A group of scientists from Cambridge is trying to grow human brains in laboratory conditions separately from the body. The fruits of their work are not at all like what one would imagine. "Brain organelles" are derived from stem cells taken from human skin and grown in giant incubators. In the absence of blood supply, they receive nutrients by soaking in a special solution.
Permeated by two million neurons, these brain structures are tiny - about four millimeters in diameter - small enough to use a Petri dish. In comparison, the developed brain of an adult mouse contains four million neurons. In the brain of the average adult, their number reaches a thousand trillion.
As in a normal brain, these cell bundles contain a mixture of gray and white matter. They even form specific areas such as the cortex, hippocampus, cerebellum, and others. By the level of development, organelles roughly correspond to the brain of a nine-week-old fetus.
However, although the neurons in these tiny organelles are connected and fired when electrical signals are applied, they are unable to think or feel in the way humans understand it. Dr. Madeline Lancaster compares the activity of neurons to how you can make heart cells beat in a petri dish. When brain cells are alive, the absence of a body or sense organs means they are not receiving information that could lead to consciousness. If you take an electroencephalogram of a brain grown in a laboratory, there will be no brain waves.
However, consciousness is not the focus of this study. Lancaster and colleagues were interested in exploring some of the key differences between humans and primates. Our DNA is only 1.2 percent different from that of chimpanzees, but somehow there is a huge difference in intelligence. Scientists have replaced individual genes involved in brain development with genes from chimpanzees to observe the results.
In other laboratories, similar organelles are used to learn more about human development - in particular, about the causes of differences in the brain of a person with schizophrenia or autism from a normal brain. Failure to identify such disorders in animals makes it impossible to study them in the laboratory. (While there are many reasons to avoid animal experimentation, dissecting the brains of living people is obviously not entirely ethical either.)
Instead, researchers can use such technology and stem cells from patients to learn more about how neurons function. This has already led to some interesting insights into the development of autism, and more such mysteries are likely to be unraveled over time.
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Sergey Lukavsky
