Does a tool eliminate spatial compatibility effects?

Why motor imagery is not really motoric: towards a re-conceptualization in terms of effect-based action control

Overt and imagined action seem inextricably linked. Both have similar timing, activate shared brain circuits, and motor imagery influences overt action and vice versa. Motor imagery is, therefore, often assumed to recruit the same motor processes that govern action execution, and which allow one to play through or simulate actions offline. Here, we advance a very different conceptualization. Accordingly, the links between imagery and overt action do not arise because action imagery is intrinsically motoric, but because action planning is intrinsically imaginistic and occurs in terms of the perceptual effects one want to achieve. Seen like this, the term 'motor imagery' is a misnomer of what is more appropriately portrayed as 'effect imagery'. In this article, we review the long-standing arguments for effect-based accounts of action, which are often ignored in motor imagery research. We show that such views provide a straightforward account of motor imagery. We review the evidence for imagery-execution overlaps through this new lens and argue that they indeed emerge because every action we execute is planned, initiated and controlled through an imagery-like process. We highlight findings that this new view can now explain and point out open questions.

Sensorimotor Challenges in Minimally Invasive Surgery: A Theoretically-Oriented Review

OBJECTIVE

This review surveys the literature on sensorimotor challenges impacting performance in laparoscopic minimally invasive surgery (MIS).

BACKGROUND

Despite its well-known benefits for patients, achieving proficiency in MIS can be challenging for surgeons due to many factors including altered visual perspectives and fulcrum effects in instrument handling. Research on these and other sensorimotor challenges has been hindered by imprecise terminology and the lack of a unified theoretical framework to guide research questions in the field.

METHOD

We conducted a systematic survey of the MIS literature, focusing on studies investigating sensorimotor challenges affecting laparoscopic performance. To provide a common foundation for cross-study comparisons, we propose a standardized taxonomy that distinguishes between different experimental paradigms used in the literature. We then show how the computational motor learning perspective provides a unifying theoretical framework for the field that can facilitate progress and motivate future research along clearer, hypothesis-driven lines.

RESULTS

The survey identified diverse sensorimotor perturbations in MIS, which can be effectively categorized according to our proposed taxonomy. Studies investigating monitor-, camera-, and tool-based perturbations were systematically analyzed, elucidating their impact on surgical performance. We also show how the computational motor learning perspective provides deeper insights and potential strategies to mitigate challenges.

CONCLUSION

Sensorimotor challenges significantly impact MIS, necessitating a systematic, empirically informed approach. Our proposed taxonomy and theoretical framework shed light on the complexities involved, paving the way for more structured research and targeted training approaches to enhance surgical proficiency.

APPLICATION

Understanding the sensorimotor challenges inherent to MIS can guide the design of improved training curricula and inform the configuration of setups in the operating room to enhance surgeon performance and ultimately patient outcomes. This review offers key insights for surgeons, educators, and researchers in surgical performance and technology development.

Environment-Related and Body-Related Components of the Minimal Self

Perceptual changes that an agent produces by efferent activity can become part of the agent’s minimal self. Yet, in human agents, efferent activities produce perceptual changes in various sensory modalities and in various temporal and spatial proximities. Some of these changes occur at the “biological” body, and they are to some extent conveyed by “private” sensory signals, whereas other changes occur in the environment of that biological body and are conveyed by “public” sensory signals. We discuss commonalties and differences of these signals for generating selfhood. We argue that despite considerable functional overlap of these sensory signals in generating self-experience, there are reasons to tell them apart in theorizing and empirical research about development of the self.

Camera realignment imposes a cost on laparoscopic performance

There is an unresolved question about whether realigned visual feedback is beneficial or costly to laparoscopic task performance. We provide evidence that camera realignment imposes a reliable cost on performance across both naive controls and experienced surgeons. This finding clarifies an important ongoing discussion in the literature about the effects of camera realignment, which could inform the strategies that laparoscopic surgeons use in the operating room.

