Did you know that the Brown thrasher is a type of songbird that can learn and sing up to 1000 different songs in its lifetime?
The songbird’s brain has a set of neurons called mirror neurons, which can help it mimic another bird’s song after merely hearing it. This auditory-vocal mirror neuron system operating in the songbird’s brain is what gives the Brown thrasher its unique singing ability and thereby the choicest of mates.
We know that neurons ‘fire’ to transmit information as electrical impulses, to and from the brain and spinal cord. This information transfer can be compared to a relay race where passing of the baton is how information from one neuron to another is transmitted. But, such information is mostly encompassed within a stimulus-response framework. So, how are mirror neurons functionally different from any other neuron? Mirror neurons fire when an animal performs a task by itself as well as when it observes another animal performing the same task. These neurons were discovered in Macaque monkeys at the University of Parma, Italy (Gallese et al., 1996) by Dr. Giacomo Rizolatti’s group in 1992. The group’s focus was the study of a specific region in the monkey brain which was known to have neurons that responded to goal-specific limb movements like grasping and holding food. When the scientists recorded activities of individual neurons in that region, they were amazed to see that the same neurons fired both, when the monkey moved its hands and when it observed an experimenter’s hands moving. The fact that these neurons ‘understood’ the action was indeed intriguing and immediately piqued the interest of other neuroscientists who took it a step ahead.
What about the existence of mirror neurons in humans? One neuroimaging study has indicated the presence of neurons similar in activity to mirror neurons, in the human brain. A study in musicians and sportspersons has shown that the effect or enjoyment of an activity is heightened in individuals who have had prior exposure to the same through learning. This suggests that learning an instrument or a sport helps the perceiver enjoy a concert or a match better than their untrained peers. However, none of these studies provide evidence for the existence or function of mirror neurons in the human brain.
Several contrasting views have emerged with respect to why the existence of mirror neurons is essential within the human brain. For instance, it is believed that mirror neurons influence social behavior by enabling one to develop linguistic skills, feel empathy, process emotions and read general social cues. The dysfunction of these neurons is believed to cause illnesses like schizophrenia and autism spectrum disorders. This was put forth as the ‘broken mirror hypothesis’ by Dr. V.S Ramachandran in 2006. To explain the secondary symptoms of autism, he further proposed the salience landscape theory. According to this theory, the emotional landscape within a child’s brain is scrambled due to the distorted connections between the amygdala (center for emotions in the brain) and sensory organs. Due to these altered connections, the body responds with hyperactivity toward many ordinary stimuli resulting in epilepsy (fits), and repetitive head motions as observed in autistic children. However, both, the hypothesis and the related theory remain highly controversial to date.
In 2014, neuroscientist Gregory Hickok explained in his book ‘The myth of Mirror Neurons: The real neuroscience of Communication and Cognition’ that most researchers have built the science of mirror neurons on mere assumptions. He used various published research spanning work done on the animal to modern neuroimaging tools to claim that the mirror neuron theory does not provide evidence for ‘action understanding’ and is only task-specific. He claimed that the firing mechanism had to be a consistent observation for all types of instructions, which was not observed in most cases. He also claimed that the mirror neuron systems in the macaque and human brains have no parallels.
So, how much can we infer based on such contrasting scientific opinions and lack of concrete evidence? In its current standing, the mirror neuron system does efficiently provide an explanation for many social behaviors in animals. The most recent research into this system describes how it helps humans understand each other’s emotional states. It was discovered through neuroimaging that humans possess shared neural activation systems to produce and perceive common facial expressions such as joy and anger. However, till a deeper understanding is achieved, let’s remain conservative about its significance in human lives, and enjoy the thrasher bird live in concert as we keep our wide-eyed wonder alive.
Author:
Amrita Anand is in her 4th year of Ph.D. in Genetics and Genomics at the Baylor College of Medicine, Houston. She studies the reprogramming potential of certain key factors in the regeneration of mouse inner ear hair cells. She has been actively pursuing Science communication over the last three years as she enjoys bridging the gap between scientists and non-experts. As an editor, she wants to make science more accessible to the public and also hopes the hard work behind the science gets due credit.
Linkedin: https://www.linkedin.com/in/amritaaiyer/
Twitter handle: @_amritanand
Editors:
Saurja Dasgupta is originally from Kolkata, India. He obtained his Ph.D. at the University of Chicago, where he studied the structure, function, and evolution of catalytic RNA. He is currently doing his postdoctoral research at Massachusetts General Hospital, Boston, where he is trying to understand the biochemical milieu that could have given birth to life on earth (and elsewhere) and reconstruct primitive cells. One of his scientific dreams is to observe the spontaneous emergence of Darwinian evolution in a chemical system. When not thinking about science, Saurja pursues his love for the written word through poetry and song-writing (and meditating on Leonard Cohen’s music). His other passions are trying to make science easier to understand, and fighting unreason and pseudoscientific thinking with a mixture of calm compassion and swashbuckling spirit.
Roopsha Sengupta is the Editor-in-Chief at ClubSciWri. She did her Ph.D. at the Institute of Molecular Pathology, Vienna and postdoctoral research at the Gurdon Institute, University of Cambridge, UK, specializing in the field of Epigenetics. During her research, she was involved in many exciting discoveries and had the privilege of working and collaborating with a number of inspiring scientists. As an editor for ClubSciWri, she loves working on a wide range of topics and presenting articles coherently, while nudging authors to give their best.
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