Microtubule Disruption does not Impair Learning in the Unicellular Organism Paramecium: Implications for Information Processing in Microtubules

Abstract

Information processing in microtubules is an open question that has not been properly addressed yet.It was suggested that microtubules could store and process information in the nervous system or even support consciousness. The unicellular organism, Paramecium caudatum, that has a microtubular structure but does not have a neuron or neural network, shows intelligent behaviors such as associative learning which may suggest the possibility of involvement of microtubules in intelligent behavior, information storage or information processing. Here, we have utilized a paramecium learning task in which the organism associates brightness in its swimming medium with attractive cathodal shocks to study the role of microtubules in paramecium learning. We used an antimicrotubular agent (parbendazole) and disrupted microtubular dynamics in paramecium to see if microtubules are an integral part of information storage and processing in paramecium's learning process. We observed that a partial allosteric modulator of GABA (midazolam) could disrupt the learning process in paramecium, but the antimicrotubular agent could not. Therefore, our results suggest that microtubules are probably not vital for the learning behavior in P. caudatum. Consequently, our results call for a further revisitation of the microtubular information processing hypothesis.