Physics has misled neuroscience for over two decades
Statistical physicists attempted to explain the brain’s functionality using Excitation-Inhibition balance similarly to magnetic models, yet the theory was experimentally disproven. A decade later a different group is righting the wrong
video: Statistical physicists attempted to explain the brain’s functionality using Excitation-Inhibition balance similarly to magnetic models, yet the theory was experimentally disproven and now, a decade later a different group of statistical physicists is righting the wrong.
Credit: Prof. Ido Kanter, Bar-Ilan University
How the brain works is a question that has intrigued scientists for centuries, raising multiple hypotheses and theories. In 1996, statistical physicists attempted to explain how the brain uses a combination of excitatory and inhibitory connections to reach a balanced network similarly to magnetic models.
This theory prevailed in the neuroscientific community for decades, until research in 2015, led by Prof. Ido Kanter (a statistical physicist himself) from Bar-Ilan University’s Gonda (Goldschmied) Multidisciplinary Brain Research Center, experimentally disproved this popular, well-received theory of excitation-inhibition neural network balance. The experiment, which consisted of blocking inhibitory synapses, showed that low firing rates are still achieved with solely excitatory synapses. This finding clearly contradicted the excitation-inhibition balance hypothesis and raised the question once more how balance is achieved in neural network activity.
This discovery spurred a decade of intensive research, in which further in-vivo experimental support, as well as emulations and simulations of neural networks, led to the discovery of simple neuronal mechanisms which enable low firing rate of brain activity. “One can think of it as a network of water pipes, where a small fraction of the connectors among the pipes are very thin, which dictate the overall water flow for the entire network”, said Prof. Kanter. “The connectors represent neurons which rarely fire, thereby lowering the firing rate for the entire network.”
This phenomenon of neuronal plasticity was found in advanced experiments to be anisotropic, depending on the directionality of the arriving signal, independent of the holding membrane potential, and found to be a source of fast dendritic learning.
This is an example where a theory from statistical physics misled neuroscience for a few decades, all while a simple experiment could have easily disproved it. Adaptation of physical concepts into biology needs to be done carefully, with experimental support.
Video: Physics has misled neuroscience for over two decades