2025-03-20 イェール大学
<関連情報>
- https://news.yale.edu/2025/03/20/why-dont-we-remember-being-baby-new-study-provides-clues
- https://www.science.org/doi/10.1126/science.adt7570
- https://www.sciencedirect.com/science/article/pii/S0960982221006199
ヒト乳幼児における記憶の海馬符号化 Hippocampal encoding of memories in human infants
Tristan S. Yates, Jared Fel, Dawoon Choi, Juliana E. Trach, […], and Nicholas B. Turk-Browne
Science Published:20 Mar 2025
DOI:https://doi.org/10.1126/science.adt7570
Editor’s summary
Humans and many other species can form memories during infancy but cannot recall these memories later in life. Yates et al. investigated the mechanism mediating this so-called infantile amnesia using functional magnetic resonance imaging (fMRI) in awake infants performing a memory task (see the Perspective by Ramsaran and Frankland). They found that infants are capable of encoding memories during infancy, and deficits in postencoding retrieval mechanisms are likely responsible for infantile amnesia in humans. —Mattia Maroso
Abstract
Humans lack memories for specific events from the first few years of life. We investigated the mechanistic basis of this infantile amnesia by scanning the brains of awake infants with functional magnetic resonance imaging while they performed a subsequent memory task. Greater activity in the hippocampus during the viewing of previously unseen photographs was related to later memory-based looking behavior beginning around 1 year of age, suggesting that the capacity to encode individual memories comes online during infancy. The availability of encoding mechanisms for episodic memory during a period of human life that is later lost from our autobiographical record implies that postencoding mechanisms, whereby memories from infancy become inaccessible for retrieval, may be more responsible for infantile amnesia.
乳児における海馬学習の証拠 Evidence of hippocampal learning in human infants
Cameron T. Ellis, Lena J. Skalaban, Tristan S. Yates, Vikranth R. Bejjanki, Natalia I. Córdova, Nicholas B. Turk-Browne
Current Biology Published: 21 May 2021
DOI:https://doi.org/10.1016/j.cub.2021.04.072
Graphical abstract
Highlights
- Hippocampus supports statistical learning of temporal regularities in infancy
- Changes in hippocampal activity emerge after only minutes of exposure
- Localization of learning effects within hippocampal system similar to adults
- Exploratory analyses suggest a selective role for medial prefrontal cortex
Summary
The hippocampus is essential for human memory. The protracted maturation of memory capacities from infancy through early childhood is thus often attributed to hippocampal immaturity. The hippocampus of human infants has been characterized in terms of anatomy, but its function has never been tested directly because of technical challenges. Here, we use recently developed methods for task-based fMRI in awake human infants to test the hypothesis that the infant hippocampus supports statistical learning. Hippocampal activity increased with exposure to visual sequences of objects when the temporal order contained regularities to be learned, compared to when the order was random. Despite the hippocampus doubling in anatomical volume across infancy, learning-related functional activity bore no relationship to age. This suggests that the hippocampus is recruited for statistical learning at the youngest ages in our sample, around months. Within the hippocampus, statistical learning was clearer in anterior than posterior divisions. This is consistent with the theory that statistical learning occurs in the monosynaptic pathway, which is more strongly represented in the anterior hippocampus. The monosynaptic pathway develops earlier than the trisynaptic pathway, which is linked to episodic memory, raising the possibility that the infant hippocampus participates in statistical learning before it forms durable memories. Beyond the hippocampus, the medial prefrontal cortex showed statistical learning, consistent with its role in adult memory integration and generalization. These results suggest that the hippocampus supports the vital ability of infants to extract the structure of their environment through experience.
