Fig. 2.

In 9 of the 28 animals used, we also recorded hyoglossus muscle EMG with hook wire electrodes, to estimate the muscle's motor unit population activity at low- and high-force levels. In this figure we look at the change (Δ) in three EMG variables as a function of the change in tongue retraction force, from the low- to the high-force condition. All three variables [mean EMG (A), peak EMG (B), and EMG area (C)] were computed from the rectified and smoothed EMG (see materials and methods). The correlation values could explain between 53 and 68% of the variance in force, depending on which variable was used for the estimate. au, Arbitrary units.