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Front. Behav. Neurosci. | doi: 10.3389/fnbeh.2018.00024

Whisker and nose tactile sense guide rat behaviour in a skilled reaching task

  • 1Department of Biomedical and Specialty Surgical Sciences, Section of Human Physiology, University of Ferrara, Italy
  • 2Center for Translational Neurophysiology, Istituto Italiano di Tecnologia, Italy
  • 3Department of Biomedical Sciences, Metabolic and Neuroscience, Section of Physiology and Neuroscience, University of Modena and Reggio Emilia, Italy

Skilled reaching is a complex movement in which a forelimb is extended to grasp food for eating. Video-recordings analysis of control rats enables us to distinguish several components of skilled reaching: Orient, approaching the front wall of the reaching box and poking the nose into the slot to locate the food pellet; Transport, advancing the forelimb through the slot to reach-grasp the pellet; and Withdrawal of the grasped food to eat. Although food location and skilled reaching is guided by olfaction, the importance of whisker/nose tactile sense in rats suggests that this too could play a role in reaching behaviour. To test this hypothesis, we studied skilled reaching in rats trained in a single-pellet reaching task before and after bilateral whisker trimming and bilateral infraorbital nerve (ION) severing. During the task, bilaterally trimmed rats showed impaired Orient with respect to controls. Specifically, they detected the presence of the wall by hitting it with their nose (rather than their whiskers), and then located the slot through repetitive nose touches. The number of nose touches preceding poking was significantly higher in comparison to controls. On the other hand, macrovibrissae trimming resulted in no change in reaching/grasping or withdrawal components of skilled reaching. Bilaterally ION-severed rats, displayed a marked change in the structure of their skilled reaching. With respect to controls, in ION-severed rats: a) approaches to the front wall were significantly reduced at 3–5 and 6–8 days; b) nose pokes were significantly reduced at 3–5 days, and the slot was only located after many repetitive nose touches; c) the reaching-grasping-retracting movement never appeared at 3–5 days; d) explorative paw movements, equal to zero in controls, reached significance at 9–11 days; e) the restored reaching-grasping-retracting sequence was globally slower than in controls, but the success rate was the same. These findings strongly indicate that whisker trimming affected Orient, but not the reaching-grasping movement, while ION severing impaired both Orient (persistently) and reaching-grasping-retracting (transiently, for 1–2 weeks) components of skilled reaching in rats.

Keywords: whisker sense, skilled reaching, Whisker trimming, ION severing, rat

Received: 31 Jul 2017; Accepted: 31 Jan 2018.

Edited by:

Nadine RAVEL, UMR5292 Centre de Recherche en Neurosciences de Lyon (CRNL), France

Reviewed by:

Cornelius Schwarz, Universität Tübingen, Germany
Ian Q. Whishaw, University of Lethbridge, Canada  

Copyright: © 2018 Parmiani, Lucchetti and Franchi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Gianfranco Franchi, University of Ferrara, Department of Biomedical and Specialty Surgical Sciences, Section of Human Physiology, Ferrara, Italy, fhg@unife.it