5 Things About the Brain You Didn’t Know

Popular culture abounds with “facts” about the brain, such as we only use 10% of it (false) it weighs three pounds (true), consumes as much energy as a 20 Watt light bulb (true), shrinks with alcohol (mostly false), shrinks with aging (truer in some people than others) and is about 50% fat (true).

These brain “truths” are well-known. But as neuroscience advances, we learn new truths, while “unlearning” old ones that turn out to be false.

Some of the most interesting emerging discoveries about the brain are the previous “truths” that turn out not to be true.

Here are five brain facts that are now brain fiction.

Myth 1: Memory and learning only occur in neurons

Plants can be trained to discriminate different lighting conditions, and planaria (flatworms) who have regrown heads from their severed tails after maze training retain the original training. Colonies of fungal cells can recognize and remember spatial patterns, and new research shows that non-neural tissue, such as kidney cells, collects and stores information similar to memories [1,2,3,4].

These newly discovered phenomena all support the conclusion that brains, let alone neurons, are not necessary for perception, learning, memory, and decision-making. The underlying mechanisms for these forms of “cellular cognition” are poorly understood, but popular sayings such as “listen to your gut” and “follow your heart” may now have scientific validity.

Myth 2: You can’t learn unless you pay attention

Anyone who has been caught not listening to their spouse knows that you can’t remember things you don’t pay attention to. Or can you?

Through a process called “implicit memory,” you can indeed form memories without paying attention. For instance, even if someone makes no noise sneaking up behind you, you often will know the person is immediately behind you because their body absorbs and reflects sound, creating a “sound shadow” that attenuates background noise to your rear. Over the years, you’ve unconsciously learned the connection between sound shadows and the presence of someone behind you, even though you never were conscious of or paid attention to the connection between decreased background noise and an obstruction behind you [5,6].

Myth 3: Neurons only communicate through chemical synapses

Neurons send and receive signals by releasing and responding to neurotransmitters that either excite or inhibit neural activity. The connections where axons release neurotransmitters that influence activity in neuronal cell bodies, dendrites, or even other axons, are called ‘synapses.’

Here is an illustration of a typical synapse showing the chemical transmission of signals between neurons with neurotransmitters.

Source: Laboratoires Servier Creative Commons Attribution-Share Alike 3.0

Neuroscientists have known for decades that neurons sometimes also communicate with adjacent neurons via gap junctions where the membranes of two neurons anatomically fuse in such a way that electrical changes in one neuron directly alter the electrical properties of another neuron without the release of neurotransmitters. Such nodes are called electrical vs. chemical synapses.

But recent research also shows that when neurons polarize or depolarize, they produce bioelectric fields that propagate over distances greater than the distance between presynaptic and postsynaptic membranes through a process called volume conduction. Thus neuron-to-neuron signaling is also possible without either chemical or electric synapses. Although it is too early to say whether such long-distance signaling is functionally significant, aggregate bioelectrical fields propagating through brain volume conduction create the electrical signals picked up by EEG (electroencephalograph) machines [7,8,9].

Myth 4: All taste receptors are in the mouth

We have taste receptors for sweet, sour, bitter, salty, and umami (meaty) on our tongues and nearby oral cavity tissues, but new research reveals taste receptors are also present in our gut, brain, lungs, and heart [11,12,13,14].

Unlike oral taste receptions, we are not consciously aware of the outputs of these non-oral receptors, but they are likely involved in digestion and regulation of our metabolism. Some scientists even speculate that sweet receptors in the gut may respond to artificial sweeteners in ways that stimulate appetite and lead to overeating, obesity, and diabetes.

Myth 5: We only have five senses

Another myth about human sensory receptors is that we only have five senses (smell, taste, touch, hearing, and vision).

Although the underlying sensory mechanisms are murky, there is accumulating evidence that some humans possess the ability to sense magnetic fields, such as the earth’s magnetic field, that birds and fish use to navigate. Magnetic fields can induce changes in human brain wave activity, and some test subjects (mostly male) can be classically conditioned for food rewards using the direction of a magnetic field as a conditioned stimulus [15,16].

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The sensory receptors involved in magneto-reception in humans have not been identified, but visual receptors likely play a role because the ability of humans to sense the direction of magnetic fields is dependent upon the wavelength of light present when such discriminations are made (blue light is essential)[16].

Source: Copyright Eric Haseltine with DallE3

More myths to fall soon?

Science advances not only by learning new truths but also by unlearning obsolete truths. As new investigational neuroscience tools emerge, such as AI, it is likely, if not certain, that the five myths described here are just the first of a long list of brain myths that will fall in the future.

As comedian Will Rogers observed, “It ain’t so much what we don’t know that hurts us, but what we do know that ain’t so!”