Long-term memory research proposal in non-primate animals

Fruit Flies

The Importance of Long-Term Memory:

Studying the Fruit Fly

The most fascinating of all abilities of life on Earth is the utilization of memory to survive. Memory can be utilized by animals, insects, reptiles, and even fish to find food and shelter. Long-term memory in particular is a fascination of both public and scientists alike. With new experiments in this category every day, the benefits of long-term memory are no longer any secret from a scientific standpoint. Of course, in daily life, one knows what it means to remember, both good and bad memories, and how these can help an individual. This paper will attempt to study long-term memory in a non-primate animal, however, namely the fruit fly, and will attempt to incorporate both previous research and its own proposed methodology to assess the benefits of long-term memory in fruit flies, and its more general implications.

Before beginning with the literature review, this section will also examine some specifics of long-term memory and fruit flies, to prepare the background for this study. According to Science Daily, the mechanism of long-term memory was identified in a study at the Scripps Research Institute in Florida. The subject was none other than the fruit fly. According to the article,

"Using advanced imaging technology, scientists from the Florida campus of The Scripps Research Institute have identified a change in chemical influx into a specific set of neurons in the common fruit fly that is fundamental to long-term memory."

Due to the findings, we now have even more data on long-term memory and its functioning, but one must also define this concept before delving further into the study.

Long-term memory, according to the Kendra Sherry who writes an article on the subject, is "continuing storage of information."

Another reference to this, and a nod to Sigmund Freud, would be to classify it as the preconscious or unconscious. Either way, information stored in our long-term memory is "outside of our awareness," according to Sherry, but "can be called into working memory to be used when needed." This description alone is fascinating, and perhaps even more fascinating than the words in Sherry's article, is the fact that fruit flies, that are infinitesimal in size compared to humans, also possess long-term memory capacities which, in fact, helped scientists pinpoint the mechanism for long-term memory.

According to Eric Sauter, who writes for Scripps Research, the scientists, who studied fruit fly learning and long-term memory storage, observed "an increase in calcium influx into a specific set of brain neurons in normal fruit flies that was absent in 26 different mutants known to impair long-term memory."

Due to these findings, the scientific conclusion was that the increase, or a memory trace, was an important aspect of long-term memory, according to Sauter. This trace was further indentify as associated with the part of the insect brain known as "mushroom bodies," by the researchers, which are defined as "a pair of oversized lobes known to mediate learning and memory, particularly the memories of smell" by the article.

These "mushroom bodies" are similar to the human hippocampus. Due to this similarity, scientists are quite certain that a similar relationship also exists in humans.

Literature Review

The study presented above is so important, that it must be further examined, especially as it deals with both of the issues of concern for this paper. Firstly, it is clear that this research proves that fruit flies do, indeed, have long-term memory, which is very similar to human abilities. The methodology employed in the study by the researchers above first involved measuring certain changes in neurons, such as the Drosophila neurons. In order to do this, Sauter states, the scientists "used functional optical imaging, an advanced technology that his laboratory helped pioneer for the study of learning and memory." Sauter further adds,

"Using protein sensors that become fluorescent when calcium levels are increased, the team was able to highlight changes in the levels of calcium influx into the mushroom body neurons in response to odor learning. These observed memory traces occur in parallel with behavioural changes. Interestingly, these memory traces occur only with spaced conditioning -- where the insects receive multiple episodes of learning but with periods of rest between each episode. Spaced conditioning is required for long-term memories to form."

The study here indeed proves that fruit flies are a phenomenal subject to be studied and determine a relationship with long-term memory. "The phenomenon of spaced conditioning is conserved across all species," The scientists added, "No one really knows why it's important to long-term memory formation but there appears to be something magical about that rest period during learning."

According to the study's predecessor in December, which was published in The Journal of Neuroscience, head scientist Davis found that those fruit flies that received spaced conditioning exhibited a long-term memory trace, and that their memories lasted "between four and seven days."

Other flies, especially those that only received one episode of learning, this formation lasted only one day and the trace failed to form. Therefore, it is safe to say that those flies which subject to spaced conditioning will form long-term memories, but others, especially those that only received a singular episode will have such proclivity.

