## 4 Discussion  
The purpose of this study was to explore the effectiveness of ANNs to identify an MCI diagnosis associated with depression. According to our results, the ANN allowed distinguishing between MCI patients with and without depression with an accuracy of 86% (sensitivity = 82%, specificity = 89%, AUC = 0.95). Those results were based on the application, for the first time, of ANNs to identify an MCI subtype associated with depression. Therefore, it is difficult to compare our results with previous studies. A similar study [16], although it used an inverse approach, tried to discriminate between LLD patients who were diagnosed with MCI or dementia using a random forest classifier and neuroimaging biomarkers. The authors predicted MCI and dementia diagnoses in LLD patients with an accuracy of 81% (sensitivity = 75% and specificity = 86%). We reached a superior classification performance in our study. Sensitivity and specificity results demonstrated that ANNs performed better in identifying MCI patients non-associated with depression than in MCI patients associated with depression. The reason that might explain these results was the heterogeneity in the depression group, where there could be patients with LLD and, theoretically, the depression would be one more symptom of vascular damage and there could be patients who had cognitive impairment and depression but due to a different profile or cause. The group with depression had a higher variability due to the symptom spectrum of cognitive impairments. This study highlights the value of neuropsychological data, a relatively inexpensive and non-invasive technique required for diagnosis purposes whose predictive power has not been fully exploited, as it has been addressed mostly by classical statistical methods. From a cognitive point of view, the results showed a below-average performance in memory tasks in both groups, worse in those patients without depression. Performance improved slightly with the use of cues in depressed patients. Other studies [41; 42] found a similar memory profile in patients with depression, characterized by difficulties in the recovery processes that were more influenced by executive functions such as free recall, as opposed to other recovery processes using cues and recognition. The fact that patients with depression score better in memory tests supports the idea that, in the group of patients complaining of memory problems and who are not depressed, there are more patients in a prodromal phase of [PERSON]'s disease and that, in the group of patients with cognitive impairment and depression, there are more patients with a small vessel disease as the origin (that disease affects the executive functions more than memory, because it affects connection areas and frontal lobes more than structures such as the hippocampus, which are affected early in [PERSON]'s disease). In addition, a worse performance was found in the Rey complex figure for patients with depression. This test evaluates visuo-constructional praxis, but also executive functions. A recent study [43] shows that patients with vascular MCI scored worse than patients with MCI associated with a degenerative cause. Although this study did not consider a qualitative evaluation, the quantitative assessment showed a deficit that could be the cause of this executive dysfunction, since patients with depression did show a very similar or even better performance in the copy of the figure than in memory (the patients with depression did show a worse performance in the copy of the figure). On the contrary, the group without depression performed worse in memory tasks than in the copy. This would be in favor of an equally dysevecutive profile of these patients as it appears in the literature. In the specifically frontal test, the FAB, patients with depression obtained an average affectation of two standard deviations below their normative group.