Stimulus-response compatibility effects during object semantic categorisation: Evocation of grasp affordances or abstract coding of object size?

When the size of visual objects matches the size of the response required to perform the task, a potentiation effect has been reported, with faster responses in compatible than incompatible situations. Size compatibility effects have been taken as evidence of close perception-action interrelations. However, it is still unclear whether the effect arises from abstract coding of the size of stimulus and response or from the evocation of grasp affordances from visual objects. We aimed to disentangle the two interpretations. Two groups of 40 young adults categorised small and large objects presented in standardised size as natural or artefact objects. One group categorised manipulable objects that may be associated with small or large size properties and evoke power or precision grasp affordances. The other group categorised non-manipulable objects that may only be associated with small or large size properties. Categorisation responses were made by reaching and grasping a monotonic cylindric device with a power or precision grip in a grasping condition and with large or small touch responses in a control condition. Compatibility effects were found in both grasping and control conditions, independently of the manipulability or category of objects. Participants were faster when the size of the expected response matched the size of the object than when they mismatched, especially for power grasps or whole-hand touch responses. Overall findings support the abstract coding hypothesis and suggest that compatibility between the conceptual size of the object and the size of the hand response is sufficient to facilitate semantic categorisation judgements.

Glaucoma-associated abnormalities in cortical activity during a visuocognitive task.

OBJECTIVE: To investigate neurophysiological dynamics during a visuocognitive task in glaucoma patients vs. healthy controls. METHODS: Fifteen patients with early-stage primary open-angle glaucoma (POAG) and fifteen age-matched healthy participants underwent a "go/no-go" task, monitored with EEG. Participants had to semantically categorize visual objects in central vision, with animal or furniture as targets according to the experimental block. RESULTS: Early visual processing was delayed by 50 ms in patients with POAG compared to controls. The patients displayed a smaller difference between animal and furniture categorization during higher-level cognitive processing (at 400-600 ms). Regarding behavioral data, the groups differed in accuracy performance and decision criterion. As opposed to the control group, patients did not display facilitation and a higher accuracy rate for animal stimuli. However, patients maintained a consistent decision criterion throughout the experiment, whereas controls displayed a shift towards worse decision criteria in furniture trials, with higher error rate. CONCLUSIONS: The comparative analysis of behavioral and neurophysiological data revealed in POAG patients a delay in early visual processing, and potential high-level cognitive compensation during late, task-dependent activations. SIGNIFICANCE: To our knowledge, our findings provide the first evidence of modification in cognitive brain dynamics associated with POAG.

Too much to handle? Interference from distractors with similar affordances on target selection for handled objects.

The existence of handle affordances has been classically demonstrated using the Stimulus-Response Compatibility paradigm, with shorter response times when the orientation of the object handle and the response hand are compatible in comparison to incompatible. Yet the activation of handle affordances from visual objects has been investigated in very simple situations involving single stimulus and motor response. As natural perceptual scenes are usually composed of multiple objects that could activate multiple affordances, the consequence of multiple affordance activation on the perception and processing of a given object of the scene requires more investigation. The aim of this study was to determine the impact of distractor affordances on the processing of a target object in situations involving several familiar graspable objects. In two online experiments, 229 participants had to select a target object (the kitchen utensil or the tool) in a visual scene displaying a pair of objects. They performed left key presses when the target was on the left and right key presses when the target was on the right. Target handle orientation and response side could be compatible or incompatible. Critically, target and distractor objects had similar or dissimilar handle affordances, with handles oriented for left- or right-hand grasps. Results from the two experiments showed slower response times when target and distractor objects had similar handle affordances in comparison to dissimilar affordances, when participants performed right hand responses and when target orientation and response were compatible. Thus, affordance similarity between objects may interfere rather than facilitate object processing and slow down target selection. These findings are in line with models of affordance and object selection assuming automatic inhibition of distractors' affordances for appropriate object interaction.

Congruent action context releases Mu rhythm desynchronization when visual objects activate competing action representations.

