Hippocampal subfield volumes correlate with memory training benefit in subjective memory impairment

Although some older adults experiencing memory problems have been shown to benefit from cognitive training, evidence regarding who will improve from this type of intervention is lacking. Automated hippocampal volumetry might be used to foresee treatment outcomes. We hypothesized that larger hippocampal volumes are associated with greater memory performance changes following training, and that effects are selectively related to specific hippocampal subfields. 19 memory clinic outpatients with subjective memory impairment (mean age=60.9 years) underwent MRI-scanning and then followed an eight week training scheme aimed at improving verbal memory. We assessed verbal memory before and after training, and tested whether pretraining hippocampal volumes were related to memory improvements. To delineate regional specificity, we employed a new technique enabling automated volumetry of seven hippocampal subfields - including the cornu ammonis (CA) sectors and the dentate gyrus (DG). The results showed that larger hippocampal volumes before training were related to greater verbal recall improvements. Subfield volumetry revealed specific correlations between memory improvement and pretraining volumes of the left CA2/3 and CA4/DG. Depressive symptoms further gave a unique contribution in predicting gain of the intervention, independent of hippocampal volume. The results indicated that subjects with a stronger depressive symptom load benefited more from the training. A prediction model including baseline CA2/3-volume and depressive symptoms explained 42% of the variation in recall improvement. Our results are the first to suggest that hippocampal subfield volumetry is related to intervention outcomes in older adults experiencing memory problems. Also, previous studies have tended to exclude patients with concomitant depressive symptoms and memory complaints. The present results, however, strengthen the rationale and potential for cognitive intervention in these patients.