October 19, 2013
Time to rethink the brain as the sole repository of consciousness?
"Flatworms remember their surroundings, even after being decapitated and growing a new head" — that's the subhead of Arielle Duhaime-Ross's interesting Scientific American article, excerpts from which appear below.
Up top, a flatworm's head.
The flatworms known as planarians are neuroscience darlings. Their centralized brain, complex sensory abilities, and rapid regenerative capacities make these nonparasitic worms ideal for studying the mechanisms that regulate stem cell function, neuronal development, and limb regrowth. To this repertoire, scientists have now added a new trick: these invertebrates can store memories outside their brain and retrieve them after losing their head and growing a new one.
Researchers at Tufts University tested the worms' recall by leveraging a quirk of planarian behavior: worms that recognize a familiar locale will settle in to feed more quickly than planarians that find themselves in a new environment. Such newcomers typically need time to explore their surroundings to ensure their safety before they eat. So the researchers introduced planarians to a textured petri dish and allowed them to get acquainted with their environs. Next they decapitated the worms and waited two weeks for their heads to grow back.
The scientists then jogged the worms' memory by briefly returning them to the dish and feeding them. The idea was to revive the dormant memory from the body through a short exposure to familiar turf.
When the researchers returned the trained flatworms to the same dish, the planarians initiated feeding much more quickly than worms that had gone through the same routine but had not explored the dish prior to decapitation.
The experiment upholds a controversial, decades-old finding by a colorful neuroscientist named James V. McConnell. In the 1950s and 1960s McConnell performed similar tests on planarians — going as far as to feed bits of trained worms to their untrained brethren in an effort to transfer molecules of memory. But some researchers questioned the objectivity of his experiments, many of which were detailed not in mainstream journals but in his own Worm Runner's Digest. The Tufts group aimed to minimize observer bias by using a machine to track and analyze the worms' behavior.
The new research, published in the Journal of Experimental Biology, could have implications for the development of artificial memory and the study of neurodegenerative diseases, which researchers hope to treat by someday replacing damaged brain tissue. "We really don't know what that could do to a patient's personality or memories," Levin says. "Planarians are the model that might finally enable us to start looking at that."
Below, the abstract of the the Journal of Experimental Biology paper.
Planarian flatworms are a popular system for research into the molecular mechanisms that enable these complex organisms to regenerate their entire body, including the brain. Classical data suggest that they may also be capable of long-term memory. Thus, the planarian system may offer the unique opportunity to study brain regeneration and memory in the same animal. To establish a system for the investigation of the dynamics of memory in a regenerating brain, we developed a computerized training and testing paradigm that avoided the many issues that confounded previous, manual attempts to train planaria. We then used this new system to train flatworms in an environmental familiarization protocol. We show that worms exhibit environmental familiarization, and that this memory persists for at least 14 days — long enough for the brain to regenerate. We further show that trained, decapitated planaria exhibit evidence of memory retrieval in a savings paradigm after regenerating a new head. Our work establishes a foundation for objective, high-throughput assays in this molecularly-tractable model system that will shed light on the fundamental interface between body patterning and stored memories. We propose planaria as a key emerging model species for mechanistic investigations of the encoding of specific memories in biological tissues. Moreover, this system is likely to have important implications for the biomedicine of stem cell-derived treatments of degenerative brain disorders in human adults.
October 19, 2013 at 08:01 PM | Permalink
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I'd wager quite a pretty sum that every BOJ reader of the feminine gender would be willing to sign an affidavit that all conscious acts of males of a certain age are controlled from an area south of the navel.
Posted by: 6.02*10^23 | Oct 21, 2013 3:14:57 AM
Might explain why transplant recipients have reported taking on certain characteristics of their donors, ie food preferences or love of specific activities. One never knows, do one?
Posted by: tamra | Oct 21, 2013 2:47:50 AM
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