Recent findings demonstrated that object perception is affected by the competition between action representations. Simultaneous activation of distinct structural ("grasp-to-move") and functional ("grasp-to-use") action representations slows down perceptual judgements on objects. At the brain level, competition reduces motor resonance effects during manipulable object perception, reflected by an extinction of µ rhythm desynchronization. However, how this competition is solved in the absence of object-directed action remains unclear. The present study investigates the role of context in the resolution of the competition between conflicting action representations during mere object perception. To this aim, thirty-eight volunteers were instructed to perform a reachability judgment task on 3D objects presented at different distances in a virtual environment. Objects were conflictual objects associated with distinct structural and functional action representations. Verbs were used to provide a neutral or congruent action context prior or after object presentation. Neurophysiological correlates of the competition between action representation were recorded using EEG. The main result showed a release of µ rhythm desynchronization when reachable conflictual objects were presented with a congruent action context. Context influenced µ rhythm desynchronization when the action context was provided prior or after object presentation in a time-window compatible with object-context integration (around 1000 ms after the presentation of the first stimulus). These findings revealed that action context biases competition between co-activated action representations during mere object perception and demonstrated that µ rhythm desynchronization may be an index of activation but also competition between action representations in perception.

Dynamics of low-pass-filtered object categories: A decoding approach to ERP recordings.

Rapid analysis of low spatial frequencies (LSFs) in the brain conveys the global shape of the object and allows for rapid expectations about the visual input. Evidence has suggested that LSF processing differs as a function of the semantic category to identify. The present study sought to specify the neural dynamics of the LSF contribution to the rapid object representation of living versus non-living objects. In this EEG experiment, participants had to categorize an object displayed at different spatial frequencies (LSF or non-filtered). Behavioral results showed an advantage for living versus non-living objects and a decrease in performance with LSF pictures of pieces of furniture only. Moreover, despite a difference in classification performance between LSF and non-filtered pictures for living items, the behavioral performance was maintained, which suggests that classification under our specific condition can be based on LSF information, in particular for living items.

Self-partner inclusion predicts performance of romantically involved individuals in a body-scaled action-anticipation task.

Previous research has shown that romantic relationships can lead to the cognitive inclusion of a romantic partner into one's own self-representation, resulting in blurred boundaries between self and intimate other. Recent work suggests that this self-other integration process encompasses the two dimensions of the self-the conceptual and the bodily self. In line with this, it has been proposed that romantic love is associated with cognitive states that blur or reduce the saliency of self-boundaries in the bodily domain. The present study tested this hypothesis by investigating the influence of the self-other integration process in romantic love on passability judgments of door-like apertures, an action-anticipation task that rests on the representation of bodily boundaries. Romantically involved and single participants estimated whether they could pass through apertures of different widths. Moreover, inclusion of romantic partner in the self was assessed using the Inclusion of Other in the Self (IOS) scale. The pattern of correlation and the ratio between participants' shoulder width and aperture judgments did not differ between romantically involved participants and singles. However, our results revealed that in romantically involved participants, the relationship between individuals' shoulder width and aperture judgements was moderated by IOS scores. A greater inclusion of romantic partner in the self was associated with a weaker prediction of aperture judgment by participants' shoulder width. A similar moderating effect of the intensity of romantic feelings (as measured by the passionate love scale) on shoulder width-aperture judgment relationship was found. IOS scores, but not romantic feelings, also moderated aperture judgments made for another individual (third person perspective). Together, these findings are consistent with the view that inclusion of romantic partner in the self triggers cognitive states affecting self-boundaries in the bodily domain.

Short-term upper-limb immobilization alters peripersonal space representation.

Peripersonal space is a multisensory interface between the environment and the body subserving motor interactions with the physical and social world. Although changing body properties has been shown to alter the functional processing of space, little is known about the effect of short-term limb immobilization specifically on the motor representation of peripersonal space. In the present study, we investigated the effect of a right upper-limb immobilization for a duration of 24 h on a reachability judgment task and a brightness judgment task. Analyses of perceptual thresholds revealed a reduction of peripersonal space representation after the immobilization period, which was not observed when there was no immobilization (control group). In contrast, no variation appeared in the brightness judgment task, suggesting no presence of specific visual perception or decisional deficits in the limb immobilization group. Considered together, the results confirm the crucial role of the motor system in the representation of peripersonal space. They also highlight the plasticity of the motor system resulting in a rapid change of its activity following limb immobilization, with a concomitant effect on motor-related perceptual and cognitive processes.

Does the motor system contribute to the perception of changes in objects visual attributes? The neural dynamics of sensory binding by action.

