New evidence for innate knowledge
Neuron connexions © Blue Brain EPFL
Do we have innate knowledge? Neuroscientists working on Blue Brain Project at EPFL (Ecole Polytechnique Fédérale de Lausanne) are finding proof that this is the case. They’ve discovered that neurons make connections independently of a subject’s experience. Their results have been published in an article in the Proceedings of the National Academy of Sciences (PNAS).
We have known for a long time that neuronal circuits become established and get reinforced via experience – it’s a phenomenon known as “synaptic plasticity.” For example, this is how memories become anchored in the brain. The team working on the Blue Brain Project at EPFL, led by Professor Henry Markram, however, is offering radically new evidence that this may not be the whole story. The researchers were able to demonstrate that small clusters of pyramidal neurons in the neocortex interconnect according to a set of immutable and relatively simple rules. They published their discovery in an article that appeared in the last issue of the Proceedings of the National Academy of Sciences.
These clusters contain an estimated fifty neurons, on average. The scientists look at them as essential building blocks, which contain in themselves a kind of fundamental, innate knowledge – for example, representations of certain simple workings of the physical world. Acquired knowledge, such as memory, would involve combining these elementary building blocks at a higher level of the system. “This could explain why we all share similar perceptions of physical reality, while our memories reflect our individual experience”, explains Markram.
The principle determining the formation of these microcircuits is astonishingly simple. Basically, when two neurons are each connected to the same neighboring neuron, the probability that they are also interconnected is greater than average. The researchers were able to build a statistical model based on this observation.
When the scientists tested in vitro neuronal circuits from different rats, they all presented very similar characteristics. If the circuits had only been formed from the experiences lived by the different animals, the values should have diverged considerably from one individual to the next. Thus, the neuronal connectivity must in some way have been programmed in advance.
"Since John Lock, about 400 years ago, research into how the brain learns and remembers has been guided by the belief that we start from a clean slate and then print memories with each new experience. The idea that memory is like building lego with fundamental building blocks of knowledge opens up an entirely new door for research", explains Markram.
Current technology is now allowing us to qualify the “tabula rasa” hypothesis, which argues that our brains are a “blank slate” at birth, and we only gain knowledge through experience. It’s an idea that has permeated science for centuries. There is no question that knowledge, in the sense that we typically understand it (reading and writing, recognizing our friends, learning a language), is the result of our experiences. But the EPFL team’s work demonstrates that some of our fundamental representations or basic knowledge is inscribed in our genes. This discovery redistributes the balance between innate and acquired, and represents a considerable advance in our understanding of how the brain works.