Abstract
BackgroundTheories of embodied language suggest that the motor system is differentially called into action when processing motor-related versus abstract content words or sentences. It has been recently shown that processing negative polarity action-related sentences modulates neural activity of premotor and motor cortices.Methods and FindingsWe sought to determine whether reading negative polarity sentences brought about differential modulation of cortico-spinal motor excitability depending on processing hand-action related or abstract sentences. Facilitatory paired-pulses Transcranial Magnetic Stimulation (pp-TMS) was applied to the primary motor representation of the right-hand and the recorded amplitude of induced motor-evoked potentials (MEP) was used to index M1 activity during passive reading of either hand-action related or abstract content sentences presented in both negative and affirmative polarity. Results showed that the cortico-spinal excitability was affected by sentence polarity only in the hand-action related condition. Indeed, in keeping with previous TMS studies, reading positive polarity, hand action-related sentences suppressed cortico-spinal reactivity. This effect was absent when reading hand action-related negative polarity sentences. Moreover, no modulation of cortico-spinal reactivity was associated with either negative or positive polarity abstract sentences.ConclusionsOur results indicate that grammatical cues prompting motor negation reduce the cortico-spinal suppression associated with affirmative action sentences reading and thus suggest that motor simulative processes underlying the embodiment may involve even syntactic features of language.
Highlights
According to standard cognitive theories, language is processed amodally [1,2] and in higher-order anatomo-functional systems largely unrelated to sensory and motor networks [3]
Our results indicate that grammatical cues prompting motor negation reduce the cortico-spinal suppression associated with affirmative action sentences reading and suggest that motor simulative processes underlying the embodiment may involve even syntactic features of language
The robustness of the classical dissociation between apraxic and aphasic deficits (e.g. [28,29,30]) is not at stake here, many studies have shown that such a pattern has been observed in a variety of patients showing sensorimotor deficits associated to Parkinson disease [31,32,20], cortico-basal degeneration [18], subcortico-frontal diseases [33], left frontal atrophy [34] and motor neurone disease [16,17]
Summary
According to standard cognitive theories, language is processed amodally [1,2] and in higher-order anatomo-functional systems largely unrelated to sensory and motor networks [3]. Growing behavioral [4,5,6,7], neuroimaging [8,9,10], neurophysiological [11,12,13,14,15] and neuropsychological [16,17,18,19,20] evidence indicates that sensorimotor simulation is at play during a variety of language related tasks Such evidence brought experimental support to the Embodied Cognition framework [21] according to which actionrelated concepts are represented within the same brain circuitry responsible for executing the actions linked to the expressed concepts. It has been recently shown that processing negative polarity action-related sentences modulates neural activity of premotor and motor cortices
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