The Groundless Myth of Superagers Growing More Brain Cells

 Never forget there's a "profess" in the word "professor."  And "profess" is defined as "to affirm one's faith in or allegiance to (a religion or set of beliefs)."  A recent press release from the rather strangely named University of Illinois Chicago gives us an example of a neuroscientist professor professing, and incorrectly boasting about grand things that were not at all done. 

We have a headline of "What makes superagers’ brains special?"  So-called superagers are very old people with very good memories. The press release attempts to suggest the story line that these superagers can remember better because they had higher rates of neuron creation (neurogenesis).  It's a story line that fits in with the idea that brains store memories. But it's not a story line backed up by any good evidence. 

Neurons are created before humans reach adulthood. But there is no robust evidence that significant number of neurons are created in adulthood. 

In the UIC press release we have this extremely glaring example of a scientist crowing about some grand and glorious result, when the research is actually very low-quality research because of its use of way-too-small study group sizes.  The press release says this:

" 'This is a big step forward in understanding how the human brain processes cognition, forms memories and ages. Determining why some brains age more healthily than others can help researchers make therapeutics for healthy aging, cognitive resilience and the prevention of Alzheimer’s disease and related dementia,' said Orly Lazarov, a professor in UIC’s College of Medicine and director of the Alzheimer’s Disease and Related Dementia Training Program."

But the truth is that we have here neither a  "big step forward" nor an example of a decently done scientific study. The reason is the tiny study group sizes, which were only 8 subjects per study group. 

When we look at the scientific paper "Human hippocampal neurogenesis in adulthood, ageing and Alzheimer’s disease," and search for the study group size (using the search phrase "n=") we find that the study group sizes were only 8 subjects per study group. No study like this should be taken seriously unless it used a study group size of at least 15 or 20 subjects per study group. 

There is simply no basis for concluding that super-agers have neuron creation rates any different from old people with poor memories, nor is there any good basis for thinking that adults create new neurons in significant numbers. No such generalization can be made with any reliability when you do a way-too-small study group size of only 8 people. 

Did the UIC press release tell us that only 8 subjects per study group were used? No, it conveniently forgot to mention how many subjects were used. 

We should note that in the text of the paper Lazarov sings a tune very different from her boasts in the press release. In the paper we read this (with "power" referring to statistical power):

". Notably, we observed a general increase in the number of immature neurons in SA; however, inter-sample variability and low sample number compromised the power of our analysis. It should be noted that the high level of variability from sample-to-sample in cell-type abundance limited the quantitative power of our study. Future experiments with a greater number of human brain samples will be needed to study this aspect in depth."

Wow, that sounds like kind of a confession of failing to do the work in a way that would inspire confidence. So why on Earth was Lazarov boasting in the press release that this study was "a big step forward in understanding how the human brain processes cognition, forms memories and ages"?  

Let us now look at some neuroscientists who have denied the doctrine of adult human neurogenesis, by denying that human adults  create new brain cells. 

• A 2018 paper states, "Our recent observations suggest that newborn neurons in the adult human hippocampus (HP) are absent or very rare (Sorrells et al., 2018)." The paper notes that "studies supporting the presence of adult human hippocampal neurogenesis are not consistent with each other: some report a sharp decline and small, negligible contribution in adults...others support continuous high levels of neurogenesis in old age (Spalding et al., 2013; Boldrini et al., 2018), but show extremely high variability."
• A 2018 paper states "2 independent papers coming from different parts of the world have used a similar approach and methodology leading to converging results and the following similar conclusions: hippocampal neurogenesis in humans decays exponentially during childhood and is absent or negligible in the adult." It says these papers "are Sorrells et al. (2018) from the lab of Alvarez-Buylla in USA published in March in Nature, and the study by Cipriani and coworkers from the Adle-Biassette’s lab in France published in this issue of Cerebral Cortex (2018; 27: 000–000)."
• A 2018 article in The American Scientist (co-authored by Sorrells and Alvarez-Buylla) is entitled "No Evidence for New Adult Neurons."  It said, "Adult human brains don’t grow new neurons in the hippocampus, contrary to the prevailing view." The authors criticize previous reports of adult neurogenesis partially by saying they "frequently used only a single protein to identify new neurons," which was a faulty technique because "we found that the protein most often used, one called doublecortin, can also be seen in nonneuronal brain cells (called glia) that are known to regenerate throughout life." A 2022 article entitled "Doublecortin and the death of a dogma" refers to work by Franjic, saying, "out of the 139,187 nuclei sequenced, only 2 showed appropriate transcriptomes for neural precursor cells... suggesting adult human neurogenesis is rare, if it occurs at all."
• A 2019 paper says that "a balanced review of the literature and evaluation of the data indicate that adult neurogenesis in human brain is improbable," and that "several high quality recent studies in adult human brain, unlike in adult brains of other species, neurogenesis was not detectable."
• A 2018 paper claimed that "New neurons continue to be generated in the subgranular zone of the dentate gyrus of the adult mammalian hippocampus," but the paper's title was "Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults."
• Describing his research, the neuroscientist  Ashutosh Kumar stated in 2020 that he had found this: "Progression of neurogenesis is restricted after childhood, and reduces to negligible levels around adolescence and onwards."
• A 2022 paper was entitled "Mounting evidence suggests human adult neurogenesis is unlikely."
• A 2022 paper states, "In this review, we will assess critically the claim of significant adult neurogenesis in humans and show how current evidence strongly indicates that humans lack this trait." The paper states that "In summary, a thorough review of the literature shows that there is no scientific convincing evidence of the generation and incorporation of new neurons into the circuitry of the adult human brain, including the dentate gyrus of the hippocampus."  Noting how false claims persist within neuroscience, the paper states, "As Victor Hamburger, co-discoverer of the nerve growth factor, said at an informal meeting: 'A single report of an incorrect finding that many people like, takes more than hundreds of papers with negative findings to make an acceptable correction.' ” 
• A 2021 paper was entitled "Positive Controls in Adults and Children Support That Very Few, If Any, New Neurons Are Born in the Adult Human Hippocampus."

There is another reason for disbelieving the "superagers make more neurons" story, besides the lack of evidence for adult neurogenesis. The additional reason is that when asked to explain memory creation, neuroscientists typically appeal not to neurons but to synapses existing outside of neurons.  The senseless story that neuroscientists keep telling is that memory creation occurs by "synapse strengthening," an idea that makes no sense for a variety of reasons, including the fact that information is never stored by an act of mere strengthening, and also the fact that synapses are made up of proteins with an average lifetime 1000 times shorter than the longest length of time that humans can remember things (50 years or more). Conceivably a neuroscientist might get a talking point in favor of such a theory of synaptic memory storage if he were to show that the synapses of superagers are stronger or more abundant than the synapses of typical agers. But you would not get a talking point to support such a theory of synaptic memory storage if you merely showed that superagers created more neurons than normal agers.