What are mirror neurons doing?

G Hickok has a paper, Eight Problems for the Mirror Neuron Theory of Action Understanding in Monkeys and Humans, and a blog posting (here). He is saying that the conventional idea of mirror cells is wrong.

First he examines what other cells are doing.

Mirror neurons are cells in monkey frontal area F5 that respond both during the execution of action and during the perception of action. Explaining why these cells respond during action execution is easy and uncontroversial: they are motor cells in a motor area — they respond during action execution because they are involved in the coding of actions. The perceptual response is more difficult to explain. Think first about “canonical neurons”, neighbors of mirror neurons in F5. Like mirror neurons, these cells respond during action execution, e.g., grasping, and they also have sensory properties, e.g., responding to the presentation of graspable objects. The sensory responses of canonical neurons have a fairly intuitive and standard explanation: the grasping of objects needs to be informed by the shape of the object (you grasp a paperclip differently than a grapefruit) and so the sensory input is used to drive appropriate grasping gestures. Importantly, canonical neurons are not assumed to be responsible for visual recognition, they just receive relevant input from areas involved in the processing of visual features… the theory that was proposed early on and completely dominates (suffocates even) thought on mirror neuron function is that these cells support action understanding. According to this view, the sensory response of mirror neurons is not relevant to the monkey’s own actions, unlike canonical neurons. It is rather a mechanism for understanding what other animals are doing via motor simulation. The logic is, if I understand what I’m doing when I reach for a peanut, then if I can simulate another’s peanut-reaching action in my motor system, I can understand what s/he’s doing.

Then he proposes that mirror neurons are doing a similar thing but with actions rather than objects.

… at least consider the possibility that mirror neurons, like their canonical neighbors, take sensory input for a motor purpose… The point here is that it is not hard to imagine sensory-motor circuits that take observed actions as input and use these actions as triggers for any number of executed actions via regular old sensory-motor association. The cells underlying these circuits would probably behave like canonical neurons responding both to the execution and observation of the (non-mirror) actions.

He uses descriptions of playing with a dog to illustrate the need for the motor areas to have information from the sensory areas on the actions of others in the same way that information of objects is needed from sensory areas.

In my view this is another illustration of a neuron/s in effect standing for a concept. Mirror neurons may be a type of ‘grandmother’ cell.

2 thoughts on “What are mirror neurons doing?

  1. I think the function of motor neurons is to allow emulation of the mental processes of others by mimicking the neural processes that have been used to generate the motor actions. I suspect that social animals will have the most robust mirror neurons (to emulate and so understand communication motor actions), but predator and prey species may have neuronal structures that are mirror neuron-like to allow emulation of prey or predator actions.

    JanetK: I don’t think that Hickok is saying that the conventional explanation is wrong but just that it is not proven and there is another explanation that he finds it simpler.

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