Scientists from UCLA recently conducted some rather bizarre experiments. For me, it’s these types of things that make it so much fun to be a scientist.
Biologists transferred memories from one sea slug to another by extracting RNA from the nervous system of a trained sea slug and then injecting the extract into an untrained sea slug.1 After the injection, the untrained sea snails responded to environmental stimuli just like the trained ones, based on false memories created by the transfer of biomolecules.
Why would researchers do such a thing? Even though it might seem like their motives were nefarious, they weren’t inspired to carry out these studies by Dr. Frankenstein or Dr. Moreau. Instead, they had really good reasons for performing these experiments: they wanted to gain insight into the physical basis of memory.
How are memories encoded? How are they stored in the brain? And how are memories retrieved? These are some of the fundamental scientific questions that interest researchers who work in cognitive neuroscience. It turns out that sea slugs belonging to the group Aplysia (commonly referred to as sea hares) make ideal organisms to study in order to address these questions. The fact that we can gain insight into how memories are stored with sea slugs is mind-blowing and indicates to me (as a Christian and a biochemist) that biological systems have been designed for discovery.
Sea hares have become the workhorses of cognitive neuroscience. This creature has a nervous system that’s complex enough to allow neuroscientists to study reflexes and learned behaviors, but simple enough that they can draw meaningful conclusions from their experiments. (By way of comparison, members of Aplysia have about 20,000 neurons in their nervous systems compared to humans who have 85 billion neurons in our brains alone.)
Toward this end, neuroscientists took advantage of a useful reflexive behavior displayed by sea hares, called gill and siphon withdrawal. When these creatures are disturbed, they rapidly withdraw their delicate gill and siphon.
The nervous system of these creatures can also experience sensitization, which is learned by repeated exposure to stimuli, resulting in an enhanced and broad response by the nervous system to stimuli that are related—say, stimuli that connote danger.
What Causes Memories?
Sensitization is a learned response that is possible because memories have been encoded and stored in the sea hares’ nervous system. But how is this memory stored?
Many neuroscientists think that the physical instantiation of memories (called engrams) reside in the synaptic connections between nerve cells (neurons). Other neuroscientists hold a differing view. Instead of being mediated by cell-cell interactions, others think that engrams form within the interior of neurons, through biochemical events that take place within the cell nucleus. In fact, some studies have implicated RNA molecules in memory formation and storage.2 The UCLA researchers sought to determine if RNA plays a role in memory formation.
Memory Transfer from One Sea Hare to Another
To test this hypothesis, the researchers sensitized sea hares to painful stimuli. They accomplished this feat by inserting an electrode in the tail regions of several sea hares and delivering a shock. The shock caused the sea hares to withdraw their gill and siphon. After 20 minutes, they repeated the shock protocol and continued to do so in 20-minute intervals five more times. Twenty-four hours later, they repeated the shock protocol. By this point, the sea hare test subjects were sensitized to threatening stimuli. When touched, the trained sea hares would withdraw their gill and siphon for nearly 1 minute. Untrained sea hares (who weren’t subjected to the shock protocol) would withdraw their gill and siphon when touched for only about 1 second.
Next, the researchers sacrificed the sensitized sea hares and isolated RNA from their nervous system. Then they injected the RNA extracts into the hemocoel of untrained sea hares. When touched, the sea hares withdrew their gill and siphon for about 45 seconds.
To confirm that this response was not due to the injection procedure, they repeated it by injecting RNA extracted from the nervous system of an untrained sea hare into untrained sea hares. When touched, the gill and siphon withdrawal reflex lasted only about 1 second.
Figure: Sea Hare Stimulus Protocol. Image credit: Alexis Bédécarrats, Shanping Chen, Kaycey Pearce, Diancai Cai, and David L. Glanzman, eNeuro 14 May 2018, 5 (3) ENEURO.0038-18.2018; doi:10.1523/ENEURO.0038-18.2018.
