tDCS to premotor cortex changes action verb understanding: Complementary effects of inhibitory and excitatory stimulation

Abstract

Processing the meaning of action language correlates with somatotopic activity in premotor cortex (PMC). A previous neurostimulation study supported a causal contribution of PMC activity to action verb understanding, but the direction of the effect was unexpected: inhibiting PMC made participants respond faster to action verbs. Here we investigated the effects of PMC excitation and inhibition on action verb understanding using tDCS. Right-handed participants received tDCS stimulation with the anodal electrode (presumed to be excitatory) and cathodal electrode (presumed to be inhibitory) placed over left and right PMC, respectively, or with the reverse configuration. After completing the stimulation protocol, participants made lexical decisions on unimanual action verbs (e.g., throw) and abstract verbs (e.g., think). tDCS configuration selectively affected how accurately participants responded to unimanual action verbs. When the anode was positioned over left PMC we observed a relative impairment in performance for right-hand responses (i.e. the hand with which these participants typically perform unimanual actions). By contrast, when the cathode was positioned over left PMC we observed a relative improvement. tDCS configuration did not differentially affect responses to abstract verbs. These complementary effects of excitatory and inhibitory tDCS clarify the functional role of premotor hand areas in understanding action language.

Motor experience influences object knowledge.

“…In the present study, therefore, the observed effects would reflect participants reenacting their prior experiences of interacting with the specific stimulus objects. Alternatively, simulations could be “pre-enactments” of potential future experiences (Willems, Toni, Hagoort, & Casasanto, 2010; see also Adams, Shipp, & Friston, 2013; Casasanto & Gijssels, 2016; Chrysikou, 2014; Zwaan, 2004; Zwaan & Kaschak, 2008). On the pre-enactment view, symbol-driven simulations constitute partial preparation of neural systems that would be needed to engage physically with the symbol’s referent.…”

Beyond the target area: an integrative view of tDCS-induced motor cortex modulation in patients and athletes

“…: right M1); Dystonia [142]: 5x7 cm; 2 mA; 20 min; 1 session; simultaneous inhibitory and excitatory stimulation on M1 (the cathodal electrode on the affected M1 and the anodal electrode on the unaffected M1); Traumatic Brain Injury [143]: 2x2 cm; 1.5 mA, 15 min; 24 sessions (3 days/week); the anodal electrode placed over the ipsilesional M1 and the cathodal electrode over the contralesional M1. c Language [144]: 5x7 cm; 2 mA; 20 min; the cathodal placed at FC3 and the anodal at FC4. d Language [145]: 5x7 cm; 2 mA; tDCS started 4 min before the beginning of the task and was delivered for the whole course of the task execution (about 2 min); the cathodal electrode positioned over the left M1 and the anodal electrode placed on the skin overlying the left shoulder region.…”

Embodied Semantics in a Second Language: Critical Review and Clinical Implications

“…This may be crucial, as we do know, from studies on monolinguals, that experimental manipulations of the sensorimotor system can affect lexico-semantic processing. Sensorimotor system manipulations have been as diverse as motor training (e.g., in healthy Glenberg et al, 2008; Locatelli et al, 2012; in experts Beilock et al, 2008; or with dyslexic children Trevisan et al, 2017), motor limitation (e.g., Bidet-Ildei et al, 2017), or motor brain area stimulation (Willems et al, 2011; Tremblay et al, 2012; Vukovic et al, 2017; Gijssels et al, 2018). To the best of our knowledge, no study has directly assessed motor-to-language effects in healthy bilinguals, linking the sensorimotor system and lexico-semantic processing.…”

“…As mentioned earlier, experimental manipulations of language in healthy monolinguals (e.g., Aziz-Zadeh et al, 2006; Boulenger et al, 2009; Alemanno et al, 2012; Ghio et al, 2018) and bilinguals (see section Behavioral Studies and (Neuro-)physiological Studies) have been shown to impact the motor system. Conversely, experimental manipulations of the motor system in healthy monolinguals have been shown to impact lexico-semantic processing (e.g., Beilock et al, 2008; Glenberg et al, 2008; Willems et al, 2009; Locatelli et al, 2012; Tremblay et al, 2012; Bidet-Ildei et al, 2017; Vukovic et al, 2017;Gijssels et al, 2018). Moreover, experimental manipulations of the motor system in healthy bilinguals has been shown to impact visual perception of motor speech movements (e.g., Swaminathan et al, 2013).…”

“…Others have also shown correlations between the impairment in action word processing (e.g., “to pour,” “to wave”) and the impairment in action performance, assessed using a visually guided reaching task (e.g., Desai et al, 2015). Finally, some have also shown that a virtual transient lesion induced by repetitive Transcranial Magnetic Stimulation (TMS) or transcranial Direct Current Stimulation (tDCS) over the premotor and motor cortex affects comprehension of action related language (e.g., Willems et al, 2011; Tremblay et al, 2012; Vukovic et al, 2017; Gijssels et al, 2018).…”