Tion Cube Analysis doi:10.1371/journal.pone.0068398.t003 19.50 (0.70) 18.95 (1.31) 19.31 (5.02) 15.68 (2.76) 11.27 (2.72) 9.70 (0.67) 19.23 (1.03) 8.64 (1.70) 8.86 (1.52)Mild AD Patients Mean (SD) 18.90 (1.33) 16.58 (4.06) 12.10 (4.55) 12.52 (3.47) 14.45 (2.84) 9.48 (0.96) 18.61 (1.73) 6.68 (2.64) 6.55 (2.85)Mann- Whitney p-value 0.052 0.004 ,0.001 ,0.001 ,0.001 0.252 0.120 ,0.001 ,0.Visuospatial Function in Early Alzheimer’s DiseaseTable 4. ROC curve analysis for VOSP subtests.AUC (95 CI) Incomplete Letters Silhouettes Object Decision ML 264 Progressive Silhouettes Number Location Cube Analysis *p,0.01. doi:10.1371/journal.pone.0068398.t004 0.689* (0.566?.812) 0.859* (0.771?.947) 0.755* (0.648?.863) 0.785*(0.679?.891) 0.737* (0.622?.852) 0.736* (0.614?.859)Cut-off scores 18 16 15 14 93PO sensitivity 88 76 66 71 63 75Specificity 42 83 68 77 74 68According to the results, most of the subtests of the VOSP battery effectively differentiated the patients with mild AD from the controls; therefore, we suggest that AD patients visuospatial function is impaired even in the early stages of the disease. This finding corroborates previous studies, noted by Paxton et al. [36], stating that early-stage AD patients often have compromised abilities to draw or copy images and to recognize objects visually in addition to compromised perceptual organization and space perception [13,37,38]. However, this finding has been refuted by other studies, which showed impairment of visuospatial functions not in early-stage AD but only in more advanced stages of the disease [17,21]. It is important to note that the screening test showed sensitivity in discriminating between groups, showing a difference between groups that was close to statistically significant. This finding is important because it shows that in this study we were able to discriminate healthy elderly from AD patients using the Screening test, implying it is a good screening test to aid in diagnosis. In this study, we observed that some of the subtests of this battery are even more sensible to the initial impairment of visuospatial function in AD, such as the Silhouettes, the Progressive Silhouettes, and the Cube Analysis. Therefore, we recommend the use of these subtests, if the battery cannot be used in its full version. About the subtests, the results of this study also show that in all tests that evaluated object perception, there was a significant difference between the AD patients and controls. Moreover, this difference was observed in two space perception tests. These Table 5. Correlations of the VOSP subtests.variations in the results concerning the perception of objects and space may be related to the fact that distinct neural circuits are responsible for each kind of perception. Visual information is 22948146 divided into two pathways: the occipito-parietal (dorsal) and the occipito-temporal (ventral). The dorsal pathway processes the information of space (“where”) and controls and guides motor activities, whereas the ventral pathway deals with object recognition and perceptual judgment (“what”) [10,11,12,16,39]. According to this, a study that examined two groups of patients with AD, one with and one without visuospatial difficulties, using positron emission tomography (PET) found that the two groups had reduced cerebral metabolism in the parietal and the medial and superior temporal regions compared with controls. However, patients with visuospatial symptoms showed even greater metabolic deficits.Tion Cube Analysis doi:10.1371/journal.pone.0068398.t003 19.50 (0.70) 18.95 (1.31) 19.31 (5.02) 15.68 (2.76) 11.27 (2.72) 9.70 (0.67) 19.23 (1.03) 8.64 (1.70) 8.86 (1.52)Mild AD Patients Mean (SD) 18.90 (1.33) 16.58 (4.06) 12.10 (4.55) 12.52 (3.47) 14.45 (2.84) 9.48 (0.96) 18.61 (1.73) 6.68 (2.64) 6.55 (2.85)Mann- Whitney p-value 0.052 0.004 ,0.001 ,0.001 ,0.001 0.252 0.120 ,0.001 ,0.Visuospatial Function in Early Alzheimer’s DiseaseTable 4. ROC curve analysis for VOSP subtests.AUC (95 CI) Incomplete Letters Silhouettes Object Decision Progressive Silhouettes Number Location Cube Analysis *p,0.01. doi:10.1371/journal.pone.0068398.t004 0.689* (0.566?.812) 0.859* (0.771?.947) 0.755* (0.648?.863) 0.785*(0.679?.891) 0.737* (0.622?.852) 0.736* (0.614?.859)Cut-off scores 18 16 15 14 9Sensitivity 88 76 66 71 63 75Specificity 42 83 68 77 74 68According to the results, most of the subtests of the VOSP battery effectively differentiated the patients with mild AD from the controls; therefore, we suggest that AD patients visuospatial function is impaired even in the early stages of the disease. This finding corroborates previous studies, noted by Paxton et al. [36], stating that early-stage AD patients often have compromised abilities to draw or copy images and to recognize objects visually in addition to compromised perceptual organization and space perception [13,37,38]. However, this finding has been refuted by other studies, which showed impairment of visuospatial functions not in early-stage AD but only in more advanced stages of the disease [17,21]. It is important to note that the screening test showed sensitivity in discriminating between groups, showing a difference between groups that was close to statistically significant. This finding is important because it shows that in this study we were able to discriminate healthy elderly from AD patients using the Screening test, implying it is a good screening test to aid in diagnosis. In this study, we observed that some of the subtests of this battery are even more sensible to the initial impairment of visuospatial function in AD, such as the Silhouettes, the Progressive Silhouettes, and the Cube Analysis. Therefore, we recommend the use of these subtests, if the battery cannot be used in its full version. About the subtests, the results of this study also show that in all tests that evaluated object perception, there was a significant difference between the AD patients and controls. Moreover, this difference was observed in two space perception tests. These Table 5. Correlations of the VOSP subtests.variations in the results concerning the perception of objects and space may be related to the fact that distinct neural circuits are responsible for each kind of perception. Visual information is 22948146 divided into two pathways: the occipito-parietal (dorsal) and the occipito-temporal (ventral). The dorsal pathway processes the information of space (“where”) and controls and guides motor activities, whereas the ventral pathway deals with object recognition and perceptual judgment (“what”) [10,11,12,16,39]. According to this, a study that examined two groups of patients with AD, one with and one without visuospatial difficulties, using positron emission tomography (PET) found that the two groups had reduced cerebral metabolism in the parietal and the medial and superior temporal regions compared with controls. However, patients with visuospatial symptoms showed even greater metabolic deficits.
