A Study on The Roles of Mirror Neurons

Mirror neurons are neurons located in the brain. They allow one to mirror another’s behaviour as though the observer washimself (or herself). Mirror neurons are not form-sensitive and have been directly observed in primate species.They fire when an animal acts or when the animal observes the same action performed by another and only in responseto meaningful actions. Light dots showing plausible kinematics are often also enough to trigger mirror neurons to fire.Brain activity consistent with that of mirror neurons has been found in the premotor cortex, the supplementary motor area,the primary somatosensory cortex and the inferior parietal cortex.Mirror neurons were discovered in the early 1990s. A team of Italian researchers found individual neurons in macaquebrains that fired both when a monkey grabbed an object and also when it watched another primate grab the same object.Another experiment saw gave insight into the notion of action understanding which was demonstrated as follows monkeys were not allowed to see the actions performed by others, but were given clues for understanding them.(noisymotor acts like peanuts breaking, paper earing). They were allowed to either both see and hear or only hear. It was foundthat many mirror neurons in area F5 of the monkey’s brain responded to the sound of the motor act, even when it was notvisible.

The next step was to try to identify mirror neurons in humans, but researchers couldn’t record activity from single neuronsin humans as they could in monkeys, because doing so requires attaching electrodes directly to the brain. An alternativewas to go ahead with FMRI.From FMRI, we can understand activity of neurons in a little box of (3mm x 3mm x 3mm) but we cannot say if they are thesame neurons or just neighbours.Empathy is defined in Wikipedia as “The ability to identify with the feelings, thoughts, or mental states of other people(putting yourself “in the shoes” of someone else), as opposed to sympathyAcknowledging another person's emotional hardships and providing comfort and assurance”.Mirror neurons or indications leading to them are not new. Lipps (1903) noted how on watching an acrobaton a suspended wire, he could feel himself doing the same (“IchFühlemich so in ihm“).The above indicates how intersubjectivity is an essential function of mirror neurons. In fact, mirror neurons fire both when we observe and perform anaction. Vittorio Gallese calls this the “mirror-matching mechanism. Gallese states that this same mechanism helps usempathize with others’ pain and emotions displayed by them.

In another experiment, Hutchinson et al. noticed that some neurons fired when inflicted pain and also when the subjectobserved pinpricks to examiner’s fingers. Explaining the mechanism, Ramachandran states that neurons anteriorcingulate respond to pain. A subset of these same neurons fire after observing someone else in pain.

There was another experiment which was conducted using monkeys. A box with a mirror was placed in front of themonkey. The mirror did not enable the monkey to see its contents. The box was then lit up and the monkey was able tosee the contents and grab the object inside. The door of the box was opened and the monkey was allowed to grab foodkept in well under the object. Arm and hand movements were recorded using ELITE

Next they tested the mirror properties, Experimenters grasped food in front of the monkeys amongst other activities. Toensure that neurons fired in response to hand-object interactions, they observed neural activity for activities likepretending to grasp objects etc. They finally recorded their observations and these observations seemed in sync withthose predicted by the ‘mirror-matching’ mechanism.

Action Understanding Hypothesis:

The theory of mirror neurons and action-understanding is one that has not yet been sufficiently developed to produce arigorous framework that can be considered a firm scientific background. However, a lot of speculation on the basis ofexperiments has been done to form a rough idea of the substance that we are working with.

We, as of today, do not know whether the mirror neurons are simply neurons which suddenly take on a specific functionas a response to external sensory stimuli, in which case a good question to ask is “What triggers them to respond to thechange?”, or whether they are, in fact, different from other neurons in structure, and are specifically activated in caseswhere a response of “empathy” is called upon. As for the location of these mirror neurons, experiments have shown thatthey are present in the motor-cortex-region of the brain. However, the mirror neurons that fire during the observation of anaction may or may not be the neurons that fire during the performance of that action, for the response of the neurons canbe calculated to a precision of only 3 cubic millimetres, thereby resulting in the filtering for both the performance and theobservation reaction-triggering neurons, down to the small volume of 3 mm 3, but not more. Hence, we do not know forabsolute certainty, whether the same neurons are firing, but it has been considered, for very unclear reasons, a safeassumption to make.

