Increasing the size of neural circuits in the brain can boost learning performance, but this increased connectivity also has the potential to impede learning, new research has revealed.

Cambridge neuroscientists predict that there is an “ideal” brain circuit size suited to carrying out particular tasks. The study, published in the journal PNAS, looked at how neural circuits can use additional connectivity to achieve faster and more precise learning.

The research showed that adding apparently “redundant” neurons (cells that make your brain work) and synaptic connections (that enable information to flow from one neuron to another) to a network is, in fact, a double-edged sword. On the one hand an increase in connectivity can make a task easier to learn. On the other hand, 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. These 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.

Dr. Timothy O’Leary, Lecturer in Information Engineering and Medical Neuroscience, who led the study, said: “Our research shows that adding ‘spare’ or redundant connections to brain circuits can, in fact, boost learning performance. These additional connections—which don’t appear strictly necessary for brain function—can make a new task easier to learn.

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