Investigating Somatosensory-Evoked Potentials in Conditions of Active Touch

Exploratory movements are a key component of tactile sensing to extract haptic information from the external world. While much of the research in the somatosensory field has employed artificial tactile stimuli delivered in passive touch conditions, more recently, much interest has been put in the study of active, dynamic touch. An ecological study of tactile processing during active touch comes with several challenges, particularly with regard to electrophysiological techniques, such as scalp electroencephalography. Here, we report a novel experimental setup to record somatosensory evoked potentials in conditions of active, dynamic touch, where participants performed voluntary and minimally controlled exploratory finger-sliding movements against a surface to come into contact with an edged haptic stimulus. Our results showed that it is possible to record cortical responses to a physical, transient haptic stimulus. The pattern of responses revealed early-latency components with a contralateral topography, consistent with activity originating from the primary somatosensory cortex, followed by later components displaying a more central/bilateral pattern of activity, consistent with activity originating from higher-order areas. In summary, our results reveal the feasibility of recording time-locked cortical responses to tactile stimuli in conditions of active touch, with important implications to study somatosensory processing related to active tactile sensing.