Influence of prior use of the same or different effectors in a reaching action

The influence of sentence focus on motor system activity in language comprehension and its temporal dynamics: Preliminary evidence from sEMG

Previous research has shown that individual experiences and experimental tasks can influence the occurrence of mental simulation during sentence comprehension. However, little research has focused on the effect of sentence focus on mental simulation and its temporal dynamics. Sentence focus refers to the hierarchical structure of information within a sentence, where focused information represents the most prominent and essential information. In contrast, nonfocused information provides a background for the focused information. The present study investigated whether sentence focus would affect the activity of the motor system in language comprehension and at which stage the effect of sentence focus occurred. We measured spontaneous arm muscle electrical activity by surface electromyography (sEMG) while participants read action-focused, nonaction-focused, and control sentences. We observed greater spontaneous muscle electrical activity in the flexor common muscle of the fingers when participants read action-focused sentences compared to nonaction-focused and control sentences. Additionally, there was an interactive trend between sentence type and time, spontaneous muscle electrical activity while reading action-focused sentences was observed in both early (1 ms to 300 ms after the presentation of the action phrase) and late time windows (901 ms to 1500 ms after the action phrase). The findings suggest that the motor system exhibits flexible engagement during language comprehension and the impact of sentence focus on motor system activity may be throughout both the lexical-semantic retrieval and sentence-meaning integration stages.

Multiple-object tracking and visually guided touch

Multiple-object tracking (MOT) involves keeping track of the positions of multiple independent target items as they move among distractors. According to Pylyshyn (Cognition, 80, 127-158, 2001), the item individuation mechanism used in MOT is also used in visually guided touch. To test this, we compared single-task MOT (MOT alone) with dual-task MOT (MOT while touching items that changed colour), looking for interference: cases where single-task performance was worse than dual-task. Touching items that changed colour interfered with MOT, but effects varied depending on whether the item touched was a target or distractor in MOT. Touching distractors always reduced MOT performance more than touching targets. Touching targets during MOT did not interfere when there was only a single target to track but interfered more once there were two or more targets. We also measured interference based on latencies to touch items that changed colour, comparing single and dual-task conditions (touch alone, touch + track). MOT interfered with touch, increasing RT to touch items that changed colour, with latencies significantly higher when those items were distractors rather than targets. Overall, there was general interference (differences between single and dual-task performance), as might be expected if coordinating the two tasks required a common limited resource such as general attention or working memory. However, there was also differential interference that varied based on whether the touched item was a target or distractor in MOT. This differential interference suggests the specific mechanisms used in MOT may also play a role in visually guided touch.

Muscle activation in semantic processing: An electromyography approach

In this study, we focus on the spontaneous activity related to manual verbs to determine the extent to which semantic processing of manual verbs affects spontaneous arm muscle activity. For this purpose, we recorded the arm's electromyographic activity while participants read manual and non-manual verbs, focusing their attention on the semantic content or a specific letter. In addition, we manipulated the arm position (in front of the body or behind the back) to observe postural priming effects for spontaneous muscle activity. Our results show that when arms were placed forward and the attention was directed to the semantic content, there was an enhanced spontaneous activation. Our results suggest that spontaneous motor responses are related to the involvement of the motor system in action language comprehension as suggested by language embodiment theories.

Prolonged subjective duration near the hands: Effects of hand proximity on temporal reproduction

It has been reported that human visual perception and attention are altered when the hands are nearby. Previous studies indicate that placing hands near stimuli enhances a subject's temporal sensitivity. However, few researchers have investigated the effect of hand proximity on reproducing temporal duration. Moreover, the delayed attentional disengagement and enhanced magnocellular visual processing theories provide two distinct predictions of the hand proximity effect on reproduced duration. Delayed attentional disengagement near hands will cause prolonged reproductions, whereas enhanced magnocellular visual processing predicts more accurate reproduction in the peri-hand space. The current study is the first to show that a short temporal duration is reproduced for a longer period near hands than far from hands in the dual-responding-hand condition, and this hand-proximity effect is attenuated in the single-responding-hand condition. These findings together with two further studies suggest that reproducing a temporal duration is modulated by hand proximity through prolonged attentional switch.

Hand Switching Costs are not Uniform Across Response Components

We investigated the extent to which a complex finger sequence impacts on hand switching costs in a sequential action. Response component latencies (premotor, motor, and movement) were compared in no-switch (same finger performed the action of pressing and reaching) and switch conditions (pressing with one finger and completing the reaching action with the homologous finger from the other hand). Results showed that the switch condition presented longer latency for premotor and movement components. For the motor component, however, switch condition was faster. This expands the previous literature investigating switching costs using simple finger movements in more complex tasks. A mechanical explanation of the interplay between response subcomponents is provided to explain the inversion of response pattern for the motor component.