Motion monitoring system

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Mental representations of hand actions form part of our knowledge of manipulable objects, such as calculators and spray-cans. Evidence indicates that such representations are invoked dynamically when perceiving objects or understanding sentences describing interactions with objects. These representations are evoked even in tasks that have nothing to do with holding or using an object. The role played by higher level motor systems in cognition is therefore of fundamental interest, as is the kind of motor representation evoked in particular contexts. We have developed a novel experimental method to assess the evocation of specific hand action representations to words, objects or sentences in real time. Our approach requires participants to carry out speeded reach and grasp actions on an eight-element response apparatus. Each element affords a unique action and participants learn to produce a given action in response to a visual cue like a color patch. We then measure the influence of an object, word or sentence (a priming event) on reach and grasp performance, time-locked to the visual cue, yielding evidence on the nature and time course of the motor representations evoked by the priming event. The method has proved very fruitful but we lack the means to assess the dynamics of the hand in flight, a crucial aspect of performance that will reveal how the temporal parameters of the underlying motor representation can automatically influence an action as it unfolds in real time. The equipment we request will allow us: (i) To determine how reaching and grasping with either hand is influenced by a handled object (like a beer mug), when the handle is aligned or misaligned with the response hand. (ii) We will also evaluate how reach and grasp responses are influenced by functional and volumetric aspects of a pictured object (e.g., a calculator), and (iii) assess the dynamics of hand action representations evoked by auditory words referring to manipulable objects, presented in isolation or in different sentence contexts. The research will add to our understanding of the interaction between the mechanisms that determine the identification of objects and words, and motor systems that govern the dynamic control of the reach and grasp response.