How many neurons does a human have

To overcome this problem, the researchers utilized a method that involved dissolving the cell membranes in order to create a sort of "brain soup" so that they could then count the number of cell nuclei in a sample. How many neurons did the researchers find in the brains they analyzed?

And not one that we looked at so far has billion. Even though it may sound like a small difference the 14 billion neurons amount to pretty much the number of neurons that a baboon brain has or almost half the number of neurons in the gorilla brain. So that's a pretty large difference actually," explained Herculano-Houzel.

So, according to this new research, the human brain likely has somewhere around 86 billion neurons. According to Herculano-Houzel, human brains are remarkably similar to primate brains with one important distinction: we have far more brain cells that require a tremendous amount of energy to fuel and maintain.

The sheer number of neurons present in the human brain becomes more apparent when compared to other species. So how many neurons are in the brains of other animals? While the human brain might not have the mythic billion neurons as long suspected, 86 billion is still nothing to sneeze at. Ever wonder what your personality type means? Sign up to find out more in our Healthy Mind newsletter. Herculano-Houzel S. The human brain in numbers: a linearly scaled-up primate brain. Front Hum Neurosci.

The search for true numbers of neurons and glial cells in the human brain: A review of years of cell counting.

J Comp Neurol. The remarkable, yet not extraordinary, human brain as a scaled-up primate brain and its associated cost. Kohl J, Jefferis GS. Neuroanatomy: decoding the fly brain. Curr Biol. Williams RW. As it turned out, there are many ways to put brains together: Primates like us have more neurons in the cerebral cortex than most other mammals, no matter the size of the brain. A brain can be large but made of relatively few neurons if those neurons are huge, like in an elephant; primate neurons are small, and bird neurons are even tinier, so even the smallest bird brains can hide lots of neurons.

But never as many as the largest primate brain: ours. And not just that: I recently found that the more cortical neurons, the longer the species takes to develop into adulthood , just like it takes longer to assemble a truckload of Legos into a mansion than a handful into a little house. And for as yet unknown reasons, along with more cortical neurons comes a longer life.

Getting more cortical neurons thus seems to be a two-for-one bargain: Buy more mental capabilities, and along comes more lifetime to learn to use them.

Lots more neurons cost lots more energy , though. If people had kept exclusively eating raw foods, like all other primates do, they would need to spend over nine hours every single day searching, collecting, picking and eating to feed their 16 billion cortical neurons. Forget about discovering electricity or building airplanes. There would be no time for looking at the stars and wondering about what could be. Our great ape cousins, ever the raw foodies, still have at most half as many cortical neurons as we do — and they eat over eight hours per day.

But our ancestors figured out how to cheat nature to get more from less, first with stone tools and later with fire. They invented cooking and changed human history. In fact, although men have been reported to have more neurons in the cerebral cortex than women Pakkenberg and Gundersen, ; Pelvig et al. Across these individuals, other factors such as variations in number and identity of synaptic connections within and across structures, building on a statistically normal, albeit variable, number of neurons, and depending on genetics and life experiences such as learning, are more likely to be determinant of the individual cognitive abilities see, for instance, Mollgaard et al.

Novel quantitative data on the cellular composition of the human brain and its comparison to other primate brains strongly indicate that we need to rethink our notions about the place that the human brain holds in nature and evolution, and rewrite some of the basic concepts that are taught in textbooks.

Accumulating evidence Deacon, ; Roth and Dicke, ; Deaner et al. Now that these numbers can be determined in various brains and their structures, direct comparisons can be made across species and orders, with no assumptions about body—brain size relationships required.

Complementarily, however, it now becomes possible to examine how numbers of neurons in the brain, rather than brain size, relate to body mass and surface as well as metabolism, parameters that have been considered relevant in comparative studies Martin, ; Fox and Wilczynski, ; MacLarnon, ; Schoenemann, , in order to establish what mechanisms underlie the loosely correlated scaling of body and brain. According to this now possible neuron-centered view, rather than to the body-centered view that dominates the literature see Gazzaniga, , for a comprehensive review , the human brain has the number of neurons that is expected of a primate brain of its size; a cerebral cortex that is exactly as large as expected for a primate brain of 1.

This final observation calls for a reappraisal of the view of brain evolution that concentrates on the expansion of the cerebral cortex, and its replacement with a more integrated view of coordinate evolution of cellular composition, neuroanatomical structure, and function of cerebral cortex and cerebellum Whiting and Barton, Finally, if being considered the bearer of a linearly scaled-up primate brain does not sound worthy enough for the animal that considers himself the most cognitively able on Earth, one can note that there are, indeed, two advantages to the human brain when compared to others — even if it is not an outlier, nor unique in any remarkable way.

First, the human brain scales as a primate brain: this economical property of scaling alone, compared to rodents, assures that the human brain has many more neurons than would fit into a rodent brain of similar size, and possibly into any other similar-sized brain.

And second, our standing among primates as the proud owners of the largest living brain assures that, at least among primates, we enjoy the largest number of neurons from which to derive cognition and behavior as a whole.