The contribution of the motor system to perception has been highlighted in research investigating the effect of performing an action on the conscious processing of information received from the sensory systems. For example, the perceptual temporal asynchrony observed when passively reporting changes in visual object attributes (e.g., colour and position) was found to disappear virtually when the changes resulted from a voluntary motor action. Although the spatio-temporal constraints of sensory binding by action have been broadly investigated, the underlying neural correlates are still largely unknown. In the present study, participants performed temporal order judgments of changes in the colour and position of a visual stimulus, while adapting to a 750 ms delay between a sound (perceptual condition) or the end of a manual reaching action (motor condition), and the visual changes. Behavioural observations indicated that temporal asynchrony (-30.2 ms) decreased in the motor condition (2.7 ms), as a result of sensorimotor adaptation, but not in the perceptual condition (-29.6 ms). EEG-evoked potentials on posterior visual regions showed that early components were altered by sensorimotor adaptation, with in particular a broad reduction in the amplitude of the early P1 component. Furthermore, time-frequency analysis of EEG signals during the 350 ms period preceding the visual changes revealed an increase of the 15-25 Hz frequency band amplitude in the central region and a decrease of the 8-12 Hz frequency band amplitude in the posterior region. Overall the results suggest that sensory binding by action depends on an early top-down modulation of the visual regions by the motor system - in agreement with the pre-activation theory of action-perception coupling - associated with an increase of attentional resources.

Do manufactured and natural objects evoke similar motor information? The case of action priming.

There is considerable evidence that visually presented manipulable objects evoke motor information, supporting the existence of affordance effects during object perception. However, most arguments come from stimulus-response compatibility paradigms, raising the issue of the automaticity of affordance effects. Action priming paradigms overcome this issue but show less reliable results, possibly because affordance effects are moderated by additional factors. The present study aimed to assess whether affordance effects highlighted in action priming paradigms could be affected by object category (manufactured or natural). A total of 24 young adults performed a semantic categorisation task on natural and manufactured target objects presented after neutral (non-grasping hand postures) or action (congruent power or precision grips) primes. Results revealed a modulation of action priming effects as a function of object category. Object semantic categorisation was faster after action than neutral primes, but only for manufactured objects. Results suggest that natural and manufactured objects evoke distinct types of affordances and that action priming paradigms favour the evocation of functional affordances during object semantic categorisation. This finding fuels the debate on the nature of the motor information evoked by visual objects.

Conflict between gesture representations extinguishes µ rhythm desynchronization during manipulable object perception: An EEG study.

Recent findings showed that competition between object structural ("grasp-to-move") and functional ("grasp-to-use") gestures slows down the initiation of object-directed actions but also object visual processing. The present study investigates the neurophysiological correlates of the competition between gesture representations during object perception. 3D conflictual objects (distinct structural and functional gestures) and non-conflictual objects (similar structural and functional gestures) were presented in three spaces (peripersonal, boundary of peripersonal, and extrapersonal) in a virtual environment. Participants performed reach-to-grasp and semantic judgments on objects while EEG was recorded. Results revealed that the conflict between evoked gestures impacts 8-12 Hz desynchronization at both central (µ rhythm) and posterior (α rhythm) sites. Critically, µ rhythm desynchronization was suppressed when conflictual objects were presented in peripersonal space. Findings indicate that µ rhythm desynchronization is reduced by the competition between evoked gestures and suggest that neural motor resonance may also reflect action selection processes during object perception.

Conflict between object structural and functional affordances in peripersonal space.

Recent studies indicate that competition between conflicting action representations slows down planning of object-directed actions. The present study aims to assess whether similar conflict effects exist during manipulable object perception. Twenty-six young adults performed reach-to-grasp and semantic judgements on conflictual objects (with competing structural and functional gestures) and non-conflictual objects (with similar structural and functional gestures) presented at difference distances in a 3D virtual environment. Results highlight a space-dependent conflict between structural and functional affordances. Perceptual judgments on conflictual objects were slower that perceptual judgments on non-conflictual objects, but only when objects were presented within reach. Findings demonstrate that competition between structural and functional affordances during object perception induces a processing cost, and further show that object position in space can bias affordance competition.

EEG µ rhythm in virtual reality reveals that motor coding of visual objects in peripersonal space is task dependent.