Suppression of mutually incompatible proprioceptive and visual action effects in tool use

Movements of a tool typically diverge from the movements of the hand manipulating that tool, such as when operating a pivotal lever where tool and hand move in opposite directions. Previous studies suggest that humans are often unaware of the position or movements of their effective body part (mostly the hand) in such situations. It has been suggested that this might be due to a "haptic neglect" of bodily sensations to decrease the interference of representations of body and tool movements. However, in principle this interference could also be decreased by neglecting sensations regarding the tool and focusing instead on body movements. While in most tool use situations the tool-related action effects are task-relevant and thus suppression of body-related rather than tool-related sensations is more beneficial for successful goal achievement, we manipulated this task-relevance in a controlled experiment. The results showed that visual, tool-related effect representations can be suppressed just as proprioceptive, body-related ones in situations where effect representations interfere, given that task-relevance of body-related effects is increased relative to tool-related ones.

Spatial action-effect binding depends on type of action-effect transformation

Spatial action-effect binding denotes the mutual attraction between the perceived position of an effector (e.g., one's own hand) and a distal object that is controlled by this effector. Such spatial binding can be construed as an implicit measure of object ownership, thus the belonging of a controlled object to the own body. The current study investigated how different transformations of hand movements (body-internal action component) into movements of a visual object (body-external action component) affect spatial action-effect binding, and thus implicit object ownership. In brief, participants had to bring a cursor on the computer screen into a predefined target position by moving their occluded hand on a tablet and had to estimate their final hand position. In Experiment 1, we found a significantly lower drift of the proprioceptive position of the hand towards the visual object when hand movements were transformed into laterally inverted cursor movements, rather than cursor movements in the same direction. Experiment 2 showed that this reduction reflected an elimination of spatial action-effect binding in the inverted condition. The results are discussed with respect to the prerequisites for an experience of ownership over artificial, noncorporeal objects. Our results show that predictability of an object movement alone is not a sufficient condition for ownership because, depending on the type of transformation, integration of the effector and a distal object can be fully abolished even under conditions of full controllability.

Compatibility Effects in Young Children's Tool Use: Learning and Transfer

An inherent component of tool-use actions is the transformation of the user's operating movement into the desired effect. In this study, the relevance of this transformation for young children's learning of tool-use actions was investigated. Sixty-four children at the age of 27-30 months learned to use levers which either simply extended (compatible transformation) or reversed (incompatible transformation) their operating movements. Data revealed a compatibility effect as well as transfer effects originating from the two different types of transformations. Furthermore, results suggest that young children's tool-use learning is not a uniform process, but has to be regarded individually depending on the type of transformation.

A one- and two-phased model of aimed movement with eye-hand incompatibility

Aimed movement is ubiquitous and has been extensively investigated. However, little research exists when the hand movements are incompatible with eye movements such as when viewing through a mirror or when performing laparoscopic surgery. An experiment was designed to investigate how individuals perform under one-dimensional and two-dimensional inversion with direct viewing as a reference condition. Twenty-four right-handed university students participated in this experiment and completed all aimed movements with a full-factorial design of movement amplitude at three levels and index of difficulty at 10-levels in three visual conditions of direct, viewing through a mirror (1D inversion) and observing through a right-angled mirror (2D inversion). Learning is rather rapid with direct viewing and with 1D inversion. However, participants take a longer time to stabilize their performance in the 2D inversion condition. Fitts' law is robust under all visual conditions. The eye-hand incompatibility increases movement time with 2D inversion taking the longest movement time. Movement time (MT) was split into initiation time (IT), distance covering time (DCT) and acquisition time (AT) based on submovements. The distance covering part is the first submovement that is primarily ballistic and covers around 90% or more of total amplitude. Furthermore, AT allows the aimed movement to be split into two phases: ballistic and visual control. The results show that the transition from ballistic to visual control happens at lower Index of difficulty (ID) values as the level of incompatibility increases. Based on the experiment and prior research, it is appropriate to use the model MT = a + b ID + c√A as it can account for the two phases of ballistic and visual control.

