Correlations of Neural Activity with Behavioral Kinematics during Active Tactile Decision Making

Most real-world decisions rely on active sensing, a dynamic process for directing our sensors (e.g. eyes or fingers) across a stimulus in order to reduce uncertainty and maximize information gain. Though ecologically pervasive, relatively limited work has focused on identifying neural correlates of the active sensing process. In tactile perception, we often make decisions about an object or surface by actively exploring its shape and texture. Here we investigate the neural mechanisms of active tactile sensing by simultaneously measuring electroencephalography (EEG) and finger kinematics while subjects interrogated a haptic surface to make perceptual judgements. We hypothesized that one's sensorimotor behavior provides a view into the cognitive processes leading to decision formation, and the neural correlates of these processes would be detectable by relating kinematics to neural activity. Using an adaptation of canonical correlation analysis (CCA), we regressed the EEG onto kinematics and found three distinct, task-related EEG components that localized to right-lateralized occipital cortex (LOC), middle frontal gyrus (MFG), and supplementary motor area (SMA), respectively. To probe the functional role of these components, we fit their single-trial activity to behavior using a hierarchical drift diffusion model (HDDM), revealing that the LOC modulated the encoding of the tactile stimulus whereas the MFG predicted the rate of information integration towards a choice. This study provides direct evidence that, how we explore the stimulus yields insight into how our brain is forming a decision and uncovers the neural correlates of distinct sensory encoding and evidence accumulation processes during active tactile sensing.