**4. Conclusion**

52 Neuroimaging for Clinicians – Combining Research and Practice

and then compare it with the second angle to make a judgment. The working memory contributed to the performance of the somatosensory discrimination (Bodegård et al., 2001; Kitada et al., 2006). Therefore, the present study suggests that the impaired working memory of MCI and AD patients is one factor that contributes to the decline of angle

Moreover, we found that the mean accuracy of AD patients was significantly lower than the accuracy of the MCI and NC groups, and the mean threshold of AD patients was also reduced compared to the other two groups. Specifically, the mean threshold of AD patients was almost double the threshold of the MCI patients. However, we also found that there was a significant difference in the mean threshold between the MCI patients and the NC group, whereas the mean accuracy of the MCI patients and the NC group remained unchanged. There are two possible reasons to explain this phenomenon. First, AD is a neurodegenerative brain disease. Unlike patients with MCI, AD patients have more severe working memory impairments (Blatow et al., 2005). Second, the isolated memory impairment found in patients with MCI is more severe than the impairment observed in healthy aging individuals, whereas other cognitive functions remain normal. In contrast, AD patients have further deficits in spatial learning and memory and planning and problem solving (Kalman et al., 1995; Förstl & Kurz, 1999). These profound cognitive impairments of AD patients may explain the more severe deficits in angle discrimination found in patients

In addition, the tactile spatial discrimination procedure activates a diverse cerebral network (Bodegård et al., 2001; Kitada et al., 2006; Wu et al., 2010). The results from these neuroimaging studies also support our findings. For example, the intraparietal sulcus (located on the lateral surface of the parietal lobe) is engaged in multisensory spatial processing during the classification of grating and shape, and it has been shown that the intraparietal sulcus is a high-class area for computations and elaborates shape reconstructions (Bodegård et al., 2001). Neuroimaging studies (Delbeuck et al., 2003; Dickerson & Sperling, 2009; Huang et al., 2010) have demonstrated that abnormalities in the frontal, temporal, and parietal cortices contribute to the functional deficits in AD patients. Consequently, our results suggest that both the impairment of working memory and spatial discrimination of AD patients contribute to the lowest angle that is discernible compared to

The MMSE is a brief mental status examination designed to quantify the cognitive status in adults (Folstein et al., 1975). Recently, MMSE has been commonly used to test for complaints of memory problems or when a diagnosis of dementia is being considered. We plotted the ROC curves for the angle discrimination accuracy and MMSE score. We found that used the angle discrimination accuracy was better anbe to differentiate the MCI patients from older individuals than the MMSE score because the MMSE also has limitations. For example, previous studies (Anthony et al., 1982; Galasko et al., 1990) have suggested that the sensitivity of the MMSE has been rated at approximately 80%. Thus, the MMSE score may not represent the cognitive function deficits of all individuals. In contrast, we specifically focused on the difference in tactile angle discrimination in MCI and AD patients compared to the NC group. Although the present angle discrimination experiment examined working memory, spatial discrimination and problem-solving processes, there were limitations to this study. Despite these limitations, we have found a significant decline in tactile angle

discrimination performance.

the MCI patients and the NC group.

with AD.

Audiovisual spatial and temporal orienting attention studies were examined in our study to further our understanding of neuroimaging studies for early detection of dementia. By using another method to compare the cognitive ability of tactile angle discrimination, we initially found that at the early stages of Alzheimer's disease, the behavioural cognition was decreased. These basic data that obtained from our studies, we consider that they are able to apply for a clinical diagnosis method of dementia early detection after enough confirm experiments.
