There is an “ideal” brain circuit size suited to carrying out particular tasks, a study has found.Researchers from the University of Cambridge in the UK found increasing the size of neural circuits in the brain can boost learning performance.However, this increased connectivity also has the potential to impede learning, they said.
Published in the journal PNAS, the study looked at how neural circuits can use additional connectivity to achieve faster and more precise learning.It showed that adding redundant neurons and synaptic connections, that enable information to flow from one neuron to another, to a network on one hand can make tasks easier to learn with increased connectivity.
Due to inherent noisiness in signal-carrying connections, increased connectivity will eventually hinder both learning and task performance once a circuit exceeds a certain size.The findings suggest a new potential reason why excessive numbers of noisy connections can lead to learning disorders that are associated with brain hyperconnectivity, including some developmental forms of autism.
“However, we found that, if each new pathway adds ‘noise’ to the signal it transmits, the overall gain in learning performance will eventually be lost as a circuit increases in size,” said Timothy O’Leary, lecturer at Cambridge, who led the study. Adding neurons and connections to a brain can help learning — up to a point. After that, an increase in size could actually impair learning, they said.