The interplay of predictive and postdictive components of experienced selfhood

Objects that we affect by our body movements can be experienced as being controlled by (agency) and belonging to the own body (ownership). Such impressions of minimal selfhood arise when objects move as predicted prior to the action (predictive component). But they can also arise when otherwise unpredictable object movements turn out to be consistent with (e.g. spatially compatible to) preceding actions (postdictive component). Here we studied how the impact of postdictive components of inferred minimal selfhood in terms of action-object compatibility is shaped by different levels of predictability of these object movements. We found that compatibility between actions and object movements, and to a lesser extent predictability of object movements, affected reported agency while only compatibility affected reported ownership. Importantly, predictive and postdictive factors influenced these measures in an independent manner. We discuss these results against the background of models that assume multiple components of experienced minimal selfhood.

Are Effects of Action on Perception Real? Evidence from Transformed Movements

It has been argued that several reported non-visual influences on perception cannot be truly perceptual. If they were, they should affect the perception of target objects and reference objects used to express perceptual judgments, and thus cancel each other out. This reasoning presumes that non-visual manipulations impact target objects and comparison objects equally. In the present study we show that equalizing a body-related manipulation between target objects and reference objects essentially abolishes the impact of that manipulation so as it should do when that manipulation actually altered perception. Moreover, the manipulation has an impact on judgements when applied to only the target object but not to the reference object, and that impact reverses when only applied to the reference object but not to the target object. A perceptual explanation predicts this reversal, whereas explanations in terms of post-perceptual response biases or demand effects do not. Altogether these results suggest that body-related influences on perception cannot as a whole be attributed to extra-perceptual factors.

Linking perception and action by structure or process? Toward an integrative perspective

Over the past decades cognitive neuroscience's renewed interest in action has intensified the search of principles explaining how the cognitive system links perception to action and vice versa. To date, at least two seemingly alternative approaches can be distinguished. Perception and action might be linked either by common representational structures, as assumed by the ideomotor approach, or by common attentional processes, as assumed by the attention approach. This article first reviews the evidence from different paradigms supporting each approach. It becomes clear that most studies selectively focus either on actions directed at goals outside the actors' perceptual range (supporting the ideomotor approach) or on actions directed at targets within the actors' perceptual range (supporting the attention approach). In a second step, I will try to reconcile both approaches by reviewing recent eye movement studies that abolish the classical combination of approach and goals under study. Demonstrating that both approaches cover target- as well as goal-directed actions, it is proposed that operations addressed in both conceptual frameworks interact with each other.

Tactile stimulations and wheel rotation responses: toward augmented lane departure warning systems

When an on-board system detects a drift of a vehicle to the left or to the right, in what way should the information be delivered to the driver? Car manufacturers have so far neglected relevant results from Experimental Psychology and Cognitive Neuroscience. Here we show that this situation possibly led to the sub-optimal design of a lane departure warning system (AFIL, PSA Peugeot Citroën) implemented in commercially available automobile vehicles. Twenty participants performed a two-choice reaction time task in which they were to respond by clockwise or counter-clockwise wheel-rotations to tactile stimulations of their left or right wrist. They performed poorer when responding counter-clockwise to the right vibration and clockwise to the left vibration (incompatible mapping) than when responding according to the reverse (compatible) mapping. This suggests that AFIL implements the worse (incompatible) mapping for the operators. This effect depended on initial practice with the interface. The present research illustrates how basic approaches in Cognitive Science may benefit to Human Factors Engineering and ultimately improve man-machine interfaces and show how initial learning can affect interference effects.

