Mechanism for top-down control of working memory capacity
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Summary
This study addresses the mechanistic basis of visuospatial working memory (vsWM) capacity, specifically investigating how the dorsolateral prefrontal cortex (dlPFC) exerts top-down control over memory storage in the intraparietal sulcus (IPS). While previous research identified the IPS as the primary site for memory retention, the role of the dlPFC in pure information storage remained unclear. The authors propose that the dlPFC boosts parietal memory capacity by counteracting lateral inhibition, a mechanism that inherently limits the number of items that can be stored. To test this hypothesis, the researchers developed a biophysically detailed computational model of cortical microcircuits in the IPS, consisting of excitatory pyramidal cells and inhibitory interneurons. They derived a mathematical framework showing that lateral inhibition between neural populations coding for different stimuli destabilizes memory states as load increases, limiting capacity to approximately 2–7 items. The model predicted that nonspecific excitatory input from the dlPFC could counteract this inhibition, thereby increasing capacity. These predictions were validated using functional magnetic resonance imaging (fMRI) data from 25 healthy adults performing vsWM tasks with varying loads (3 or 5 items). The results confirmed that lateral inhibition limits mnemonic capacity and explains the sublinear relationship between neural activity and memory load, including the observed dip in activity at supracapacity loads. Crucially, the fMRI analysis revealed that individuals with stronger dlPFC activation during high-load trials performed significantly better than those with weaker activation. Furthermore, the functional correlation between dlPFC and IPS activity was significantly higher during high-load trials compared to low-load trials, and this correlation predicted individual performance differences. In contrast, other frontal regions did not show this specific load-dependent coupling with IPS or behavioral performance. The study concludes that working memory capacity is determined by two distinct components: the parietal cortex, which stores memories but is limited by lateral inhibition, and the prefrontal cortex, which provides top-down excitatory signals to boost this capacity. This mechanism explains why interindividual differences in working memory capacity are partly determined by the strength of prefrontal control. The findings provide a mechanistic framework for understanding how top-down signals regulate cognitive performance and suggest that the dlPFC’s role is to dynamically adjust the stability of parietal memory representations rather than storing information itself.
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | OpenAlex-citations | — | — | 1 | 2026-06-20 |
| archive | success | semantic_scholar | — | — | 6 | 2026-06-26 |
| extract | success | cached | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-20 |
| chunk | success | chunk | — | — | 1 | 2026-06-20 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-20 |
| promote | success | — | — | — | 1 | 2026-06-20 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-26 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-20 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.
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