Tongue protrusions modify the syntax of skilled reaching for food by the mouse: Evidence for flexibility in action selection and shared hand/mouth central modulation of action

• Published in: Behavioural brain research 2018-04, Vol.341, p.37-44
• Main Authors: Whishaw, Ian Q., Mirza Agha, Behroo, Kuntz, Jessica R., Qandeel, Faraji, Jamshid, Mohajerani, Majid H.
• Format: Article
• Language: English
• Subjects: Action pattern; Animals; Appetitive Behavior - physiology; Biomechanical Phenomena; Food; Forelimb - physiology; Hand and tongue; Male; Mice, Inbred C57BL; Motor Skills - physiology; Skilled reaching; Smell; Tongue - physiology; Tongue protrusion
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2017.12.006

•Syntax of mouse skilled reaching for food is a sequence of movements that brings a hand to the food and the food to the mouth.•At the time of Aim movement a mouse might advance a hand or its tongue to the food.•Tongue protrusion is not correlated with reaching success.•There are vast individual differences with some mice never protruding and some nearly always protruding.•That Aim is a choice point for a tongue protrusion or a reach suggests neural connections between hand and tongue movements. Skilled reaching for food by the laboratory mouse has the appearance of an action pattern with a distinctive syntax in which ten submovements occur in an orderly sequence. A mouse locates the food by Sniffing, Lifts, Aims, Advances, and Shapes the hand to Pronate it over a food target that it Grasps, Retracts, and Withdraws to Release to its mouth for eating. The structure of the individual actions in the chain are useful for the study of the mouse motor system and contribute to the use of the mouse as a model of human neurological conditions. The present study describes tongue protrusions that modify the syntax of reaching by occurring at the point of the reaching action at which the hand is at the Aim position. Tongue protrusions were not related to reaching success and were not influenced by training. Tongue protrusions were more likely to occur in the presence of a food target than with reaches made when food was absent. There were vast individual differences; some mice always make tongue protrusions while other mice never make tongue protrusions. That the syntax of reaching can be altered by the insertion of a surrogate (co-occurring) movement adds to a growing body of evidence that skilled reaching is assembled from a number of relatively independent actions, each with its own sensorimotor control that are subject to central modulation. That tongue and hand reaching movements can co-occur suggests a privileged relation between neural mechanisms that control movements of the tongue and hand.