It will now be interesting to determine whether humans, indeed, have the largest number of neurons in the brain among mammals as a whole. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Thanks to Roberto Lent and Jon Kaas for continued support and encouragement, to Bruno Mota for insightful discussions, and to the colleagues who participated in the quantification of the cellular composition of the brain of various species. Supported by CNPq-Ed. National Center for Biotechnology Information , U. Journal List Front Hum Neurosci v. Front Hum Neurosci. Published online Nov 9. Prepublished online Aug 5. Author information Article notes Copyright and License information Disclaimer.

Received Jul 15; Accepted Sep This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

This article has been cited by other articles in PMC. Keywords: brain scaling, number of neurons, human, encephalization. Introduction The human brain as a special brain What makes us human? The human brain in numbers How many neurons does the human brain have, and how does that compare to other species?

Why bother with cell numbers? Open in a separate window. Figure 1. Assumption 2: brain size matters Brain size varies across mammals by a factor of approximately , Tower, ; Stolzenburg et al. Figure 2. A New View: Scaling of Neuronal Numbers Cellular scaling rules for rodent, insectivore, and primate brains Our group has been investigating the cellular scaling rules that apply to brain allometry in different mammalian orders using the novel method of isotropic fractionation, which produces cell counts derived from tissue homogenates from anatomically defined brain regions Herculano-Houzel and Lent, Figure 3.

Table 1 Power law exponents that apply to the scaling of brain mass, or structure mass, as a function of the number of neurons they contain in rodents, insectivores and primates. Not all brains are created equal: cognitive abilities and numbers of neurons The different cellular scaling rules that apply to rodent, primate and insectivore brains show very clearly that brain size cannot be used indiscriminately as a proxy for numbers of neurons in the brain, or even in a brain structure, across orders.

Figure 4. The cellular composition of the human brain The determination of the cellular scaling rules that apply to primate brains Herculano-Houzel et al. Table 2 Expected values for a generic rodent and primate brains of 1.

Figure 5. Predictions for great apes The finding that the same cellular scaling rules apply to humans and non-anthropoid primate brains alike, irrespective of body size, indicates that the brains of the great apes, which diverged from the hominin lineage before humans, should also conform to the same cellular scaling rules.

Do we have the most neurons? Table 3 Predicted cellular composition of whale and elephant brains if they scaled according to rodent or primate cellular scaling rules. What Now? Cognitive abilities, brain size and number of neurons To conclude that the human brain is a linearly scaled-up primate brain, with just the expected number of neurons for a primate brain of its size, is not to state that it is unremarkable in its capabilities.

Intraspecific variability in size, numbers and abilities One final caveat to keep in mind when studying scaling of numbers of brain neurons, particularly in regard to cognition, is that relationships observed across species need not apply to comparisons across individuals of the same species. Concluding remarks: our place in nature Novel quantitative data on the cellular composition of the human brain and its comparison to other primate brains strongly indicate that we need to rethink our notions about the place that the human brain holds in nature and evolution, and rewrite some of the basic concepts that are taught in textbooks.

Conflict of Interest Statement The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Acknowledgments Thanks to Roberto Lent and Jon Kaas for continued support and encouragement, to Bruno Mota for insightful discussions, and to the colleagues who participated in the quantification of the cellular composition of the brain of various species.

References Allen N. Glia — more than just brain glue. Nature , — A quantitative study of the human cerebellum with unbiased stereological techniques. Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. How did brains evolve?

Primate brain evolution: integrating comparative, neurophysiological, and ethological data. Mosaic evolution of brain structure in mammals. Learning causes synaptogenesis, whereas motor activity causes angiogenesis, in cerebellar cortex of adult rats. USA 87 , — Total number and volume of Von Economo neurons in the cerebral cortex of cetaceans. Scalable architecture in mammalian brains.

What makes the human brain different? Overall brain size, and not encephalization quotient, best predicts cognitive ability across non-human primates. Brain Behav.

The glial identity of neural stem cells. Changes in grey matter induced by training. Linked regularities in the development and evolution of mammalian brains.

Science , — Allometry of major CNS divisions: towards a reevaluation of somatic brain-body scaling. Quantitative share of the glia in development of the cortex. Acta Anat. L, Allman J. Brain of the African elephant Loxodonta africana : neuroanatomy from magnetic resonance images. Von Economo neurons in the elephant brain. Modeling physiological and anthropometric variables known to vary with body size and other confounding variables.

Brain sizes, surfaces, and neuronal sizes of the cortex cerebri: a stereological investigation of man and his variability and a comparison with some mammals primates, whales, marsupials, insectivores, and one elephant. Science , 76— Do you know your brain? A survey on public neuroscience literacy at the closing of the decade of the brain. Neuroscientist 8 , 98— Encephalization, neuronal excess, and neuronal index in rodents. Cellular scaling rules for primate brains.

USA , — The basic nonuniformity of the cerebral cortex. Isotropic fractionator: a simple, rapid method for the quantification of total cell and neuron numbers in the brain. Cellular scaling rules for rodent brains.

Dendritic spine structural anomalies in fragile-X mental retardation syndrome. Cortex 10 , — Evolution of the Brain and Intelligence. Animal intelligence as encephalization. Cell number and cell density in the cerebellar cortex of man and some other mammals.