Illuminating the Spatiotemporal Dynamics of Somatosensory Pre-attentive Change Detection Brain Networks with the Event-related Optical Signal (EROS)

We perceive the world through various sensory modalities (e.g., auditory: hear the bird singing; visual: see the cat running; somatosensory: feel the fluffy dog next to the leg). Human brain can automatically and constantly monitor unexpected changes in the environment through these sensory modalities without conscious awareness (e.g., even while we are focused on reading a book at an outdoor coffee shop, our brain can still automatically detect changes in the environment, such as a dropped coffee cup, a car appearing nearby, or a customer's sharp bag accidentally brushing against your arm). This ability is known as pre-attentive change detection. It is crucial for human survival which prepares us for the remedial actions (e.g., avoid being hurt by the dropped coffee cup, being hit by the car and being hurt by the sharp things) with our limited attentional resources. According to the prediction violation theory (Winkler, 2007), human brains automatically search for regularities in the environment to build predictive models for anticipating future events. An error signal (i.e., a mismatch response) is elicited when the prediction and the incoming events do not match. This error signal prepares us to update our predictive model and initiate remedial actions. We proposed a generic fronto-sensory brain network supporting the prediction violation hypothesis across different sensory modalities involving an early inferior frontal cortex (IFC) - sensory cortices (e.g., superior temporal, occipital cortices, and somatosensory cortices; STC, OC, and SMC) - late IFC brain network (Tse et al., 2021). The early IFC and late IFC are responsible for none-modality specific prediction model establishment/fitting process, respectively. While the sensory cortex is associating with modality-specific prediction error generation. Our previous studies using Event-related optical signal (EROS) have consistently demonstrated similar mismatch response brain activation sequence in pre-attentive visual and auditory change detection (i.e., early IFC - OC – late IFC and early IFC – STC – late IFC) which support the prediction violation hypothesis. However, the brain dynamics and potential mechanisms underlying somatosensory pre-attentive change detection is still largely unknown. The current study proposes four experiments to establish a generic fronto-sensory brain network and to test the prediction violation hypothesis underlying pre-attentive change detection in somatosensory modality. Understanding the neural basis of somatosensory mismatch responses is essential for developing training protocols for people who cannot rely on visual or auditory information in their daily life, such as blind or deaf people.