How do we truly know where we are? How do we find our way from one place to another? How does the storage of this information enable us to remember the way for the next time we repeat the same journey without needing to look at any external maps? Your inner GPS enables you to find your way around by processing where you are and the relationship between yourself to the space. The power of the hippocampus in the brain functions to represent the places, distances and directions, and postulates what we know as the Cognitive Map Theory – how you already know where you are.
The idea of a cognitive map derives from the 18th century German philosopher and Enlightenment thinker Immanuel Kant of whom proposed that humans and animals have innate perceptual intuition for processing sensory information, with the geometrical-spatial framework being one of them.[1] This theory was extended by the early 20th century psychologist Edward Chance Tolman who in 1948 published Cognitive Maps in Rats and Men: proposing the notion that rats had cognitive maps that enabled them to effectively navigate themselves through their surroundings.[2]
What was ground-breaking was the discovery in the main part of the brain that processes this information: the hippocampus and its related areas. This was notable in John O’Keefe’s and Jonathan Dostrovsky’s study published in 1971: ‘The Hippocampus as a spatial map…’.[3] Through anaesthetising rats with a sedative chloral hydrate and planting a micro-drive into their skulls, O’Keefe and Dostrovsky were able to identify the nerve cell that was activated when a rat was at a specific place in a room.[4] Other nerve cells were stimulated when the rat was in other areas and O’Keefe named these ‘place cells’ that essentially formed a map of the room.
Figure 1: O’Keefe and Dostrovsky – ‘Responses of a hippocampal unit to a restraining tactile stimulus as a function of the rat’s spatial orientation’.[5]
The hippocampus is a small yet complex brain structure that is located in one of the main four lobes of the cerebral cortex: the medial temporal lobe and is involved in the role of learning and memory.[6] The human brain has two hippocampi on each side of the brain, and it is a crucial component of the limbic system that plays a significant role in how memory is processed from short-term to long-term memory. Hence, it is also responsible for dealing with our spatial memory that enables navigation and spatially codes out where we really are.
Figure 2: Posterior and inferior cornua of left latral ventricle exposed from the side.
Source: Henry Gray, Anatomy of the Human Body, (1918)
Available From:https://upload.wikimedia.org/wikipedia/commons/2/2e/Gray739-emphasizing-hippocampus.png
In 2005 May-Britt and Edvard Moser discovered another crucial component of the brain’s navigation system. The discovery of ‘grid-cells’ that generated a coordinative system that allowed for accurate pathfinding. [7] These discoveries enabled scientists and philosophers to understand how various cells processed spatial information, for example different cells were specifically associated to representing places, directions and distances. Collectively these nerve cells create a cognitive map that is the framework which identifies where you are and what surrounds you so that you may get from one place to another.[8]
To no surprise, the 2014 Nobel Prize was awarded with one half to John O’Keefe and the other jointly to May-Britt Moser and Edvard I. Moser for their ground-breaking discoveries of cells that constitute a positioning system in the brain and formulated what we now know as cognitive map theory.[9] This notion currently extends to patients with Alzheimer’s disease whereby the hippocampus is adversely affected at an early stage causing the individual to often become lost and not recognise their environment.[10] The epistemology of this theory may potentially be crucial to understanding the working of the spatial memory loss that affect people with a disease like Alzheimer’s.
Let us conclude by experimenting the idea of knowing where we are already. If I asked you to close your eyes and walk yourself outside of the room that you are currently seated in, you would most probably be able to achieve this whilst walking backwards - for you are aware that the potential trip hazards and the distance between yourself and the door. If you don’t believe me and these remarkable innovators of neurology – try it yourself and the next time you instinctively know that it is a left turning at the end of the road, give thanks to your hippocampus.
Written by Natalie Spencer, MSc History of Science, Medicine and Technology, Linacre College.
References
[1]Binder M.D., Hirokawa N., Windhorst U., ‘Cognitive Map Theory.’, Encyclopedia of Neuroscience. Springer, (Berlin, 2009), Available from: [https://doi.org/10.1007/978-3-540-29678-2_1117].
[2] Tolman, E. C., Cognitive maps in rats and men. Psychological Review, (1948)., 55(4), 189–208.Available From [https://doi.org/10.1037/h0061626].
[3] J. O’Keefe, J. Dostrovsky, ‘The Hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat’, Brain Research, (1971), 171-175.
[4] Ibid.
[5] O’Keefe and Dostrovsky, 173.
[6] Erika P., ‘How Does the Hippocampus Affect Bodily Functions?’, The Science Times, (September 15 2020), Available From: https://www.sciencetimes.com/articles/27300/20200915/hippocampus-bodily-functions.htm, [Accessed 1 October 2020].
[7] The Nobel Prize, ‘Press Release’ Nobelfösamlingen, (10 July 2014), Available From: https://www.nobelprize.org/prizes/medicine/2014/press-release/, [Accessed 1 October 2020].
[8] Nobel Prize, “The cognitive map is how we know where we are”. John O’Keefe explains his Prize-awarded work’, 8 December 2000, Available From: https://www.youtube.com/watch?v=favAUcplFKI, [Accessed 1 October 2020].
[9] The Nobel Prize, ‘Press Release’.
[10] Ibid.