The Functional Role of the Mirror Neuron System--论文代写范文精选

对于STS的视觉描述行动，是一个非常有用的编码方式,这个高阶视觉信息，需要额外的机制来赋予其意义。观察到一个特定的视觉事件导致的后果,观察者理解是另一种可能性。下面的paper代写范文进行阐述。

Since the discovery of mirror neurons, it has been proposed that they are involved in understanding actions. The core of this proposal is that an observed action acquires meaning for the observer when it activates motor schemas whose outcomes are known to the observer (see Rizzolatti et al., 2001). There is an obvious objection to this proposal. Is motor activation really necessary to understand actions? In principle, an action could be understood in purely visual terms. Indeed, the data by Perrett and co-workers (see ch. 1.3) indicate that ‘‘prototypes’’ describing actions are present in STS.

In addition, in humans, a rich description of body parts and body actions is present, not just in the STS region (see Allison et al., 2000), but also in the occipital cortex (Downing et al., 2001; Malach et al., 2002). There is, however, a fundamental requirement that a description of actions must satisfy in order to provide meaning for the individual: It must link the external information to something that the individual knows. The visual system, like all sensory systems, is (by definition) a system that receives information. It does not generate it. In contrast, the motor system generates behavior and, on the basis of its consequences, is able also to ‘‘validate’’ the behavior produced. 

Thus, while the visual description of actions in STS is very useful for coding actions in a compressed way, this high-order visual information needs an additional mechanism to give it a meaning. F5 mirror neurons can effect this transformation. When the motor templates represented by mirror neurons resonate, the meaning of the observed action becomes transparent, because, when other contingencies are met, the activation of the same templates produces action. The activation of representations of motor action is not the only way in which a visually described action may become meaningful. The observation that a certain visual event leads to consequences that the observer understands is another possibility. 

Note, however, that if the consequences of the observed actions do not directly concern the observer (such as a threatening gesture and its consequences), this type of understanding is different from that provided by motor mapping. It is a logical understanding, not a direct personal comprehension of what the other is doing. An association between STS visual templates and subcortical centers also may give significance to an event. STS, besides sending information to PF, is part of a circuit that includes the amygdala and other centers related to emotions (Amaral et al., 1992). Activation of this circuit could give a personal significance to visual stimuli similar to that due to the activation of PF and F5 neurons. This, of course, assumes that there is a mirror neuron system for ‘‘hot,’’ emotionally laden actions that is similar to that for the ‘‘cold actions’’ discussed earlier. Preliminary evidence suggests that this is the case (Wicker et al., 2003; see also Iacoboni, vol. 1, ch. 2).1

New Evidence of a Role for F5 Mirror Neurons in Action Understanding 
The idea that the mirror neuron system is involved in action understanding can be tested by placing a monkey in situations in which the monkey is able to understand the meaning of an action, but the experimental sensory conditions are different from those that typically trigger mirror neurons. If mirror neurons are involved in action understanding, their activity should reflect the action meaning and not the sensory contingencies leading to action understanding. A possible way to test this prediction is to present the monkey with auditory stimuli that evoke the idea of an action. 

This experiment was recently performed (Kohler et al., 2002). Activity in F5 mirror neurons was recorded while the monkey was observing a ‘‘noisy’’ action (e.g., ripping a piece of paper), or was presented with the same noise without seeing the action. The results showed that most mirror neurons that discharge on presentation of actions accompanied by sounds also discharge in response to the sound alone (audiovisual mirror neurons). Further testing showed that a large number of audiovisual mirror neurons respond selectively to a specific sound of an action. These results strongly support the notion that the discharge of F5 neurons correlates with the understanding of an action. The stimuli leading to action understanding are irrelevant. They could be visual or acoustical. Once the meaning of the action is specified, the neuron fires. 

If mirror neurons are involved in action understanding, they should also discharge in this condition. An experiment testing this hypothesis was recently carried out by Umilta` et al. (2001). The experimental paradigm consisted of two basic conditions (figure 1.2). In one, the monkey was shown a fully visible action directed toward an object (‘‘full vision’’ condition). In the other, the monkey saw the same action, but with its final critical part hidden (‘‘hidden’’ condition). Before each trial, the experimenter placed a piece of food behind the screen so that the monkey knew that there was an object behind it. Only those mirror neurons were studied that discharged at the observation of the final part of a grasping movement and/or holding. Figure 1.2 shows the main result of the experiment. The neuron illustrated in the figure responded to the observation of grasping and holding (A, full vision). 

The neuron also discharged when the stimulus triggering features (a hand approaching the stimulus and subsequently holding it) were hidden from the monkey’s vision (B, hidden condition). As is the case for most mirror neurons, the observation of a mimed action did not activate the neuron (C, full vision and D, hidden condition). Note that from a physical point of view, B and D are identical. It was therefore the understanding of the meaning of the observed actions that determined the discharge in the hidden condition. In total, more than half of the tested neurons discharged in the hidden condition. Out of them (n ¼ 19), 7 did not show any difference between the hidden and full vision conditions, while 9 responded more strongly in the full vision condition. Of the remaining 3, the response was either more pronounced in the hidden condition than in full vision (1 neuron) or showed a temporal shift in response intensity.(paper代写)

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