What Was Observed? (Introduction)

• Planaria are simple flatworms with amazing regenerative abilities – they can regrow their entire body, including their brain.
• This study used a fully automated training system (ATA) to expose planaria to a specific environment.
• The worms learned to associate a rough-textured surface with food (liver drops) and showed that they remembered this familiar environment for at least 14 days.
• Even after the worms were decapitated and regenerated a new head, they retained some memory of the familiar environment, as shown by a faster feeding response (a “savings” effect).

Key Terms and Concepts

• Planaria: Simple flatworms known for their ability to regenerate their body parts. Think of them as nature’s ultimate “reset button” for the body.
• Regeneration: The process by which planaria regrow lost parts – in this case, the head and brain.
• Familiarization: The training process during which worms are repeatedly exposed to a specific environment so that they form an association with it.
• Automated Training Apparatus (ATA): A computerized system that tracks each worm’s movements and standardizes the training and testing environment.
• Savings Paradigm: A method where previously trained worms learn a task faster when retrained, indicating that some memory has been retained even after major changes (like head regeneration).

Experimental Subjects and Methods

• Subjects: The study used planaria (specifically, Dugesia japonica) because of their robust regenerative and learning capabilities.
• Environment Setup:
  • Two groups were used: a familiarized group (exposed to rough-textured Petri dishes) and an unfamiliarized group (control group in smooth dishes).
• Training:
  • The training lasted for 10–11 consecutive days.
  • During training, worms were kept in darkness, at controlled temperature, and housed in the ATA chambers.
  • They were fed small drops of liver on scheduled days to create a positive association with the environment.
• Testing:
  • After training, individual worms were placed back into the ATA chambers with a rough floor.
  • A small spot of liver was applied in the middle of the chamber and a strong blue LED light illuminated that quadrant.
  • The test measured how long each worm took to spend 3 consecutive minutes near the food spot.
• Decapitation and Regeneration:
  • Some worms were decapitated (removal of the head between the auricles and the pharynx) 24 hours after final feeding.
  • They were allowed to regenerate their head in controlled conditions, then later tested to see if they could recall the familiar environment.

Step-by-Step Procedure (Like a Cooking Recipe)

• Step 1: Divide the worms into two groups – one to be familiarized with a rough-textured dish and one to serve as the control in a smooth dish.
• Step 2: Place groups of 20–40 worms into each ATA chamber.
• Step 3: For 10 consecutive days, maintain the worms in darkness at a controlled temperature (around 18°C) and clean the chambers daily to ensure consistency.
• Step 4: Feed the worms with 1–2 drops of liver on specific days (e.g., days 1, 4, 7, and 10) to build a positive association with the environment.
• Step 5: After training, transfer the worms individually into testing chambers that mimic the familiar environment (rough floor, specific electrode walls).
• Step 6: Apply a small dried liver spot away from the edge and illuminate that quadrant with blue light to motivate the worms to leave their comfort zone.
• Step 7: Record the time it takes for each worm to spend 3 consecutive minutes near the food spot.
• Step 8: For regeneration experiments, decapitate the worms and allow them to regenerate their head over 7–10 days.
• Step 9: Retest the regenerated worms using the same testing setup to assess memory retrieval (check for a “savings” effect where trained worms respond faster).
• Step 10: Analyze the data for statistically significant differences between the familiarized and control groups.

Results

• Worms in the familiarized group reached the food area significantly faster than the unfamiliarized group.
• Statistical analysis confirmed that the difference in feeding latency was significant – indicating that learning had occurred.
• Even after decapitation, the regenerated worms from the familiarized group showed a tendency to feed faster, supporting the idea that memory traces survived head regeneration.
• The savings paradigm demonstrated that retrained worms learned the task quicker, further confirming memory retention.

Key Conclusions and Implications

• Planaria can learn and retain complex environmental information through a process of familiarization.
• The memory is robust enough to persist for at least 14 days and can survive drastic physical changes such as head removal and regeneration.
• This work establishes a modern, automated, and quantitative method for studying learning and memory in a regenerative model organism.
• It suggests that memory might be stored outside the brain or that the new brain is imprinted by residual signals from the original training.
• These findings have important implications for understanding brain repair and may inspire new strategies in regenerative medicine and stem cell therapies.

Future Directions

• Further studies could explore the molecular mechanisms (such as epigenetic modifications and RNA interference) underlying memory retention during regeneration.
• Understanding how memory is encoded and retrieved in planaria may shed light on similar processes in more complex organisms, including humans.
• This research opens the door to investigating how non-neural tissues might contribute to memory and learning.
• The automated system used here offers a platform for high-throughput and unbiased behavioral studies, paving the way for future innovations.

