The Human Memory

The Human Memory

There are numerous brain circuits and anatomical structures known particularly to be necessary for human memory. The hippocampus, for example, is a brain structure often associated with multiple memory functions. Dentate gyrus and Ammon’s Horn are the two structures that make up the hippocampus. It is also important to note that this brain structure lies next to the medial temporal lobe and is one of the circuits found in the limbic system.

In humans, the hippocampus has cognitive maps. In one recent study, scientists took single-cell recordings from electrodes implanted in the hippocampus of a rat test subject. What they found out is that some particular neurons were strongly responsive especially when the rat was in a specific location (Hariri et al., 2013). Cells such as these are referred to as place cells and their collections in humans are considered as mental maps. However, the place cells are not only responsive to one unique area. It discovered recently that their activation patterns overlap randomly to form mental maps in the hippocampus. Interestingly, the right side of the hippocampus responds strongly to spatial aspects even as the left side is more oriented to gather context information. Over time, humans that perform a certain task for a prolonged period of time gain experience that builds up useful mental maps. Therefore, professionals like taxi drivers increase the volume of their hippocampus through memorization of city streets and driveways.

            It is true that humans and animals get their environment’s spatial map through hippocampus because this part of the brain stores important information on non-egocentric space. In essence, an ability such as this supports the notion of independence of spatial memory hence the thought process can be manipulated easily. Considering this, it is safe to say that the retrieval of and maintenance of memories are context-dependent and relational. Most importantly, the hippocampus utilizes the reference and working memory.

A person’s ability to remember particular locations precisely is impaired by blocking plasticity in the brain circuits and structures responsible for memory (Zatorre et al., 2014). For example, if the hippocampus of an amnesic patient is severely damaged, he cannot remember or learn the spatial layouts. Even worse, it is a common knowledge that the removal of hippocampus leads to acute impairment of spatial navigation. There are large spatial impairment differences observed in the ventral hippocampus in comparison to the dorsal hippocampus. Ventral hippocampus lesions do not necessarily affect spatial memory. On the other hand, short-term memory processing and retrieval requires dorsal hippocampus. Furthermore, studies indicate that the infusion of amphetamine into this hippocampal region enhances the previously learned spatial locations.

            Notably, the hippocampus has two distinctive memory circuits. One of the circuits (which includes entorhinal-CA1 system) is used in place recognition based on recollection memory. The other circuit has entohinal-debtate-CA1-CA, also referred to as trisynaptic loop and is used to recall memory on places. Trisynaptic loop circuit also facilitates entorhinal-dentate plasticity to boost place recall.

In neuroscience and cognitive psychology, spatial memory records information on an individual’s spatial orientation and his surroundings. Therefore, this allows the person to easily navigate around a familiar geographical location just as a rat uses spatial memory to locate food at the end of a complex maze (Casey et al., 2011). In animals and humans, spatial memory is considered as a cognitive map. Additionally, both long-term and short-term working memory represent spatial memory, specifically in human beings.

References

Casey, B. J., Giedd, J. N., & Thomas, K. M. (2011). Structural And Functional Brain Development and Its Relation to Cognitive Development. Biological Psychology, 54(1), 241-257.

Hariri, A. R., Goldberg, T. E., Mattay, V. S., Kolachana, B. S., Callicott, J. H., Egan, M. F., & Weinberger, D. R. (2013). Brain-Derived Neurotrophic Factor Val66met Polymorphism Affects Human Memory-Related Hippocampal Activity And Predicts Memory Performance. The Journal Of Neuroscience,23(17), 6690-6694.

Zatorre, R. J., Fields, R. D., & Johansen-Berg, H. (2014). Plasticity In Gray And White: Neuroimaging Changes In Brain Structure During Learning. Nature Neuroscience, 15(4), 528-536.