Orientation of Tactile Attention on the Surface of the Tongue

The tongue is an incredibly complex sensory organ, yet little is known about its tactile capacities compared to the hands. In particular, the tongue receives almost no visual input during development and so may be calibrated differently compared to other tactile senses for spatial tasks. Using a cueing task, via an electro-tactile display, we examined how a tactile cue (to the tongue) or an auditory cue can affect the orientation of attention to electro-tactile targets presented to one of four regions on the tongue. We observed that response accuracy was generally low for the same modality condition, especially at the back of the tongue. This implies that spatial localization ability is diminished either because the tongue is less calibrated by the visual modality or because of its position and orientation inside the body. However, when cues were provided cross-modally, target identification at the back of the tongue seemed to improve. Our findings suggest that, while the brain relies on a general mechanism for spatial (and tactile) attention, the surface of the tongue may not have clear access to these representations of space when solely provided via electro-tactile feedback but can be directed by other sensory modalities.