Mild neurocognitive disorder is best defined as a condition in which there is a modest decline in cognitive functioning from previous levels a disease that can cause dementia and that involves the degeneration of neurons in the subcortical structures that control motor movements a relatively rare degenerative disease that affects the frontal and temporal lobes of the cerebral cortex a hereditary condition causing dementia that involves a widespread deterioration of the subcortical brain structures and parts of the frontal cortex that control motor movements