Primary motor cortex functionally contributes to language comprehension: An online rTMS study

Abstract

ABSTRACT:Among various questions pertinent to grounding human cognitive functions in a neurobiological substrate, the association between language and motor brain structures is a particularly debated one in neuroscience and psychology. While many studies support a broadly distributed model of language and semantics grounded, among other things, in the general modality-specific systems, theories disagree as to whether motor and sensory cortex activity observed during language processing is functional or epiphenomenal. Here, we assessed the role of motor areas in linguistic processing by investigating the responses of 28 healthy volunteers to different word types in semantic and lexical decision tasks, following repetitive transcranial magnetic stimulation (rTMS) of primary motor cortex. We found that early rTMS (delivered within 200 ms of word onset) produces a left-lateralised and meaning-specific change in reaction speed, slowing down behavioural responses to action-related words, and facilitating abstract words -an effect present only during semantic, but not lexical, decision. We interpret these data in light of action-perception theory of language, bolstering the claim that motor cortical areas play a functional role in language comprehension.2

Sensorimotor experience and verb-category mapping in human sensory, motor and parietal neurons

“…Magnetoencephalography (MEG) studies further show that these responses occurred earlier than the typical semantic processing window for words (Mollo, Pulvermüller, & Hauk, 2016). This supports the hypothesis that sensorimotor mapping is not merely from post-comprehension processes (see also Vukovic, Feurra, Shpektor, Myachykov & Shtyrov, 2017, for evidence that repetitive Transcranial Magnetic Stimulation (rTMS) to motor cortex impairs retrieval of actions verbs). Rather, these sensorimotor mappings may in fact be a fundamental neural mechanism of verb-semantic processing.…”

“…The existence of bimodal units responding to both visual depictions of actions and verbs describing actions (discussed further below) provides additional evidence consistent with this hypothesis. Also consistent with this is the fact that transcranial magnetic stimulation to motor areas interferes with action-verb processing (Vukovic, et al, 2017). …”

“…Hypothesis III : these spike modulations will occur prior to the semantic processing window, consistent with previous MEG findings (Mollo et al, 2016). This would be evidence that sensorimotor activations are not simply epiphenomenal but are critical to verb-semantic processing (see also Vukovic, et al 2017). We do not have strong hypotheses regarding whether spike modulations in response to verb-category features will also occur in early time windows, or will overlap in time with sensorimotor spike modulations; these questions have not been examined to date.…”

The role of the motor system in action understanding and communication: Evidence from human infants and non‐human primates

“…Studies using fMRI, TMS, MEG, and the EEG mu rhythm have found activation of the motor system when adults process (hear or read) verbs or phrases about actions (Di Cesare, Errante, Marchi, & Cuccio, ; Egorova, Shtyrov, & Pulvermüller, ; Hauk, Johnsurde, & Pulvermüller, ; Moreno et al, ; Moreno, de Vega, & León, ) or while decoding degraded speech sounds (d'Ausilio, Bufalari, Salmas, & Fadiga, ). Indeed, there is evidence that the motor system is functionally linked to representing action‐related language (Vukovic, Feurra, Shpektor, Myachykov, & Shtyrov, ), and some studies have also found left‐hemisphere specificity for the action‐language link (e.g., Pulvermüller, Hauk, Nikulin, & Ilmoniemi, ). Other TMS studies show motor areas are involved during the hearing of speech sounds or phonemes with no clear meaning, thus suggesting a phonological resonance within the motor cortex (d'Ausilio et al, ; Fadiga, Craighero, Buccino, & Rizzolatti, ; Roy, Craighero, Fabri‐Destro, & Fadiga, ).…”

Affordance Compatibility Effect for Word Learning in Virtual Reality

“…Pulvermüller, Hauk, Nikulin, and Ilmoniemi () found that priming the respective effector representation area of primary motor cortex (M1) using single‐pulse transcranial magnetic stimulation (TMS) decreased reaction times for responding to words describing actions performed by the stimulated effector. Vukovic, Feurra, Shpektor, Myachykov, and Shtyrov () found that online repetitive TMS to the motor cortex slowed reaction times to action words, while leaving reactions to abstract words unaffected. These experiments bolster the view that sensorimotor systems in the brain are not only activated by language comprehension but play active roles in understanding.…”