The question of how many brain cells humans have has been one of the most popular questions in neuroscience.
Despite many scientific investigations, scientists are still uncertain about the number of brain cells. The problem with this exact number is that the human brain is a complex organ where researchers are still working to understand its functions and features.
Fortunately, with recent advances in scientific research, today it is possible to get a closer estimate of the total number of cells in the brain through novel methods for counting specific types of cells.
So, in this article, we will explore the findings of studies that measure the number of brain cells in humans, including their different types.
Counting Human Brain Cells
To determine how many human brain cells exist, first, you need to note that the complex organ consists of two main types of cells—neurons and glial cells.
Each of these cell types plays a different role in the brain’s function. Neurons, for example, transmit electrical and chemical signals throughout the brain, while glial cells support and protect neurons.
However, counting the human brain, when its fully developed, cells is challenging because it includes considering neurons and glial cells of different sizes and shapes.
Fortunately, there are three principal approaches or methods to estimating the number of cells in the human brain.
The three methods are :
- Histological Sections : This is the most often used approach. The method involves counting the number of cells present in a defined area of tissue.
- DNA extraction : An alternative technique for histology sections is extracting and measuring DNA content and then calculating cell numbers based on knowledge of DNA content per nucleus.
- Isotropic Fractionator : The Isotropic Fractionator is used to determine the cellular composition of nervous tissue. It’s very useful when trying to differentiate neurons and glial cells.
For example, using the isotropic fractionator (IF) method, neuroscientists have challenged the long-held notion that the human brain contains 100 billion neurons and one trillion glial cells. And they are getting closer to the ideal answer.
How many Neurons do Humans Have?
A neuron, also known as a nerve cell, is a specialized type of cell that is present in the nervous system. The primary function of a neuron is to transmit electrical and chemical signals throughout the body. But also have the tasks of processing and storing information.
For example, neurons allow us to move our muscles and feel the external world. They also help us think, form memories ,and respond to stimuli.
Experts in quantitative neuroscience used histological method to determine the number of neurons in the brain[1], and the conclusion was the following :
Number of Neurons | Researcher and Year |
---|---|
30 billion | Szentagothai, 1983 |
70–80 billion | Haug, 1986 |
85 billion | Williams & Herrup, 1988 |
67–86 billion | Andrade-Moraes, 2013 |
As you can see in these studies, there is no specific number of neurons in the human brain; however, the most notable range is between 80 and 85 billion neurons.
Although there are billions of neurons and extensive variations, they can be classified into three primary groups according to their function[2]:
- Sensory neurons : These neurons acquire information from the senses, such as sight, touch , and sound; and transmit this information to the central nervous system
- Motor neurons : These neurons transmit signals from the central nervous system to the muscles, regulating movement and other physiological processes
- Interneurons : These neurons are found within the central nervous system and are responsible for processing and relaying information between sensory and motor neurons. Interneurons are the most abundant of the three main neuron types.
The following table shows a listing of the approximate number of each type of neuron.
Type of Neuron | Approximately Number |
---|---|
Sensory Neuron | 10 million |
Motor Neurons | 500,000 |
Interneurons | 80 billion |
How many Glial Cells do humans have?
A glial cell, also known as neuroglia or simply glia, is a non-neuronal cell in the nervous system that provides support and protection for neurons.
Neurons can’t recreate their function without glial cells. For example, glial cells perform functions, such as providing structural support, insulation, and nourishment for neurons and also helping remove dead neurons.
Two different researchers estimated the number of glial cell in the entire human brain based on glial cells densities (histological method):
- 100 – 130 billion glial cells (Blinkov & Glezer, 1968)
- 40 – 50 billion glial cells (Haug, 1986)
Despite these two investigations, a recent study using the IF method found that the human brain’s total number of glial cells is closer to Haug’s estimate of 40–50 billion. This recent study put the total number of glial cells at approximately 60 billion.
Like its contemporary cells (Neurons), there are different types of glial cells: astrocytes, oligodendrocytes, and microglia.
The following table briefly summarizes the proportions of different types of glial cells in the brain.
Oligodendrocytes | Astrocytes | Microglia | Portion of the Brain | Author - Year |
---|---|---|---|---|
29 % | 61.5 % | 9.5 % | Visual Cortex | Kryspin-Exner, 1952 |
51 % | 40 % | 9 % | Motor Cortex | Brownson, 1956 |
50.9% | 40.8% | 16.7% | Frontal Cortex | Schloe, 1959 |
75% | 20% | 5% | Neocortex | Verkhratsky & Butt , 2013 |
Several researchers have examined the roles of astrocytes, oligodendrocytes, and microglia. In particular, most of their work has focused on the cerebral cortex.
Not surprisingly, oligodendrocytes are more frequent than other glial cell types in brain tissue. Primary sources indicate that in different brain regions, including neocortical gray matter, oligodendrocytes are the most frequent at 45–75% of glial cells; astrocytes (19–40%) and microglia contribute 10% or less.
Conclusion
Many investigations have attempted to count the exact number of brain cells, including their different types of cells, such as neurons and glial cells.
Although scientists cannot precisely count the number of brain cells, recent studies have determined a close range between 80-85 billion neurons and 60 billion glial cells, which gives a total of about 140 billion brain cells including different types of neurons and glial cells such as astrocytes, oligodendrocytes, and microglia.
Although the number of brain cells is vast, it is essential to note that the total number of brain cells does not determine cognitive ability or intelligence.

Video
Bibliography
1]           C. S. von Bartheld, J. Bahney, y S. Herculano-Houzel, «The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting», J. Comp. Neurol., vol. 524, n.o 18, pp. 3865-3895, 2016, doi: 10.1002/cne.24040.
[2]          O. Guy-Evans, «Neuron Function, Parts, Structure, and Types», SimplyPsychology.org, 15 de February de 2021. https://www.simplypsychology.org/neuron.html .