Contribution
A short announcement, by its authors, of the result in Shomrat and Levin 2013: a learned familiarity in planarians survives the removal and regrowth of the head. It explains why the lab built an automated training device and what it takes the result to mean.
Key insight
The authors read the result as showing memory held outside the brain and copied into the new one: “not only can memories be stored somewhere outside of the brain, but … they can be imprinted on a naïve regenerated brain” (paragraph 7).
Assumptions
- Feeding readiness measures familiarity. Recognition is “measured by their willingness to eat a piece of liver rather than spend time exploring a new environment as controls do” (paragraph 6).
- A refresher does not create the memory. The worms “need a brief refresher after head regeneration in order to show good recall” (paragraph 6). The inference to a surviving memory assumes the refresher alone would not give naive worms the same result. The post does not say this was tested.
- Non-neural cells can compute. The proposed store rests on the lab’s work on bioelectric signalling in patterning (paragraphs 4 and 8).
Key results
- Why automate (paragraph 3). Hand-run training gave low Ns and weak memories, was open to subjective scoring and depended on the operator’s skill. McConnell’s results were “confirmed in some labs but not reproduced in some others”, and the area was forgotten.
- The device (paragraph 5). It tracks planaria and gives individual rewards and punishments to 12 worms at a time, “24*7”, with computer-scored analysis. It also works for Xenopus and zebrafish. It took “Five years and many engineering problems”.
- The result (paragraph 6). Worms trained to a chamber with a “specifically rough (laser-etched) surface” recognised it after “complete head removal and regeneration”, given a brief refresher. “A complex brain-derived behavior was driven by a memory that survived complete head regeneration.”
- What comes next (paragraph 7). Which tissues hold the memory (are neoblasts required?), what pathways imprint it on the brain, and how memories are encoded in and decoded from tissue.
- The hypothesis (paragraph 8). Memory “could be globally distributed throughout the body”, in non-neural cells linked by gap junctions into “a neural-like network”. “At the moment, we do not know where and how the memory is encoded in the body.”
Claims
| id | claim | strength | support |
|---|---|---|---|
| C1 | Planarians trained to an etched chamber recognise it after head regeneration, with a brief refresher | not assessable here: reported without data | paragraph 6 |
| C2 | Memories can be stored outside the brain and imprinted on a regenerated one | interpretive: the authors’ reading of C1 | paragraph 7 |
| C3 | The store may be a bioelectric network of non-neural cells | hypothesis, stated as a possibility | paragraph 8 |
Concepts
- refresher: a brief re-exposure to training after regeneration, needed for good recall.
- neoblasts: planarian adult stem cells, from which a lost part regrows.
- bioelectric network: non-neural cells signalling through resting potentials and gap junctions.
Connections
- Shomrat and Levin 2013 (LIT-1732), unread; this post is its announcement. See section 3.
- Blackiston, Shomrat and Levin 2015 (LIT-1707) restate the same result in one sentence and expand the hypothesis.
- Blackiston, Silva Casey and Weiss 2008 (LIT-1680) is cited as showing memory survives insect metamorphosis.
Bearing on the record
- QUESTION-302. The post confirms the question’s account of the planarian result, the reminder included. It adds the authors’ answer to “what carries it across”: something outside the head, perhaps a bioelectric network of the body’s cells. The authors say they do not know. Inference: the reminder matters to how much the result shows. A memory that needs a refresher may be a savings effect, faster relearning, rather than recall, and the post does not report the control that would separate them.
- Identity. No discussion. If the authors are right, psychological continuity in a planarian does not run through the brain, which the philosophers’ brain cases (LIT-469; THEORY-464) take as its bearer. That is an inference from a hypothesis.
- The owner’s thesis (CLAIM-491). No bearing. No dated note.
- No THEORY filed. No ML instruction.
Limitations
- A blog post. No Ns, durations, statistics or controls; the reader cannot check the result here.
- The refresher control is not mentioned.
- Which fragment regenerated (tail, trunk) and how long regeneration took are not said.
- Citation oddity. Sheiman and Tiras 1996, titled “Memory and morphogenesis in planaria and beetle”, is cited for memory through insect metamorphosis.
- Typos: a mismatched closing quotation mark in the Chakravarthy and Ghosh reference (“‘cardiac memory””).
Open questions
- Do naive worms given only the refresher after regeneration show the same feeding readiness? That control decides between recall and savings.
- Which tissue holds the memory, and are neoblasts required? The authors’ own first question.