Fig. 3

Progression of neuropathology and cognitive impairment in AD. The earliest AD neuropathology develops in medial temporal lobe and gives rise to episodic memory deficit followed by impairment in semantic memory (preclinical AD). As the patient progresses to MCI stage, higher cognitive domains such as attention, executive function, visuospatial memory, and verbal recall become impaired. Also, general cognition starts to decline. As the patient progresses to mild to moderate AD stages, the neuropathology spreads to frontal and parietal lobes, and all cognitive domains become affected. In severe stage of AD, the neuropathology spreads to involve all brain lobes, and a profound deficit in all cognitive domains is noted