Previous fMRI studies have shown that the visual perception of manipulable objects spontaneously involves the sensorimotor system, especially when the objects are located in peripersonal space. However, it has also been suggested that the motor coding of manipulable objects perceived in peripersonal space depends on an anticipation to interact with them. The present study aims at clarifying this issue by analyzing healthy adults' EEG activity on the centro-parietal region while perceptually judging intrinsic (prototypical or distorted shape) or extrinsic (reachable or not reachable location) properties of visual objects. In both the object identification and reachability judgment tasks, time-frequency decomposition of EEG signals was performed across the first 1000 ms following object presentation for trials on which no post-stimulus response was required (90% of the trials). Event-Related-(De)Synchronization (ERD/S) of µ rhythm was computed using the 150 ms pre-stimulus period as baseline. In the reachability judgment task, EEG analysis showed a desynchronization of µ rhythm starting 300 ms after object presentation, but only when the objects were presented with a prototypical shape in peripersonal space. For those objects, desynchronization of µ rhythm diminished progressively from peripersonal to extrapersonal space. By contrast, no such gradient was observed in the object identification task. On the whole, these data indicate that motor coding of visual objects expressed in the µ rhythm depends on an object's shape and location in space, but also on the goal of the perceptual task.

Impact of action primes on implicit processing of thematic and functional similarity relations: evidence from eye-tracking.

The aim of this study was to specify the role of action representations in thematic and functional similarity relations between manipulable artifact objects. Recent behavioral and neurophysiological evidence indicates that while they are all relevant for manipulable artifact concepts, semantic relations based on thematic (e.g., saw-wood), specific function similarity (e.g., saw-axe), and general function similarity (e.g., saw-knife) are differently processed, and may relate to different levels of action representation. Point-light displays of object-related actions previously encoded at the gesture level (e.g., "sawing") or at the higher level of action representation (e.g., "cutting") were used as primes before participants identified target objects (e.g., saw) among semantically related and unrelated distractors (e.g., wood, feather, piano). Analysis of eye movements on the different objects during target identification informed about the amplitude and the timing of implicit activation of the different semantic relations. Results showed that action prime encoding impacted the processing of thematic relations, but not that of functional similarity relations. Semantic competition with thematic distractors was greater and earlier following action primes encoded at the gesture level compared to action primes encoded at higher level. As a whole, these findings highlight the direct influence of action representations on thematic relation processing, and suggest that thematic relations involve gesture-level representations rather than intention-level representations.

A saw is first identified as an object used on wood: ERP evidence for temporal differences between Thematic and Functional similarity relations.

The role of functional and motor information in manipulable artifact object semantic organization is still poorly understood. In particular, several types of semantic relations involving object functional knowledge may be distinguished. Functional similarity relations group objects with similar functions at relatively specific (e.g. saw-axe, both used to cut wood) or general (saw-knife, both used to cut) levels. Thematic relations group objects based on their complementarity in events (saw used upon/with wood). Recent eye-tracking data showed distinct temporal time courses for the different semantic relations, with fastest processing of thematic relations and slowest processing of general function similarity relations. Behavioral data suggest the involvement of distinct cognitive mechanisms in manipulable artifact object semantic processing. The aim of the present study was to assess the neural correlates of thematic, and specific and general function similarity relation processing. Specifically, we investigated whether time course differences between semantic relations could be highlighted at the neurophysiological level. We used a protocol combining semantic priming with electroencephalography, and manipulated the type of semantic relation and the duration of the interval between prime and target objects. Two consistent and complementary results were shown. On N1 and P3 components, semantic priming was observed for thematic relations only. On N400 component, the type of semantic relation interacted with interval duration, and semantic priming was visible for all 3 relations after the longest interval only. Results revealed graded processing time courses for thematic, specific function similarity, and general function similarity relations at the neural level, and further indicate that thematic relations impact object processing during the early stages of object recognition. Findings suggest a hierarchical organization of three types of semantic relations based on functional knowledge. The parallel between semantic relations involving manipulable artifact objects and levels of action representations is discussed.

Temporal dynamics of action perception: differences on ERP evoked by object-related and non-object-related actions.

While neuropsychological dissociations suggest that distinct processes are involved in execution or perception of transitive (object-related) and intransitive (non-object-related) actions, the few neuroimaging studies that directly contrasted the brain activations underlying transitive and intransitive gesture perception failed to find substantial differences between the two action types. However, the distinction could be visible on brain activity timing within the fronto-parietal network. In this study, we used Event-Related Potential (ERP) method to assess the temporal dynamics of object-related and non-object-related action processing. Although both meaningful, only object-related actions involve object motor features. Accordingly, perception of the two action types would show distinct neural correlates. Participants were presented with four movie types (ORA, Object-Related Action, NORA: Non-Object-Related Action and 2 control movies) and were instructed to perform tasks that required explicit or implicit action recognition (specific action recognition or color change detection). Movies were presented as Point-Light Display (PLD) and thus provided only information about gesture kinematics regardless of action type. ERP were computed during movie visual perception and analyzed as a function of movie type and task. The main result revealed a difference between ORA and NORA on the amplitude of the P3a component in the fronto-parietal region. The difference observed around 250 ms after movie onset do not likely origin from variation in low-level visual features or attention resource allocation. Instead, we suggest that it reflects incidental recruitment of object attributes during object-related action perception. The exact nature of these attributes is discussed.

