Microtubule Disruption Without Learning Impairment in the Unicellular Organism, Paramecium: Implications for Information Processing in Microtubules

INTRODUCTION: Information processing in microtubules is an open question that has not been adequately addressed. It was suggested that microtubules could store and process information in the nervous system or even support consciousness. The unicellular organism, Paramecium caudatum, has a microtubular structure but lacks a neuron or neural network. However, it shows intelligent behaviors such as associative learning. This property may suggest that the microtubules are involved in intelligent behavior, information storage, or information processing in this organism. METHODS: To test this hypothesis and study the role of microtubules in P. caudatum learning, we utilized a learning task in which the organism associates brightness in its swimming medium with attractive cathodal shocks. To see if microtubules are an integral part of information storage and processing in P. caudatum, we disrupted the microtubular dynamics in the organism using an antimicrotubular agent (parbendazole). RESULTS: We observed that while a partial allosteric modulator of GABA (midazolam) could disrupt the learning process in P. caudatum, the antimicrotubular agent could not interfere with the learning. CONCLUSION: Microtubules are probably not vital for the learning behavior in P. caudatum. Consequently, our results call for further investigation of the microtubular information processing hypothesis. HIGHLIGHTS: Importance of Information processing in microtubules; Microtubules could store and process information in the nervous system; Unicellular organism, Paramecium caudatum, has a microtubular structure but lacks a neuron or neural network. PLAIN LANGUAGE SUMMARY: Information processing in microtubules is an open question that has not been adequately addressed. It was suggested that microtubules could store and process information in the nervous system or even support consciousness. The unicellular organism, Paramecium caudatum, has a microtubular structure but lacks a neuron or neural network. However, it shows intelligent behaviors such as associative learning. This property may suggest that the microtubules are involved in intelligent behavior, information storage, or information processing in this organism. To test this hypothesis and study the role of microtubules in P. caudatum learning, we utilized a learning task in which the organism associates brightness in its swimming medium with attractive cathodal shocks. To see if microtubules are an integral part of information storage and processing in P. caudatum, we disrupted the microtubular dynamics in the organism using an antimicrotubular agent (parbendazole). We observed that while a partial allosteric modulator of GABA (midazolam) could disrupt the learning process in P. caudatum, the antimicrotubular agent could not interfere with the learning. Microtubules are probably not vital for the learning behavior in P. caudatum. Consequently, our results call for further investigation of the microtubular information processing hypothesis.