RESUMEN
People with mild cognitive impairment (MCI) are at an elevated risk of developing Alzheimer's disease or other forms of dementia. Although the neural correlates of successful memory performance in MCI have been widely investigated, the neural mechanisms involved in unsuccessful memory performance remain unknown. The current study examines the differences between patients suffering from stable amnestic MCI with multiple deficit syndromes and healthy elderly controls in relation to the neural correlates of both successful and unsuccessful encoding and recognition. Forty-six subjects (27 controls, 19 MCI) from the HelMA (Helmholtz Alliance for Mental Health in an Aging Society) completed a comprehensive neuropsychological test battery and participated in an fMRI experiment for associative face-name memory. In patients, the areas of frontal, parietal, and temporal cortices were less involved during unsuccessful encoding and recognition. A temporary dysfunction of the top-down control of frontal or parietal (or both) areas is likely to result in a non-selective propagation of task-related information to memory.
RESUMEN
Mild cognitive impairment (MCI) could be an auspicious candidate for an early marker of a beginning dementia. However, although MCI is accepted as a heterogeneous condition by now, performance testing or diagnosis is often based on a limited number of cognitive tests. Furthermore, there is still disagreement about the necessity to include subjective cognitive complaints as a diagnostic criterion. The current study intends to examine the character of MCI when diagnosis is based upon multiple cognitive domains and does not require the presence of subjective complaints. 130 subjects from the HelMA (Helmholtz Alliance for Mental Health in an Ageing Society) longitudinal study completed a comprehensive neuropsychological test-battery and were diagnosed as either normally-ageing controls or patients with MCI. The prevalence rate of MCI was as high as 46.2%, hereby exceeding most estimates of other studies. Patients with MCI performed worse than controls in each of the 29 administered tests with memory being the predominant impaired cognitive domain. Surprisingly, there was no single patient with a purely non-amnestic impairment, considerably contradicting hitherto existing studies. The rather different distribution of impairment and prevalence rate emphasizes the demand of testbatteries including all cognitive domains so that inferences about MCI are as all-encompassing as possible.