Are Neurons Required for Cognition and Memory?

After decades of practicing medicine, my wife, Chris became convinced that the human body has a “mind” separate and distinct from the brain, and that listening to what the “body’s mind” is constantly telling our brains is vital to diagnosing, and curing illness. [1]

Watching Dr. Chris work, I came to believe that that our bodies do indeed have minds of their own. But as a neuroscientist, I attributed the body’s savvy to neurons in the peripheral nervous system, such as the hundreds of millions of nerve cells that comprise the enteric and cardiac nervous systems.

But recent research in the emerging field of basal cognition suggests that I was wrong: Neurons are likely not the only parts of our bodies that perceive, think, remember, and communicate with our brains.

Dethroning Neurons As the Only Cells That Think

The most startling and impressive evidence of the incredible “cognitive” abilities of non-neurons comes from a video of a single-cell neutrophil (part of the immune system) chasing and eating a bacterium in a petri dish containing red blood cells. From the video, it’s clear that the blob-monster-like neutrophil senses the presence and location of the bacteria and propels itself towards its hapless target, all the while morphing and transforming its shape to move around red blood cells. [2]

The fleeing bacteria, for its part, clearly senses the danger, knows the macrophage’s direction, and flees in the opposite direction, also slipping through gaps between cells in the culture.

Every time I watch that video, I wonder, "How the heck can single cells do all of those amazing things without any sort of neural processing?" We don’t yet know, but tantalizing hints are emerging in fields as diverse as botany, cell biology, and neuroscience.

Dr. Michael Levin of Tufts University recently showed that memory can be stored in non-neuronal cells of planaria (flatworms). He trained flatworms to cross a corrugated floor for food rewards, then cut the worms in half, discarding the heads while letting the tails re-grow a head.

When he placed the whole, regenerated worms back in their training environment, they retained memories of their previous training, exhibiting the same conditioned behaviors that they had acquired before, literally, losing their heads. [3] Dr. Levin speculates that these non-neuronal memories are encoded in bio-electric signals that govern other cell behaviors such as cell division and differentiation during development.

Here’s more evidence for basal cognition in non-neurons:

• Plants (that have no neurons) can be classically conditioned just like animals. [4,5]
• In colonies made up of many individual cells (slime molds, pond scum), cells cooperate among themselves, dividing and coordinating tasks such as detecting food, moving the colony, defending against attack, digesting food, and sharing nutrients. [6,7]
• A variety of “aneural” organisms such as plants and predatory bacteria sense, react, and communicate danger to others of their species. [8].
• Individual immune cells “remember” and attack pathogens they have seen before. [9]

Underlying Mechanisms

In a sweeping review of basal cognition, Dr., Pamela Lyon and colleagues at Adelaide University identify several candidates for aneural perception, cognition, and learning [10}, including:

• Bio-electric phenomena
• Ion currents
• Bio-mechanical transduction (sensing vibration/movement)
• Pheromones
• Other types of chemical signaling

The main conclusion of the fast-growing field of basal cognition is that neurons and non-neurons differ only by degree, not by absolute kind (information processing/storage vs non-information processing/storage). And the implications of this growing understanding are profound.

For instance, can we learn the “thought processes” and “language” of cancer cells and convince them to stop their runaway replication? Can we teach immune cells to better detect and kill pathogens? Can we understand, listen to, and ultimately persuade over-active immune systems to stop allergic reactions, rheumatoid arthritis, and other devastating autoimmune diseases such as MS? Or even, someday, engage in deep mind-body conversations that effectively let us cure ourselves without medical treatment?

I’m not sure, but somewhere in my gut, heart, and maybe my little toe, I suspect the answer to all of those questions is yes.