Notes on Mirror Neurons

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Description of mirror neutrons and how they work
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  Expertise modulates FFA activation in experts processing: There is no denying the importance of the FFA in face perception. Damage to and around the FFA results in the inability to perceive faces (Barton,  2008 ; Mayer & Rossion,  2007 ; Barton, Press, Keenan, & O'Connor,  2002 ), and faces commonly activate the FFA twice as much as any other stimuli (Kanwisher & Yovel,  2006 ). However, the heightened response to faces in the FFA could also be a consequence of our extensive experience and expertise in dealing with faces. This is the essence of the expertise hypothesis. One way to investigate this possibility is to compare the FFA response in people who have experience with certain nonface stimuli with the response in people who have less experience with the particular stimulus category. The expertise hypothesis has been tested with a number of nonface stimuli, ranging from birds (Gauthier et al.,  2000 ), to cars (McGugin, Van Gulick, Tamber-Rosenau, Ross, & Gauthier,  2015 ; McGugin, Newton, Gore, & Gauthier,  2014 ; Gilaie-Dotan, Harel, Bentin, Kanai, & Rees,  2012 ; McGugin, Gatenby, Gore, & Gauthier,  2012 ; Xu,  2005 ; Grill-Spector, Knouf, & Kanwisher,  2004 ; Gauthier et al.,  2000 ), butterflies (Rhodes, Byatt, Michie, & Puce,  2004 ), Pokémon characters (James & James,  2013 ), and novel object types (Gauthier et al.,  1999 ). The results have been mixed, and their interpretation has been the focus of an extensive debate (Op de Beeck & Baker,  2010 ; Bukach, Gauthier, & Tarr,  2006 ; Kanwisher & Yovel,  2006 ). A factor that further complicates the interpretation is the visual similarity of the investigated stimuli with faces: Cars, birds, and even butterflies have face-like features (Kanwisher & Yovel,  2006 ).    An obvious way around the resemblance problem is to find stimuli that do not look like faces. Radiological stimuli, such as thorax x-rays, would fit the not-face-like description. Harley and colleagues ( 2009)  demonstrated that expert and novice radiologists have similar activation levels when quickly examining x-rays for abnormalities. The experts' behavioral performance, however, was reliably correlated with the activation in the FFA, whereas the FFA activation in novices was not predictive of how well they identified abnormalities within the x- rays. Together with my colleagues (Bilalić, Grottenthaler, Nägele, & Lindig,  2016 ), I have recently shown that there were indeed no differences in the FFA activation between experienced radiologists and medical students during the perception of radiological stimuli when the classical univariate analysis was performed. However, when we employed the more sensitive multivariate pattern analysis (MVPA), the FFA could differentiate between radiological images and other neutral stimuli in radiologists, but the FFA in medical students was still not sensitive enough to differentiate between the stimuli within and outside specialization.  Mirror Neurons…. The adaptation account has largely been set out in discussions of the “evolution” of MNs (Gallese & Goldman, 1998; Rizzolatti & Arbib, 1998; Rizzolatti & Craighero, 2004; Rochat et al. , 2010). For example, it was suggested that “the mirror neuron mechanism is a mechanism of great evolutionary importance through which primates understand actions done by their conspecifics” (Rizzolatti & Craighero, 2004, p. 172). A number of discussions have also suggested that MNs are present at birth (Ferrari et al. , 2009; Gallese et al. , 2009; Lepage & Theoret, 2007; Rizzolatti & Fadiga, 1998), a feature commonly associated with adaptations (Mameli & Bateson, 2006). In contrast, the associative account suggests that the matching properties of MNs are not a product of a specific genetic predisposition, but instead result from domain‐ general processes of associative learning (Catmur et al. , 2014; Cook et al. , 2014; Heyes, 2010). Associative learning is found in a wide range of vertebrate and inverte- brate species, indicating that it is an evolutionarily ancient and highly conserved adaptation for tracking predictive relationships between events (Heyes, 2012; Schultz & Dickinson, 2000). Thus, the associative account identifies sources in everyday life of the kind of correlated sensorimotor experience necessary for MN development, and many of these sources are sociocultural; to a large extent, MNs are built through social interaction. In summary: The associative account implies that the characteristic, matching properties of MNs result from a genetically evolved process, associative learning, but that this process was not “designed” by genetic evolution specifically to produce matching MNs. It just happens to produce matching MNs when the developing system receives correlated experience of observing and executing similar actions. When the system receives correlated experience of observing objects and executing actions, the same associative process produces canonical neurons. When the system receives correlated experience of observing one action and executing a different action, the same associative process produces logically related MNs. Thus, the adaptation account says that genetic evolution has played a specific and decisive role, and learning plays a merely facilitative role, in the development of matching MNs. In contrast, the associative account says that evolution has played a nonspecific background role, and that the characteristic matching properties of MNs are forged or “induced” (Gottlieb, 1976) by sensorimotor learning . The associative learning of MN explained: Correlated (i.e., contiguous and contingent) excitation of sensory and motor neurons that code similar actions produce MNs. For example, when an adult imitates an infant’s facial movements, there might be correlated excitation of neurons that are responsive to the observation and execution of lip protrusion. Correlated excitation of the sensory and motor neurons increases the strength of the connection between them, so that subsequent excitation of the sensory neuron propagates to the motor neuron. Thereafter, the motor neuron fires, not only during execution of lip protrusion, but also  during observation of lip protrusion, via its connection with