“Scientists successfully transfer memory of one animal to another,” the headline screamed. All it needed was an exclamation point or two.
Wow! I thought, did this UCLA study team, led by David Glanzman, do a Star Trek Vulcan mind meld on a couple of chimpanzees and share their memories?
Oh no. Chimps are ‘way too high an order of animal for this landmark medical case. The subject animals are … [drumroll] … slugs. And not ordinary garden slugs – no, these were gigantic sea slugs:
Since sea slugs (Aplysia, called also sea hares) can’t talk or text, just how do these UCLA scientists know that their experiment was a success? Just what is memory anyway? Dictionary.com can help us out with a simple definition:
MEMORY – the mental capacity or faculty of retaining and reviving facts, events, impressions, etc., or of recalling or recognizing previous experiences.
There are three different types of memory: sensory, short-term (or working), and long-term.
Anything perceived through one of our basic senses has to pass through sensory memory, the first part of your mind’s memory system. If the sensory neural stimulation is important enough, it goes into short-term memory, which is how we file information we perceive for future access. MedicineNet.com tells us that short-term memory is:
“A system for temporarily storing and managing information required to carry out complex cognitive tasks such as learning, reasoning, and comprehension. Short-term memory is involved in the selection, initiation, and termination of information-processing functions such as encoding, storing, and retrieving data.”
A long-term memory is “anything you remember that happened more than a few minutes ago. Long-term memories can last for just a few days, or for many years.”
Memory is tricky. A person with Alzheimers Disease (a common form of senility) might not remember family members who enter the room, but can recall the lunch menu earlier that day. The opposite condition may also occur, where long-term memory is strong – the person remembers many details from events far past – but doesn’t know what was just discussed conversationally.
The condition where a person can’t remember anything – long, short or in between – is called amnesia.
Neurologists, biologists, and psychologists, along with scientists from multiple other disciplines, are probing the mysterious mechanism that drives human memory. Although it’s easy to represent memory as a big filing cabinet, it is actually much more complicated than that.
Current thought is that the entire brain may be involved in creating, keeping – and losing – memories. howstuffworks explains it this way:
Memory is “the result of an incredibly complex constructive power – one that each of us possesses – that reassembled disparate memory impressions from a web-like pattern of cells scattered throughout the brain…a group of systems that each play a different role in creating, storing, and recalling your memories. When the brain processes information normally, all of these different systems work together perfectly to provide cohesive thought.”
Armed with all this background knowledge about memory, what results justified the claim that these UCLA researchers have “transferred a memory between two sea slugs,” as reported by ARS Technica?
First, understand that the study was testing a genetic component called RNA to see if it holds memories that could be literally transplanted from one test subject to another. It isn’t clear what role RNA plays in human memory, which is why experiments like this are so interesting.
Sea slugs have a reflex action. When alarmed, they quickly retract a “siphon that they can extend out from a protective pouch” and wait for the danger to pass. It turns out that a mild electric shock is distressing enough to speed up the reflex: “the siphon would get withdrawn for longer periods.”
Similar to Pavlov’s famous salivating dog, the sea slug kept its siphon retracted for as long a period of time while experiencing electric shocks as it did when researchers stopped administering the extra neural stimulation.
At this point, the researchers concluded that their test subject had “formed an associative memory.” This, too, is a debatable point, but we’ll give it to the science team for now.
In the simplest terms, using proper methodology and a control group, the scientists injected slugs with no enhanced siphon response with RNA extracted from the shocked slugs. Lo and behold, the unconditioned slugs also kept their siphon retracted for the longer time period, as if they, too, remembered receiving mild electric shocks.
So, using the researcher’s definition of what a memory is, they achieved a successful transplant of a conditioned reflex response. But is that really a memory?Without a doubt, human memory is vastly more complicated than slug memory. Still, ya gotta start somewhere.
Up until recently, the role of RNA as a “messenger and a template for protein formation” has been eclipsed by the theory that “synapses and connection between neurons have been the basis for memory and learning.”
Lead researcher Glanzman “said that the memories seem to be stored within the nucleus of these neurons where these RNA can stimulate or block the actions of the genes by turning them off or on,” and “he is convinced that memories may remain even if the synapses come and go. This has to mean that the memories are stored in some form within the nucleus.”
Hats off to a good start determining the role RNA plays in animal memory. But come get me when they develop the Vulcan mind meld, ok?