Amplitude and bilateral coherency of facial and jaw‐elevator EMG activity as an index of effort during a two‐choice serial reaction task

Abstract

In earlier studies, positive but inconsistent relationships have been reported between mental effort and electromyogram (EMG) amplitude in task-irrelevant limb muscles. In this study, we explored whether facial EMG activity would provide more consistent results. Tonic EMG activity of six different facial and jaw-elevator muscles was bilaterally recorded during a two-choice serial reaction task with paced presentation of auditory or visual signals. In Experiment 1, task load (signal presentation rate) was kept constant for 20 min at the level of the subject's maximal capacity. In Experiment 2, task load was increased in a stepwise fashion over six successive 2-min periods from sub- to supramaximal capacity levels. EMG amplitude and coherency between momentary bilateral amplitude fluctuations were measured. In Experiment 1, EMG amplitude of frontalis, corrugator supercilii, and orbicularis oris inferior showed a strong gradual increase throughout the task period, whereas taks performance remained fairly stable. Orbicularis oculi, zygomaticus major, and temporalis EMG showed a much smaller increase or no increase. In Experiment 2, the first three muscles showed a fairly consistent increase in EMG amplitude with increasing task load. Orbicularis oculi and zygomaticus major were not active until task load became supramaximal. Effects of stimulus modality or laterality were not found in any experiment. These results are consistent with the notion that EMG amplitude of frontalis, corrugator, and orbicularis oris provides a sensitive index of the degree of exerted mental effort.

Orofacial electromyographic correlates of induced verbal rumination

“…This finding is consistent with previous findings of higher EMG 536 amplitude in the lower lip during speech and inner speech (e.g., Barlow & Netsell, 1986 However, although a functional distinction can be drawn between the forehead and the lip 546 muscles, one should acknowledge the fact that these two sets of muscles can be commonly 547 activated during some behaviours. For instance, Van Boxtel & Jessurun (1993) have shown that 548 orbicularis oris inferior and frontalis were both activated during a two-choice serial reaction task 549 in which nonverbal auditory or visual signals were presented. Moreover, there was a gradual 550 increase in EMG activity in these muscles during the task, either when the task was prolonged or 551 when the task was made more difficult.…”

The emotive nature of conflict monitoring in the medial prefrontal cortex

“…As such, activation of the corrugator muscle putatively reflects the bipolar valence dimension (positive-negative) that is central to core affect (Larsen, Norris, & Cacioppo, 2003). Although consistent with the negative valence of conflict, alternate accounts propose that the corrugator muscle tracks cognitive demand (de Morree & Marcora, 2010;van Boxtel & Jessurun, 1993). Therefore, because conflict is tightly coupled with effort, error-related corrugator engagement might reflect demand, rather than affect.…”

Orofacial electromyographic correlates of induced verbal rumination

“…For instance, Van Boxtel & Jessurun (1993) have shown that 545 orbicularis oris inferior and frontalis were both activated during a two-choice serial reaction task 546 in which nonverbal auditory or visual signals were presented. Moreover, there was a gradual 547 increase in EMG activity in these muscles during the task, either when the task was prolonged or 548 when the task was made more difficult.…”