the sensory neuron; what was srcinally a motor neuron has become a lip protrusion MN In adults, the extent of mirror activation during action observation is dependent on the observer's experience of physically performing this action [61  –  63]. If an action that is outside of the human repertoire is observed (such as barking), there is typically little activation found in the premotor areas [64]. Expert dancers who watch another person dancing show stronger motor activation than control subjects who are trained in another dance style. For acquired motor skills, motor activation thus is modulated by the observer's level of proficiency and motor familiarity with that skill [65], whereas solely visual familiarity with the action acquired through observation seems to have far less impact [66]. Probably owing to enhanced simulation of the observed kinematic acts ([67  –  70]; cf. [71]), observers are better at predicting the outcome of actions [72] and at estimating the duration [73] of motorically familiar actions when they watch them performed by others. Moreover, experienced adults tend to outperform novices when asked to recognize, categorize and recall observed actions [74  –  77]. Also, motor experience can have a direct impact on visual action recognition without being mediated by visual experience. If adult participants are trained on a novel coordinated body movement while being blindfolded, they improve in their visual recognition of this movement without having received any visual feedback about this new action [74]. The adult literature thus provides us with broad evidence that motor expertise fundamentally changes how humans perceive and process actions they observe in others, which leads to the question of whether motor experience is as powerful at changing action  perception and augmenting action understanding early in life. Infants: which infants develop the capacity of action understanding. Their active experiences provide infants with rich, multi-faceted representations of actions and the corresponding action effects (cf. [84,85]). Through repeated execution of actions, infants form associations  between these motor acts and their sensory consequences [86]. When infants subsequently observe these actions in others, they can use their motor system to predict the outcome of the ongoing actions. A broad body of studies on the relationship between infants’ action experience and action  perception are in support of this view. First of all, studies employing a broad range of methods (such as EEG, fNIRS or electromyographic recordings) have shown that when infants observe others’ actions, their neural motor system becomes activated [ 87  –  90,28,39]. However, how exactly the mirror system develops in infancy and early childhood is still a matter of debate [91]. Whereas some researchers suggest that humans are equipped with an innate matching system, at least in a rudimentary form [92,93], others propose that the mirror  properties of the human brain develop as a result of sensorimotor learning [57,94,95]. Both notions, however, acknowledge that the mirror system is modulated by sensorimotor learning throughout the course of development.  2018 research: Action understanding, mediated by MNS may depend on experience…innate rough ability refined through experience….   Heyes Theory that MNS is formed through experience! Catmur et al. (2007) showed that the human MNS also could adapt. Heyes (2010) suggests that the MNS could be formed through experience. It could be a byproduct of associative learning, rather than a system designed for action understanding. This theory is consistent with the evidence that the MNS can adapt to new experiences. It is also consistent with the idea that we can understand actions even if they are not in our motor repertoire. Seeing a dog  barking does not activate the MNS. We do however understand what the dog is doing. Also, if the dog is barking at a certain time of the day, we have learned through experience that the dog wants to be taken for a walk. Therefore, we understand for what purpose the dog is  barking. Lignau et al. (2009) also suggested that the mirror neuron activity could be a consequence of action understanding instead of the other way around. This is consistent with the MNS as a  byproduct of associative learning. It is also consistent with the findings of Kohler et al. (2002) in Macaque monkeys. They found that a sound could activate the mirror neurons that are normally activated when a particular action is observed. This sound could be linked with the action through experience and therefore produce mirror neuron activity Motor Theory of action understanding: (evidence against)   It is hard to distinguish the three accounts, in part because there has been little direct investigation aimed at teasing them apart. It is, however, relatively easy to rule out the action understanding account as it has been investigated extensively, particularly in the domain of speech, which is a function that mirror neurons were generalized to in the earliest publications [5, 21]. A straightforward prediction of the action understanding theory is that damage to the motor speech system should cause significant receptive speech deficits. This is not the case however. The ability to perceive speech sounds has been demonstrated in patients who have severely impaired speech production due to chronic stroke [18, 25], in individuals who have acute and complete deactivation of speech production due to left carotid artery injection of sodium amobarbital (Wada procedure) [12], in individuals who never acquired the ability to speak due to congenital disease or pre- lingual brain damage [1, 3, 15, 17], and even in nonhuman mammals (chinchilla) and birds (quail) [14, 16 ] which don’t have the biolo gical capacity to speak. These facts are flatly inconsistent with a motor theory of action understanding. Refuting evidence against Mirror neurons enabling action understanding   Despite nearly two decades of research on mirror neurons, there is still much debate about what they do. The most enduring hypothesis is that they enable ‘action understanding’. However, recent critical reviews have failed to find compelling evidence in favour of this view. Instead, these authors argue that mirror neurons are produced by associative learning
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