Dr Muireann Irish from Neuroscience Research Australia (NeuRA) found that dementia patients who can no longer recall general knowledge – for example, the names of famous people or popular songs – are also unable to imagine themselves in the future.
"We already know that if memory of past events is compromised, as is the case in Alzheimer's disease, then the ability to imagine future scenarios is also impaired,” says Dr Irish.
"We have now discovered that damage to parts of the brain that store knowledge of facts and meanings can also produce the same effect," she says.
Thinking about the future is an important ability because it helps us to plan and anticipate the consequences of our actions.
"For example, a person with dementia who may leave the oven on, partly because they forget the appropriate action, but also because they cannot project forward in time to anticipate the dangerous consequences this might have," says Dr Irish.
Dr Irish and colleagues used MRI to study people with Alzheimer's disease (memories of past experiences are lost) as well as patients with semantic dementia who have lost the ability to remember facts (semantic memory) but have little problem remembering past experiences.
Surprisingly, she found that the semantic dementia group was as impaired as the Alzheimer's group when imagining future events, even though their memory of past experiences was relatively intact.
"This is an important finding, as it points to multiple regions in the brain that are responsible for our ability to imagine and plan for the future," she says.
This research is published in the journal Brain.