The discovery of mirror neurons has allowed for a new way of understanding the relationship between cognition and actions. In a recent review, "Mirror neurons and their relationship with neurodegenerative disorders" by Farina et al, looked further into the mechanisms of these mirror neurons when it came to neurodegenerative diseases.
Traditionally, it was thought that functions such as cognition, perception, and any type of execution are separate, however, with the discovery of mirror neurons, it can be seen that actually these functions might not be separated but rather are associated using mirror neurons. It has also been shown that the motor and cognitive symptoms that come with many neurodegenerative diseases appear to be associated with each other, and so attempting to look into mirror neurons which also connect such associations, can potentially be used as a therapy for such diseases.
What makes mirror neurons particularly interesting is they will activate when you carry out an action but they will also activate when you see someone else carry out that same action. These type of neurons were first seen in monkeys are researches were recording from neurons in the ventral premotor area and the inferior parietal lobe. They noted that these neurons were activate when a monkey saw another monkey grabbing a cup or even during chewing motions. That neuron would also fire when the monkey was carrying that particular action themself. In another study done on monkeys, an interesting observation was made where mirror neurons might also be involved with other cognitive functions such as determining intentions as they can incorporate actions with conditions and ultimately associate them. They noted that this might be done as a form of trying to understand other behaviors and finding a way to response to those observed behaviors.
Mirror neurons have also been observed in humans using fMRI (functional magnetic resonance imaging) imaging and EEG (electroencephalography) recordings. In humans, mirror neurons are typically seen in the premotor cortex, primary motor cortex, and the hippocampus. The mechanisms of neuronal activation when a perceived grabbing action is observed, is also seen in humans. In fact, in some EEG recordings, it has been shown that the mirror neuron mechanism is linked to a suppression of micro rhythms that were seen when someone observed someone else carry out an action. As it was noted in monkeys, mirror neurons can be used when recognizing actions, interpretation, and also when it comes to learning motor skills. This was particularly done by having participants, who have never played the guitar before, watch a video a tutorial on how to play certain chords. The video was then paused and the participants had to play what was just shown in the video. Researchers found there to be an activation of the mirror neurons when this was done. Mirror neurons have also been shown to be involved in functions such as language and even memory since these functions come from actions themselves.
When it comes to mirror neurons and neurodegenerative diseases, there is slightly more information with regards to Parkinson's disease. As is known, Parkinson's disease involves the degeneration of dopamine neurons in the substantia nigra which lead to motor deficits and even changes in behaviors. When it comes of mirror neurons, their functions seem to be disrupted with the degeneration of pathways in Parkinson's disease. However, there have also been studies to show that if mirror neurons are stimulated, it can help with some functions carried out by these neurons like motor skills and cognition. When it comes to neurodegenerative diseases such as frontotemporal dementia and amyotrophic lateral sclerosis, it has been thought that mirror neurons take on mostly motor functions, and the language decline that is typical of these diseases can be explained as the mirror neurons are also decaying. With regards to Alzheimers' disease and mild cognitive impairment, there is still more research that needs to be done to investigate mirror neurons. There are some potential treatments that can target mirror neurons when it comes to neurodegenerative disease such as AOT (action observation training) which can help in motor and cognitive functions and even memory. However, this might only be a temporary solution as the diseases would still progress.
Overall, mirror neurons have been shown to be involved in varying functions which include those of learning, motor, and cognitive functions. Although there is still more research that needs to be done regarding some neurodegenerative disease and mirror neurons the information that is already known can point to another way of understanding higher level functions and learning motor functions.
Reference:
Farina E, Borgnis F, Pozzo T. Mirror neurons and their relationship with neurodegenerative disorders. J Neuro Res. 2020; 98: 1070–1094. https://doi- org.dml.regis.edu/10.1002/jnr.24579