…by Elizabeth / from Australia / MSc Neuroscience 2017-2018
It’s been a while since my last post, and I sincerely apologize for that! I have been very busy with experiments, data analysis and working, while also maintaining some sort of social life! This next post will explain more about my current project and what I experience day to day.
I work in Dr. Richard Morris’s lab. You may have heard of the Morris Water Maze, which is a test for spatial learning and memory. This task involves rats to navigate through a swimming arena to locate a submerged escape platform (apparently, the rats do not want to be in the water!) When the platform is absent, the rat swims above where the location should be, representing the rat’s ability to learn and remember. It’s very clever since to control for the rat’s ability to “see” the platform, Morris mixed the water with powdered milk. Thus, the task relied on the rat’s spatial memory. I do not work with this specific apparatus, but I work with a spatial arena exploring everyday memory and the phenomenon of flashbulb memories.
Before I begin explaining my project, I’ll like to take the time as to why I started started studying memory. I discussed earlier how my neuroscience interests evolved during my undergraduate career. I became fascinated by how the midbrain could control many behaviors our society deemed as controlled by “free will.” Our midbrain controls motivations, habitual behavior, our emotions and our memories. These areas are some of the oldest and evolutionary conserved parts of our brain. Hence, they are easier to study in animals than consciousness or frontal cortex functions.
Therefore, my main areas of interest centers around how much control we have over our consciousness, the production of thought and behavior. Do we have control over our brain processes (that are ultimately defined by our genetics and environment) or do we have “free will” where we can rationally make decisions regardless of our brain biochemistry? This is a considerable debate on many topics, philosophy, psychology, criminology, education, medicine, public health, and neuroscience. Nevertheless, my question is why do we do what we do. Memories are predictive of behavior, giving an animal perspective and understanding about the real world around them. New memories can become part of pre-existing memories, and in turn, previous experiences can become active in our current mindset. Understanding how our memories create our perspective and help guide our behavior remains a crucial part of answering my many questions. Now, I can explain my topic!
When a memory is created, there is no guarantee you will be able to remember it. Some memories may be recalled more than others, and experimenters have found that certain events can increase the success of memory retention. High reward or repeated spaced intervals can improve your memory. For example, giving yourself a treat, such as chocolate, and coming back over and over again can help you remember for an exam. However, other phenomena can increase retention or remembering as well. Many papers have explored “environmental novelty” (i.e., something unexpected happening in the environment that is unrelated to the memory) which is a paradigmatic example of a “flashbulb memory.” A flashbulb memory is a very detailed and vivid memory that is stored on one occasion and is always remembered. Such memories are the memories associated with the day of 9/11, assassination of J.F Kennedy, or the election of Donald Trump. Flashbulb memories are very powerful, as the event in question, causes the person to remember everyday memories that would otherwise be forgotten over time. I was only seven years old when 9/11 happened, but I can remember who informed me, what we did that day, my emotions, the emotions, and faces of other people and excreta. I will forever remember the election of Donald Trump. Elderly people can paint a picture of J.F Kennedy’s assignation. Some even older people can vividly explain the mundane details of their day when they heard the announcement of the end of World War 2.
Papers have explored how environmental novelty increases the success of consolidating a memory. To test this in a behavioral rat paradigm, we have an arena where the rats are taught a location where food is, but changes every day. This symbolizes a similar human model of the various places you will leave your keys or park your car. The environmental novelty causes these everyday memories to become retrieved quickly and more efficiently. An example of environmental novelty for a rat is changing the floor surface, as rats are susceptible to these changes.
The idea behind why environmental novelty or perhaps any type of novelty increases memory consolidation is dopamine. The VTA, or Ventral tegmental area, is home to many dopaminergic pathways and is responsible for many natural and drug reward pathways. When a reward, unexpected or expected occurs, dopamine is released from the VTA to other areas of the brain. The hippocampus is associated with memories. Past literature has discussed that dopamine may be released from the VTA to the Hippocampus (HPC) when something unexpected occurs. However, new research from this lab (Takeuchi et al.) has found that dopamine may not be released from the VTA, but the Locus Coeruleus (LC). The LC is the principal area for noradrenaline or arousal. Novelty is arousing so this may be why the dopamine is released from this area to the HPC and not from the VTA. Therefore, the dopamine released from the LC to the HPC during novelty, causes memories to be consolidated. For further and more intensive reading on how this may work, please look up (Redondo & Morris).
Since January, the undergraduates and I have been working on the behavioral aspect of this experiment, by training the rats every day. Soon we will be looking at the effect of sleep on memory consolidation. We will be then looking at some new types of novelty which I was able to propose to my supervisors! This was very exciting for me because I know I have the opportunity to make this project more my “own.”
I am fortunate with my project because I have the opportunity to test some of my own ideas. However, I am even more fortunate to have an excellent supervisor. When looking for a project, as I mentioned in my second post, it is essential to meet and work with someone you feel comfortable with to ask questions and to ask for guidance. I am new to biomedical sciences, research and a laboratory. This was a considerable risk and challenge for me, so to have all these opportunities is a fantastic blessing. Hope you enjoyed this post about my interests, why I study memory and what my project is about. Next time I hope to talk more about the challenges I deal with every day.
I have put some references below which discuss some of the everyday memory paradigms and protocols.
Frey, U., Morris, R.G., 1997. Synaptic tagging and long-term potentiation. Nature 385, 533–536.
Nonaka, M., Fitzpatrick, R., Lapira, J., Wheeler, D., Spooner, P.A., Corcoles-Parada, M.,
Redondo, R.L., Morris, R.G.M., 2011. Making memories last: the synaptic tagging and capture hypothesis. Nat. Rev. Neurosci. 12, 17–30.
Takeuchi, T., Duszkiewicz, A.J., Sonneborn, A., Spooner, P.A., Yamasaki, M., Watanabe,
Wang, S.-H., Redondo, R.L., Morris, R.G.M., 2010. Relevance of synaptic tagging and capture to the persistence of long-term potentiation and everyday spatial memory. Proc. Natl. Acad. Sci. U. S. A. 107, 19537–19542.