Memory storage and retrieval has long been one of the main puzzles of psychology and neuroscience. Who we are and how we think is deeply influenced by the memories of our experiences and sensations. Memory is far from perfect, however. We all struggle with corrupted memories and blockages that stop us from retrieving information. For many people, however, especially those of an older age, memory is much more complicated and problematic. For decades, medical researches have tirelessly looked for answers to Alzheimer’s, brain degeneration that causes severe memory loss. It is a devastating disease that eventually renders loved ones unaware of even the simplest facts of their existence. They slip further and further from reality as their memory becomes more and more distorted. Alzheimer’s, as with many things in the brain, has proved very difficult to truly understand.
Recently, however, a group of researchers have made a breakthrough working with mice. They have engineered these mice to develop a form of Alzheimer’s. Using a flash of blue light, they were able to help the mice recall memories that had become distorted (1).
Before I explain how they pulled that off, I should explain some of what we know about how memory works. Memories first enter the short-term memory, which can hold around seven items. These items can then be specially encoded and stored in the long-term memory, where they await retrieval. When we recall a memory, it is taken out of long-term memory for a period of time. Whenever this occurs, however, we tend to modify that memory with what we are experiencing at the current moment. Thus, the reason all those lovely memories you have of your ex are now soured. There is a lot more to the psychology of information which I encourage you to look into if you want to improve your studying.
There is also another neural level of memory. One possible and fascinating explanation of memory is long-term potentiation. This is thought to happen in the hippocampus. Basically, memories are created by strengthening connections between neurons. Two neurons communicate with each other by releasing neurotransmitters across the synapse upon stimulation by an action potential (a change in charge). If strong enough, a summation of these action potentials can create a conformational change in the neurons. A greater number of receptors can build up and more neurotransmitters are released upon excitation in the future. This makes the connection between the neurons stronger and more easily to excite (2).
If you are struggling to make the connection between this explanation and the psychological explanation, you can join me. It is complicated, but that is why I find neuroscience so fascinating. We take our ability to think and experience for granted, but it is actually allowed by many incredibly complicated and sensitive processes.
Unfortunately, that is what makes a disease like Alzheimer’s so difficult to understand. The cause of the memory degeneration is the buildup of amyloid plaques and neurofibrillary tangles (3). These developments are build-ups of potentially toxic substances intracellularly and extracellularly. These are thought to cause damage and death of brain cells (3).
Over time, these patients lose episodic memory and eventually many more memories, and then face a continuing loss of cognitive function, which often leads to death (4).
This group of scientists set out to discover exactly what part of the memory process AD affects. The scientists first “marked the memory” by tagging specific neurons related to each memory (1). They used a virus to implant a gene into these neurons that associated with flashes of light. This blue light was fired through an implanted optic fiber. The scientists marked the memory of the fear the mice felt when shocked in a cage. It was not until stimulated with blue light that the mice recalled the fear they had originally felt (1). To relate to earlier ideas, they are optogenetically stimulating the process of long-term potentiation at specific pathways (4).
So, why do people looking for a cure for Alzheimer’s care about mice with optic fibers in their brain? What these researchers have been able to determine is that Alzheimer’s is a problem with the retrieval of information, not with the storage and maintenance of that information (1). This gives the scientific community a better understanding of what they are facing. Think of it as a maze, and they have finally found where to start on a new level of research.
It is easy to believe that our memories are permanent. We treasure some, but take many for granted. The brain is, however, in certain ways, quite fragile. There are currently more than 5.4 million people in American alone with AD. The number is thought to triple in the next few decades (5).
Imagine being unable to access your memories. Imagine being unable to remember your name or your children. As a human society, we put great import on such details. We are defined by our names, our past, and the people who surround us. As they lose their details, they lose their identity. It is terrifying and isolating, both for those suffering from the disease and their caregivers.
There are answers, hiding with in our own brains. We just have to find a way to understand those mysteries.
Katherie Estep is a sophomore BIC student majoring in neuroscience.
Sources:
(1) https://www.sciencenews.org/article/lost-memories-retrieved-mice-signs-alzheimers?tgt=nrhttp://neuroscience.uth.tmc.edu/s4/chapter07.html
(2) http://www.sciencedirect.com/science/article/pii/S0140673610613499
(3) http://www.nature.com/nature/journal/v531/n7595/full/nature17172.html
(4) http://www.huffingtonpost.com/rebecca-laclair/how-alzheimers-caregivers_b_9460712.html?utm_hp_ref=science&ir=Science