論文

査読有り 国際誌
2015年

Planarian shows decision-making behavior in response to multiple stimuli by integrative brain function.

Zoological letters
  • Takeshi Inoue
  • ,
  • Hajime Hoshino
  • ,
  • Taiga Yamashita
  • ,
  • Seira Shimoyama
  • ,
  • Kiyokazu Agata

1
開始ページ
7
終了ページ
7
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1186/s40851-014-0010-z

INTRODUCTION: Planarians belong to an evolutionarily early group of organisms that possess a central nervous system including a well-organized brain with a simple architecture but many types of neurons. Planarians display a number of behaviors, such as phototaxis and thermotaxis, in response to external stimuli, and it has been shown that various molecules and neural pathways in the brain are involved in controlling these behaviors. However, due to the lack of combinatorial assay methods, it remains obscure whether planarians possess higher brain functions, including integration in the brain, in which multiple signals coming from outside are coordinated and used in determining behavioral strategies. RESULTS: In the present study, we designed chemotaxis and thigmotaxis/kinesis tracking assays to measure several planarian behaviors in addition to those measured by phototaxis and thermotaxis assays previously established by our group, and used these tests to analyze planarian chemotactic and thigmotactic/kinetic behaviors. We found that headless planarian body fragments and planarians that had specifically lost neural activity following regeneration-dependent conditional gene knockdown (Readyknock) of synaptotagmin in the brain lost both chemotactic and thigmotactic behaviors, suggesting that neural activity in the brain is required for the planarian's chemotactic and thigmotactic behaviors. Furthermore, we compared the strength of phototaxis, chemotaxis, thigmotaxis/kinesis, and thermotaxis by presenting simultaneous binary stimuli to planarians. We found that planarians showed a clear order of predominance of these behaviors. For example, when planarians were simultaneously exposed to 400 lux of light and a chemoattractant, they showed chemoattractive behavior irrespective of the direction of the light source, although exposure to light of this intensity alone induces evasive behavior away from the light source. In contrast, when the light intensity was increased to 800 or 1600 lux and the same dose of chemoattractant was presented, planarian behaviors were gradually shifted to negative phototaxis rather than chemoattraction. These results suggest that planarians may be capable of selecting behavioral strategies via the integration of discrete brain functions when exposed to multiple stimuli. CONCLUSIONS: The planarian brain processes external signals received through the respective sensory neurons, thereby resulting in the production of appropriate behaviors. In addition, planarians can adjust behavioral features in response to stimulus conditions by integrating multiple external signals in the brain.

リンク情報
DOI
https://doi.org/10.1186/s40851-014-0010-z
PubMed
https://www.ncbi.nlm.nih.gov/pubmed/26605052
PubMed Central
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657317
ID情報
  • DOI : 10.1186/s40851-014-0010-z
  • PubMed ID : 26605052
  • PubMed Central 記事ID : PMC4657317

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