Using tools with real and imagined tool movements

When using lever tools, subjects have to deal with two, not necessarily concordant effects of their motor behavior: the body-related proximal effects, like tactile sensations from the moving hand, and/or more external distal effects, like the moving effect points of the lever. As a consequence, spatial compatibility relationships between stimulus (S; at which the effect points of the lever aim at), responding hand (R) and effect point of the lever (E) play a critical role in response generation. In the present study we examine whether the occurrence of compatibility effects needs real tool movements or whether a similar response pattern can be already evoked by pure mental imaginations of the tool effects. In general, response times and errors observed with real and imagined tool movements showed a similar pattern of results, but there were also differences. With incompatible relationships and thus more difficult tasks, response times were reduced with imagined tool movements than compared with real tool movements. On the contrary, with compatible relationships and thus high overlap between proximal and distal action effects, response times were increased with imagined tool movements. Results are only in parts consistent with the ideomotor theory of motor control.

Die Planung und kognitive Repräsentation von Handlungen mit Werkzeugen

Zusammenfassung. Der vorliegende Artikel gibt einen Überblick über Studien zur Planung und Repräsentation von Handlungen mit Werkzeugen. In Abgrenzung zu bisheriger Forschung, die sich vorwiegend mit Prozessen der Bewegungskontrolle bei intransparenten, dem Handelnden nicht unmittelbar einsichtigen Transformationen von Körperbewegungen in entsprechende Werkzeugbewegungen befasst hat, wird besonderes Augenmerk auf frühe Planungsprozesse und auf die mentale Repräsentation von transparenten Beziehungen zwischen Körperbewegungen und Werkzeugbewegungen gelegt. Die Ergebnisse aus Studien zu Vorbereitungseffekten, Sequenzeffekten und bimanueller Koordination bei Werkzeughandlungen sprechen dafür, dass Menschen schon früh im Verlauf der Handlungsplanung eine Repräsentation des zu benutzenden Werkzeugs implementieren. Diese Repräsentation kann als motorisches Schema betrachtet werden, in dem die Werkzeugtransformation, also die allgemeine Beziehung zwischen Körperbewegungen und Werkzeugeffekten, als Invariante fungiert. Studien zur Beobachtung von Werkzeughandlungen zeigen, dass dieses motorische Schema bei der Beobachtung automatisch aktiviert wird. Weitere Untersuchungen sprechen zudem dafür, dass transparente Werkzeugtransformationen genau wie intransparente Werkzeugtransformationen abstrakt repräsentiert sein können und leicht auf andere Bewegungs-Effekt-Instanzen, Werkzeuge mit anderer Mechanik oder auf Handlungen mit einem anderen Effektor generalisieren.

What to do and how to do it: action representations in tool use

Research on bimanual coordination has shown that the efficiency of programming an action is determined by the way the action is cognitively represented. In tool use, actions can be represented with respect to the spatial goal of the action (e.g., the nail that is to be hit by a hammer) or with respect to the tool and its transformation (i.e., the function that maps external target locations onto corresponding bodily movements). We investigated whether the way of cuing bimanual actions with tools affects their cognitive representation and the efficiency with which they are programmed. In one group of participants, tool transformations were specified by symbolic cues, whereas the targets were indicated by direct spatial cues. In another group of participants, symbolic cues specified the targets of the tool-use actions, whereas tool transformations were indicated by direct spatial cues. In a third group, both targets and tool transformations were cued directly by spatial cues. It was hypothesized that different cognitive representations would result in more or less efficient programming of the action. Results indicated longer reaction times and a higher error rate in the group with symbolic cuing of the targets as compared to the group with symbolic cuing of the transformations. The latter did not differ much from the direct cuing group. These results suggest that it is more efficient to represent bimanual tool-use actions in terms of the tool transformations involved than in terms of the targets at which they are directed.

