Chronic alcoholism often leads to a thiamine (vitamin B1) deficiency in the brain, causing Korsakoff's syndrome, a neurological disorder which is generally preceded by an acute neurological condition known as Wernicke's encephalopathy (WE). The memory impairment that is pathognomonic to Korsakoff's syndrome predominantly affects the declarative memory, leaving non-declarative memory that is often procedural in nature relatively intact.[7] The disproportionate severity in anterograde episodic memory processes in contrast to other cognitive processes is what differentiates Korsakoff syndrome from other conditions such as alcohol-related dementia. Evidence for the preservation of certain memory processes in the presence of severe anterograde episodic memory serve as experimental paradigm to investigate the components of human memory.