[Specificity of visual evoked potential alterations in Alzheimer's disease]

We have studied visual evoked potentials (VEP) in four groups: healthy young and aged subjects and aged patients suffering from depression or Alzheimer's disease (AD). In the flash modality, peak IV delay in AD patients as compared to aged controls corresponded to lengthened III-IV interlatency (IL). When AD and depressed patients were compared, peak IV delay in the former did not reach significance. Normal aging resulted in delayed peaks II and III, without IL modification. In the pattern reversal modality, no difference was observed between AD patients and aged, healthy or depressed controls. Aging delayed peaks P50 to P180. The abnormality exhibited by AD patients was specific to this group. However, the lack of significant difference between AD and depressed groups argues against the ability of VEP to differentiate those conditions.