Abstract
Visual and haptic unisensory object processing show many similarities in terms of categorization, recognition, and representation. In this review, we discuss how these similarities contribute to multisensory object processing. In particular, we show that similar unisensory visual and haptic representations lead to a shared multisensory representation underlying both cross-modal object recognition and view-independence. This shared representation suggests a common neural substrate and we review several candidate brain regions, previously thought to be specialized for aspects of visual processing, that are now known also to be involved in analogous haptic tasks. Finally, we lay out the evidence for a model of multisensory object recognition in which top-down and bottom-up pathways to the object-selective lateral occipital complex are modulated by object familiarity and individual differences in object and spatial imagery.
Highlights
Despite the fact that object perception and recognition are invariably multisensory processes in real life, the haptic modality was for a long time the poor relation in a field dominated by vision science, with the other senses lagging even further behind (Gallace and Spence, 2009; Gallace, 2013)
Changes in orientation and size present a major challenge to within-modal object recognition. These obstacles seem to be absent in cross-modal recognition and we show that a shared representation underlies both cross-modal recognition and view-independence
A shared representation for vision and touch suggests shared neural processing and we review a number of candidate brain regions, previously thought to be selective for visual aspects of object processing, which have subsequently been shown to be engaged by analogous haptic tasks
Summary
Despite the fact that object perception and recognition are invariably multisensory processes in real life, the haptic modality was for a long time the poor relation in a field dominated by vision science, with the other senses lagging even further behind (Gallace and Spence, 2009; Gallace, 2013). A shared representation for vision and touch suggests shared neural processing and we review a number of candidate brain regions, previously thought to be selective for visual aspects of object processing, which have subsequently been shown to be engaged by analogous haptic tasks This reflects the growing consensus around the concept of a “metamodal” brain with a task-based organization and multisensory inputs, rather than organization around discrete unisensory inputs (Pascual-Leone and Hamilton, 2001; Lacey et al, 2009a; James et al, 2011). With increasing accuracy, from a “grasp and lift” stage that extracts basic low-level information about a variety of object properties to a series of hand movements that extract more precise information (Klatzky and Lederman, 1992) These hand movements, known as “exploratory procedures,” are property-specific, for example, lateral motion is used to assess texture and contour-following to precisely assess shape (Lederman and Klatzky, 1987). These properties differ in salience to haptic processing depending on the context: under neutral instructions, salience progressively decreases in this order: hardness > texture > shape; under instructions that emphasized haptic processing, the order changes to texture > shape > hardness www.frontiersin.org
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