Which statement best describes Korsakoff syndrome?

Korsakoff syndrome is primarily characterized by an inability to form new memories, which stems from thiamine (vitamin B1) deficiency often associated with chronic alcohol abuse and other nutritional deficiencies. This syndrome affects the brain's ability to encode new information, leading to profound anterograde amnesia, which means individuals struggle to learn and retain new information after the onset of the disorder. Additionally, those with Korsakoff syndrome may experience confabulation, where they fill in gaps in their memory with fabricated stories, often unaware that these stories are not true.

The other statements do not accurately capture the defining aspects of Korsakoff syndrome. While memory loss related to traumatic experiences aligns more closely with post-traumatic stress disorder, vivid dream recollections are not specifically tied to this syndrome but might be more relevant to sleep disorders or REM sleep phenomena. The development of dissociative identity disorder is a separate mental health condition that does not pertain to the memory impairments specifically associated with Korsakoff syndrome. Thus, the inability to learn new information is the most fitting description of this disorder, highlighting its profound impact on memory function.