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. 2018 May 8;2:2398212818772179. doi: 10.1177/2398212818772179

Figure 9.

Figure 9.

Neurophysiological data and simulations of monkey sequential copying data. (a) Each plot shows the recorded cell activity profiles that control drawing of each segment for each time bin (at 25 ms) of the task. The number of movement segments is due to the starting positions of each movement sequence on the corresponding geometrical figure. Time 0 indicates the onset of the template. Lengths of segments were normalised to permit averaging across trials. Plots show parallel representation of segments before initiation of copying. Furthermore, rank order of strength of representation before copying corresponds to the serial position of the segment in the series. The rank order evolves during the drawing to maintain the serial position code. At least four phases of the Averbeck et al. (2002; Figure 9(a)) curves should be noted: (1) presence of a primacy gradient, that is, greater relative activation corresponds to earlier eventual execution in the sequence during the period prior to the initiation of the movement sequence (period −500 to 400 ms); (2) contrast enhancement of the primacy gradient to favour the item to be performed (greater proportional representation of the first item) prior to first item performance (period ~100–400 ms); (3) inhibition of the chosen item’s activity just prior to its performance and preferential relative enhancement of the representation of the next item to be preformed such that it becomes the most active item prior to its execution (period ~400 ms to near sequence completion); and (4) possible re-establishment of the gradient just prior to task completion. Reprinted with permission from Averbeck et al. (2002). (b) Simulations of item activity across the motor plan field of the LIST PARSE model for 3, 4, and 5 item sequences versus simulation time. In both (a) and (b), line colours correspond to representations of segments as follows: yellow, segment 1; green, segment 2; red, segment 3; cyan, segment 4; magenta, segment 5. Reprinted with permission from Grossberg and Pearson (2008).