Neuropsychological Laboratory

Paris, France

Neuropsychological Laboratory

Paris, France
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Valero-Cabre A.,French Institute of Health and Medical Research | Valero-Cabre A.,Pierre Mendès-France University | Valero-Cabre A.,Boston University | Valero-Cabre A.,Harvard University | And 2 more authors.
Revue Neurologique | Year: 2011

Introduction: Non-invasive brain stimulation methods such as transcranial magnetic stimulation (TMS) are starting to be widely used to make causality-based inferences about brain-behavior interactions. Moreover, TMS-based clinical applications are under development to treat specific neurological or psychiatric conditions, such as depression, dystonia, pain, tinnitus and the sequels of stroke, among others. Background: TMS works by inducing non-invasively electric currents in localized cortical regions thus modulating their activity levels according to settings, such as frequency, number of pulses, train and regime duration and intertrain intervals. For instance, it is known for the motor cortex that low frequency or continuous patterns of TMS pulses tend to depress local activity whereas high frequency and discontinuous TMS patterns tend to enhance it. Additionally, local cortical effects of TMS can result in dramatic patterns in distant brain regions. These distant effects are mediated via anatomical connectivity in a magnitude that depends on the efficiency and sign of such connections. Perspectives: An efficient use of TMS in both fields requires however, a deep understanding of its operational principles, its risks, its potential and limitations. In this article, we will briefly present the principles through which non-invasive brain stimulation methods, and in particular TMS, operate. Conclusion: Readers will be provided with fundamental information needed to critically discuss TMS studies and design hypothesis-driven TMS applications for cognitive and clinical neuroscience research. © 2011 Elsevier Masson SAS. All rights reserved.


Perez C.,French National Center for Scientific Research | Perez C.,Rothschild | Peyrin C.,French National Center for Scientific Research | Cavezian C.,Rothschild | And 14 more authors.
Brain Topography | Year: 2013

The current study aims to investigate visual scene perception and its neuro-anatomical correlates for stimuli presented in the central visual field of patients with homonymous hemianopia, and thereby to assess the effect of a right or a left occipital lesion on brain reorganization. Fourteen healthy participants, three left brain damaged (LBD) patients with right homonymous hemianopia and five right brain damaged (RBD) patients with left homonymous hemianopia performed a visual detection task (i.e. "Is there an image on the screen?") and a categorization task (i.e. "Is it an image of a highway or a city?") during a block-designed functional magnetic resonance imaging recording session. Cerebral activity analyses of the posterior areas - the occipital lobe in particular - highlighted bi-hemispheric activation during the detection task but more lateralized, left occipital lobe activation during the categorization task in healthy participants. Conversely, in patients, the same network of activity was observed in both tasks. However, LBD patients showed a predominant activation in their right hemisphere (occipital lobe and posterior temporal areas) whereas RBD patients showed a more bilateral activation (in the occipital lobes). Overall, our preliminary findings suggest a specific pattern of cerebral activation depending on the task instruction in healthy participants and cerebral reorganization of the posterior areas following brain injury in hemianopic patients which could depend upon the side of the occipital lesion. © 2012 Springer Science+Business Media, LLC.


Coubard O.A.,Neuropsychological Laboratory
Biocybernetics and Biomedical Engineering | Year: 2013

As frequency of falls increases in older adults, understanding how motor training programs counteract motor decline is a challenging issue. This study examined ocular saccades to test the effects of fall prevention (FP) on central motor control of older fallers. Saccades were recorded using a saccadometer in twelve participants aged 64-91 years before and after 2.5-month training in FP. We performed LATER analysis enabling us to examine the changes in motor control. FP decreased saccade latency and increased left-right symmetry of motor responses. LATER analysis showed that FP modulated decisional thresholds extending our knowledge of FP influence on motor control. © 2013 Published by Elsevier Urban & Partner Sp. z o.o.


Duchesne J.,Agrocampus Ouest | Bouvier V.,Agrocampus Ouest | Guilleme J.,University of Angers | Coubard O.A.,Neuropsychological Laboratory
The Scientific World Journal | Year: 2012

When we explore a visual scene, our eyes make saccades to jump rapidly from one area to another and fixate regions of interest to extract useful information. While the role of fixation eye movements in vision has been widely studied, their random nature has been a hitherto neglected issue. Here we conducted two experiments to examine the Maxwellian nature of eye movements during fixation. In Experiment 1, eight participants were asked to perform free viewing of natural scenes displayed on a computer screen while their eye movements were recorded. For each participant, the probability density function (PDF) of eye movement amplitude during fixation obeyed the law established by Maxwell for describing molecule velocity in gas. Only the mean amplitude of eye movements varied with expertise, which was lower in experts than novice participants. In Experiment 2, two participants underwent fixed time, free viewing of natural scenes and of their scrambled version while their eye movements were recorded. Again, the PDF of eye movement amplitude during fixation obeyed Maxwell's law for each participant and for each scene condition (normal or scrambled). The results suggest that eye fixation during natural scene perception describes a random motion regardless of top-down or of bottom-up processes. © 2012 Jean Duchesne et al.


