Hippocampus and Dense Amnesia: A Study on the Human Memories and Recognition Ability

In new studies, researchers aim to discover the ways animal brains with fornix lesions behave in instances where they must rely on their recognition ability, which allows them optimum choice, when it is hard or impossible to recall (Clayton & Dickinson, 1998). From this research, the hippocampus is believed to be the region responsible for the episodic behaviours of the animals. For some of the results, the animals are seen to display the medial temporal lobe (Wolfe, 1999). Thus these specimen triple demonstrate the acts of dissociation although they recognize objects that they have seen before (Rogers, Farlow, Doody, Mohs & Friedhoff, 1998). Creatures with lesions in the fornix are also seen to have equal difficulty recollecting scattered information.

Traditionally the effects of dense amnesia have been associated with damage to the hippocampus. In the case where the hippocampus is affected by an injury, a lesion or a bacterial infection, then the victim is prone to developing the conditions of amnesia. If not these it was believed that the conditions of dense amnesia could also arise as a result of hindering the connection of the afferent vessels from the medial temporal lobe (Eacott & Norman, 2004). These two issues bear little accuracy on the matter and hence must be examined further to be more valid. It is clear amnesia is linked to “infections of the temporal lobe,” but the exact regions must be known with clarity to understand it better. Despite being responsible for memory storage, the hippocampus may be affected, but it does not cause amnesia.

An experiment on monkeys was conducted to determine the exact parts of the medial temporal lobe in that, when affected, results in dense amnesia (Easton, Zinkivskay & Eacott, 2009). The temporal lobe is made of three sensitive sections that are most likely to be based on the effects of the amnesia. They are the anterior temporal stem, which is the position on the front side as well as the amygdala, and the fornix-fimbria. In the experiments, each of the parts is injured, but only some mild effects are manifested when the anterior medial lobe, the amygdala, and the fornix-fimbria defect as one each time (Easton, Zinkivskay & Eacott, 2009). However, the specimens start to manifest severe conditions where any pair of the three crucial parts is tampered with. For example when fornix was added to the amygdala and the anterior temporal lobe, the conditions created were severe but similar to amnesia. For this the effects of amnesia seem to be dissociative because the damage of any part of the temporal medial lobe only causes mild memory problems that cannot stand as amnesia.

The other experiment was when the crucial parts were impaired collectively which also made the creatures experience severe impacts. Finally, “the anterior temporal lobe, the amygdala, and the fornix” were all impaired while the hippocampus was left unharmed the creatures underwent a painful struggle that was very similar to the dense amnesia in human beings (Eacott & Norman, 2004). In a way, the test was meant to show that there is a minor contribution of the hippocampus in the conditions (Easton & Eacott, 2010). However, all the same, the lesions in the monkey experiments and demonstration show that the case for the humans and the monkeys are very distinct (Eichenbaum, 1993). On most occasions when the temporal lobe of the creatures is tampered with they experience severe learning impairments. However, the cases of brains in the monkeys is not completely similar to the behaviour of the human brain thus despite the conditions in monkeys being dissociative, the human brain might be different.

One of the essential components of the hippocampus is the acetylcholine. It is found in the fluid form of the hippocampus and is vital in the transmissions of naval impulses to the brain receptors (Squire & Alvarez, 1995). Within the hippocampus, the acetylcholine functions as part of the process of determining the nature of the effects that are caused by the lesions and infections (Easton, Douchamps, Eacott & Lever, 2012). The acetylcholine aids the hippocampus in many events. It functions as the agent that reduces the interference of learning. It achieves this by ensuring that there is a correct timing in doing the activities. It also acts to separate the retrieval and to code the places. Moreover, the fluid also reduces the interferences brought about by movements in learning.

Besides, the impairments of human memory due to the interferences of the medial temporal lobe some cases that result from the Loss of cortical cholinergic input. This one is especially associated with the loss of memory. However, the cortical cholinergic input plays a major role in the human mind where it is used for ensuring episodic-like memories for issues that have not yet been investigated (Rogers, Farlow, Doody, Mohs & Friedhoff, 1998). Examining rats injected with cholinergic lesions as specimens, it was determined that the cholinergic neurons which are irked in the medial septal have a significant role in context‐place memory, contrasting with the argument that it is localized in episodic‐like memory (Easton, Ridley, Baker & Gaffan, 2002).

This is because the rats with the lesions could perform as well as the rest. The only weaknesses that the lesion rats had, was they were quite impaired when it came to the issues of tasks. With this, amnesia could not be linked with the defect of the context alone but also with the other minor regions responsible for memory retrieval and uses. This argument makes the disorder dissociative but it is important to note that the behaviour in rats is not exactly alike to that of humans considering their inability to respond clearly such as through speech in human beings.

For the human brain, recognition memory and episodic memory are clearly explained as with their respective constraints. Since the two are not related, a person may be impaired in cognitive memory while they remain competent in using their episodic memory. Consequently, re-collective memory is argued to contain two types of memories, one based on recognition and the other based on the familiarity (Easton, Fitchett, Eacott & Baxter 2011).

However, research indicates that recollective memory is dependent on episodic memory. Despite being dependent it is also linked to familiarity memory, which is independent. The purpose of recollective memory is to find the location of the place seen concerning the experience. Relying on this argument, we can see that amnesia is quite dissociative in this case since the brain parts are somewhat independent but maintain effective communication among themselves.

Additionally, research has concluded that damage to the medial temporal lobe is capable of causing impairments especially of the memory in areas where the cortex and the anterior medial lobe (Valenstein et al. 1987). This damage could arise from lesions formed in the memory-developed region, the hippocampus. The level of likely impairments also varies as regards the point of contact with the lesions (Davis, Easton, Eacott & Gigg 2013). The cortex is seen to cause more severe impairments that it is in the hippocampus regions. This is also the case that is seen when the levels of amnesia are viewed as being associative. To achieve a varied extent of effects of the lesions on the parts of the medial temporal lobe, they are examined closely with less regard to which part is more damaged than the others, but associating the whole memory system makes it too broad and thus inaccurate.

In conclusion, research practices on the relationships of the brain regions that are crucial like the hippocampus, the cortex and way memory is allocated, gives rise to an understanding of the nature of the condition. As of now, it is suggested that recollection memory is independent to familiarity memory because one can be defective without necessarily ruining the other. Thus the condition of amnesia is dissociative, but how analogous the two brains are has not been well proven considering the experiments on animals.