观察到了什么？（引言）

• 扁虫是一种具有惊人再生能力的简单生物——它们可以再生整个身体，包括大脑。
• 本研究使用了一种全自动训练系统（ATA），使扁虫暴露于特定的环境中。
• 扁虫学会将粗糙的表面与食物（肝脏滴液）联系起来，并表现出至少14天的记忆保留。
• 即使在扁虫被去头并再生新头后，它们依然保留了对熟悉环境的记忆，表现为更快的进食反应（“节约”效应）。

关键术语和概念

• 扁虫：一种因其强大再生能力而闻名的简单生物，就像大自然的“重置按钮”。
• 再生：扁虫再生失去部分（如头部和大脑）的过程。
• 熟悉化：通过反复暴露于特定环境中，使扁虫形成环境关联的训练过程。
• 自动训练装置（ATA）：一种计算机控制系统，用于跟踪扁虫的行为，并标准化训练与测试环境。
• 节约范式：一种通过再训练表现出更快学习速度的实验方法，表明即使在重大改变（如头部再生）后仍保留部分记忆。

实验对象与方法

• 实验对象：本研究使用了扁虫（特别是 Dugesia japonica），因其强大的再生和学习能力。
• 环境设置：
  • 分为两组：一组在粗糙表面培养（熟悉组），另一组在光滑表面培养（对照组）。
• 训练：
  • 训练持续10至11天。
  • 在整个训练期间，扁虫在黑暗中、受控温度下被安置在ATA腔室中。
  • 按计划在特定日子喂食少量肝脏，以建立对环境的正向联结。
• 测试：
  • 训练结束后，将单个扁虫放入与熟悉环境相似的测试腔室（粗糙底部）。
  • 在腔室中一小块区域施加干燥的肝斑，并用蓝色LED灯照亮该象限，迫使扁虫离开边缘。
  • 记录每只扁虫在靠近食物区域连续停留3分钟所用的时间。
• 去头与再生：
  • 在最后一次喂食后24小时，对部分扁虫进行去头处理（在耳状体与咽部前端之间切除）。
  • 在受控条件下允许扁虫再生头部，随后用相同测试方案检测其记忆恢复情况。

步骤详解（如同烹饪食谱）

• 步骤1：将扁虫分成两组——一组放在粗糙的培养皿中进行熟悉化训练，另一组作为光滑培养皿的对照组。
• 步骤2：将每组20–40只扁虫放入各自的ATA腔室中。
• 步骤3：连续10天保持扁虫处于黑暗、受控温度（约18°C）的环境中，每天清洁腔室，确保环境一致。
• 步骤4：在特定日子（如第1、4、7、10天）喂食1–2滴肝脏，建立环境与食物的正向联结。
• 步骤5：训练结束后，将扁虫单独转移到具有熟悉环境特征（粗糙底部、特定电极围壁）的测试腔室中。
• 步骤6：在测试腔室内施加一小块干燥的肝斑，并用蓝光照射该区域以吸引扁虫离开边缘。
• 步骤7：记录每只扁虫在食物区域连续停留3分钟所需的时间。
• 步骤8：对于再生实验，对扁虫进行去头处理，并在7–10天内允许其再生新头。
• 步骤9：用相同测试方法重新检测再生扁虫，观察其是否能快速恢复进食反应（体现“节约”效应）。
• 步骤10：统计并比较熟悉组与对照组之间的进食延迟时间，验证实验结果的显著性。

结果

• 熟悉组扁虫比对照组更快地到达食物区域。
• 统计分析显示，进食延迟的差异具有显著性，这证明了学习效果的存在。
• 即使在去头后，再生扁虫仍显示出一定的记忆效应，表明部分记忆得以保存。
• 节约范式显示，再训练的扁虫学习速度更快，进一步确认了记忆的保留。

主要结论及意义

• 扁虫能够通过环境熟悉化学习并保留复杂的环境信息。
• 这种记忆至少能维持14天，甚至在去头和头部再生后依然存在。
• 本研究建立了一种全自动、客观、定量的扁虫学习记忆研究方法，具有较高的重复性。
• 结果暗示记忆可能不仅仅储存在大脑内，或在新大脑再生过程中受到原始信号的“烙印”。
• 这些发现对理解大脑修复及再生机制具有重要意义，并可能为再生医学及干细胞治疗提供新思路。

未来研究方向

• 未来研究可进一步探讨调控记忆保留的分子机制，如表观遗传调控和RNA干扰等。
• 研究扁虫如何在大脑再生过程中编码和提取记忆，可能为复杂生物（包括人类）的记忆机制提供启示。
• 这一自动化系统为高通量、无偏差的行为学研究提供了平台，为今后相关领域的创新奠定基础。
• 此外，还可探索非神经组织在记忆存储中的作用，以及大脑与身体其它部位之间的信息交互机制。