The researchers then applied the RNA extracts from both trained and untrained sea hares to sensory neurons grown in the lab. The RNA extracts from the trained sea hares caused the sensory neurons to display heightened activity. Conversely, the RNA extracts from the untrained sea hares had no effect on the activity of the cultured sensory neurons.
Finally, the researchers added compounds called methylase inhibitors to the RNA extracts before injecting them into untrained sea hares. These inhibitors blocked the memory transfer. This result indicates that epigenetic modifications of DNA mediated by RNA molecules play a role in forming engrams.
Based on these results, it appears that RNA mediates the formation and storage of memories. And, though the research team does not know which class of RNAs play a role in the formation of engrams, they suspect that micro RNAs may be the biochemical actors.
Now that the UCLA researchers have identified RNA and epigenetic modifications of DNA as central to the formation of engrams, they believe that it might one day be possible to develop biomedical procedures that could treat memory loss that occurs with old age or with diseases such as Alzheimer’s and dementia. Toward this end, it is particularly encouraging that the researchers could transfer memories from one sea hare to another. This insight might even lead to therapies that would erase horrific memories.
Of course, this raises questions about human nature—specifically, the relationship between the brain and mind. For many people, the fact that there is a physical basis for memories suggests that our mind is indistinguishable from the activities taking place within our brains. To put it differently, many people would reject the idea that our mind is a nonphysical substance, based on the discovery of engrams.
Engrams, Brain, and Mind
However, I would contend that if we adopt the appropriate mind-body model, it is possible to preserve the concept of the mind as a nonphysical entity distinct from the brain even if engrams are a reality. A model I find helpful is based on a computer hardware/software analogy. Accordingly, the brain is the hardware that manifests the mind’s activity. Meanwhile, the mind is analogous to the software programming. According to this model, hardware structures—brain regions—support the expression of the mind, the software.
A computer system needs both the hardware and software to function properly. Without the hardware, the software is just a set of instructions. For those instructions to take effect, the software must be loaded into the hardware. It is interesting that data accessed by software is stored in the computer’s hardware. So, why wouldn’t the same be true for the human brain?
We need to be careful not to take this analogy too far. However, from my perspective, it illustrates how it is possible for memories to be engrams while preserving the mind as a nonphysical, distinct entity.
Designed for Discovery
The significance of this discovery extends beyond the mind-brain problem. It’s provocative that the biology of a creature such as the sea hare could provide such important insight into human biology.
This is possible only because of the universal nature of biological systems. All life on Earth shares the same biochemistry. All life is made up of the same type of cells. Animals possess similar anatomical and physiological systems.
Most biologists today view these shared features as evidence for an evolutionary history of life. Yet, as a creationist and an intelligent design proponent, I interpret the universal nature of the cell’s chemistry and shared features of biological systems as manifestations of archetypical designs that emanate from the Creator’s mind. To put it another way, I regard the shared features of biological systems as evidence for common design, not common descent.
This view leads to the follow-up rebuttal: Why would God create using the same template? Why not create each biochemical system from scratch to be ideally suited for its function? There may be several reasons why a Creator would design living systems around a common set of templates. In my estimation, one of the most significant reasons is discoverability. The shared features of biochemical and biological systems make it possible to apply what we learn by studying one organism to all others. Without life’s shared features, the discipline of biology wouldn’t exist.
This discoverability makes it easier to appreciate God’s glory and grandeur, as evinced by the elegance, sophistication, and ingenuity in biochemical and biological systems. Discoverability of biochemical systems also reflects God’s providence and care for humanity. If not for the shared features, it would be nearly impossible for us to learn enough about the living realm for our benefit. Where would biomedical science be without the ability to learn fundamental aspects of our biology by studying model organisms such as yeast, fruit flies, mice—and sea hares?
The shared features in the living realm are a manifestation of the Creator’s care and love for humanity. And there is nothing bizarre about that.