Brain and Mind

, Volume 1, Issue 1, pp 7-23

First online:

Why is Brain Size so Important:Design Problems and Solutions as Neocortex Gets Biggeror Smaller

  • Jon H. KaasAffiliated withDepartment of Psychology, Vanderbilt University

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As bridges or brains become bigger or smaller, the changes pose problems of design thatneed to be solved. Larger brains could have larger or more neurons, or both. With largerneurons, it becomes difficult to maintain conduction times over longer axons andelectrical cable properties over longer dendrites. With more neurons, it becomes difficultfor each neuron to maintain its proportion of connections with other neurons. Theseproblems are addressed by making brains more modular, thereby reducing the lengths ofmany connections, and by altering functions. Smaller brains may not have enoughneurons for all circuits, and they may lose modules and functions. Mammals with moreneocortex tend to have more cortical areas and more columns and types of columnswithin the larger areas.

area axon column evolution module neuron scaling