Talk:Mirror neurons

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    Comments: R: Indicates comment by reviewer {...} includes suggested change in text.

    Mirror neurons represent a distinctive class of neurons that discharge both when the monkey executes a motor act and when it observers another individual (a human being or another monkey) performing the same or a similar motor act (Figure 1).

    R: Maybe just add a note on strict versus broad congruence?

    Thus, the effective visual stimulus is the observation of a hand interacting with an object {in a manner more-or-less specific to the particular mirror neuron}(Gallese et al. 1996, Rizzolatti et al. 1996a).

    Originally discovered in a subdivision of the monkey’s premotor cortex, area F5, mirror neurons [were later} also found

    Neurophysiological (EEG, MEG, and TMS) and brain-imaging (PET and fMRI) experiments provided strong evidence that a fronto-parietal circuit with properties similar to the monkey’s mirror neuron system is also present in humans (Rizzolatti and Craighero 2004). As in the monkey the mirror neuron system is constituted of IPL and a frontal lobe sector formed by the ventral premotor cortex plus the posterior part and the inferior frontal gyrus (IFG) (Figura 3).

    R: Add "As we shall see below, the human mirror system seems to be involved in functions, such as imitation and language, that are rudimentary or absent in the macaque.

    From this perspective, mirror neurons could represent a "core mechanism" from which other functions branched off {in the evolution of humans}.

    Although the hypothesis that mirror neurons are involved in intention understanding has been proposed several years ago (Buccino et al. 2004), only recently, however, this hypothesis has been supported by an fMRI experiment.

    R: Missing reference to Iacoboni et al 2005? In the reviewer's opinion, this was not a convincing experiment.

    These data indicate that the mirror neuron system is involved in intention understanding, without providing, however, information on the specific mechanisms underlying it. In order to elucidate these mechanisms monkeys were trained to perform two actions with different goals (Fogassi et al. 2005). ... Some of these "action-constrained" motor neurons had mirror properties and selectively discharged during the observation of motor acts when these were embedded in a given action (e.g., grasping-for-eating but not grasping-for-placing). understand the intentions of the action’s agent.

    R: I like this paper very much, but since the cue was the position of the container, one should discuss the evidence for "intention" rather than "visual-motor association".

    It has been suggested that there is a link between autism and mirror neuron system. According to this view, the inability of autistic children to relate to people and life situations in the ordinary way depends on a lack of a normally functioning mirror neuron system. Recent neurophysiological and brain imaging studies provided evidence in favor of this hypothesis (Ramachandran and Oberman 2006).

    R: But is this due to a mirror system for grasping, or one for facial expression including shared attention? If the latter, what is the evidence for a single mirror system serving both functions?

    Recent evidence suggests that the mirror mechanism is also involved in empathy, that is in the capacity of feeling the same emotions that others feel. ... It was found that the exposure to disgusting odorants specifically activates the anterior insula and the anterior cingulate. Most interestingly, the observation of the facial expression of disgust activated the same sector of the anterior insula

    R: This seems relevant to the answer to the preceding question. Perhaps it is important to stress the notion of "Multiple Mirror Systems" rather than "the Mirror System" and then discuss their relationship, perhaps from an evolutionary perspective.

    First adaptation?

    Is your argument that the very first adaptive advantage of mirror neurons, the reason why they were originally selected by the evolutionary process, is action understanding? I believe it is, but i think it would be better if you spell it out clearly. There are so many functions attached to mirror neurons that i think it is important now to be clear about the evolutionary trajectory of this system. Although it makes sense to posit that action recognition came first, and imitation followed (while empathy, intention understanding and language were likely subsequent exaptations), there is one aspect of the mirror neuron system that is not emphasized enough, in my opinion: if one looks at the anatomical location of the mirror neuron system, one finds that this system is embedded in a massive and and parallel fronto-parietal architecture for sensory-motor integration. Thus, it also makes sense to posit that mirror neurons were selected for some form of sensory-motor integration that is related to actions of other individuals and of the self. Action understanding does not seem to map this definition. My hypothesis is that the very first adaptive advantage that mirror neurons provided had to do with some rudimentary social interactions.

    problems with references

    I believe there is some confusion with regard to the references. The Iacoboni et al 1999 paper is cited with regard to imitation learning, whereas I think the Buccino et al 2004 in Neuron is the appropriate reference

    Also, the Buccino et al 2004 paper is cited as first source of the hypothesis that mirror neurons are concerned with intention understanding, whereas I believe you meant to cite Gallese and Goldman 1998

    Furthermore, the Gallese and Goldman 1998 paper is cited as an imaging study on mirror neurons and intention understanding, whereas the appropriate paper to cite is Iacoboni et al, PLoS Biology 2005

    The links between autism and mirror neuron deficits have been nicely demonstrated by Dapretto et al, Nature Neuroscience 2006, a study that shows correlations between reduced mirror neuron activity and severity of disease in patients with autism performing a social mirroring task

    mirror neurons fire upon visualizaiton?

    I read somewhere of a study that suggests that mirror neuron fire not only when observing a particular action but visualizing or creating mental imagery of an action as well. That is, I do not need to observe a monkey grabbing a banana to have the mirror neurons fire; I merely need to visualize, in my mind, a monkey grabbing a banana. Does anyone know if this is correct and if there is an appropriate cite for it? If so, it would be a good addition to the article. Thanks!

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