Serial-position effect as a biomarker in the diferential diagnosis of mild cognitive impairment. A multimodal biomarkers aproach. (P3.1-018)

Abstract

Objective: To study the serial-position effect in a hippocampal disease as early stages of Alzheimer’s disease.

Background: The serial-position effect, present in the learning of lists of words, is divided in primacy (PE) and a recency effect (RE), which consists of better recall of first and last elements respectively. Its study has provided insight into the memory system functioning.

Design/Methods: Observational study with 168 subjects. Classified according to cognitive performance into mild amnestic cognitive impairment (aMCI) and cognitively normal (NC) and classified by their Alzheimer biomarkers profile (NCBk− = 31, NCBk + = 21, aMCIBk-=45 and aMCIBk + = 71). All subjects were studied with MRI, and voxel-based morphometry was performed to evaluate hippocampal volume. The Rey Auditory Verbal Learning Test (RAVLT) performance and serial position effect on learning and delayed memory were registered.

Results: aMCI showed deficit in total learning and delayed recall compared with controls; the was no difference between biomarker profiles. In the first trial, the PE between CNBk− was significantly higher (p=0.03) compared with aMCIBk− and aMCIBk+. In total delayed recall there were non-significant differences between aMCI groups, but RE of delayed recall, showed a significantly better performance of aMCIBk− against aMCIBk+(p=0.028).

RE in Trial6 and delayed recall correlated with T-tau levels (r2= −0.39, p= 0.01 and r2= −0.26 p= 0.027, respectively). Levels of Ab42, hippocampal volume and cortical thickness of the parahippocampal regions did not correlate with any of the effects.

Conclusions: These results show that serial-position effect in the delayed recall is a measure superior to the conventional test scores for the detection of positive biomarkers in aMCI. This effect correlates with the increase in Tau-T in CSF but not with hippocampal volume. This finding suggests serial position effect could be a biomarker of neurodegeneration earlier than MRI.