News,
A study published in July in Nature Neuroscience by Thompson et al. has revealed that replay and consolidation of procedural memories do occur during sleep; however, the process involves another structure called the striatum (associated with motor/procedural functions), and not the hippocampus.
One of the hypotheses about the function of sleep is related to memory consolidation. “Sleep on it!”, we have heard many times. However, it is usually with regard to episodic and semantic memories, such as experiences or something we have read about during our day rather than procedural memories. Consolidation of these memories is hypothesised to involve brain structures like the hippocampus, which generates the “replay,” and the neocortex, which “broadcasts” the memories.
What about procedural memories?
After football practice, or after practising for a driving licence, should you sleep well to consolidate those memories? Researchers have been contemplating this for a while. Conflicting evidence about hippocampal involvement in non-declarative memory consolidation during sleep remains an unresolved debate. Does it work in the same way, and is the hippocampus still the central consolidator?
In the Thompson et al. study, Neuropixel probes were implanted (probes that can record neuronal activity from hundreds to thousands of neurons at the same time) in the dorsolateral striatum (DLS) of mice, and neural activity was recorded during sleep, specifically after the mice had been trained in a motor task. Furthermore, to make sure that the observed replay was not hippocampus-dependent, researchers lesioned both hippocampi. They observed replay occurring in the striatum, independently of the hippocampus, and blocking synaptic plasticity in the DLS disrupted consolidation.
Imagine a theatre where the striatum or hippocampus acts as a computer, running different movies, while the neocortex serves as the projector. In your dreams you are basically viewing the effects of the replays and processing of these memories, strengthening and organising the neuronal architecture of daily experiences. However, unlike a movie, dreams are a chaotic orchestra, likely because the system’s priority is memory consolidation and not thematic arts.
This study directly challenges the prevailing model of hippocampus-centred memory consolidation during sleep and suggests a parallel memory system involving motor/procedural-related structures. Although the study includes causal manipulations (lesions and pharmacological inactivation), the direct link between striatal replay itself and consolidation remains correlational, and further causal experiments need to be conducted to strengthen the empirical evidence.
Declaration of AI use: This article was written with the assistance of Lumo AI for grammar, spell checking, and proofreading. The author takes full responsibility for the final published text and its accuracy.
References
Thompson, E.J., Rollik, L.B., Waked, B. et al. Replay of procedural memory is independent of the hippocampus. Nat Neurosci (2026). https://doi.org/10.1038/s41593-026-02362-5
Further reading:
Rasch B, Born J. About Sleep’s Role in Memory. Physiol Rev. 2013 Apr ;93(2):681-766. doi: 10.1152/physrev.00032.2012.
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