Online research in philosophy

Selected contributions to the symposium on "Mirror neurons and the evolution of brain and language" held on July 5-8, 2000 in Delmenhorst, Germany.

This article distinguishes three archetypal ways of articulating spatial cognition: (1) via metric representation of objective geometry, (2) via somatosensory constitution of the peripersonal environment, and (3) via pragmatic comprehension of the finalistic sense of action. The last one is documented by neuroscientific studies concerning mirror neurons. Bio-robotic experiments implementing mirror functions confirm the constitutive role of goal-oriented actions in spatial processes.

This commentary points to the lack of sound data supporting Corballis's thesis that there is a general left-hemisphere dominance for nonverbal vocal production in mammals. I also point out that area F5 in the rhesus monkey, which Corballis considers as homologous to Broca's area, contains not only visual “mirror” neurons but also auditory “mirror” neurons. This weakens Corballis's thesis that language developed exclusively at the gestural level.

Mirror neurons are a particular class of visumotorical neurons, originally discovered in area F5 of the monkey premotorical cortex. They discharge both (1) when the animal performs a specific action and (2) when it observes a similar action. Actually, it is often assumed that this unique functioning could explain different abilities ranging from imitation behaviour to faculty of speech. In this article, we discuss the question what is meant by the expression: The neuron x mirrors the action y by perception z . The problem resulted from the fact, that neurons cannot mirror anything—except in the light of a metaphorical description. How can this metaphorical description be dissolved for a distinct and explicit scientific terminology? The basic steps of our argumentation are as follows. (1) The expression to mirror can be defined in mutual relation between different types of actions in respect of at least two participants: the proponent A, who conducts a special action x (e.g. grapping a peanut (A(x)) and the opponent B who observes these actions y (B(y)) and vice versa. (2) In order to detect different tokens as a type of action and to guarantee the changes of the participants there must be constituted a speech act in a dialogue, in which types of actions are defined by the invariance of special equivalence. (3) The change of the participants represents and defines the metaphorical expression to mirror in the light of a non-metaphorical and reproducible schema. (4) Then, the invariance of the type of action can be identified in different speech acts. Three of them (called narratives) were defined paradigmatically: (4.1) the ethological-narrative; (4.2) the neurophysiological-narrative; (4.3) the language-narrative. (5) These narratives are the modelling and explicit formulations of the primarily metaphorical expression: The neuron x mirrors the action y by perception z.

Various deficits in the cognitive functioning of people with autism have been documented in recent years but these provide only partial explanations for the condition. We focus instead on an imitative disturbance involving difficulties both in copying actions and in inhibiting more stereotyped mimicking, such as echolalia. A candidate for the neural basis of this disturbance may be found in a recently discovered class of neurons in frontal cortex, 'mirror neurons' (MNs). These neurons show activity in relation both to specific actions performed by self and matching actions performed by others, providing a potential bridge between minds. MN systems exist in primates without imitative and ‘theory of mind’ abilities and we suggest that in order for them to have become utilized to perform social cognitive functions, sophisticated cortical neuronal systems have evolved in which MNs function as key elements. Early developmental failures of MN systems are likely to result in a consequent cascade of developmental impairments characterised by the clinical syndrome of autism.

The evolutionary continuity between the prespeech functions of premotor cortex and its new linguistic functions, the main thesis of MacNeilage's target article, is confirmed by the recent discovery of “mirror” neurons in monkeys and a corresponding action-observation/action-execution matching system in humans. Physiological data (and other considerations) appear to indicate, however, that brachiomanual gestures played a greater role in language evolution than MacNeilage would like to admit.

Mirror neurons are neurons which fire in two distinct conditions: (i) when an agent performs a specific action, like a precision grasp of an object using fingers, and (ii) when an agent observes that action performed by another. Some theorists have suggested that the existence of such neurons may lend support to the simulation approach to mindreading (e.g. Gallese and Goldman, 1998, 'Mirror neurons and the simulation theory of mind reading'). In this note I critically examine this suggestion, in both its original and a revised form (due to Iacoboni et al., 2005, 'Grasping the intentions of others with one's own mirror neuron system'), and argue that the existence of mirror neurons can in fact tell us very little about how intentional attribution actually proceeds.

In a New York Times article last month, entitled Cells that read minds, the neuroscience reporter, Sandra Blakeslee (January 10, 2006) provided a list of all the things that mirror neurons can explain. As we know, mirror neurons, discovered by Rizzolattis group in Parma, are neurons that are activated when we engage in action, and when we perceive intentional movement in another person. According to Blakeslee and the scientists she interviewed, mirror neurons explain not only how we are capable of understanding another persons actions, but also language, empathy, how children learn, why people respond to certain types of sports, dance, music and art, why watching media violence may be harmful and why many men like pornography. Let me set aside the controversial questions about whether mirror neurons can explain all of these things, and accept that mirror neurons are clearly smart little cells. But let me ask whether Blakeslee and her scientists are expressing things in the right way.

Both macaque monkeys and humans have been shown to have what are called ‘mirror neurons’, a class of neurons that respond to goal-related motor-actions, both when these actions are performed by the subject and when they are performed by another individual observed by the subject. Gallese and Goldman (1998) contend that mirror neurons may be seen as ‘a part of, or a precursor to, a more general mind- reading ability’, and that of the two competing theories of mind-reading, mirror neurons lend support to simulation theory. I here offer four reasons why I think mirror neurons do not provide support for simulation theory over its contender, theory theory.

The discovery of mirror neurons has been hailed as one of the most exciting developments in neuroscience in the past few decades. These neurons discharge in response to the observation of others’ actions. But how are we to understand the function of these neurons? In this paper I defend the idea that mirror neurons are best conceived as components of a sensory system that has the function to perceive action. In short, mirror neurons are part of a hitherto unrecognized “sixth sense”. In this spirit, research should move toward developing a psychophysics of mirror neurons.