain to be established. This study aims to assess the role that primary somatosensory cortex may play to validate auriculotherapy mechanisms. Aim This study examined whether tactile stimulation at specific auricular points is correlated with distinct cortical activation in the primary somatosensory cortex. Approach Seventeen healthy adults participated in the study. Tactile stimuli were delivered to the thumb, shoulder, and skin master points on the ear using von Frey filaments. Functional near-infrared spectroscopy was used to measure and spatially map cortical responses. Results This study revealed distinct hemodynamic activity patterns in response to ear point stimulation, consistent with the classic homunculus model of somatotopic organization. Ipsilateral stimulation showed specific cortical activations for the thumb and shoulder points, while contralateral stimulation showed less significant activity. Functional near-infrared spectroscopy effectively captured localized cortical responses to ear tactile stimuli, supporting the somatotopic mapping hypothesis. Conclusion These findings enhance the understanding of sensory processing with auricular stimulation and supports the concepts of auricular cartography that underpins some schools of auriculotherapy practice. Future research should explore bilateral cortical mapping and the integration of other neuroimaging techniques.