Crosstalk Between Proximal and Distal Action Effects During Tool Use

When using a tool, proximal action effects (e.g., the hand movement on a digitizer tablet) and distal action effects (e.g., the cursor movement on a display) often do not correspond to or are even in conflict with each other. In the experiments reported here, we examined the role of proximal and distal action effects in a closed loop task of sensorimotor control. Different gain factors perturbed the relation between hand movements on the digitizer tablet and cursor movements on a display. In the experiments, the covert hand movement was held constant, while the cursor amplitude on the display was shorter, equal, or longer, and vice versa in the other condition. When participants were asked to replicate the hand movement without visual feedback, hand amplitudes varied in accordance with the displayed amplitudes. Adding a second transformation (Experiment 1: 90°-rotation of visual feedback, Experiment 2: 180°-rotation of visual feedback) reduced these aftereffects only when the discrepancy between hand movement and displayed movement was obvious. In conclusion, distal action effects assimilated proximal action effects when the proprioceptive/tactile feedback showed a feature overlap with the visual feedback on the display.

On the Persistence of Tool-Based Compatibility Effects

Using tools, such as simple levers, makes specific demands on the motor system. Two related performance decrements have been reported: The costs that arise when required tool movements and movements of the operating hand are spatially incompatible (hand-tool compatibility), and the costs that arise when relevant stimuli and tool movements are spatially incompatible (stimulus-tool compatibility). We performed two experiments to test the boundary conditions of both effects. Experiment 1 revealed a strong hand-tool compatibility effect despite visual occlusion of the hand and instructions to ignore hand movements. Experiment 2 revealed influences of stimulus-tool compatibility despite instructions to ignore the tool and to pay attention to the operating hand alone. These results suggest that lever movements of the type studied here become automatically represented and constrain motor performance.

Compatibility relationships with simple lever tools

OBJECTIVE

The study focuses on potential compatibility relationships when simple lever tools are used.

BACKGROUND

Spatial compatibility between stimuli and responses determines performance. However, many tasks require the use of simple tools, such as levers that transform hand movements into tool movements. We explore with such a tool whether and how the correspondence or noncorrespondence between stimulus-side and hand movement (stimulus-response compatibility), between stimulus-side and tool-effect movement (stimulus-effect compatibility), and/or between hand movement and tool-effect movement (response-effect compatibility) affects performance.

METHOD

U-shaped and inverted-U-shaped levers were used as tools,allowing us to examine the contribution of each compatibility relationship to response times and errors without any confounds and omissions.

RESULTS

Responding was delayed and error prone when the hand movement and the movement of the effect point of the tool did not correspond. Effects of stimulus-response compatibility and stimulus-effect compatibility were observed only when the hand movement direction remained untransformed in the tool-effect movement

CONCLUSION

The results point out that the inversion or noninversion of tool-effect movements plays an underlying role when handling a tool.

APPLICATION

Potential applications of this research include the prediction and possibly manipulation of unwanted behavioral tendencies in laparoscopic surgery and other lever movements.

Type of visual feedback during practice influences the precision of the acquired internal model of a complex visuo-motor transformation

This study investigated the influence of the type of visual feedback during practice with a complex visuo-motor transformation of a sliding two-sided lever on the acquisition of an internal model of the transformation. Three groups of participants, who practised with different types of visual feedback, were compared with regard to movement accuracy, curvature and movement time. One group had continuous visual feedback during practice and two groups were presented terminal visual feedback, either only the end position of the movement or the end position together with the trajectory of the cursor. Results showed that continuous visual feedback led to more precise movement end positions during practice than terminal visual feedback, but to less precise movements during open-loop tests. This finding indicates that terminal visual feedback supports the development of a precise internal model of a new visuo-motor transformation. However, even terminal feedback of the cursor trajectory during practice did not result in an internal model, which includes appropriate curvatures of hand movements. STATEMENT OF RELEVANCE: This paper presents results on the influence of type of visual feedback on learning the complex motor skill of controlling a sliding lever. These findings contribute to the conceptual basis of optimised training procedures for the acquisition of sensori-motor skills required for the mastery of instruments utilised in minimally invasive surgery.

