The Brain’s Balancing Act: Exciting and Inhibiting Neurons

Researchers at the University of California, San Diego School of Medicine have discovered how neurons equalize between excitation and inhibition. Specifically, the scientists have shown that there is a constant ratio (E/I ratio) between the total amount of pro-firing stimulation that a neuron receives from the hundreds or thousands of excitatory neurons that feed into it, and the total amount of red-light stop signaling that it receives from the equally numerous inhibitory neurons. This study, recently described online in Nature, shows that the E/I ratio is constant across multiple neurons in the cortex of mice and likely also humans. In experiments, the scientists also showed how the brain maintains a constant E/I ratio across neurons: The adjustment is carried out by the inhibitory neurons through the appropriate strengthening or weakening of inhibitory synapses. In terms of clinical applications, the scientists said that neurological diseases, such as autism, epilepsy and schizophrenia, are believed  to be a problem, at least in part, of the brain’s ability to maintain an optimal E/I ratio. Scientists have also proposed that some neurodegenerative diseases, such as Parkinson’s and Huntington’s disease, may be associated with a shift in the E/I balance. To learn more about the study, click here.