2024-10-11 ハーバード大学
<関連情報>
- https://seas.harvard.edu/news/2024/10/how-do-you-remember-how-ride-bike-thank-your-cerebellum
- https://www.pnas.org/doi/10.1073/pnas.2411459121
小脳は感覚運動記憶のための内側側頭葉のアナログとして働く The cerebellum acts as the analog to the medial temporal lobe for sensorimotor memory
Alkis M. Hadjiosif, Tricia L. Gibo, and Maurice A. Smith
Proceedings of the National Academy of Sciences Published:October 7, 2024
DOI:https://doi.org/10.1073/pnas.2411459121
Significance
A key discovery about the neural underpinnings of memory, made more than half a century ago, is that long-term, but not short-term, memory formation depends on neural structures in the brain’s medial temporal lobe (MTL). However, this dichotomy holds only for declarative memories (memories for explicit facts such as names and dates) as long-term procedural memories (memories for implicit knowledge such as sensorimotor skills) are largely unaffected even with substantial MTL damage. Here, we demonstrate that the formation of long-term, but not short-term, sensorimotor memory depends on a neural structure known as the cerebellum, and we show that this finding explains much of the variability previously reported in the extent to which cerebellar damage affects sensorimotor learning.
Abstract
The cerebellum is critical for sensorimotor learning. The specific contribution that it makes, however, remains unclear. Inspired by the classic finding that for declarative memories, medial temporal lobe (MTL) structures provide a gateway to the formation of long-term memory but are not required for short-term memory, we hypothesized that for sensorimotor memories, the cerebellum may play an analogous role. Here, we studied the sensorimotor learning of individuals with severe ataxia from cerebellar degeneration. We dissected the memories they formed during sensorimotor learning into a short-term temporally-volatile component, that decays rapidly with a time constant of just 15 to 20 s and thus cannot lead to long-term retention, and a longer-term temporally-persistent component that is stable for 60 s or more and leads to long-term retention. Remarkably, we find that these individuals display dramatically reduced levels of temporally-persistent sensorimotor memory, despite spared and even elevated levels of temporally-volatile sensorimotor memory. In particular, we find both impairment that systematically worsens with memory window duration over shorter memory windows (<12 s) and near-complete impairment of memory maintenance over longer memory windows (>25 s). This dissociation uncovers a unique role for the cerebellum as a gateway for the formation of long-term but not short-term sensorimotor memories, mirroring the role of the MTL for declarative memories. It thus reveals the existence of distinct neural substrates for short-term and long-term sensorimotor memory, and it explains both the trial-to-trial differences identified in this study and long-standing study-to-study differences in the effects of cerebellar damage on sensorimotor learning ability.
