TMZ said he burst into a UW system board of regents meeting Thursday, shouting and holding up a sign depicting a cat with metal implanted in its head at a UW-Madison lab.
People for the Ethical Treatment of Animals spokesman Jeremy Beckham was arrested with Cromwell, and both were charged with disorderly conduct, TMZ said.
"Today's events are just another attempt by outside activists to draw attention to a cause. They have attacked and distorted this research -- which has very real benefits for people who are deaf -- from every angle imaginable," the director of the UW-Madison Research Animal Resources Center said in a statement.
"Exhaustive independent investigation by the USDA, which regulates the use of animals in research, concluded that PETA's allegations are baseless."