Reconsidering the evidence for learning in single cells

• Published in: eLife Vol. 10
• Main Authors: Gershman, Samuel J, Balbi, Petra EM, Gallistel, C Randy, Gunawardena, Jeremy
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 04.01.2021; eLife Sciences Publications, Ltd
• Subjects: 20th century; Associative learning; Behavior; Cell Physiological Phenomena; Computational and Systems Biology; Conditioning, Classical; DNA methylation; Gene expression; Learning; Memory; Neuroscience; Organisms; Paramecium; Pavlovian conditioning; Review; single cell; Single-Cell Analysis; United States > US; computational biology; systems biology; single cell; Pavlovian conditioning; neuroscience; Paramecium; learning
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.61907

The question of whether single cells can learn led to much debate in the early 20th century. The view prevailed that they were capable of non-associative learning but not of associative learning, such as Pavlovian conditioning. Experiments indicating the contrary were considered either non-reproducible or subject to more acceptable interpretations. Recent developments suggest that the time is right to reconsider this consensus. We exhume the experiments of Beatrice Gelber on Pavlovian conditioning in the ciliate Paramecium aurelia , and suggest that criticisms of her findings can now be reinterpreted. Gelber was a remarkable scientist whose absence from the historical record testifies to the prevailing orthodoxy that single cells cannot learn. Her work, and more recent studies, suggest that such learning may be evolutionarily more widespread and fundamental to life than previously thought and we discuss the implications for different aspects of biology.