The STS-90 mission, known as Neurolab, sees Space Shuttle Columbia transformed into an orbiting laboratory for neurosciences. The EEG (electroencephalogram) waves emanating from the Shuttle represent the experiments conducted during the mission. There are four waves: one for each of the payload crew members who carried out the experiments. The constellation Ophiucus ("The Serpent Bearer"), associated with Asclepius, the Greek god of medicine, appears in the upper right side of the patch.
The caduceus on the left is the international emblem of physicians. The traditional wings of the emblem have been modified to aviation "flight wings", symbolizing Dave Williams' combined experience as medical doctor, neurophysiologist and Mission Specialist.
The nine stars in the constellation represent the nine crew members who have trained for STS-90. A graphic illustration of a neuron stretches over the Earth below, representing the application of Neurolab's research to terrestrial neurosciences.