Explicit and implicit memory for the QWERTY keyboard: the role of motor simulation and deictic gestures

In three experiments, we investigated explicit and implicit knowledge about the location of letters on the QWERTY keyboard in young students, and the mechanisms involved. Participants completed a verbal report task in which they were asked to locate the 21 letters of the Italian alphabet on a blank QWERTY keyboard (explicit memory). Subsequently, they carried out a motor production task, i.e., typing letters on a blank keyboard (implicit memory). Consistent with previous studies and several theories emphasizing the importance of implicit knowledge in typing, results showed that explicit knowledge about the QWERTY keyboard is systematically worse than procedural knowledge (Experiment 1). These two types of knowledge, however, are related. Second, we showed that explicit memory for letter position was affected when participants were engaged in a secondary task that required hands/arms movements. Specifically, loading participants' sensorimotor resources led to a decrease in explicit memory performance when the secondary task required hand/arm movements (hand/arms tapping) compared to when it required legs-feet movements (control condition). This result suggests that explicit knowledge is modulated by sensorimotor simulation (Experiment 2). Third, compared to a purely verbal response, pointing to the key on the keyboard did not improve explicit memory accuracy (Experiment 3). Taken together, the results indicate that sensorimotor simulation, and not just gestures, modulates the accessibility to explicit mental representations of verbal/spatial material, like letters on a keyboard.

Manipulating objects during learning shrinks the global scale of spatial representations in memory: a virtual reality study

Goal-directed approaches to perception usually consider that distance perception is shaped by the body and its potential for interaction. Although this phenomenon has been extensively investigated in the field of perception, little is known about the effect of motor interactions on memory, and how they shape the global representation of large-scale spaces. To investigate this question, we designed an immersive virtual reality environment in which participants had to learn the positions of several items. Half of the participants had to physically (but virtually) grab the items with their hand and drop them at specified locations (active condition). The other half of the participants were simply shown the items which appeared at the specified position without interacting with them (passive condition). Half of the items used during learning were images of manipulable objects, and the other half were non manipulable objects. Participants were subsequently asked to draw a map of the virtual environment from memory, and to position all the items in it. Results show that active participants recalled the global shape of the spatial layout less precisely, and made more absolute distance errors than passive participants. Moreover, global scaling compression bias was higher for active participants than for passive participants. Interestingly, manipulable items showed a greater compression bias compared to non-manipulable items, yet they had no effect on correlation scores and absolute non-directional distance errors. These results are discussed according to grounded approaches of spatial cognition, emphasizing motor simulation as a possible mechanism for position retrieval from memory.

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.

Motor fluency makes it possible to integrate the components of the trace in memory and facilitates its re-construction

The aim of this work was to test the hypothesis that motor fluency should help the integration of the components of the trace and therefore its re-construction. In the encoding phase of each of the three experiments we conducted, a word to be remembered appeared colored in blue or purple. Participants had to read these words aloud and, at the same time, execute a gesture in their ipsilateral (fluent gesture) or contralateral space (non-fluent gesture), according to the color of the word. The aim of the first experiment was to show that the words associated with a fluent gesture during the encoding phase were more easily recognized than those associated with a non-fluent gesture. The results obtained supported the hypothesis. In the second experiment, our objective was to show that the fluency of a gesture performed during encoding in order to associate a word with a color can facilitate the integration of the word with its color. Here again, the results obtained supported the hypothesis. While in Experiment 2 we tested the effect of motor fluency during encoding on word-color integration, the objective of Experiment 3 was to show that motor fluency was integrated in the word-color trace and contributed to the re-construction of the trace. The results obtained supported the hypothesis. Taken together, these findings lead us to believe that traces are not only traces of the processes that gave rise to them, but also traces of the way in which the processes took place.

