Spatial representations from perception and cognitive mediation: The case of ultrasound

Spatial representations can be derived not only by direct perception, but also through cognitive mediation. Conventional or ex-situ ultrasound displays, which displace imaged data to a remote screen, require both types of process. To determine the depth of a target hidden beneath a surface, ultrasound users must both perceive how deeply the ultrasound transducer indents the surface and interpret the on-screen image to visualize how deeply the target lies below the transducer. Combining these perceptual and cognitive depth components requires a spatial representation that has been called amodal. We report experiments measuring errors in perceptual and cognitively mediated depth estimates and show that these estimates can be concatenated (linked) without further error, providing evidence for an amodal representation. We further contrast conventional ultrasound with an in-situ display whereby an ultrasound image appears to float at the precise location being imaged, enabling the depth of a target to be directly perceived. The research has the potential to enhance ultrasound-guided surgical intervention.