In the research article, “Acute Neuroinflammation Impairs Context Discrimination Memory and Disrupts Pattern Separation Processes in the Hippocampus”, there was an interesting connection made to the elevation of the neural cytokine levels to the alteration of memory within the hippocampus. Although it is established that cytokines affect memory, cellular signaling, and neurotransmitter release, there was a need for literature on how the cytokines are affecting the cognitive processes. When studying memory, the hippocampus serves as a model, especially when dealing with context discrimination. Context discrimination occurs when a neural input is highly similar; however, the brain computes this type of information into an orthogonal or dissimilar output. To concretely observe distinct pattern separation, non-overlapping or separate neuronal ensembles must be present. This ensures that different inputs are facilitating two separate responses. The overall concept of this experiment was to test see the effect of acute neuroinflammation on discrimination in rats.
In this experiment, rats were taken to two similar apparatuses, and obtained a discriminative fear response to shock chambers. Once it was determined the rats were discriminating, two different injections were given: LPS or sterile saline. Then, the rats’ brains were subjected to a Arc/Homer 1 a (H1a) cellular analysis by fluorescence in situ hybridization (catFISH), which is an immediate-early gene imaging way to study the neuronal ensembles of the samples. Through this method, it was found that the cytokines were expressed in the dorsal hippocampus at its peak at six hours for TNF- α and LPS, while IL-1β peaked at three hours. With these results, experimenters used the time of six hours after LPS injection to evaluate the cognitive processes. Next, it was determined that discrimination did occur in the rats prior to the additional injections. More resulting data suggested that the cytokines influence gene expression in both CA3 and CA1. There was a clear connection made between neuronal ensemble activity, context discrimination, and the hippocampus. The rats that were injected with LPS had impaired discrimination, so neuroinflammation negatively interacts with pattern separation. Consistently, there is connections being made about the interactions of anatomical systems. This study shows how the immune system and cognitive processes interact in a complex ways. The deficiency with the immune system negatively impacts other parts of the body, like neural pathways. In the bigger picture, this research has implications on the effects of aging and cognitive decline. A probable reason why elderly people have a hard time grasping new information is because of the neurological changes in the body, which are only propagated by a decreased immune system.
This interaction between the immune system and hippocampus prompts endless questions about the role that the hippocampus plays in memory. By reaching out to more literature on the hippocampus, it is clear of its dynamic and expansive role. Understanding the deterioration of discrimination memory by cytokines can help to reach understanding on the development of memory and learning in an healthy individual. Though immune deficiencies can alter neural activity, healthy neural functioning develops ways to take in new information and establish memory and learning. Research articles regarding the hippocampus incorporates its complex nature of the aspects of human memory. From memory discrimination to exploration behavior, the hippocampus is a critical functioning brain part that prompts research and further discussion.
In the research article, “Brain Networks for Exploration Decisions Utilizing Distinct Modeled Information Types during Contextual Learning” there is another dimension of memory that is linked with hippocampus activity. Specific areas of the hippocampus serve as ways that humans display exploration behavior. In regards to learning, there are specific exploration patterns that enhance learning. One primary method of exploration and learning interactions occurs when one re-introduces oneself to previously seen material. Most people who be able to relate to the notion that the more you see something, the better you remember it. In this experience, the researchers analyzed participants who received newly available information (NAI) that subjects a person to new information for associations, and accumulated available information (AAI) that is the total information one saw during exploration. These two factors worked to target the participants in active learning where they could manipulate and control exploration. On the other hand, participants were taught through passive learning to serve as a contrasting sample. The researchers predicted that active learning from NAI would activate exploratory brain regions. To further validate this reasoning, the prefrontal cortex and hippocampus showed interactions, which means participants were utilizing the information soon after it was introduced. This exemplifies a person using exploration in decisions. AAI and active learning were displayed in the dorsal striatum of the hippocampus. This complements previous literature on the dorsal striatum, exploration of accumulated information, leading to the neural functioning of strategic planning.
This specific experiment started by showing participants a series of objects and faces. This information was used for the observation of NAI and AAI. To fully test exploration, a series of trails targeted NAI, AAI, active learning, and passive learning to isolate distinct behaviors. Then, the use of fMRI located the neural regions interacting with NAI and AAI decisions. NAI interacts with the anterior hippocampus, anterior prefrontal cortex, and even reached as far as the orbiofrontal cortex. On the other hand, AAI with active and passive learning showed active regions of the inferior parietal lobule and dorsal striatum. Exploration was further analyzed by the behavior of eye movements that solidified a link between NAI or AAI and active learning. Overall, the fMRI and trail data pointed to a combined effort of hippocampus and prefrontal cortex activation in NAI. The prefrontal cortex and hippocampus are suggested to be vital for short term or immediate memory and exploration in decision making. With the connections with the inferior parietal lobule and dorsal striatum, AAI displayed exploration that was not based on rewards. It was thought that strategic exploration and the dorsal striatum associate with each other that results in reinforcement models of behavior; however, this was not the case. The overall picture of exploration depicts a set of existing information that is added to by new information. New information that facilitates exploration has a critical interaction with the hippocampus and prefrontal cortex. In people who are memory deficient, these same people should also struggle with exploration. Further studies of these mechanisms will provide critical information on succeeding or failing in terms of learning and memory.
It is clear that the hippocampus is an elaborate structure that affects a large portion of memory, learning, as well as a number of other behaviors. Learning, memory, exploration, and discrimination is just a small window into the diverse roles of this brain region.
Czerniawski, J., & Guzowski, J. F. (2014). Acute neuroinflammation impairs context discrimination memory and disrupts pattern separation processes in hippocampus. The Journal of Neuroscience, 34(37), 12470-12480.
Wang, J. X., & Voss, J. L. (2014). Brain networks for exploration decisions utilizing distinct modeled information types during contextual learning. Neuron,82(5), 1171-1182.
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