Reach-to-Grasp: A Multisensory Experience

Abstract

The reach-to-grasp movement is ordinarily performed in everyday living activities and it represents a key behavior that allows humans to interact with their environment. Remarkably, it serves as an experimental test case for probing the multisensory architecture of goal-oriented actions. This review focuses on experimental evidence that enhances or modifies how we might conceptualize the "multisensory" substrates of prehension. We will review evidence suggesting that how reach-to-grasp movements are planned and executed is influenced by information coming from different sensory modalities such as vision, proprioception, audition, taste, and olfaction. The review closes with some considerations about the predominant role of the multisensory constituents in shaping prehensile behavior and how this might be important for future research developments, especially in the rehabilitative domain.

Keywords: grasping; kinematics; multisensory integration; reach-to-grasp; sensory perception.

Figure 1

(A) Schematic representation of the experimental setup used in Patchay et al. (2003) to study how haptic and proprioceptive inputs coming from an unseen distractor grasped by a non-reaching hand influenced reach-to-grasp actions toward a visual target performed by the other hand. Both the target and the distractor occupied spatially coincident locations, and the distractor could have a smaller or greater size relative to the target. (B) Graphical representation of contact points for the index finger and thumb from a representative participant in Castiello's et al. (2010) study, where the influence of contact sound on grasping actions was investigated. A sound congruent with the material covering one of the two parts of a visual target made participants more likely to grasp the object from the surfaced covered by the same material (e.g., paper, wool).

Figure 2

(A) The experimental set up and examples of visual targets used in Castiello's et al. (2006) study, in which the existence of cross-modal links between olfaction and vision during grasping movements was investigated. (B) Graphical representation of the amplitude and the time (filled arrow) of maximum hand aperture for small (upper panel) and large (lower panel) targets in congruent, incongruent and control odor conditions. The time course of maximum hand aperture is expressed in terms relative to the overall reach duration (%). The amplitude and time of maximum hand aperture is, respectively, greater and delayed for an action toward a small target when olfactory information evokes an object requiring an incongruent large grasp. Conversely, when an action toward a large target is coupled with olfactory information evoking an incongruent small object, maximum hand aperture is smaller and anticipated. Hand aperture reported in the plots is averaged across trials and subjects for each experimental condition.