1. C. When the weight is larger than expected, the object slips initially, but force is increased before lifting begins. When the subject begins to lift a 400 g object, Pacinian corpuscles in the skin are activated and a burst of action potentials occurs in the afferent RA2 fibers, signaling the beginning of the hold phase during which the grip force is constant. After being presented with the 400 g object for several trials (dashed lines), the subject is given an 800 g object (solid lines). When the subject begins to lift the 800 g object, the object slips, and the RA2 fibers are not activated. The absence of RA2 signals triggers a slow increase in force that is terminated when lifting begins. (Reproduced, with permission, from Johansson et al )
Source: The Organization and Planning of Movement, Principles of Neural Science, Fifth Editon
Citation: Kandel ER, Schwartz JH, Jessell TM, Siegelbaum SA, Hudspeth AJ, Mack S. Principles of Neural Science, Fifth Editon; 2012 Available at: Accessed: October 03, 2017
Copyright © 2017 McGraw-Hill Education. All rights reserved