Coubard O.A.,Neuropsychological Laboratory
Statistics in Medicine | Year: 2013

Traditional displays of principal component analyses lack readability to discriminate between putative clusters of variables or cases. Here, the author proposes a method that clusterizes and visualizes variables or cases through principal component analyses thus facilitating their analysis. The method displays pre-determined clusters of variables or cases as urchins that each has a soma (the average point) and spines (the individual variables or cases). Through three examples in the field of neuropsychology, the author illustrates how urchins help examine the modularity of cognitive tasks on the one hand and identify groups of healthy versus brain-damaged participants on the other hand. Some of the data used in this article were obtained from the Alzheimer's Disease Neuroimaging Initiative database. The urchin method was implemented in MATLAB, and the source code is available in the Supporting information. Urchins can be useful in biomedical studies to identify distinct phenomena at first glance, each having several measures (clusters of variables) or distinct groups of participants (clusters of cases). © 2013 John Wiley & Sons, Ltd.


Coubard O.A.,Neuropsychological Laboratory
Frontiers in Aging Neuroscience | Year: 2012

As society ages and frequency of falls increases in older adults, counteracting motor decline is a challenging issue for developed countries. Physical activity based on aerobic and strength training as well as motor activity based on skill learning both help benefit balance and reduce the risk of falls, as assessed by clinical or laboratory measures. However, how such programs influence motor control is a neglected issue. This study examined the effects of fall prevention (FP) training on saccadic control in older adults. Saccades were recorded in 12 participants aged 64-91 years before and after 2.5 months training in FP. Traditional analysis of saccade timing and dynamics was performed together with a quantitative analysis using the LATER model, enabling us to examine the underlying motor control processes. Results indicated that FP reduced the rate of anticipatory and express saccades in inappropriate directions and enhanced that of express saccades in the appropriate direction, resulting in decreased latency and higher left-right symmetry of motor responses. FP reduced within-participant variability of saccade duration, amplitude, and peak velocity. LATER analysis suggested that FP modulates decisional thresholds, extending our knowledge of motor training influence on central motor control. We introduce the Threshold Interval Modulation with Early Release-Rate of rIse Deviation with Early Release (TIMER-RIDER) model to account for the results.


Viret A.-C.,Rothschild | Cavezian C.,University of Paris Descartes | Coubard O.,Rothschild | Vasseur V.,Neuropsychological Laboratory | And 6 more authors.
Behavioural Neurology | Year: 2013

Optic Neuritis (ON) has been associated to both parvocellular dysfunction and to an alteration of the magnocellular pathway. After objective visual field and acuity recovery, ON patients may complain about their vision suggesting a residual subclinical deficit. To better characterize visual abnormalities, 8 patients recovering from a first ON episode as well as 16 healthy controls performed a simple detection task and a more complex categorization task of images presented in low spatial frequencies (to target the magnocellular system) or in high spatial frequencies (to target the parvocellular system) or of non-filtered images. When completing the tasks with their (previously) pathologic eye, optic neuritis patients showed lower accuracy compared to controls or to their healthy eye for low spatial frequency images only. Conjointly, the longest reaction times were observed with the previously pathologic eye regardless the type of images and to a greater extent in the categorization task than in the detection task. Such data suggest two distinct, although associated, types of residual dysfunction in ON: a magnocellular pathway alteration and a more general (magno and parvocellular) visual dysfunction that could implicate the cognitive levels of visual processing. © 2013 - IOS Press and the authors. All rights reserved.


Coubard O.A.,Neuropsychological Laboratory | Coubard O.A.,CNRS Laboratory of Physiology of Perception
Revue Neurologique | Year: 2015

Knowledge of cognitive and neural architecture and processes that control eye movements has advanced enough to allow precise and quantitative analysis of hitherto unsolved phenomena. In this review, we revisit from a neuropsychological viewpoint Hering vs. Helmholtz' hypotheses on binocular coordination. Specifically, we reexamine the behavior and the neural bases of saccade-vergence movement, to move the gaze in both direction and depth under natural conditions. From the psychophysical viewpoint, neo-Heringian and neo-Helmholtzian authors have accumulated arguments favoring distinct conjugate (for saccades) and disconjugate (for vergence) systems, as well as advocating for monocularly programmed eye movements. From the neurophysiological viewpoint, which reports brain cell recordings during the execution of a given task, neo-Heringian and neo-Helmholtzian physiologists have also provided arguments in favor of both hypotheses at the level of the brainstem premotor circuitry. Bridging the two, we propose that Hering and Helmholtz were both right. The emphasis placed by the latter on adaptive processes throughout life cycle is compatible with the importance of neurobiological constraints pointed out by the former. In the meanwhile, the study of saccade-vergence eye movements recalls how much the psychophysical definition of the task determines the interpretation that is made from neurophysiological data. © 2014 Elsevier Masson SAS.

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