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Spatial Memory
The hippocampus has been demonstrated to be involved in various processes of cognition. The first and most widely researched area concerns memory,spatial memory in particular. Spatial memory was found to have many sub-regions in the hippocampus, such as the dental gyrus (DG) in the dorsal hippocampus, the left hippocampus, and the parahippocampal region. The dorsal hippocampus was found to be an important component for the generation of new neurons, called adult-born granules (GC), in adolescence and adulthood. These new neurons contribute to pattern separation in spatial memory, increasing the firing in cell networks, and overall causing stronger memory formations. While the dorsal hippocampus is involved in spatial memory formation, the left hippocampus is a participant in the recall of these spatial memories. Eichenbaum and his team found, when studying the hippocampal lesions in rats, that the left hippocampus is “critical for effectively combining the ‘what, ‘when,’ and ‘where’ qualities of each experience to compose the retrieved memory.” This makes the left hippocampus a key component in the retrieval of spatial memory. However, Spreng found that the left hippocampus is, in fact, a general concentrated region for binding together bits and pieces of memory composed not only by the hippocampus, but also by other areas of the brain to be recalled at a later time. Eichenbaum’s research in 2007 also demonstrates that the parahippocampal area of the hippocampus is another specialized region for the retrieval of memories just like the left hippocampus.

Learning
The hippocampus, over the decades, has also been found to have a huge impact in learning. CurlikShors examined the effects of neurogenesis in the hippocampus and its effects on learning. This researcher and his team employed many different types of mental and physical training on their subjects, and found that the hippocampus is highly responsive to these latter tasks. Thus, they discovered an upsurge of new neurons and neural circuits in the hippocampus as a result of the training, causing an overall improvement in the learning of the task. This neurogenesis contributes to the creation of adult-born granules cells (GC), cells also described by Eichenbaum in his own research on neurogenesis and its contributions to learning. The creation of these cells exhibited “enhanced excitability” in the dentate gyrus (DG) of the dorsal hippocampus, impacting the hippocampus and its contribution to the learning process.

Hippocampal Damage
Damage relayed to the hippocampal region of the brain has reported vast effects on overall cognitive functioning, particularly memory such as spatial memory. As previously mentioned, spatial memory is a cognitive function greatly intertwined with the hippocampus. While damage to the hippocampus may be a result of a brain injury or other injuries of that sort, researchers particularly investigated the effects that high emotional arousal and certain types of drugs had on the recall ability in this specific memory type. In particular, in a study performed by Parkard, rats were given the task to correctly make their way through a maze. In the first condition, rats were stressed by shock or restraint, causing a high emotional arousal. When completing the maze task, these rats, compared to the control group, had an impaired effect on their hippocampal-dependent memory. Then, in a second condition, a group of rats were injected with anxiogenic drugs. Like the latter, these results reported similar outcomes, in that hippocampal-memory was also impaired. Studies such as these reinforce the impact that the hippocampus has on memory processing, particularly the recall function of spatial memory.

Episodic-autobiographical memory (EAM) networks
The amygdala, another integrative part of the limbic system, is also involved in many cognitive processes. Just like in the hippocampus, memory seems to be impacted by processes in the amygdale; however, it is not spatial memory like the hippocampus, but episodic-autobiographical memory (EAM) networks. The amygdala, as researched by Markowitsch, was found to be responsible for the encoding, storage, and retrieval of these types of memories. To delve deeper into these types of processes by the amygdala, the Markowitsch and his team provided extensive evidence through investigations that the “amygdala’s main function is to charge cues so that mnemonic events of a specific emotional significance can be successfully searched within the appropriate neural nets and re-activated.” These cues for emotional events created by the amygdala encompass the EAM networks previously mentioned.

Attentional and Emotional Processes
Besides memory, the amygdala also seems to be an important brain region involved in attentional and emotional processes. First, to define attention in cognitive terms, attention is the ability to hone in on some stimuli while ignoring others. Thus, the amygdala seems to be an important structure in this ability. Foremost, however, this structure was historically thought to be linked to fear, allowing the individual to take action to rid that fear in some sort. However, as time has gone by, researchers such as Pessoa, generalized this concept with help from evidence of EEG recordings, and concluded that the amygdala helps an organism to define a stimulus and therefore respond accordingly. However, when the amygdala was initially thought to be linked to fear, this gave way for research in the amygdala for emotional processes. Kheirbek demonstrated research that the amygdala is involved in emotional processes, in particular the ventral hippocampus. He described the ventral hippocampus as having a role in neurogenesis and the creation of adult-born granule cells (GC). These cells were not only a crucial part of neurogenesis and the strengthening of spatial memory and learning in the hippocampus, but also appear to be an essential component in the amygdale. A deficit of these cells, as Pessoa (2009) predicted in his studies, would result in low emotional functioning, leading to high retention rate of mental diseases, such as anxiety disorders.

Social Processing
Social processing is an area of cognition specific to the amygdala. More specifically, the evaluation of faces in social processing is of particular importance. In a study done by Todorov, fMRI tasks were performed with participants to evaluate whether the amygdala was involved in the general evaluation of faces. After the study, Todorov concluded from his fMRI results that the amygdala did indeed play a key role in the general evaluation of faces. However, in a study performed by researchers Koscik and his team, the trait of truthworthiness was particularly examined in the evaluation of faces. They investigated how brain damage to the amygdala played a role in truthworthiness, and found that individuals that suffered damage tended to confuse trust and betrayal, and thus placed trust in those who had did them wrong. So Koscik demonstrated that the amygdale was involved in evaluating the truthworthiness of an individual. Yet, a man named Rule, along with his colleagues, expanded on the idea of the amygdala in its critique of truthworthiness in others and performed a study in 2009 in which he examined the amygdala in its role of evaluating general first impressions and relating them to real-world outcomes with his study involving first impressions of CEO’s. Rule demonstrated that while the amygdala did play a role in the evaluation of truthworthiness, as observed by Koscik in his own research two years later in 2011, the amygdale played a generalized role in the overall evaluation of first impression of faces. This latter conclusion, along with Todorov’s study on the amygdala’s role in general evaluations of faces and Koscik’s research on truthworthiness and the amygdala, further solidified evidence that the amygdala plays a role in overall social processing.