How Dementia Disrupts Memory Formation
Memory formation is like building a new house in your brain. It starts when you experience something new, like meeting a friend or learning a recipe. Your brain takes that information, processes it, and stores it for later use. This happens mainly in a part of the brain called the hippocampus, which acts as the main workshop for creating fresh memories.[5] In dementia, this process gets broken, making it hard for people to hold onto new information.
Dementia is not just one problem. It is a group of conditions that harm brain cells over time. The most common type is Alzheimer’s disease. In Alzheimer’s, harmful proteins build up in the brain. These proteins damage and kill cells, especially in the hippocampus.[2][5] As a result, the hippocampus shrinks. This shrinkage stops the brain from forming new memories properly.[3] People might forget what they ate for breakfast but remember events from years ago.
The trouble often starts small. Early signs include forgetting recent events or facts just learned. Someone might repeat the same question because they cannot keep track of the answer.[2][6] This is because short-term memory, which feeds into long-term storage, fails first. The brain struggles to move new details from a temporary spot to a permanent one. Over time, even older memories fade as the damage spreads.[2]
Different types of dementia hit memory in slightly different ways. In Alzheimer’s, new learning is hit hardest at first. People lose the ability to pick up facts or events right away.[2] Vascular dementia, caused by poor blood flow to the brain, can also block memory formation by starving brain cells of oxygen.[1] Another type called LATE makes the hippocampus shrink even more than in Alzheimer’s, leading to strong memory issues with fewer other problems like mood changes.[3]
Why does this happen? Brain cells need to connect and talk to each other to form memories. In dementia, those connections break down. The hippocampus cannot team up with other areas to lock in details. For example, emotional events might stick better at first because the brain prioritizes them. But even that fades as the disease grows.[4] People may feel a vague sense that something is familiar but cannot recall the details, leading to mix-ups.[4]
Daily life changes a lot. Simple tasks like following a conversation or planning a meal become tough. The person might not remember words or steps needed to do things they once knew well.[1][6] This is not just forgetting. It is the brain’s memory factory shutting down, piece by piece.
Sources
https://int.livhospital.com/amnesia-vs-dementia-the-critical-differences/
https://en.wikipedia.org/wiki/Alzheimer’s_disease
https://www.sanjuandailystar.com/post/a-different-type-of-dementia-is-changing-what-s-known-about-cognitive-decline
https://www.psypost.org/listening-to-music-immediately-after-learning-improves-memory-in-older-adults-and-alzheimers-patients/
https://www.oreateai.com/blog/the-impact-of-dementia-on-the-brain-a-journey-through-memory-and-identity/b4f3c25ce2f9efaedc281bb89ebea702
https://www.dementia.org.au/about-dementia/alzheimers-disease-everything-you-need-know
https://news.utexas.edu/2025/12/09/tackling-dementia-from-every-angle/
