Cassie Widdison and Dr. Christopher Kirwan, Psychology
Regions of the brain, such as the medial temporal lobe (MTL), including the hippocampus and the adjacent MTL cortex, facilitate recognition memory performance (Squire, Stark, & Clark, 2004). The hippocampus is known for its ability to encode and retrieve memories through two processes called pattern separation and pattern completion (Mcclelland, Mcnaughton, & Oreilly, 1995). Pattern separation is a computational process in which the memory representations of similar stimuli are made as dissimilar as possible. This allows one to recall differences between old stimuli and similar, but novel stimuli. Pattern completion is a computational process where a memory representation is retrieved by a degraded or particle cue. This process may result in an old stimulus being recalled but the differences between the old and the similar not being registered. In separate research it was found that the neurotransmitter dopamine is involved in the role of memory acquisition (Apitz & Bunzeck, 2013; El- Ghundi, O’Dowd, & George, 2007). However, there are no data bearing upon the role of dopamine in the processes of pattern separation and pattern completion.
In this study participants completed a task where they had to pick a winning square from three options. Figure 1 shows what the participant saw if they correctly chose the winning card. After the guessing task participants were showed an image of an object; an example of this can be seen in figure 2 When the image was on the screen participants were told to classify the object as something that belonged “indoor” or “outdoor”, as seen in the second figure. After this initial task participants would then complete a memory test where they would classify the objects they saw on a six point scale ranging from definitely sure it’s old to definitely sure it’s new.
As shown in the graph below what we have found thus far in our study is that when the participants are presented with an old stimuli they are more confident that it is old. Interestingly, we found that when a lure is presented they are less accurate but equally as confident in their responses. As an adaptation to this study to improve it and potentially find result that accurately capture what we are looking for we can change the task slightly. The task could instead have two groups. In one group the participants would receive a reward if they chose a card with a blue outline; in the other group they would be told that they would receive a reward if they remembered the card with the blue outline. By changing our research in this way we would hope to more accurately test the reward responses relation to memory.
References
Apitz, T., & Bunzeck, N. (2013). Dopamine Controls the Neural Dynamics of Memory Signals and Retrieval Accuracy. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology. doi: 10.1038/npp.2013.141
Bakker, A., Kirwan, C. B., Miller, M., & Stark, C. E. L. (2008). Pattern separation in the human hippocampal CA3 and dentate gyrus. Science, 319(5870), 1640-1642. doi: 10.1126/Science.1152882
El-Ghundi, M., O’Dowd, B. F., & George, S. R. (2007). Insights into the role of dopamine receptor systems in learning and memory. Reviews in the Neurosciences, 18(1), 37-66.
Hirsch, E., Graybiel, A. M., & Agid, Y. A. (1988). Melanized Dopaminergic-Neurons Are Differentially Susceptible to Degeneration in Parkinsons-Disease. Nature, 334(6180), 345-348. doi:10.1038/334345a0
Mcclelland, J. L., Mcnaughton, B. L., & Oreilly, R. C. (1995). Why There Are Complementary Learning-Systems in the Hippocampus and Neocortex – Insights from the Successes and Failures of Connectionist Models of Learning and Memory. Psychological Review, 102(3), 419-457. doi: 10.1037/0033- 295x.102.3.419
Squire, L. R., Stark, C. E., & Clark, R. E. (2004). The medial temporal lobe. [Research Support, Non-U.S. Gov’t Research Support, U.S. Gov’t, Non-P.H.S. Research Support, U.S. Gov’t, P.H.S. Review]. Annual Review of Neuroscience, 27, 279- 306. doi: 10.1146/