Another study, this time at Harvard, points to having found a "molecular pathway active in neurons that interact with RNA to regulate the formation of long-term memory in fruit flies." This study focuses on the pathway, also found in mammals, due to the fact that it could actually be utilized to treat those with memory loss. According to Sam Kunes, professor at Harvard,

"It has been known for some time that learning and long-term memory require synthesis of new proteins, but exactly how protein synthesis activity relates to memory creation and storage has not been clear, […] We have been able to monitor, for the first time, the synthesis of protein at the synapses between neurons as an animal learns, and we found a biochemical pathway that determines if and where this protein synthesis happens. This pathway, called RISC, interacts with RNA at synapses to facilitate the protein synthesis associated with forming a stable memory. In fruit flies, at least, this process makes the difference between remembering something for an hour and remembering it for a day or more."

The scientists here also performed a breakthrough study by analyzing RNA as it relates to memory in fruit flies, and once again, the test subjects proved worthy. The study here was conducted much in the same way as the Scripps Research study above. Very technical equipment was utilized, of course very advanced technologically, but also the expertise of very select individuals was utilized to analyse the results and monitor the advancement of the experiment.

A third experiment in the wealth of research being done on fruit flies focuses on a laboratory in New York, part of the project at Cold Spring Harbor Laboratory. Here, the scientist who is joking referred to by the writer as "lord of the flies," utilizes a dark closet to conduct research, and theorizes that long-term memory is indeed common to all nerve cells in all species. Also part of this research is the potential for drugs to combat such diseases as Alzheimer's which are very exciting for the people working here, which have made progress on the issue with the experiment. Just the previous year, Dr. Tully, the head scientist, and his colleagues "showed for the first time that it is possible to enhance the long-term memory of fruit flies through genetic manipulation," according to Ulman.

The scientists go on to say that due to the relative ease of housing population of these flies, which mature and reproduce very quickly, the species is ideal for genetic studies. The basic set-up of extraction, however, takes some time. One must sit in "a darkened, windowless closet in Dr. Tully's lab […] and spend eight hours a day watching over an array of fly-filled test tubes that are attached to computer-controlled coils and pumps." This, at least is the set-up of this particular study, according to Neil Ulman of the Wall Street Journal.

According to Ulman, "the apparatus allows the scientists to measure the learning capacity of the flies. It gives a batch of flies an electrical shock in the presence of an odor, then observes whether they later choose to move into a test tube containing that odor or another."

The set up of this particular experiment allows for avoidance of the "odor" which is associated with shocks, and further relays evidence of memory formation for some of the insects. A normal fruit fly would, therefore, after a relatively short number of "lessons," be able to consolidate the information to memory, therefore proving its long-term abilities.

Methodology

The three studies presented above form a strong basis for the literature review part of this paper, and specifically for the fact that they deal with long-term memory in fruit flies, describe both the processes of conducting these complicated experiments, as well as the final results of what has been found. The chronological order of these studies, having started with most recent ones, also proves that constant advancements have been made in this particular arena. Thus, some important conclusions can be drawn for a further study.

First, in order to properly study long-term memory in fruit flies, it is essential to have both qualified individuals and qualified equipment. This will necessitate some funds, or at least the inclusion of the experimenter in a laboratory which can furnish him or her with these particulars. In other words, this is not an easy experiment. This is, in part, due to the nature of studying long-term memory, which cannot easily be observed, especially in animals, but also to the fact that the behaviours that demonstrate long-term memory in this particular species are quite hard to observe with the naked eye. However, the species does prove the best possible for such studies, for its behaviour has been proven as evidencing long-term memory time and again, as described above.

Further Studies

In order to further study the species, various methods can be employed. The first can be observation, where one can simply look at the fruit flies and devise a way by which it can see whether these flies are affected in any way by events which can impact their long-term memory (i.e. The shocks in the experiment above). Another method, which is the best method, is the combination of observation with specific triggers, such as the shocks mentioned above, which can then further elucidate the events to which the fruit flies may be reacting.