Symposium in honour of Jean-Louis Thonnard

Detailed program

Alan Tennant, Professor, University of Leeds

Bringing the science of measurement to Patient Reported Outcome Measures (PROM’s).

Almost 60 years ago Georg Rasch, a Danish mathematician, introduced his dichotomous model for responses to a test. Subsequently expanded to polytomous items, such as found in many modern PROM’s, the model has had a profound effect on the creation of new PROM’s and the evaluation of existing PROM’s, particularly in the field of rehabilitation. Jean-Louis Thonnard and his group were at the forefront of this revolution.

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Luigi Tesio, Professor, University of Milan

Measuring the intangible through rasch modelling: a way to disentangle existing from imaginary persons' variables.

In 1628 William Harvey published his fundamental findings on the circulation of blood. He considered himself an anatomist: yet, he founded Physiology. Perhaps Georg Rasch thought he just improved psychometric measurement: yet, he gave us a general method to measure intangible human variables. This method gave the behavioural researchers not only a statistical tool but, also, a robust chance to reflect on what is real and what is imaginary across human traits. If human behaviour or perception can be validly measured, it can become an object of scientific inquiry. However, it does not necessarily exist. We can measure precisely the radius of a circular UFO captured by a picture. Rasch gave us a wind-proof torch to advance in the dark towards knowledge: a necessary, not yet a sufficient instrument. Like a mirage, real person’s variables are far from us, but they are reflected from infinite tangible behaviours (a sample of which makes the items of a Rasch-consistent questionnaire). The mirage allows us to discover a remote yet existing object. Imaginary variables are artificial “constructs” formed by the items we place in a questionnaire. In making the questionnaires, we think we discovered these variables, while actually, we invented them. Unawareness of this difference may lead to severe mistakes in biomedical and social sciences. Rasch modelling revitalized the debate on reflective and formative variables. Unidimensionality of the items, perhaps the main requirement of the model, is a bright flag of the potential existence of the hypothesised “dimension”. It soon became apparent, however, that unidimensionality can be claimed for also by formative questionnaires, provided the items are carefully selected and the sample made of model-fitting individuals. Did the Rasch torch lead us onto a blind corner? The answer is: no, provided we are not satisfied with the internal consistency emphasized by the estimation of data-model fit. The word “data” should remind us of the unavoidable sample-dependence of our inferences. First, item and persons’ fit must persist across time, samples, and even substitutions of items. Second, Rasch measures must be consistent with (and predictive of) measures of extraneous variables, linked to the tested one by models based on a-priori, external knowledge. Like a domestic canary, artificial formative variables do not survive in the varied wild world, while a real variable, lying safe far from its reflections, does. Rasch researchers like Jean-Louis Thonnard and his group made significant, pioneering work in demonstrating with many experimental examples the unprecedented conceptual validity of scales built in agreement with the Rasch theorem. The next generation is now called to use Rasch modelling to measure people not less than scales, and to demonstrate its superiority in clinical and practical usefulness, not less than in metric quality.

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Joseph McIntyre, Ikerbasque Research Professor, Tecnalia

Multi-sensory reference frames for human motor control.

When planning and executing motions of the body, be they simply movements to raise the arm or more complex tasks of eye-hand coordination, humans anticipate and exploit the force of gravity in order to achieve more accurate or more efficient movements. Experiments in weightlessness have demonstrated that graviception per se does not provide the only cue that allows the CNS to anticipate the effects of gravity. Indeed, human motion is tuned to a multi-sensory representation of “up” and “down” that combines prior knowledge with sensory signals from visual, kinesthetic and vestibular organs. Here we will present an overview of a range of experiments performed on the ground and in weightlessness that have contributed to our knowledge and understanding of the mechanisms underlying multi-sensory coordination.

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Benoni Edin, Professor, University of Umea

Independent Fingertip Control during Manipulation.

Behavioral and physiological analyses imply that during multi-finger manipulation tasks the applied force vectors are controlled within boundaries determined by the local frictional conditions. Recently this concept has been implemented in robotic devices and shown to provide a reliable framework for stable manipulation of objects in robotic hands as well as during robot-human interaction.

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Allan Smith, Professor, Université de Montréal

Tactile sensitivity in the rat: a correlation between receptor structure and function.

Single cutaneous fibers were recorded in the median nerve of the anesthetized rat and the receptor morphology in the forelimb glabrous skin was analyzed to establish a probable correlation between receptor anatomy and physiology. The data support the statistical probability that Meissner corpuscles are the anatomical substrate of rapidly adapting type 1 receptors and that Merkel complexes are the source of slowly adapting type 1 responses.

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Mike Adams, Professor, University of Birmingham

Grip function of the epidermal ridges of primates.

There has been considerable debate about the functional advantages of the epidermal ridges for improving grip, which depends upon friction. The interlocking of the ridges with surface topographical features has been proposed to increase the friction but, for smooth surfaces, the ridges will decrease the contact area, and hence the friction. Interlocking occurs, for example, when rubbing a hair fibre between a thumb and finger towards the scalp due to the saw-tooth geometry of the cuticles, and also for slip against rough surfaces. Sweating is a critical factor for improving the grip of primates and the precise role of moisture is not understood since the friction of both ridged and flat skin increase with increasing hydration due plasticisation that increases the contact area. Here, we propose that the ridges provide a moisture regulation mechanism, which leads to a path independent optimal hydration condition, and that, under wet conditions, they reduce the probability of gross slip due to fluid lubrication. For a finger pad in contact with a glass plate, we found that when moisture accumulates either by secretion from the sweat pores or from an external source, it is only partially absorbed by the skin while the residue is located in the furrows as free water. The moisture is squeezed out of the ridge contact regions into the furrows, thus preventing a fluid film being formed. Unlike flat skin, the moisture is able to evaporate and thus inhibit excessive hydration that is known to cause a reduction in the friction. Thus, we have established why the role of moisture is important in understanding the evolutionary advantages of epidermal ridges in the grip function of primates.

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Vincent Hayward, Professor, Sorbonne Université

Tactile Mechanics.

The astonishing variety of phenomena resulting from the contact between fingers and objects is a formidable trove of information that can be extracted by organisms to learn about the nature and the properties of objects. This richness is likely to have fashioned our somatosensory system at all levels of its organisation, from early mechanics to cognition. I will illustrate this idea through examples and show how the physics of mechanical interactions shape the messages that are sent to the brain; and how the early stages of the somatosensory system en route to the primary areas are organised to process these messages.

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Organizing comittee

• Yannick Bleyenheuft
• Frédéric Crevecoeur
• Benoît Delhaye
• Philippe Lefèvre
• André Mouraux
• Massimo Penta

Logistic support:

• Cathy Friand