Bimanual interference with compatible and incompatible tool transformations

The present study investigates bimanual interference in a tool-use task, in which two target locations had to be touched concurrently with two tools, one for each hand. Target locations were either in the same, or in different directions for the two hands. Furthermore, the tools implemented either a compatible or an incompatible relationship between the direction of target locations and the direction of associated bodily movements. Results indicated bimanual interference when the tools had to be moved to targets in different directions. Furthermore, this interference was much more pronounced when the tools required body movements that were spatially incompatible to the cued target locations as compared to when they were compatible. These results show that incompatible relationships between target directions and bodily movement directions can aggravate bimanual interference in tool use.

Action control while seeing mirror images of one's own movements: Effects of perspective on spatial compatibility

It is examined whether and how the perspective of seeing one's own movements exerted an influence on action control. Such change in the perspective challenges an information processor, as she or he has to handle successfully the discrepancies between the tactile/proprioceptive feedback and the visual feedback on a projection screen. In the experiments participants responded to visual stimuli, but saw their responses either from the top or with an x-axis reflection, a y-axis reflection, or a reflection about both axes. The results showed that a change in perspective did not impair performance as long as the left–right relations corresponded with the body space (e.g., with visual feedback reflected about the x-axis). By contrast, performance was drastically reduced when visual feedback was reflected about the y-axis or about both axes, so that performed left-side (right-side) movements were seen as right-side (left-side) movements. It is concluded that an actor preferably relies on the information of the visual system, but refers to the tactile/proprioceptive information when it facilitates the task demands.

Learning the visuomotor transformation of virtual and real sliding levers: simple approximations of complex transformations

Learning to operate a complex tool such as a sliding lever can be conceived as learning both a kinematic and a dynamic transformation. We investigated whether the presence of the dynamic transformation has an inhibitory or a facilitative effect on learning to control a sliding lever. Furthermore, we examined the characteristics of the internal model of the kinematic transformation of the lever in visual open-loop trials. In the experiment, one group of participants practiced with only the kinematic transformation of the lever (virtual lever), the other group practiced with both the kinematic and the dynamic transformation (physical lever). Visual feedback was continuously present during practice. Results showed only marginal differences between both groups in open-loop tests. This finding is likely to be related to the fact that in both groups a simplified approximation of the kinematic transformation was acquired, in particular a symmetry approximation. With such an approximation the target for the hand movement is derived from the visual target for the tip of the lever as the position which is symmetric around a sagittal axis.

Perceiving one's own movements when using a tool

The present study examined what participants perceive of their hand movements when using a tool. In the experiments different gains for either the x-axis or the y-axis perturbed the relation between hand movements on a digitizer tablet and cursor movements on a display. As a consequence of the perturbation participants drew circles on the display while their covered hand movements followed either vertical or horizontal ellipses on the digitizer tablet. When asked to evaluate their hand movements, participants were extremely uncertain about their trajectories. By varying the amount of visual feedback, findings indicated that the low awareness of one's own movements originated mainly from an insufficient quality of the humans' tactile and proprioceptive system or from an insufficient spatial reconstruction of this information in memory.

Action planning with two-handed tools

In tool use, the intended external goals have to be transformed into bodily movements by taking into account the target-to-movement mapping implemented by the tool. In bimanual tool use, this mapping may depend on the part of the tool that is operated and the effector used (e.g. the left and right hand at the handle bar moving in opposite directions in order to generate the same bicycle movement). In our study, we investigated whether participants represent the behaviour of the tool or only the effector-specific mapping when using two-handed tools. In three experiments, participants touched target locations with a two-jointed lever, using either the left or the right hand. In one condition, the joint of the lever was constant and switching between hands was associated with switching the target-to-movement-mapping, whereas in another condition, switching between hands was associated with switching the joint, but the target-to-movement-mapping remained constant. Results indicate pronounced costs of switching hands in the condition with constant joint, whereas they were smaller with constant target-to-movement mapping. These results suggest that participants have tool-independent representations of the effector-specific mappings.