The Star Wars Neuron

With the Star Wars hype full on the way, many of you may not have realised that the Star Wars saga assisted us in one of the most important neuroscientific discoveries of  recent years. In this particular case Star Wars not only aids us to explain one of the most central concepts of our brain but at the same time helped to discover it.

All of us learn better when we are able to connect newly acquired facts and knowledge with something we already know - a central and crucial process in learning which helps us to learn more efficiently. The same is not only true for learning but also for recalling and remembering certain things. Germans (as always) have a specific name for this: "Eselsbrücke" (donkey bridge). It goes back to the fact that the only way to get a stubborn donkey to cross a stream is to send him over a bridge. And sometimes a donkey bridge is the only way to get our stubborn memories to remember something. So essentially it is easier to remember a name of a river if you have already been there and can link the name with a memory already available in your mind. 

So in order to form connections between certain elements we need to understand concepts. We would not see an obvious link, between a cow and a pencil, however between a cow and a farm or between a cow and cheese. You can also think of each concept as a bucket, once you learn something new, you decide in which buckets your new item will fit. Now what has it all to do with Star Wars. Rodrigo Quiroga and his team had a unique chance when he was allowed to record from actual neurons within the brains in awake patients. Sounds like science-fiction not really. In severe cases of epilepsy it is required to perform a brain surgery to identify the location of the seizure. This procedure requires the introduction of an electrode to stimulate certain areas. With a small tweak you can not only stimulate but also record the neuronal activity from a small and selected population of cells within the brain without any further harm or danger to the patient. 

During one of those procedures (the patients are awake as they would have to respond to stimulations of the brain) they were also shown a set of pictures. After recording a number of neurons the team realised one particular neuron which increased its firing activity when the patient saw pictures of Luke Skywalker (see the figure below). Not particularly surprising, however, the same neuron responded similarly when the name Luke Skywalker was shown on screen or spoken by a female or male voice. So now you may be wondering why we do not call the neuron - The Luke Skywalker Neuron - as the neuron did not respond to any other picture of people or objects in the test set. And yet it responded to one more picture -  the picture of Yoda. This proved that the neuron did not respond only to Luke Skywalker himself but characters associated with it. Due to time constraints they could not test more items and characters but in further experiments the team proved that these neurons would be able to form the basis of how we form associations and concepts and at the same time would explain why the hippocampus (a central brain structure where those cells were recorded) is so important for encoding and recalling of episodes and memories.

Those individual neurons would be able to form the building blocks of a network that would represent our bucket from earlier on. Now if Disney decides to introduce a new character (like the BB-8 droid) in the series your neurons could find anchor points in the Star Wars network/bucket. The neuronal connections to this neuronal network would strengthen everytime you recall the memory of BB-8  or experience it in another episode on or of the screen. Their finding not only awakened the Star Wars Neuron in Neuroscience but at the same time and for the first time in humans identified brain cells which could perform one of the most crucial tasks in our brains.

The response of an individual brain cell in answer to certain visual and auditory stimuli. Note that the neuron increases its activity only when a star wars related item is presented. (Figure adapted from Ref 1)

To quote Quiroga himself in a recent publication the characteristics of this concept cells, as he calls them  as following: 

1. These neurons have a relatively long latency, suggesting lateral processing to extract the meaning of the stimulus
2. They tend to fire to personally relevant concepts, namely, those that the subject may care to store in memory;
3. They have a high degree of invariance, which is in agreement with the fact that we tend to remember concepts and forget irrelevant details
4. They have a sparse, explicit and non-topographic representation, which is ideal for memory functions such as creating new associations 
5. Their function is beyond sensory processing, given that their firing can be triggered by different stimulus modalities or internal processes in the absence of external stimulation

Ref 1.: Nature Reviews Neuroscience 13, 587-597 (August 2012) | doi:10.1038/nrn3251