Inhibitory neuron functionality is not an immutable property of cortical cells, but a consequence of more complex network dynamics.

The two major types of neuron in the brain’s cerebral cortex are connected by intricate cortical circuits that process information. Excitatory neurons, which comprise 80 percent of all neurons in this region, increase activity in target cells. The other 20 percent of neurons are inhibitory, producing the opposite effect.

Read more: http://newsoffice.mit.edu/2014/picower-neuroscientists-reveal-fundamental-discovery-about-cortical-neurons-1211