Mirror neurons fire both during the execution and observation of actions and are widely promoted as supporting the “understanding” of actions via motor simulation (di Pellegrino et al., 1992, Gallese et al., 1996 and Rizzolatti and Craighero, 2004), although this view has been challenged on several fronts (Corina and Knapp, 2006, Emmorey et al., 2010, Hauser and Wood, 2010, Heyes, 2010, Hickok, 2009a, Hickok and Hauser, 2010, Knapp and Corina, 2010 and Mahon and

Caramazza, 2008). It is important to recognize that the discovery of mirror neurons, while interesting, does not negate the empirical evidence against a strong version of the motor theory of speech perception (Hickok, 2010b and Lotto et al., 2009) and any theory of speech perception will have to take previous evidence into account (Hickok, 2010a). Unfortunately, mirror neuron-inspired discussions of speech perception (Fadiga et al., 2009 and Pulvermüller learn more et al., 2006) have not taken this broader literature into account (Skoyles, 2010). This renewed interest

in the motor theory has generated a flurry of studies that have suggested a limited role for the motor system in speech perception. Several transcranial magnetic stimulation (TMS) and functional imaging experiments have found that the perception of speech, with no explicit motor task, is sufficient to activate (or potentiate) the motor speech system in a highly specific, i.e., somatotopic, fashion ( Fadiga et al., 2002, Pulvermüller et al., 2006, Skipper et al., 2005, Sundara et al., 2001, Watkins and Paus, 2004, Watkins et al., 2003 and Wilson et al., 2004). But it is unclear whether such activations are causally find protocol related to speech recognition or rather are epiphenomenal, reflecting spreading activation between associated networks. For this reason, more recent studies have attempted to modulate perceptual responses via motor-speech stimulation, with some success. One study showed that stimulation of premotor cortex resulted in a decline in the ability to identify syllables in noise ( Meister et al., 2007),

while another stimulated the ventral premotor cortex during the perception of clear speech stimuli and found no effect on accuracy across several measures of speech perception but reported that response for times in one task were slowed (namely, a phoneme discrimination task in which subjects judged whether pairs of syllables start with the same sound or not) ( Sato et al., 2009). A third study found that stimulation of motor lip or tongue areas resulted in a facilitation (faster reaction times) in identification of lip- or tongue-related speech sounds ( D’Ausilio et al., 2009), and a fourth found that stimulation of motor lip areas resulted in decreased ability to discriminate lip-related speech sounds ( Möttönen and Watkins, 2009). Still other work has found that motor learning can also modulate the perception of speech ( Shiller et al., 2009).