Retrospective episodic memory is the memory of moments from the past. It is frequently used in studies of Alzheimer patients and testing their dementia. A study by Livner et al. (2009) compared the effect of the disease on both prospective and retrospective memory. In this case the episodic memory being tested was the ability to remember the testing instructions. To test retrospective memory participants were presented with a list of nouns that had been divided into four categories. The results of retrospective memory were divided into three sections: number of categories, number of items remembered and forgetting ratio, in order to look at the three separate process in creating memory (encoding, retrieval, storage). Using their results and knowledge of episodic memory the researchers were able to find a pattern of functional impairments in the brain.