Goal-Selection and Movement-Related Conflict during Bimanual Reaching Movements
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Summary
This study investigates the neural and behavioral mechanisms underlying conflict during bimanual reaching movements, specifically distinguishing between conflict arising from goal selection and conflict arising from movement planning and execution. The authors address the long-standing debate regarding why humans exhibit slower reaction times and spatial assimilation effects when performing asymmetric (incongruent) bimanual movements compared to symmetric (congruent) ones. They hypothesize that two distinct types of conflict exist: "goal-selection conflict," which involves translating symbolic cues into motor responses, and "movement-related conflict," which involves the motor system's inherent preference for symmetric trajectories. To test this, nineteen participants performed bimanual reaching tasks while undergoing functional magnetic resonance imaging (fMRI). Movements were either congruent (both hands moving in the same direction) or incongruent (hands moving in orthogonal directions). Crucially, the required movements were cued either spatially, by illuminating the target locations, or symbolically, by presenting letters indicating the direction for each hand. This design allowed the researchers to isolate the cognitive load of translating arbitrary symbols from the motor load of executing asymmetric movements. Reaction times were recorded, and brain activation was analyzed using statistical parametric mapping, focusing on regions associated with motor planning and response conflict. Behavioral results revealed a significant dissociation between the two cueing conditions. The reaction time cost for incongruent movements was substantially larger for symbolic cues (148 ms) than for spatial cues (15 ms). This indicates that the primary behavioral cost of asymmetric bimanual movements stems from the difficulty of assigning symbolic cues to specific hands rather than the motor execution itself. Neuroimaging data supported this distinction. Goal-selection conflict, present only in the symbolic incongruent condition, increased activation in the pre-supplementary motor area (pre-SMA) and the rostral cingulate zone. In contrast, movement-related conflict, observed in both cueing conditions, increased activation in the superior parietal lobule (SPL). Specifically, the right SPL showed greater activation for incongruent movements under spatial cues, while the left SPL showed greater activation under symbolic cues, suggesting distinct hemispheric contributions to these processes. The findings demonstrate that the constraints on bimanual coordination are not monolithic but arise from separable neural processes. The study identifies distinct neural loci for goal-selection conflict (pre-SMA/cingulate) and movement-related conflict (SPL). This dissociation clarifies that while the motor system inherently favors symmetric movements, the most significant performance bottleneck in complex bimanual tasks often lies in the cognitive translation of abstract goals into motor commands. These results refine our understanding of the functional architecture of the action system, highlighting the specific roles of frontal and parietal regions in resolving different types of motor conflict.
Key finding
Goal-selection conflict during bimanual movements primarily engages the pre-supplementary motor area and cingulate motor areas, whereas movement-related conflict activates the superior parietal lobule, indicating distinct neural substrates for these two forms of interference.
Methodology
lab_experiment
Sample size: 19
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via author_sweep_intake on 2026-05-28.
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
| archive | success | canonical_url | — | — | 11 | 2026-06-06 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
| clean | success | clean | — | — | 1 | 2026-06-04 |
| chunk | success | chunk | — | — | 1 | 2026-06-04 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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