Therapeutic Efficacy of Categorical Language Fluency Smartphone Game Application

Inclusion Criteria: * Aged above 55 * Confirmed literacy * Diagnosed to mild cognitive impairment by International Working Group on Mild Cognitive Impairment and Clinical Dementia Rating(CDR) of 0 or 0.5. * Diagnosed to possible or probable Alzheimer's dementia by NINCDS-ADRDA and Clinical Dementia Rating(CDR) of 1 or below. Exclusion Criteria: * Evidence of delirium, confusion * Any neurological conditions causing cognitive decline such as Parkinson's disease, brain hemorrhage, brain tumor, normal pressure hydrocephalus * Evidence of severe cerebrovascular pathology * History of loss-of-consciousness over 1 hour due to head trauma or repetitive head trauma of mild severity * History of substance abuse or dependence such as alcohol * Presence of depressive symptoms that could influence cognitive function * Presence of medical comorbidities that could result in cognitive decline