Figure 1.
Experimental groups and sessions, the task and the automatic chunking procedure.
A. Control (light gray) and target (dark gray) sequences practiced by the two groups of subjects across training sessions. The numbers 1 to 4 correspond to four fingers of the left hand, from the little (1) to the index (4) finger. B. The task interface presenting the executing instructions, the block information and the type of feedback after each trial. C. Reaction time (RT) in a block for a given subject and the classification of trials into initial element of a chunk (red squares) and the body or core of the chunk (blue triangles) by our automatic clustering algorithm.
Figure 2.
A. Mean reaction time for the target sequence in the training sessions, for each group. B. Mean reaction time for the control sequence in sessions 1, 4 and 8, for each group. C. Mean reaction time for target and control sequences and for each group during the fMRI (9th) session.
Table 1.
Error rates (percentages) across sessions, type of block, experimental condition and Group.
Figure 3.
Sequence chunking and variability of performance.
A. Mean number of clusters (first row) and the percentage of clusters with 3 or more elements (second row) in session 8th (left, behavioral) and 9th (right, imaging), for participants in the two groups. B. The mean variability in motor performance during the execution of the target sequence during 8 behavioral training sessions (left) and neuroimaging runs, during 9th session (right).
Figure 4.
A. Areas in the cortico-striatal network activated more during Sequence than Control blocks, and that are commonly found in the two groups. B. Areas in ventro-orbital prefrontal cortex and parahippocampus were more activated in participants in the Global than Incremental condition, during Sequence than Control blocks.
Table 2.
Brain regions activated by contrast [Sequence blocks>Control blocks].
Figure 5.
Areas more activated during initial than the subsequent elements of a sequential chunk (orange regions), as well as areas activated more during the core than initial chunk element (blue regions).
The bar graphs show the percentage change in blood oxygenation level dependent (BOLD) signal in selected regions, for each group and type of trials. Blue stars indicate significant statistical differences (p<0.05 for one star and p<0.001 for two stars), whereas blue circles indicate no significant difference.
Table 3.
Brain regions activated in both groups by contrasts [Initial element>Core chunk] and [Core chunk>Initial element].
Table 4.
Brain regions activated by contrast [Core chunk>Initial element] more in Global than in Incremental group.
Table 5.
Brain regions activated by contrast [Core chunk>Initial element] separately within each group.