Crossing hands behind your back reduces recall of manual action sentences and alters brain dynamics

The influence of sentence focus on mental simulation: A possible cause of ACE instability

Recent studies have revealed the instability of the action-sentence compatibility effect (ACE). The current study was designed to demonstrate the hypothesis that the instability of the ACE may be attributed to the instability of focused information in a sentence. A pilot study indicated that the focused information of sentences was relatively stable in the sentence-picture verification task but exhibited significant interindividual variability in the action-sentence compatibility paradigm in previous studies. Experiments 1 and 2 examined the effect of sentence focus on the shape match effect and the ACE by manipulating the focused information of sentences using the focus marker word "" (is). Experiment 1 found that the shape match effect occurred in the original sentence, while it disappeared when the word "" (is) was used to make an object noun no longer the focus of a sentence. Experiment 2 failed to observe the ACE regardless of whether the sentence focus was on the action information. Experiment 3 modified the focus manipulation to observe its impact on the ACE using different fonts and underlines to highlight the focused information. The results indicated that the ACE only occurred when the action information was the sentence focus. These findings suggest that sentence focus influences mental simulation, and the instability of the ACE is likely to be associated with the instability of sentence focus in previous studies. This outcome highlights the crucial role of identifying specific information as the critical element expressed in the current linguistic context for successful simulation.

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.

Disturbing the activity of the primary motor cortex by means of transcranial magnetic stimulation affects long term memory of sentences referred to manipulable objects

Introduction

Previous studies on embodied meaning suggest that simulations in the motor cortex play a crucial role in the processing of action sentences. However, there is little evidence that embodied meaning have functional impact beyond working memory. This study examines how the neuromodulation of the motor cortex (M1) could affect the processing of action-related language, measuring participants' performance in a long-term memory task.

Method

Participants were submitted to two sessions in separate days, one with low-frequency repetitive transcranial magnetic stimulation (rTMS) and the other with sham rTMS. The pulses were delivered for 15 minutes over M1 or over V1, used as a control area. After each stimulation or sham period, the participants were asked to memorize a list of simple sentences, with a manual action verb or an attentional verb, followed in both cases by a noun referred to a manipulable object (e.g., to hang a cane vs. to observe a cane). Finally, they received the verbs as cues with instructions to recall the nouns.

Results

The results showed that low frequency rTMS on M1, compared to sham stimulation, significantly improved the performance in the memory task, for both types of sentences. No change in performance was found after the rTMS stimulation of V1.

Discussion

These results confirm that the perturbation on the motor system, affect the memory of manipulable object names in the context of sentences, providing further evidence of the role played by the sensorimotor system in the encoding and recall of concrete sentences of action.

Action and posture influence the retrieval of memory for objects

The embodied approach states that memory traces are retrieved, at least in part, through a sensorimotor simulation of the original events, i.e., during retrieval we use our body and its sensorimotor pathways to simulate what happened during encoding. Thus, body manipulations that are incongruent with the motor elements involved at encoding should modulate memory performance. To test this hypothesis, we devised two experiments. In Experiment 1, participants had to observe (observation task) or observe and also perform an action on (enactment task) a series of objects. At recognition, they recognised the enacted objects faster and more accurately than the observed ones. Crucially, in Experiment 2, we manipulated body posture during recognition: one group was asked to hold their hands/arms in front of them (non-interfering group), and the other group was asked to block their hands/arms behind their back (interfering group). The results on reaction times, but not those on accuracy, showed a critical interaction: while the noninterfering group recognised enacted objects faster than observed objects, this advantage disappeared for the interfering group. This suggests that adopting a posture inconsistent with action at encoding could influence the time needed to correctly recognise the objects, but not the accuracy of the recognition.

The role of implicit motor simulation on action verb memory

Observation is known to improve memory for action. Previous findings linked such an effect with an easier relation processing of action components following observation compared to mere sentence reading. However, action observation also elicits implicit motor simulation, that is a processing of one's movement through the observer own motor system. We aimed to assess whether encoding of implicit motor simulation can also explain why observation is better than reading for action memory. To prevent influence of item relation processing, two studies about isolated action verbs learning were designed. In Experiment 1, action verbs were encoded with short videos of point-light human movements or with written definitions. Subsequent free recall indicated better memory for the verbs within the video clip condition. Experiment 2 compared two encoding conditions based on point-light human movement videos. Half of the verbs were learned with their normal corresponding movement (biological kinematic). For the other half of the verbs, the velocity of point-light movements was modified to create abnormal nonbiological kinematic actions. We observed better free recall for the verbs learned with biological kinematics. Taken together, those results suggest that action observation is beneficial because it allows the encoding of motor-related information (implicit motor simulation). Semantic resonance between linguistic and motor representations of action could also contribute to memory improvement. Contrary to previous studies, our results cannot be explained by an improvement of items relation processing. However, it suggests that the basic level of action verb memory is sensorimotor perception, such as implicit motor simulation.

The Postural Effect on the Memory of Manipulable Objects

The grounded cognition approach posits the involvement of sensory-motor processes in the representation of knowledge. However, the functional impact of these processes on cognition has been questioned, and some authors have explored the effect of motor interference on memory to test causally this hypothesis. In a seminal study, Dutriaux and Gyselinck (2016) showed that keeping the hands behind the back during learning decreases the memory of manipulable objects, but not the memory of nonmanipulable objects. The aim of this paper is to shed light on the mechanism behind the effect of posture in memory observed by Dutriaux and Gyselinck. The present experiment replicated the posture manipulation during learning but asked participants to keep their hands behind the back during recall. Results showed a similar detrimental effect of the hands behind the back specific to manipulable objects. This shows that the mechanism behind this effect arises from postural interference rather than from a compatibility between the posture during learning and the posture during recall and adds new evidence in favor of the sensory-motor grounding of knowledge.