After several more stages, yellow plaques may begin appearing on some axons between neurons. A plaque blocks access to the axon and thereby the attached neuron. The quantity of these plaques will increase as the stages are completed.

Shields On 

To get through a plaque, you must burned it out by pressing the shields button and then crossing the affected axon. Once burned out, plaques will not return even if the nanobot is reversed or destroyed and reinjected. But remember - every use of the shields costs you points! Shields only last a few seconds before their charge runs out and they must be re-engaged (if needed).