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. 2018 Aug 23;8:12657. doi: 10.1038/s41598-018-31174-2

Figure 7.

Figure 7

Generalization in the synergies APs. Panel (a) shows the APs of the four synergies (color coded as in Fig. 4) at the beginning of Ad1/Ad4. Solid lines are relative to Group1, while dashed lines are relative to Group2. Shaded areas in each plot represent the activity of each AP in the 45° CCW target at B3 that theoretically represents the goal AP activity for adaptation. The black solid line represents the activity of the APs for each target at the end of B3. For the group/target combination that presents the higher level of generalization (Group1, target N, solid line) the APs at the beginning of generalization are perfectly consistent with the baseline CCW-rotated ones. We observed a significant correlation between the similarity of the APs at the beginning of Ad1/Ad4 with the baseline CCW rotated ones and the values of NC (b) indicating that adaptation and generalization in the biomechanical metric correlates with a 45° rotation of the synergies AP. This result is also confirmed by the fact that the similarity of the APs with the baseline CCW rotated ones is significantly higher for Ad4 with respect to Ad1 (c) (p = 0.03, Mann-Whitney U test). We observed a qualitative correlation between the difference in preferred angles at adaptation for the two groups and the level of generalization (d,e). Hollow bars in panel (d) represent, for each target, the sum of the difference in principal angles between the group that adapted the target during adaptation and the one that did it during generalization (as identified in Fig. 5d) for the synergies involved in the reaching to the target (represented by their individual angle difference as colored bars inside the hollow bar). Bars in panel (e) present the average + std values of AP similarity for the targets as grouped by the difference in preferred angles identified in Fig. 7d. The target presenting the higher level of generalization (both in terms of NC and synergies similarity with the baseline rotated ones) is also the target that adapts by tuning the synergies that are more similar between the two groups.