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Published March 24, 2023 | Submitted + Supplemental Material
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Preservation of Conditioned Behavior Based on UV Light Sensitivity in Dissected Tail Halves of Planarians- a Proof by DNN

Abstract

Planarians are aquatic worms with powerful regenerative and memory retention abilities. This paper examines whether a dissected tail half of a Planarian (Dugesia Dorotocephala) can retain and exhibit a previously-conditioned response, possibly before the regeneration of the head and the ganglia. We conditioned intact Planarians in a Pavlovian procedure with an electric shock (ES) as the unconditioned stimulus and weak ultraviolet (UV) light as the conditioned stimulus. Then, we dissected their bodies into halves, keeping the dissected tail halves. Starting from the 2nd day after dissection, we presented the same UV light 3 times daily while video-recording the responses. The recorded responses were then classified by a DNN: a VGG16 model was pre-trained by ImageNet for extracting features from images and additionally trained with 211 responses to ES and 118 to UV light before conditioning/dissection to categorize planarians' reactions into "UV-induced" or "ES-induced" reactions. The cross-validated accuracy in categorization was 83.6%. We then let the DNN analyze 99 recorded responses to UV from 20 individual conditioned tail halves. 96.8 % of their reactions were classified as "ES-induced" (against 22.0% wrongly classified as "ES-induced" for unconditioned samples under UV), indicating they have shown the "Conditioned Response" (p<3.06E-30). This provides evidence that planarians can conserve and reveal a learned response even without the head/ganglia, as it takes approximately 7 days for the head/ganglia to regenerate versus the given 2-3 days. Although similar findings have been reported repeatedly in the literature, this is the first positive evidence with automated procedures and DNN classification. The result implies the presence of a decentralized nervous structure outside of its head/ganglia that allows a tail half to retain memory and execute motion accordingly, despite their cephalization.

Additional Information

The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC 4.0 International license. This project was supported by the Masason Foundation (Japan) and Chen Institute for Neuroscience at Caltech. Author Contributions. K.S. and S.S. contributed to conceiving and designing the experiment. E.S. and K.S. created the setup and ran the experiment. R.K. analyzed the data by training and running the DNN, and T.A. supervised this data analysis. K.S., E.S., S.S., and R.K. contributed to the preparation of the manuscript. Data Availability. Raw video data and DNN categorization results: https://drive.google.com/drive/folders/1Y47WyJePs8N9wF3ZW73_PGn03sJ5CLck?usp=share_link The authors have declared no competing interest.

Attached Files

Submitted - 2022.10.30.514395v1.full.pdf

Supplemental Material - media-1.pdf

Supplemental Material - media-2.pdf

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Additional details

Created:
August 20, 2023
Modified:
December 22, 2023