It was supposed to be a talk about brain science – a chance for Newt Gingrich to show off his capacity for Big Ideas and his grasp of complicated policy issues.

Instead, the new Republican frontrunner found himself outsmarted and mike-checked by a small group of Occupy protesters who infiltrated the talk at a University of Iowa medical school building.

"Mike-check, mike-check. Mr Gingrich we are here to protest your speech today," the protesters chanted as the Republican candidate launched into his speech.

A bemused Gingrich was forced to watch from the podium of the packed 250-seat hall as a group of about a dozen protesters read off a list of complaints.

He was accused of a callous and arrogant attitude towards the poor, demonising welfare mothers during his time as house speaker in the 1990s, and of supporting the return of child labour in recent remarks.

Two protesters were escorted from the room, and Gingrich went on with his speech to cheers from the hall.

"I appreciate the fact that 95% of you – maybe even 99% of you – wanted to actually have an intelligent discussions and are not going to be drowned out by the 1% who imposed their will by making noise," Gingrich said.

He went on to sketch out his plan for a large scale research project into the workings of the brain. He said the results – in terms of improved diagnosis and treatment for diseases such as Alzheimer's – would help cut health care costs boost economic growth.

Gingrich told a press conference later that he wanted to inject some bold ideas into the campaign.

But he was not entirely off the hook. After remarks that veered from space science to FDR to obesity and the iron lung treatment for polio, the last questioner told Gingrich the only expertise he could reasonably claim was in cheating on his wife. "You talk about money not being everything but you have taken plenty of short cuts to get your millions publishing your books and marketing them," the protester said. "It seems like you have a PhD in cheating on your wife."