How your brain tells you where you are

Reference:

Neil Burgess - “How your brain tells you where you are”

Filmed at TEDSalon London, November 2011

http://on.ted.com/Burgess

Review:

Neil Burgess, director of the Institute of Cognitive Neuroscience at University College London, delivers an interesting speech about the brain cells’ pattern activities and how these inform our perception of the physical environment surrounding us. Burgess opens his lecture with an engaging question: When we park a car in a parking lot, how do we remember where we parked it? Here he illustrates the situation with an image from the animated sitcom The Simpsons; the image we see portrays Homer (Simpson) facing the problem presented in the opening question.

Burges then draws the audience’s attention to the hippocampus; a part of the brain that the author refers to as the “organ of memory.” This is where information from our short-term and long-term memory is processed and stored. The hippocampus also plays an important role in spatial navigation. The hippocampus, like any other part of the brain is made of neurons, and it is the first region affected in those suffering from Alzheimer’s disease. Burgess exemplifies the inner workings of the brain by showing a graphic representation of a rat’s neuronal activity while moving in an enclosed space. The experiment shows that same neurons fire electric impulses whenever the animal moves in any given direction. Burgess also refers to a study conducted on patients suffering from epilepsy; in the study the patients were asked to drive a drive simulator around a virtual town. Like in the previous experiment, same neurons would become active every time patients reached particular locations in the simulated town. In other words, our brain is constantly mapping the world around us and stores the retrieved spatial data.

 Brain cells do not only fire due to movements within explored and familiar spaces, they also react to changes in our environment by locating and mapping them into our memory. If we expand or modify the box the rat was placed in, areas in the hippocampus will expand and change accordingly. This arguably means, that detecting the boundaries and distances pertinent to our surrounding environment is the main role of hippocampus. In order to further explore this phenomena on humans, Burgess and his team created a virtual environment that simplifies the processes informing the placement of objects within the shifting boundaries of our environment. People would be given some time to explore a given environment and then, moments later, when reintroduced to it, many of them were increasingly efficient at finding objects (a flag, a car) placed within it. Moreover, when they were placed back in environments that have been purposely enlarged, neurons stretched out in the exactly same way the place did.

Finally, place cells get an important input for path matching from the cell called a grid cell. A grid cell is a type of neuron found in many mammals. As the animals explore places, these cells fire out arrays into different directions in a regular triangular grid. Burgess describes these arrays as the latitude and longitude lines marked on a map. As the animal moves around, the center of activity of the cells moves accordingly, informing the animal’s brain of where it is in the space. Burgess further states that MRI scans show that people playing a game in virtual space have an increase on the entorhinal cortex’s activity.

At the end of his speech, Burgess returns to the opening question. Homer, Burgess argues, remembers the location of his car by detecting the distances between the objects and the boundaries around them, a process regulated by the firing of boundary-detecting cells. Homer’s path to his car, however, will be directed by the firing of grid cells. By moving around, he will match firing patterns stored in his brain when he left the car with those firing at the time of his return. Additionally, Burgess hypothesizes that same neural mechanisms that carry different tasks in spatial memory, are used for generating visual imagery. This would allow us to recreate events that happened to us. At this moment Burgess introduces head direction cells, cells that fire electric impulses according to the point from where we are facing objects or events. These neurons help us define viewing directions in space. They also help us imagine past or entirely imaginary moments from different viewing perspectives.

Burgess closes his lecture by stating that we are entering a new era of cognitive neuroscience where the processes informing our capacity to remember, imagine, or perceive things around us, should be fully comprehended.    

Reflections:

In his speech, Neil Burgess introduced several types of neurons in a highly engaging manner. Place cells, grid cells, and head direction cells are all inter-directional subsystems of spatial memory, responsible for the production of cognitive maps. As a performing artist I find this insight to be of great importance, not only for understanding environments and the space around us, but for understanding how we perceive and communicate with other subjects within it. This is especially important for group performances where performers are required to be aware of the presence of other performers, audience members, and the spatial particularities of the venue. During rehearsals our firing neurons are creating cognitive maps, maps that are then used during performances. Live performances, however, are usually unpredictable and different firing cell patterns will occur in the actual moment.

Another important point introduced by Burgess is that neural mechanisms responsible for spatial memory invoke the emergence of visual imagery. Understanding the phenomena of visual imagery can be important for artists such as painters, dancers, directors, and for all of those whose works involve any kind of visualization.

Therefore, it is not surprising that contemporary classical composers consider our perception of space equally important as our perception of sound. It also evident that many creators today instruct audiences or performers on how to position themselves in space in order to improve the performance or experience of their works. During the second half of the 20^th century we saw the emergence of a new form of artistic expression called cite-specific art. In this tradition, the artwork is created to exist in a specific space, carefully chosen by the artist. Even though such locations very often include urban sites, many artists choose rural landscapes as an environment for presenting their works. Consequentially, our perception of an artwork is deemed to change according to a surrounding environment that forces us rethink our relationship to it. This way our cognitive maps would be redrawn by something more than spatial orientation.