Nobel Prize in Medicine 2014: how space is represented in our brains?

brThis year’s Nobel Prize in medicine specialty was delivered to a pair of researchers who explored how our GPS internal: the parts of our brain that allow us to locate and navigate spatially .

Full text created by Olga Rodriguez Sierra. Originally posted in Pijamasurf.

This year the Nobel Prize in Medicine was awarded to John M. O’Keefe neuroscientists, May-Britt Moser and Edvard I. Moser, for its fascinating discoveries of cells in the brain that allow the representation of place and space navigation, our Internal GPS“. His scientific work revolutionized our understanding of how the brain performs complex mental functions, as would be perceived location of the body in relation to the environment and objects around us.

For centuries, many philosophers have asked about the nature of space. Immanuel Kant devoted most of his work to this concept, since its Inaugural Dissertation(1770) noted that:

The space is a pure intuition which contains the fundamental form of all external sense, is not something objective and real, not substance, accident or relationship, but something subjective and ideal. It is continuous, and although there is no real objective is, however, not only completely true regarding all sensible things (sensibilia), but also the foundation of all truth in the external sensitivity.

That is, Kant argued that the notion of space was a priori intuition that existed in our mind regardless of experience. Many decades later, the psychologist Edward Tolman (1948), from his experiments with animals, he suggested that they were capable of representing space using a cognitive map that included relationships between places and events, allowing them to navigate from one place another. Remember that at that time experimental psychology assumed that all behavior could be understood by analyzing relationships such as stimulus-response; Tolman‘s proposal of a cognitive map strongly distanced this paradigm.

It was not until 1971 that John O’Keefe and Dostrovsky Jonathon discovered some neurons in the hippocampus were activated when the rat was in specific parts of the environment, so the called place cells” (place cells). O’Keefe showed that these cells do not merely reflect a sensory preference but represented the environment holistically as a gestalt. Furthermore, their results suggest that the combined activity of several neurons (neurons assembly) can encode a unique way, different places. The ensemble of neurons is a theoretical concept that had earlier been introduced by Donald Hebb. Undoubtedly, their findings stimulated numerous studies within the subdiscipline of systems neuroscience, which seeks to relate cognitive processes to physiological responses of the brain at the cellular and molecular level.

For some time it was believed that the signal generated by the preferred place for each neuron field came from the same place hippocampus. However, studies with hippocampal lesions revealed that the signal came from outside, in particular, the entorhinal cortex. May-Britt and Edward Moser decided record signals from neurons in the entorhinal cortex and found that the cells were activated in multiple locations in the room, forming a hexagonal grid pattern and equidistant. These neurons were called grid cells (grid cells). Moser found that the distance shown in the grid cells varied along the entorhinal cortex, the ventral portion being harboring the cells with larger fields. From these experiments it is thought that the brain is organized in functional modules, which may encode different grating space espacimiento depending on site characteristics. In addition, their research identified cells that respond to head direction (head direction cell) or boundary of the environment (border cells) that are important to give our notion of location of body in relation to the outside world.

A neuron in action

Since long ago it is known that the hippocampus is related to the processes of spatial and episodic memory. The prime example is the case of Henry Molaison (better known as HM), a patient who received treatment for epilepsy and bilateral removal of the hippocampus. After surgery I could remember old memories but could not form new memories of events that he experienced; Technically, he had lost his ability to form episodic memories. Currently, it is established that the deterioration of the hippocampal formation is an anatomical marker for neuropathology such as dementia and Alzheimer‘s disease. Furthermore, fMRI studies in London taxi drivers report that their hippocampi are much larger compared to the hippocampi of people do not have to use spatial memory frequently. Evidence suggests that episodic and spatial memory are linked, but so far there is no theory that unifies these two processes; starting from a Kantian idea, we can speculate that the measures of space and time encoded in the hippocampus help anchor memories in temporal relationships of past and present.

We now know that there is a reciprocal relationship between grid cells (grid cells) in the entorhinal cortex and place cells (place cells) in the hippocampus. In particular, the grid cells are a system of spatial coordinates metric which determines the activity of the cells in place in the hippocampus. The two types of cells found in other mammalian species, such as mice, bats and monkeys. In addition, studies in neurological patients with electrodes implanted in the temporal cortex suggesting that humans also have place cells and grid. Many of these studies are recent, less than a decade if not, a few years after its publication, so it is surprising that the Nobel Committee has chosen galardonarlos. I will not rest to extraordinary merit; undoubtedly one of the most complex functions of the brain is its ability to space navigation, as it requires the integration of multisensory information to organize memories and execution behavior of organisms. These three leading neuroscientists were instrumental to make way for biological research on cognitive functions, showing once again that our mind is not separate from our biological body.


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