Rizzolatti begins his 2008 paper by stating that his hypothesis on the function of mirror neurons is that they contribute“mediating imitation” and in “action-understanding”. Rizzolatti himself believes that both these theories are likely, and arenecessary, but possibly not sufficient to explain understanding of various situations. He first starts off by stating that whilehe believes that mirror neurons have been of great evolutionary importance, helping primates understand the actions ofother members of their species, he clarifies that he does not claim that it is their only source to understand the actions oftheir conspecifics.

This argument is supported by Iacoboni’s experiment, in which he takes photographs of a ball falling and that of a personperforming a certain activity, and shuffles the photographs in each set, still keeping the two sets distinct. Now, he handsthese photographs in their arbitrary order to persons whose cortical regions of the brain are damaged, and ask them toput it in some order. The result observed was that while the patients were able to re-order the “falling ball collection” intothe right order, they were unable to do the same for the person’s actions. Iacoboni now concludes that this is because,due to the damage to their cortical regions, the mirror neurons do not fire a response, thereby making them incapable ofunderstanding what the person has been doing, that is, they are unable to “understand”, and hence, cannot re-order thepictures in a meaningful manner. However, a valid point to ask would be this- “How, then, do they understand the falling ofa ball?” Sadly, the person who interviewed Dr.Iacoboni omitted to ask him this question, so one can only speculate as tohis response on the matter. One way of explaining it would be to say that there are varying degrees to your understandingand that the falling of a ball is so “basic”, that it struck them to expect it to go downwards. However, this is a weakargument, for it brings in a very difficult, immeasurable quantity- “so basic”. Therefore, we would personally go withRizzolatti’s argument, that the mirror neuron mechanism is not the only mechanism that stimulates understanding of agiven action, thereby showing that another mechanism may control certain understanding, yet still proving Iacoboni’spoint, that mirror neurons contribute greatly to the process of action-understanding. Another view-point that that one canthink of is that the mirror neurons are said to make you understand other people’s reactions better, stimulating similarresponse in the observer, but since the ball is an inanimate object, there is no question of “what the ball is thinking”, andtherefore its behaviour is no longer controlled by a mind, but by the laws of physics, forcing it to fall down.

Now, Rizzolatti continues to put forth his opinion on the influence of mirror neurons on action-imitation. He states that themirror neuron system forms the basis for imitation, but also says that this is not their major function. He states that whilelaymen seem to consider imitation a primitive cognitive ability, it is actually quite advanced, seen only in primates,primarily in humans and apes. From here, he concludes that the only function cannot be action-imitation, a rather blanketremark to make in a research paper, we believe. However, in an earlier paper of his, he remarks that when an observedaction is recognised, it stimulates an analogous motor-representation in the observer’s brain, thereby making the observeraware of what it happening to the other person, but that a motor-control mechanism helps to prevent the person fromactually performing the observed action. Therefore, it would appear that the function of the mirror-neurons would be notonly to elicit “blind mimicry”, but to also help in understanding why the action is being performed by making the observer“feel the action”. Once again, this is pure speculation on our part, and we claim nothing of it to be beyond questioning.

The discussion so far should have raised an important question- “How can mirror neurons activate a response without anyprior knowledge of the reactions that occur during such actions?” Rizzolatti answers this question as well in his 2008paper, in which he states that the mirror neurons induce motor-representations of observed actions if and only if theactions’ outcome are known. This is, in its essential terms, the theory of action-understanding.It was earlier thought, by subscribers to this concept that the mirror neurons helped attach meaning to a given action, butlater, scientists begun to suspect that they actually encode for an action. To this effect, Iacoboni believes that autisticpatients who lack the ability to empathize, lack functional mirror neurons due to damage to their cortex and hence, areunable to attach any meaning to any action and therefore, are incapable of learning meaning of specific actions since theydo not have the ability to attach any meaning to them.