Motor imagery and engagement favour spatial reasoning

Based on the assumption that spatial reasoning relies on the construction of mental models of the states of affairs described in the premises, and on evidence that sensory-motor imagery can enhance cognitive abilities, we hypothesised that imagining moving the objects mentioned in the premises to the specific spatial locations should favour spatial reasoning. The results of Experiment 1 confirmed the prediction: when participants imagined moving the objects mentioned in the premises (dynamic-engagement condition), they drew accurate inferences faster compared with participants who merely read the premises (static-non-engagement condition). Experiment 2 was in part a replication of Experiment 1 but included two additional experimental conditions to control for possible effects of self-engagement in reasoning: in one condition, participants imagined that someone else was moving the objects (dynamic-non-engagement condition), and in the other condition, participants imagined that they were observing the objects (static-engagement condition). The results revealed an interaction between motor imagery and engagement in decreasing response times to spatial problems. We discuss the practical implications of the current results.

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.

When the Action to Be Performed at the Stage of Retrieval Enacts Memory of Action Verbs

Abstract. According to the embodied approach of language, concepts are grounded in sensorimotor mental states, and when we process language, the brain simulates some of the perceptions and actions that are involved when interacting with real objects. Moreover, several studies have highlighted that cognitive performances are dependent on the overlap between the motor action simulated and the motor action required by the task. On the other hand, in the field of memory, the role of action is under debate. The aim of this work was to show that performing an action at the stage of retrieval influences memory performance in a recognition task (experiment 1) and a cued recall task (experiment 2), even if the participants were never instructed to consider the implied action. The results highlighted an action-based memory effect at the retrieval stage. These findings contribute to the debate about the implication of motor system in action verb processing and its role for memory.

Motor processing modulates word comprehension

We evaluated whether movement modulates the semantic processing of words. To this end, we used homograph words with two meanings, one associated with hand movements (e.g., 'abanico', 'fan' in Spanish) or foot movements ('bota', 'boot' in Spanish), and the other not associated with movement ('abanico', 'range' in Spanish; 'bota', 'wineskin' in Spanish). After the homograph, three words were presented, and participants were asked to choose the word related to one of the two homograph meanings. The words could be either related to the motor meaning of the homograph ('fan-heat'), to the non-motor meaning of the homograph ('range-possibility') or unrelated ('fan-phone'). The task was performed without movement (simple condition) or by performing hand (Experiment 1) and foot (Experiment 2) movements. Compared with the simple condition, the performance of movement oriented the preference towards the motor meaning of the homograph. This pattern of results confirms that movement modulates word comprehension.

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

The embodied meaning approach posits that understanding action-related language recruits motor processes in the brain. However, the functional impact of these motor processes on cognition has been questioned. The present study aims to provide new electrophysiological (EEG) evidence concerning the role of motor processes in the comprehension and memory of action language. Participants read lists of sentences including manual-action or attentional verbs, while keeping their hands either in front of them or crossing them behind their back. Results showed that posture impacted selectively the processing of manual action sentence, and not of attentional sentences, in three different ways: 1) EEG fronto-central beta rhythms, a signature of motor processes, were desynchronized while reading action sentences in the hands-in-front posture compared to the hands-behind posture. The estimated source was the posterior cingulate cortex, involved in proprioceptive regulation. 2) Recall of nouns associated with manual sentences decreased when learning occurred in the hands-behind posture. 3) ERPs analysis revealed that the initial posture at learning modulates neural processes during subsequent recall of manual sentences in the left superior frontal gyrus, which is related to motor processes. These results provide decisive evidence for the functional involvement of embodied simulations in the encoding and retrieval of action-related language.

