What is it about?
Salt is an essential substance for survival in many species; however, excessive salt intake is well known to be harmful to human health. Furthermore, chronic long-term consumption of a high-salt diet in rats has been reported to cause learning and memory impairments, which arise from adverse effects on the brain. Despite the fundamental role that salt has in physiological responses, its acute role in cognition has been less documented. This is partially the gap that this series of experiments fulfills, to understand the role of saline in habituation and conditioned place preferences. The present study demonstrates that planarians exposed to saline exhibit impairments in the expression of habituation and conditioned place preference (CPP) learning. Through a series of experiments, we obtained strong evidence indicating that a state-dependent failure of memory retrieval, caused by acute physiological changes induced by saline exposure immediately before testing, is responsible for the observed impairment.
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Why is it important?
State-dependent retrieval failure has been reported in grasshoppers, rats, monkeys, and humans. Documenting this phenomenon in planarians, which are phylogenetically distant from vertebrates, strengthens the possibility that state-dependent retrieval failure is a fundamental cognitive function shared across a wide range of species.
Perspectives
During my time as a visiting researcher, my co-authors introduced me to the fascinating world of planarian research. After returning to Japan, I began by establishing planarian breeding and maintenance at my university, built the experimental apparatus myself, and accumulated experiments step by step. Having our work eventually published in an APA journal is truly beyond anything I could have hoped for. I learned a great deal from my co-authors, and the opportunity to discuss research ideas with them was an invaluable experience. I would like to express my sincere gratitude to my co-authors.
Toru Tazumi
Department of Psychology, Bunkyo University
Read the Original
This page is a summary of: Salt exposure disrupts memory retrieval in habituation and conditioned place preference in planaria (Dugesia japonica)., Journal of Comparative Psychology, May 2026, American Psychological Association (APA),
DOI: 10.1037/com0000449.
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