In what format is information stored in the brain?

I was asked this question on Quora.

We don’t really know. But as one of my professors once said half-jokingly, “the brain is a bag of tricks”. There is no reason to assume that all brain regions use the same coding scheme.

Here are some basic concepts that guide how neuroscientists think about information in the brain:

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What is neuroplasticity?

I was asked this question on Quora:

Can you explain to a layman what neuroplasticity entails?

Neuroplasticity is the umbrella term for all of the brain’s mechanisms for learning and memory.

Since the average layperson already knows about learning and memory, I’m not sure whether there are any interesting implications.

Unless of course you are surprised that the brain is involved in learning and memory. Then the implications are vast. 🙂

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Is a memory a bunch of atoms? And does this mean we can transfer exact memories?

I was asked the following question on Quora.

Are specific memories just arrangements of atoms in our brains? Could you put certain molecules in someones head and give them an exact memory that you had?

Short answer: No.

Modern science has shown that every thing is an arrangement of atoms: neurons, apples, tables, rockets, asteroids, aardvarks… they are all made up of atoms.

The question now is this: is a memory a thing? Continue reading

No New Neurons? No Problem!

This answer was written in response to the following Quora question:

New research has found no neurogenesis in human adults, could this mean there is none or could it mean that neural stem cells are undetectable with the used techniques? What are your thoughts on this?

It’s good that you’re thinking of such things, since that is exactly what researchers themselves have to do, and what reviewers do. In order to show that the method works, there have to be adequate controls as part of the experiment.

And this is in fact the case. The paper would not have been published without controls.

In the study, the researchers successfully identified a class of newborn neurons in very young postmortem human brains, so the absence of them in older brains has nothing to do with the methodology.

Here’s a diagram from the paper:

If you have your heart set on adult neurogenesis for some mysterious reason, then you can argue that the ‘real’ new neurons (that other researchers say exist in human adults) are actually a different class of neuron entirely. I don’t know how far that reasoning will take you though.

If one is being intellectually honest, one must also now consider why the other studies might be wrong about their findings of neurogenesis in humans. This is exactly what the authors of this new paper do at the end of their paper. They suggest that the presence of growth factors in adult human brains may have nothing to do with cell division — they may instead be a byproduct of other phenomena. Two that come to mind are dendritic arborization and synapse formation.

No New Neurons? No Worries!

I am quite baffled by the disappointment people seem to feel in response to this study. If new neurons occur in mice and young babies, and not in adult humans, that has no bearing on the quality of memory and learning in human adults. A 70 year old can learn many things that mice and infants can never learn, regardless of their rate of birth of new neurons. So headlines like “Sorry, Adults, No New Neurons For Your Aging Brains” are extremely silly and misleading. In fact they may even be harmful, because they could encourage discrimination based on ageism.

If the current study is corroborated by other groups, and ‘triangulated’ using other methods, then neuroscientists may eventually come to agree that adult neurogenesis is not a feature of the human species. Consensus is not going to happen soon though, for a variety of reasons that I can’t get into here. Science is complex and messy!

But even if the “no adult neurogenesis in humans” idea is corroborated, it should not bother the average non-scientist interested in learning, memory or self-improvement, since everyone already knows that older humans are perfectly capable of acquiring new knowledge and skills. We have known this for thousands of years. Zero neuroscience is needed to establish the memory capacity of a human adult.

The proof of the pudding is in the eating, not in the molecular make-up of the pudding. 🙂

If you are not convinced of the extraordinary memory capacity of even older adults, see this essay I wrote:

3quarksdaily: Why human memory is not a bit like a computer’s

Image source: Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults

Perhaps neurogenesis doesn’t happen in adult humans?

A new study suggests that new neurons are not born very often in human adults.

Birth of New Neurons in the Human Hippocampus Ends in Childhood

“The lab’s new research, based on careful analysis of 59 samples of human hippocampus from UCSF and collaborators around the world, suggests new neurons may not be born in the adult human brain at all. The findings present a challenge to a large body of research which has proposed that boosting the birth of new neurons could help to treat brain diseases such as Alzheimer’s disease and depression. But the authors said it also opens the door to exciting new questions about how the human brain learns and adapts without a supply of new neurons, as in seen in mice and other animals.”

My labmates are all monkey neuroanatomists, and for years they have been skeptical about the neurogenesis narrative, particularly in primates. Another famous dissenter is Pasko Rakic. Read about his complaints in this Guardian article from 2012:

Does your brain produce new cells?


“The first rule of intelligence: Don’t talk about your intelligence”

That line is from an article in The Atlantic about how poor people are at self-assessment:

People Don’t Actually Know Themselves Very Well

“The first rule of intelligence: Don’t talk about your intelligence. It’s something you prove, not something you claim. As comedian Patton Oswalt quipped about humor, the only person who goes around saying “I’m funny” is a not-funny person. If you were really funny, you’d just make people laugh.”

To me this kind of thing is pretty obvious, but I guess some people really need to be reminded of it.

Here’s another paragraph with several important reminders, particularly for people who blather about intelligence and cognitive biases:

“This is why people consistently overestimate their intelligence, a pattern that seems to be more pronounced among men than women. It’s also why people overestimate their generosity: It’s a desirable trait. And it’s why people fall victim to my new favorite bias: the I’m-not-biased bias, where people tend to believethey have fewer biases than the average American. But you can’t judge whether you’re biased, because when it comes to yourself, you’re the most biased judge of all. And the more objective people think they are, the more they discriminate, because they don’t realize how vulnerable they are to bias.”