Looking and Doing
Mirror neurons translate what we see so we can relate to the world. The brain waves of people were recorded as they opened and closed their hands. In normal people, the patterns of brain waves were the same as when they watched a video of someone performing the same actions. For people with autism, however, the wave changed. This could indicate that autism has something to do with broken mirror neurons. Cause and effect is still unknown and additional work needs to be done (PBS, 2005).
Mirror neurons may make it possible to translate one sense into another sense. It may be that mirror neurons can help change visual information, say, into proprioception. This could be evidenced by the fact that the most common activation of mirror neurons is caused by actions of the hands such as holding or tearing. This could be because visual information of others' actions with their hands may need to be converted into one's own actions (Pines, 2002).
Mirror neurons are found in the visual brain, in the visual cortex, and in the movement brain, in the premotor cortex. They are multimodal neurons, or neurons that can be activated by different types of senses such as sight, sound, or somatosensory. The activation of the mirror neurons in the premotor cortex is affected by the proficiency of the person in the action being watched (PBS, 2005). It is theorized that mirror neurons have connections to the limbic system because when people see faces with feelings, the person will start to feel that feeling. When they imitate that face, the feeling becomes much stronger (PBS, 2005). It is unknown whether or not mirror neurons are present at birth, and if they are, it is unknown whether or not they are activated first by seeing an action or only after the association between seeing and executing is built up (Tissaw, 2007).
Possible Development of Mirror Neurons: What It Means To Be Human
Humans are intensely social animals. We have dances, handshakes, games, talking, and all other means of interacting with one another. Language and culture are what distinguish us from the great apes. V.S. Ramachandran, a leading neuroscientist who has done work with mirror neurons, suggests that at a key point in our evolution, our mirror neurons got better. He proposes that this is what makes us different from other animals. This improved mirror neuron system would allow us to thrive in all sorts of conditions. For example, it takes a bear millions of years and many generations for a bear to evolve a thick fur coat, but it takes a short amount of time for one to watch a teacher skin a bear and put it's fur on (PBS, 2005). It's possible that the mirror neuron system is an ancient recognition system, matching observations and performed actions. This would mean that it would be a source of learning from actions. This means that mirror neurons could be the foundation to dance, games, tribal rituals, and even the evolution of human language (Pines, 2002).
Daniel Glaser is a professor in the University of College London. He hooked dancers from London's Royal Ballet, and capoeira experts up to an fMRI scanner. Capoeira is a Brazilian martial arts form similar to dancing. These subjects, and a control group who weren't dancers, watched videos of ballet or capoeira while they were in the fMRI scanners. The mirror neuron system had more activity when the subject watched a dance in which he was trained. This means that mirror neurons were more active for capoeira experts when watching capoeira, and the ballet experts' mirror neurons fired more when they watched ballet. The non-dancers had much less activity than the ballet dancers or the capoeira experts. This shows that the system reacts differently depending on whether you have been trained in the action being observed (PBS, 2005).
"This is the first proof that your personal motor repertoire, the things that you yourself have learned to do, changes the way that your brain responds when you see movement."
-Daniel Glaser (PBS, 2005)
Glaser chose dance for his experiment because it has a vocabulary of movement. This means that there is a standard set of movements, each component has a name, and if anyone is asked to recreate a particular move, it will be consistently the same. The premotor cortex changed in activity depending on whether or not the subject knew that dancing style (more activity was seen for people watching their own style of dance), but the activity of the visual cortex was the same no matter which dance was being witnessed (PBS, 2005).
The intraparietal sulcus is an area of the brain behind the motor cortex, and in front of the visual cortex, it is responsible for visual-motor integration. The Dorsal premotor cortex is responsible for planning of complex actions.
This diagram shows the results of another experiment. As you can see, the activity of areas like the prefrontal cortex (the very front of the brain) is much greater in pianists, both playing and listening, than non-musicians. Some of the same areas activate for pianists when both playing and listening to music. This shows the difference between expertise and non-expertise in activations of the mirror neuron areas in the brain.