Brain disease robbed five British men of their ability to remember by inflicting permanent damage on their hippocampus--a pair of brain regions in the limbic system associated with memory and navigation. But it also robbed them of the ability to imagine the future, according to a new study published online January 15 in Proceedings of the National Academy of Sciences.

Neuroscientist Eleanor Maguire of University College London and her colleagues compared the imaginations of the aforementioned amnesiacs with 10 control subjects who had healthy hippocampi. They asked each of them to imagine and describe a range of commonplace scenarios, such as a visit to a museum. The healthy men were able to describe everything from the exhibits hanging on the walls to the musty smell of the old building. The amnesiacs told a different story:

"There's big doors," one said. "The openings would be high, so the doors would be very big with brass handles; the ceilings would be made of glass, so there's plenty of light coming through. Huge room, exit on either side of the room; there's a pathway and map through the center and on either side there'd be exhibits." He paused. "I don't know what they are … There'd be people." He paused again. "To be honest, there's not a lot coming."

"Do you hear or smell anything?" the researcher asked.

"No, it's not very real," he replied. "It's just not happening. My imagination isn't … well, I'm not imagining it, let's put it that way. Normally you can picture it, can't you? I'm not picturing anything at the moment."

Across the board the amnesiacs produced fewer details; even when one of them--who retained some function in one of his hippocampi--was given pictures, sounds and smells to help with the task, he could not provide a richer description. "It seems that not only do they have a deficit in recollecting the past, they also have a deficit in imagining the future, so they really are stuck in the present," Maguire says. "The details are not being hung together in the correct way, because it lacks a spatial backdrop."

The amnesiacs, as the above example shows, were aware of this deficit but could do nothing to rectify it. "They felt like they weren't seeing it correctly or seeing it as a whole," Maguire says. The research marks the first time an inability to remember the past has been linked to a deficit in imagining the future.

This points to a larger role for the hippocampus than simply creating memory and strengthens the case for the role of memory as a gauge for what will come. "The actual function of memory is maybe to help us plan for the future and work through various scenarios," Maguire notes. "Now we are working on what other sorts of tasks might use the processes we've uncovered here that might not have much to do with memory."