Brain responses to handwritten and printed letters differentially depend on the activation state of the primary motor cortex.

Previous studies demonstrated that visual perception of handwritten letters activates the left primary motor cortex more strongly than printed letters. Here, we used EEG to record cortical responses evoked by single letters to directly test if their visual processing is actually influenced by their motor content. We manipulated the "motor familiarity" of letters that we considered high for letters written by the observers themselves, medium for letters written by other individuals, and low for printed, machine designed letters. In order to relate the effects of motor familiarity to the activation of the primary motor cortex, we also directly manipulated its availability during the visual task: we computed Event-Related Potentials (ERPs) over the posterior cortex during a dual task where participants had to observe the letters while performing unrelated self-paced brief movements of the right hand approximately every 5s (allowing the primary motor cortex to successively activate and "idle"). At 300-350 ms and 500-600 ms after stimulus onset, the amplitude of the ERP components markedly reflected the level of motor familiarity of the observed letter. Nonetheless, this was true only when the primary motor cortex was in an "idling" state: when the motor cortex was in an activation state, this motor familiarity effect was dropped. This clearly indicates that, at these latencies, the motor information embedded in letters is processed in the brain and that this processing depends on the activation state of the left primary motor cortex.

"Biological geometry perception": visual discrimination of eccentricity is related to individual motor preferences.

BACKGROUND: In the continuum between a stroke and a circle including all possible ellipses, some eccentricities seem more "biologically preferred" than others by the motor system, probably because they imply less demanding coordination patterns. Based on the idea that biological motion perception relies on knowledge of the laws that govern the motor system, we investigated whether motorically preferential and non-preferential eccentricities are visually discriminated differently. In contrast with previous studies that were interested in the effect of kinematic/time features of movements on their visual perception, we focused on geometric/spatial features, and therefore used a static visual display. METHODOLOGY/PRINCIPAL FINDINGS: In a dual-task paradigm, participants visually discriminated 13 static ellipses of various eccentricities while performing a finger-thumb opposition sequence with either the dominant or the non-dominant hand. Our assumption was that because the movements used to trace ellipses are strongly lateralized, a motor task performed with the dominant hand should affect the simultaneous visual discrimination more strongly. We found that visual discrimination was not affected when the motor task was performed by the non-dominant hand. Conversely, it was impaired when the motor task was performed with the dominant hand, but only for the ellipses that we defined as preferred by the motor system, based on an assessment of individual preferences during an independent graphomotor task. CONCLUSIONS/SIGNIFICANCE: Visual discrimination of ellipses depends on the state of the motor neural networks controlling the dominant hand, but only when their eccentricity is "biologically preferred". Importantly, this effect emerges on the basis of a static display, suggesting that what we call "biological geometry", i.e., geometric features resulting from preferential movements is relevant information for the visual processing of bidimensional shapes.

The graphemic/motor frontal area Exner's area revisited.

OBJECTIVE: In 1881, Exner first described a "graphic motor image center" in the middle frontal gyrus. Current psycholinguistic models of handwriting involve the conversion of abstract, orthographic representations into motor representations before a sequence of appropriate hand movements is produced. Direct cortical stimulation and functional magnetic resonance imaging (fMRI) were used to study the human frontal areas involved in writing. METHODS: Cortical electrical stimulation mapping was used intraoperatively in 12 patients during the removal of brain tumors to identify the areas involved in oral language (sentence reading and naming) and writing, and to spare them during surgery. The fMRI activation experiment involved 12 right-handed and 12 left-handed healthy volunteers using word dictation (without visual control) and 2 control tasks. RESULTS: Direct cortical electrical stimulation of restricted areas rostral to the primary motor hand area (Brodmann area [BA] 6) impaired handwriting in 6 patients, without disturbing hand movements or oral language tasks. In 6 other patients, stimulation of lower frontal regions showed deficits combining handwriting with other language tasks. fMRI also revealed selective activation during word handwriting in left versus right BA6 depending on handedness. This area was anatomically matched to those areas that affected handwriting on electrical stimulation. INTERPRETATION: An area in middle frontal gyrus (BA6) that we have termed the graphemic/motor frontal area supports bridging between orthography and motor programs specific to handwriting.