Sander Daselaar from the Free University of Amsterdam made scans of the activity in various brain areas. These showed differences between elderly persons with a good memory and elderly persons with a poor memory. The research revealed that a normal deterioration of the memory in the elderly is related to a less effective storage of data.
During his research Daselaar administered various memory tasks to both young participants and healthy elderly persons who lived independently. The study subjects were placed in an MRI scanner that not only made standard brain scans but also scans which showed the quantity of oxygen in different parts of the brain. Active areas of the brain use more oxygen and so the scan could be used to determine which areas of the brain were active during the performance of a certain task. The technique is called functional MRI.
One of the study subjects' tasks was to assess a word list and to state whether the words evoked pleasant or unpleasant associations. The participants' recall of these words was then unexpectedly tested. Elderly persons with a clearly poorer memory performance during the unexpected test exhibited less activity in the mediotemporal lobe during the assessment task. The mediotemporal lobe is an area of the brain already known to be involved in the memory process.
On standard MRI scans, no difference in the shape of this area of the brain was observed between elderly persons with a good memory and those with a poor memory. Functional MRI was found to be much more sensitive in visualising small functional changes in the brain.
In Alzheimer's disease, the functioning of the mediotemporal lobe also deteriorates. At present dementia can only be diagnosed at an advanced stage of the disease. Normal MRI scans then show a clearly smaller mediotemporal lobe. In the future it might be possible to use functional MRI to differentiate normal memory problems from the initial stages of dementia.
For further information please contact Dr Sander Daselaar (Faculty of Medicine, Free University of Amsterdam, now working at Center for Cognitive Neuroscience, Duke University, United States), e-mail: daselaar@duke.edu. The doctoral thesis was defended on 12 March 2003. Dr Daselaar's supervisors were Prof. C. Jonker and Prof. J.G.W. Raaijmakers.
Image at www.nwo.nl/news.
Brain scans of three different categories of study subject. The cross indicates the position of the mediotemporal lobe. Young people and 'good' elderly people have a clearly more active mediotemporal lobe than 'bad' elderly persons.