Event-related brain potentials to Memory Workload and 'Analytical-Specific Perception' (Mangina-test) in patients with early Alzheimer's Disease and in normal controls.

Our previous research with intra-cerebral event-related potentials in conjunction with an original Memory Workload Paradigm has shown that significant load effects for the N4 latency were found only for both amygdalae and the left posterior hippocampus as well as for both anterior neo-cortical regions of the temporal gyri. These same structures are also affected in Alzheimer's Disease. Therefore, based on our previous intra-cerebral findings, our present research was to use our novel Memory Workload Paradigm in conjunction with surface ERPs as neurophysiological markers to tap cerebral regions and functions involved in memory disorders pertaining to early Alzheimer's Disease as opposed to normal memory processes in age-matched normal control subjects. Moreover, the Mangina-Test which measures varying degrees of 'Analytical-Specific Visual Perception' was individually administered to all patients and controls in separate sessions. Results indicate that for the early Alzheimer's Disease group, a significant main effect for memory load was found for the P400 amplitude (F(3,30)=4.52, P<0.02) which was absent in the normal group. In particular, the P400 amplitude was significantly higher on posterior head regions for patients with early Alzheimer's Disease as opposed to age-matched normal subjects (F(7,140)=3.54, P<0.03) which distinguished both groups (F(1,20)=6. 13, P<0.03). For the P400 latency, a significant memory load effect was present only for the normal group (F(3,30)=11.26, P<0.01). The Mangina-Test performance clearly differentiated both groups (F(1, 19)=105.85, P<0.001). The present data provide the first valuable evidence that ERPs to our novel Memory Workload Paradigm are sensitive neurophysiological diagnostic markers which delineate the early clinical brain irregularities underlying early Alzheimer's Disease as opposed to the normal memory processes of age-matched normal subjects. In addition, their use could be valuable for the objective clinical follow-up of therapeutic interventions in early Alzheimer's Disease.