An active neuron (illustrative).
(photo credit: INGIMAGE)
Bar-Ilan University physicists have disproved a century-old assumption regarding neurons and brain activity. Using new types of experiments on neuronal cultures, a group of BIU scientists led by Prof. Ido Kanter has demonstrated this error and suggested that their discovery could impact research into the origin of degenerative diseases.
Neurons are the basic computational building blocks that compose the brain. Their number is approximately one tera (trillion), similar to tera-bits in midsize hard discs. According to the neuronal computational scheme, which has been used for over 100 years, each neuron functions as a centralized excitable element. The neuron accumulates its incoming electrical signals from connecting neurons through several terminals, and generates a short electrical pulse known as a spike when its threshold is reached.
In an article just published in the journal Scientific Reports, the researchers go against conventional wisdom to show that each neuron functions as a collection of excitable elements, where each excitable element is sensitive to the directionality of the origin of the input signal. Two weak inputs from different directions (such as “left” and “right”) will not sum up to generate a spike, while a strong input from “left” will generate a different spike waveform than that from the “right.”
The new realization for the computational scheme of a neuron calls into question the spike sorting technique that is at the center of activity of hundreds of labs and thousands of scientific studies in neuroscience. This method was mainly invented to overcome the technological barrier to measure the activity from many neurons simultaneously, using the assumption that each neuron tends to fire spikes of a particular waveform which serves as its own electrical signature.
However, this assumption, which resulted from enormous scientific efforts and resources, is now questioned by the work of Kanter’s lab. “We reached this conclusion using a new experimental setup, but in principle these results could have been discovered using technology that has existed since the 1980s. The belief that has been rooted in the scientific world for 100 years resulted in this delay of several decades,” said Kanter and his team of researchers, including Shira Sardi, Roni Vardi, Anton Sheinin and Amir Goldental.