Towards Strong Inference in Research on Embodiment - Possibilities and Limitations of Causal Paradigms

A central question in the cognitive sciences is which role embodiment plays for high-level cognitive functions, such as conceptual processing. Here, we propose that one reason why progress regarding this question has been slow is a lacking focus on what Platt (1964) called “strong inference”. Strong inference is possible when results from an experimental paradigm are not merely consistent with a hypothesis, but they provide decisive evidence for one particular hypothesis compared to competing hypotheses. We discuss how causal paradigms, which test the functional relevance of sensory-motor processes for high-level cognitive functions, can move the field forward. In particular, we explore how congenital sensory-motor disorders, acquired sensory-motor deficits, and interference paradigms with healthy participants can be utilized as an opportunity to better understand the role of sensory experience in conceptual processing. Whereas all three approaches can bring about valuable insights, we highlight that the study of congenitally and acquired sensorimotor disorders is particularly effective in the case of conceptual domains with strong unimodal basis (e.g., colors), whereas interference paradigms with healthy participants have a broader application, avoid many of the practical and interpretational limitations of patient studies, and allow a systematic and step-wise progressive inference approach to causal mechanisms.

Enhancing Motor Brain Activity Improves Memory for Action Language: A tDCS Study

The embodied cognition approach to linguistic meaning posits that action language understanding is grounded in sensory-motor systems. However, evidence that the human motor cortex is necessary for action language memory is meager. To address this issue, in two groups of healthy individuals, we perturbed the left primary motor cortex (M1) by means of either anodal or cathodal transcranial direct current stimulation (tDCS), before participants had to memorize lists of manual action and attentional sentences. In each group, participants received sham and active tDCS in two separate sessions. Following anodal tDCS (a-tDCS), participants improved the recall of action sentences compared with sham tDCS. No similar effects were detected following cathodal tDCS (c-tDCS). Both a-tDCS and c-tDCS induced variable changes in motor excitability, as measured by motor-evoked potentials induced by transcranial magnetic stimulation. Remarkably, across groups, action-specific memory improvements were positively predicted by changes in motor excitability. We provide evidence that excitatory modulation of the motor cortex selectively improves performance in a task requiring comprehension and memory of action sentences. These findings indicate that M1 is necessary for accurate processing of linguistic meanings and thus provide causal evidence that high-order cognitive functions are grounded in the human motor system.

Aging and posture in the memory of manipulable objects

Thirty healthy elderly participants (mean age = 77.3) learned the names of manipulable and nonmanipulable objects while adopting a control posture (hands in front of them) or an interfering posture (holding their hands behind their back). Results on a recall task showed a postural interference (PI) effect, with the interfering posture reducing the memory of manipulable objects, but not of nonmanipulable ones. The effect was similar to the Postural Interference effect previously observed in young adults, although with a lower performance. These results call into question the embodied theory hypothesis that the deterioration of memory in aging is related to the decline of the sensorimotor system.

Absence of posture-dependent and posture-congruent memory effects on the recall of action sentences

In two experiments with large samples of participants, we explored contextual memory effects associated with body posture, which was considered a physical and proprioceptive context and, therefore, potentially relevant to the encoding and retrieval of information. In Experiment 1 (N = 128), we studied the effect of context dependence on memory by manipulating the body posture adopted by the participants during the incidental encoding and subsequent recall of a series of action sentences not intrinsically associated with particular body postures (e.g., “to put on a pair of glasses”, “to look at a postcard”). Memory performance was not affected by context manipulation, as reflected by the absence of significant differences between remembering while in the posture adopted at study or in a different posture. Experiment 2 (N = 85) was designed to analyze context congruency memory effects, and for that purpose we manipulated the participants' body posture during the recall of sentences that described actions usually performed in body postures that were congruent or incongruent with the posture of the participants (e.g., recalling the sentence “to travel by taxi” while sitting or while standing). A content-neutral posture (lying) was used for the incidental encoding phase. Memory performance was not affected by contextual congruency at the time of recall, as evidenced by the lack of significant differences between recalling in a posture congruent with the content to be recalled and recalling in an alternative posture. Bayesian analyses supported the strength of null findings in the two experiments, adding to the evidence that, when taken together, the results in this study clearly failed to show contextual memory effects of body posture on the recall of action-related verbal statements.