Many different functional roles have been ascribed to themotor system due to its prevalent recruitment in perceptualand cognitive tasks other than motor production. We discussfindings that suggest the motor system might take on multipleroles that vary with context and the brain networks involved.Using single-pulse TMS, we measured the corticospinalexcitability of the FDI muscle in primary motor cortex asparticipants viewed words that were either typed orhandwritten. We observed consistent facilitation ofcorticospinal excitability during reading of handwritten text.Although we observed facilitation in corticospinal excitabilityduring the presentation of typed text, this effect decreasedwith repetitive presentations of stimuli. We suggest that thefacilitation during presentation of typed words is a case ofaction simulation, and that the diminishing facilitation in thecase of typed stimuli is representative of sensory predictionby the motor system. These findings suggest that we shouldconsider multiple roles for motor recruitment during theobservation of visual stimuli, taking context intoconsideration.

Corticospinal excitability (CSE) in humans measured with Transcranial Magnetic Stimulation (TMS) is generally increased by the perception of other people's actions. This perception can be unimodal (visual or auditory) or multimodal (visual and auditory). The increase in TMS-measured CSE is typically prominent for muscles involved in the perceived action (muscle specificity). There are two main classes of accounts for this phenomenon. One suggests that the motor system mirrors the actions that the observer perceives (the resonance account). The other suggests that the motor system predicts the actions that the observer perceives (the predictive account). To test these accounts (which need not be mutually exclusive), subjects were presented with four versions of three-note piano sequences: sound only, sight only, audiovisual, and audiovisual with sound lagging behind (the prediction violation condition). CSE was measured in two hand muscles used to play the notes. CSE increased reliably in one muscle only for the prediction violation condition, in line with the predictive account, while the other muscle demonstrated CSE increase for all conditions, in line with the resonance account. This finding supports both predictive coding accounts as well as resonance accounts of motor facilitation during action perception.

Decades of behavioral science research have documented functional shifts in attitudes and ideological adherence in response to various challenges, but little work to date has illuminated the neural mechanisms underlying these dynamics. This paper describes how continuous theta burst transcranial magnetic stimulation may be employed to experimentally assess the causal contribution of cortical regions to threat-related ideological shifts. In the example protocol provided here, participants are exposed to a threat prime-an explicit reminder of their own inevitable death and bodily decomposition-following a downregulation of the posterior medial frontal cortex (pMFC) or a sham stimulation. Next, disguised within a series of distracter tasks, participants' relative degree of ideological adherence is assessed-in the present example, with regard to coalitional prejudice and religious belief. Participants for whom the pMFC has been downregulated exhibit less coalitionally biased responses to an immigrant critical of the participants' national in-group, and less conviction in positive afterlife beliefs (i.e., God, angels, and heaven), despite having recently been reminded of death. These results complement prior findings that continuous theta burst stimulation of the pMFC influences social conformity and sharing and illustrate the feasibility of investigating the neural basis of high-level social cognitive shifts using transcranial magnetic stimulation.

Children and adults can use cross-situational information toidentify words’ referents. What do learners retain about thepotential referents that occur with a word: do they encodemultiple referents or a single guess? We tested this questionusing novel mouse tracking and finger tracking paradigms.Adults were exposed to novel words in a series of ambiguoustraining trials and then tested on the words’ referents. In sometest trials, participants saw the target and three referents thathad never occurred with the word; other test trials included ahigh-probability competitor that had repeatedly occurred withthe word. Participants’ mouse movements were slower, lessaccurate, and took a more complex path to the selectedreferent when the competitor was present, indicating thatparticipants were aware that both the target and competitorhad previously occurred with the word. This suggests thatlearners can accrue information about multiple potentialreferents for a word, and that mouse tracking provides apromising way of assessing this knowledge. However, thisknowledge was not evident in participants’ finger movements,suggesting that the dynamics of finger movements might notcapture real-time competition between referents.