Now, Rizzolatti proceeds with his argument in favour of the action-understanding hypothesis, stating that his method ofproving his theory, should have ideally been to de-activate certain sites in the brain of monkeys where these neurons aresupposed to act and then, proceed to perform experiments on the primates to observe the differences, but says that hefinds three major problems- a) that the mirror neuron regions in the brain comprise the premotor cortex and the parietalregions, a very large part of the brain; b)that not the mirror neurons alone mediate understanding; c) that de-activation ofcertain sites may have other effects that may affect the experiments adversely, reducing accuracy.

Therefore, he proceeds to illustrate how he proves the theory using an experiment by Kohler. His idea is to perform anaction in the presence of monkeys, so that the monkeys understand the occurrence, but then, remove the visual features.If the monkeys respond still to the sound or other distinguishing sensory features of the experiment, it would mean that themonkey is not merely seeing, but actually understands what is happening. For instance, let us say that a man swings ared axe to cut off a piece of wood, necessary to build his house, and so is very pleased with his efforts. Assume that youneither have any reason to want the survival of the tree nor the construction of the man’s house. Yet, if you see that theman is pleased, you may feel the contentment that the man may feel, when the tree is cut. If the man had swung a blueaxe, your reaction would have probably not changed, for in the scope of the experiment, the colour-change means verylittle. Kohler conducted an experiment on the monkeys, showing that when the visual stimuli were removed, 15% of themirror neurons that had fired before still fired, showing that these mirror neurons were not simply sight-dependant, butcould actually understand the experiment, and probably even the motive- to chop off a block of wood. An interestingquestion to ask would be, “How is it known that in the experiment, the monkey is responding to visual stimuli at all?” Well,

Kohler did the experiment with sight-only, sound-only tests, all to which the monkeys respond, thus generallytelling usthat once the action has been recognised, the action is then being understood before the response is simulated, hence,proving the action-understanding theory.

Another experiment was conducted by Umilta, in which she keeps food in front of a monkey, and drops a screen betweenthe monkey and the screen. Then, the monkey is allowed to reach behind the screen to get the food. Then, she removedthe food and performed a similar experiment, and the monkey still performed the action of reaching, which means that themonkey had already understood the probable presence of food behind the curtain. This, of course, supports Rizzolatti’sargument that mirror neurons aid in action-understanding.

Counter-arguments to the Action-Understanding Hypothesis:

One of the vocal opponents of this hypothesis is Dr. Greg Hickok from UC Irvine. While he does not dispute the existenceof such neurons (which fire when observing an action performed by somebody else), he is against the idea that theseneurons are necessary for the observer to understand the actions of others. He believes there is not enough evidence toconclude the same and raises the possibility that the actual understanding may be taking place elsewhere in the brain (thesuperior temporal sulcus, STS, for instance) and the activation of the mirror neurons is more of a by-product in theprocess of action understanding as in the firing of mirror neurons is a kind of memory associated with the memory of theparticular action that is triggered when the brain tries to understand the observed action as opposed to the belief that themirror neurons themselves encoded the meanings of the actions themselves. In support of his argument, Hickok notesthat patients with Broca’s aphasia, who find it difficult to construct meaningful sentences, are still perfectly capable ofcomprehending sentences that they hear. Similarly, one could understand the meaning of several actions though he/shemay be incapable of performing that action like flying, slithering, etc. Hickok therefore warns against going forward withthis hypothesis and looking for cures for autism by focussing on mirror neurons because the malfunctioning of mirrorneurons may just be an effect of the lack of empathy and inability of the autistic patient to understand others’ actions(which might actually be caused due to the malfunctioning of some other part of the brain) than a cause of the same.

Dr. Vittorio Gallese, who was one of the original discoverers of mirror neurons in macaques, provides another side to theargument. He argues that though mirror neurons may not be necessary for a superficial understanding of the actions ofothers, for the observer to put himself/herself in the shoes of the performer, to inwardly experience the performance of theaction (what Gallese called as “understanding from the inside”), one needs mirror neurons. In other words, Gallesebelieves that mirror neurons are necessary to feel empathy.