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Osiurak F.,CNRS Laboratory of Cognitive Mechanisms
Cognition | Year: 2014

Tool-use representations have been suggested to be supported by the representation of hand actions and/or by the representation of tool actions. A major issue is to know which one of these two representations is preferentially activated when people intend to use a tool. To address this issue, we developed a paradigm in which, in 20% of trials, participants had to press a button and actually use pliers to move an object in response to a predefined target symbol. Importantly, two masks hiding the symbols performed "opening" or "closing" actions before symbols appeared. In Experiment 1, participants used normal pliers: Hand's opening actions induced pliers' opening actions and vice versa for hands' closing actions. Results indicated a compatibility effect between masks' actions and pliers' actions. Participants were faster to press the button in response to the target symbol when opening and closing actions of the masks were congruent with the corresponding actions of the hand. In Experiment 2 participants used inverse pliers: Hand's opening actions involved pliers' closing actions and vice versa. In this situation, results showed that the congruency of masks' actions occurred with pliers' actions and not hand's actions. Altogether, these findings demonstrate that intention of use is preferentially based on the representation of tool actions, and have important implications for the domain of neuropsychology of tool use and the theories of goal-directed behavior. © 2013 Elsevier B.V.

Jarry C.,University of Angers | Osiurak F.,CNRS Laboratory of Cognitive Mechanisms | Delafuys D.,University of Angers | Chauvire V.,University of Angers | And 2 more authors.
Cortex | Year: 2013

Various distinct cognitive processes such as semantic memory, executive planning or technical reasoning have been shown to support tool use. The aim of this study is to investigate the relationship between these processes. To do so, a large apraxia battery was submitted to 16 patients with left brain-damage (LBD) and aphasia and 19 healthy controls. The battery included: classical apraxia tests (Pantomime of Tool Use and Single Tool Use), familiar and novel tool use tests (Tool-Object Pairs and Sequential Mechanical Problem-Solving), semantic memory tests (Recognition of tool utilization gestures and Functional and Categorical Associations) as well as the Tower Of London. The Sequential Mechanical Problem-Solving task is a new task which permits the evaluation of pre-planning in unusual tool use situations. In this task as well as in the Tool-Object Pairs task, participants solved a tool use problem in a Choice and a No-Choice condition to examine the effect of tool selection. Globally, left brain damaged patients were impaired as compared to controls. We found high correlations in left brain damaged patients between performances on classical apraxia tests, familiar and novel tool use tests and Functional and Categorical Associations but no significant association between these performances and Tower Of London or Recognition of tool utilization gestures. Furthermore, the two conditions (Choice and No-Choice) of Tool-Object Pairs and Sequential Mechanical Problem-Solving were associated. In sum, all tasks involving tool use are strongly associated in LBD patients. Moreover, the ability to solve sequential mechanical problems does not depend on executive planning. Also, tool use appears to be associated with knowledge about object function but not with knowledge about tool manipulation. Taken together, these findings indicate that technical reasoning and, to a lesser extent, semantic memory may both play an important role in tool use. © 2013 Elsevier Ltd.

Awal A.-M.,CNRS Laboratory of Cognitive Mechanisms | Mouchere H.,University of Nantes | Viard-Gaudin C.,University of Nantes
Pattern Recognition Letters | Year: 2014

Despite the recent advances in handwriting recognition, handwritten two-dimensional (2D) languages are still a challenge. Electrical schemas, chemical equations and mathematical expressions (MEs) are examples of such 2D languages. In this case, the recognition problem is particularly difficult due to the two dimensional layout of the language. This paper presents an online handwritten mathematical expression recognition system that handles mathematical expression recognition as a simultaneous optimization of expression segmentation, symbol recognition, and 2D structure recognition under the restriction of a mathematical expression grammar. The originality of the approach is a global strategy allowing learning mathematical symbols and spatial relations directly from complete expressions. A new contextual modeling is proposed for combining syntactic and structural information. Those models are used to find the most likely combination of segmentation/recognition hypotheses proposed by a 2D segmentation scheme. Thus, models are based on structural information concerning the symbol layout. The system is tested with a new public database of mathematical expressions which was used in the CHROME competition. We have also produced a large base of semi-synthetic expressions which are used to train and test the global learning approach. We obtain very promising results on both synthetic and real expressions databases, as well as in the recent CHROME competition. © 2012 Elsevier B.V. All rights reserved.

Mars F.,French National Center for Scientific Research | Navarro J.,CNRS Laboratory of Cognitive Mechanisms
PLoS ONE | Year: 2012

Current theories on the role of visuomotor coordination in driving agree that active sampling of the road by the driver informs the arm-motor system in charge of performing actions on the steering wheel. Still under debate, however, is the nature of visual cues and gaze strategies used by drivers. In particular, the tangent point hypothesis, which states that drivers look at a specific point on the inside edge line, has recently become the object of controversy. An alternative hypothesis proposes that drivers orient gaze toward the desired future path, which happens to be often situated in the vicinity of the tangent point. The present study contributed to this debate through the analyses of the distribution of gaze orientation with respect to the tangent point. The results revealed that drivers sampled the roadway in the close vicinity of the tangent point rather than the tangent point proper. This supports the idea that drivers look at the boundary of a safe trajectory envelop near the inside edge line. Furthermore, the study investigated for the first time the reciprocal influence of manual control on gaze control in the context of driving. This was achieved through the comparison of gaze behavior when drivers actively steered the vehicle or when steering was performed by an automatic controller. The results showed an increase in look-ahead fixations in the direction of the bend exit and a small but consistent reduction in the time spent looking in the area of the tangent point when steering was passive. This may be the consequence of a change in the balance between cognitive and sensorimotor anticipatory gaze strategies. It might also reflect bidirectional coordination control between the eye and arm-motor systems, which goes beyond the common assumption that the eyes lead the hands when driving. © 2012 Mars, Navarro.

Vallet G.T.,Laval University | Vallet G.T.,CNRS Laboratory of Cognitive Mechanisms | Hudon C.,Laval University | Hudon C.,University of Quebec | And 2 more authors.
Cortex | Year: 2013

Implicit memory is generally supposed to be preserved in Alzheimer's disease (AD). Yet, some implicit priming effects are impaired and others are not. The preserved/impaired priming effects are often interpreted according to the perceptual/conceptual or identification/production distinctions. Perceptual-identification priming paradigms shall be preserved and conceptual-production priming paradigms impaired. A third interpretation is yet possible based on the disconnection syndrome hypothesis which states that patients with AD should fail tasks requiring relatively complex brain communications. In this case, patients with AD should not demonstrated a significant perceptual priming effect in an identification task if this one involved complex brain communications. The present study tests this latter hypothesis with two cross-modal priming experiments using a categorization task. A visual meaningless mask presented with half of the auditory primes tested the nature of the cross-modal priming effect. The control group exhibited significant priming effects for unmasked primes. The interference effect of the mask demonstrated that the priming effect was perceptually driven. Patients with AD did not present any priming effect nor mask interference. The present findings therefore showed that perceptual priming using an identification task could be impaired in AD supporting the disconnection syndrome hypothesis. © 2012 Elsevier Ltd.

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