In a neuroscience seminar class section at Loyola University Chicago (NEUR 300 001), Jelena Radulovic presented her research on mice that examined the role of the retrospenial cortex in the brain when forming memories when introduced to a stressful stimuli. Another study performed by Chen Zhao and his team looked at different activities in the brain but used similar methodology with humans as Radulovic did with mice to test their experiment. In the future, I personally think that a replicate experiment of Radulovic's using Zhao's methodology in humans could help us better understand the role of the retrospenial cortex in humans.
Radulovic and her team found that the retrospenial cortex (RSC), near the hippocampus, plays a large role in memory formation, specifically in stressful situations. To do this, viruses were injected to the RSC and the dorsal hippocampus (DH), then mapped using various dyes to see where the virus was being expressed in higher concentrations within the two structures. The result of this showed pathways between the DH and RSC that the viruses travelled and concentrated--which implies a connection between the two structures during processing. Radulvic and her colleagues hypothesized that this pathway is used in episodic memory processing. To examine this, mice were placed in a controlled environment while having these two cortical regions either excited or inhibited using chemogenetic silencing of vGlut1 or vGlut2 processes in the hypothesized pathways and introduced to a shock to frighten the mice. Analysis was conducted to measure the timing it took for the shock to register as fear in the mice brains and behavioral measures were conducted--the time each mouse remained in a frozen state. The results of this experiment was that in fact, when stress was induced to the mice via a shock, strong evidence of activity found in the DH and RSC was found. This implies that when stress-induced memories are formed in the RSC, we can predict certain behaviors to arise, such as mice to freeze.
A study performed by Chen Zhao and his colleagues demonstrated a cognitive approach to the behavioral study performed by Jelena Radulovic. While the goal of this experiment was not to measure brain activity in the DH or RSC, similar methods to conduct this research was used compared to the methods of the previous experiment. In Zhao's experiment, infants were given a chance to play in a room with their mother. Then words of encouragement, displeasure, neutrality, and anger were administered by the mother. Various areas of the cortex were then measured using infrared spectroscopy showed the researchers different areas of the brain in response to the various tones. The results that were provided in the article do not engage directly with the findings of the previous experiment performed by Radulovic and her team. However, the methods by which each experiment interested me. Both experiments placed the subject into a state of distress while measuring various areas of the brain. One experiment focused on a highly specific area of the brain while the other took a broader spectrum of activity; however, the two used the same behavioral methodology.
As a student personally hearing Radulovic's research, I would find it fascinating if the methods used in Zhao's experiment with infants and anger in a mother's tone to induce stress and memory could be a possible advancement for the already performed experiment on human subjects rather than nonhuman subjects. While we as researchers learn much from behavioral studies in animals, the best way to learn about human nature and behavior would be to learn from humans directly. However, it would be highly unethical to insert a virus to an infant brain and perform brain slicing as done with the mice. With the information we learned from Radulovic's experiment about the RSC in mice brains, I think it would be beneficial for future studies using the methodology of Zhao's study to add a cognitive approach to finding a direct use of the RSC in the human brain and stress-related memory development.
Citation
PLOS. (2019, February 27). Mother's behavioral corrections tune infant's brain to angry tone: Maternal interactions may help shape the same brain region adults use for vocal emotion processing. ScienceDaily. Retrieved February 28, 2019 from www.sciencedaily.com/releases/2019/02/190227142726.htm
Radulvic, J. (Feb 26, 2019). Processing Stress-Related Memories in Hippocampal-Cortical Circuits. [slide presentation].
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