1. B. The two hypothetical synergies in part A can generate the unique tuning curves for muscles M1 to M3 in response to all 16 directions of translation in the horizontal plane. The posture controller generates a command signal to each synergy that is tuned to direction of translation (synergy tuning curves). Muscle synergy weightings are multiplied by the synergy amplitudes. Signals from the two synergies are summated at the motor neurons, resulting in EMG activity that is tuned to a direction (the EMG tuning curve). The tuning curve for each of the three muscles is different even though only two synergy commands are used. The contribution of each synergy to the EMG tuning curve of a muscle can also be determined. The black dots indicate the amplitudes of the two synergies and resulting EMG activity of the three muscles for the direction illustrated in part A.
Source: Posture, 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 18, 2017
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