When flavor guides motor control: an effector independence study.

Research on multisensory integration during natural tasks has revealed how chemical senses contribute to plan and control movements. An aspect which has yet to be investigated regards whether the motor representations evoked by chemosensory stimuli, once established for a particular movement, can be used to control different effectors. Here, we investigate this issue by asking participants to drink a sip of flavored solution, grasp with the hand a visual target, and then bring it to the mouth, miming the action of biting. Results show that hand and lip apertures were scaled according to the size of the object evoked by the flavor. Maximum hand and lip apertures were greater when the action toward a small visual target (e.g., strawberry) was preceded by a sip of a "large" (e.g., orange) than a "small" (e.g., almond) flavor solution. Conversely, maximum hand and lip apertures were smaller when the action toward a large visual target (e.g., apple) was preceded by the presentation of a "small" (e.g., strawberry) rather than a "large" flavor solution. These findings support previous evidence on the presence of a unique motor plan underlying the act of grasping with-the-hand and with-the-mouth, extending the knowledge of chemosensorimotor transformations to motor equivalence.

Grasping a fruit. Hands do what flavour says.

Previous research on multisensory integration during goal-directed natural actions reported that visual, proprioceptive, auditory and orthonasal olfactory stimulation has the ability to influence motor control. In this study, we used kinematics to investigate the integration between vision and flavour perception during reach-to-grasp movements. Participants were requested to drink a sip of flavoured solution and then grasp an object presented in central vision. The results indicate that when the objects evoked by the flavour and by the visual target were of a similar size (i.e., large or small) and evoked the same kind of hand shaping in order to be grasped (i.e., congruent condition) facilitation effects emerged. Conversely, when the object evoked by the flavour and by the visual target was of a different size and evoked a different kind of hand shaping in order to be grasped (i.e., incongruent condition) interference effects emerged. Interference effects, however, were only evident for the combination involving a large visual target and a 'small' flavour. When comparing hand kinematics between the congruent and a 'no flavour' condition (i.e., water), facilitation effects emerged in favour of the former condition. Taken together, these results indicate the contribution of complex chemosensory stimuli for the planning and execution of visually guided reach to grasp movements. And, contribute to the current debate regarding the multisensory nature of the sensorimotor transformations underlying motor performance.