Oh! My sweet memory…
Author: Chi-Chieh Lee
If life is a road trip, you are the driver to explore your own path and make a life story. On the road you are not alone because the memory keeps you company to generate the past, face the present and expect the future.
When you drive on the road literally, your brain receives lots of inputs like vision or hearing. Every second neurons fire and different brain areas crosstalk to process the messages from the outside world. And this helps you make the decision for the next step like stopping at the red light of the crossroad. It is amazing that the brain performs the working memory temporarily storing the information essential to your responding behaviors. After you reach home getting nice sleep, your brain stores the things that surprised or scared you today as long-term memory. So the next day you can recall which crossroad is dangerous or where you can get the most perfect ice cream in the world (any salted caramel flavor is perfect!). With these two kinds of memory, you can make decisions based on the previous learned lessons.
But have you encountered a situation that you couldn't remember where the shop is? This might happen if the neural network doesn’t process the memory properly. Generally, remembering the position of the shop requires the brain region called hippocampus. Hippocampus has several subregions such as CA1, CA3 and dentate gyrus (DG), which are important in forming the cognitive map. For example, the place cells in CA1 representing the specific place are active while you explore the city to find the ice cream. Later during sleep, the trisynaptic loop, formed by CA1, CA3 and DG, generates oscillation transferring memory to the cortex to consolidate the memory. Also, memory retrieval and discrimination are processed inside the hippocampus. Therefore, abnormal neural activities or damage to the hippocampus could lead to having a bad memory.
“The advantage of a bad memory is that one enjoys several times the same good things for the first time.” ― Friedrich Nietzsche
What Nietzsche said might be recognized if one could always enjoy the amazement of the ice cream as the first time. However, sadly it is not so attractive for the people with Alzheimer’s disease.
Alzheimer’s disease is an irreversible neurodegenerative disease that the neurons die gradually, leading to massive brain atrophy. As the disease progresses, the patients start losing working memory that they forget where they put the keys. And later the long-term memory is affected that the patients forget the names of their grandchildren. Ultimately, the late stage symptom of the disease is losing the ability to perform their daily routines like eating or drinking.
Scientists already found that in the brains of the Alzheimer’s patients there are accumulation of the proteins called amyloid β and tau. The toxic accumulating proteins mostly kill the neurons in the hippocampus and later in the cortex. So the hippocampus shows dysfunction in both performing working memory and producing long-term memory.
For the Alzheimer’s patients, it is like that they meet the unlimited obstacles (toxic proteins) on life path forcing them to stop eternally. Therefore, it is important to find treatments against the disease. Currently, FDA-approved drugs could only relieve the symptoms but not halt the disease progression. So lots of scientific research explores other possibilities such as targeting the toxic proteins by antibodies (removing the obstacles on the road) or generating more neurons to compensate for the neuronal loss (making a vehicle carry you passing those obstacles). Hopefully in the near future, there will be therapies letting the Alzheimer’s patients regain control of their life and generate memories along the life path.
Memory is our partner, who always supports you fighting through life. If you feel exhausted and need a new fresh, use your memory to get your favorite ice cream!
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Cowan N. What are the differences between long-term, short-term, and working memory?. Prog Brain Res. 2008;169:323-338.
Jahn H. Memory loss in Alzheimer's disease. Dialogues Clin Neurosci. 2013;15(4):445-454.
Photo credit: https://www.farmpride.com.au/recipe/salted-caramel-icecream/