Our aim is to study the mechanisms underlying the neural control of movement, interacting with vision. The oculomotor system is characterized by the interaction between peripheral reflexes and central motor commands of visual origin. The dynamical properties of the oculomotor plant are very simple, thus it is a good testing bench for studying interfaces between sensory and motor systems in the brain. Moreover, in gaze orientation, combined eye and head motions are good examples of the control of imbedded platforms. In addition, the neural control of gaze in natural conditions requires the interaction between different strategies of oculomotor control. In particular, some eye movements are controlled by visual feedback (smooth pursuit : slow movements) whereas others are controlled in open loop with respect to vision (saccades : fast movements).

People Academic staff Philippe Lefèvre Marcus Missal PhD. students Renaud Ronsse : juggling in robots and humans Olivier White : prehesion under different gravity fields Jean-Jacques Orban de Xivry : prediction, saccades and pursuit Céline Schreiber : 2D catchup saccades Pierre Daye - cerebellum and motor control Demet Yuksel : Duane syndrome Frédéric Crèvecoeur : eye-hand coordination in different gravity field Thibaut André : motor control in microgravity Coralie de Hemptinne : neurons showing anticipation in SEF Former coworkers Gunnar BLOHM Sophie de BROUWER

Research

• Modeling the neural control of movement. We are deeply involved in developing mathematical models of the oculomotor system : the vestibulo-ocular reflex, saccades and smooth pursuit. Different types of models are developed : distributed parameters models (detailed models of particular brain structures like the superior colliculus or the cerebellum) or lumped models based on transfer functions (models describing the global input/output behaviour).
• Interaction between saccades and smooth pursuit. We created an experimental condition that forces the oculomotor system to combine saccades and smooth eye movements in tracking moving visual stimuli. This was done by combining target steps in position and in velocity during steady-state pursuit. This allowed us to obtain a wide range of position error, retinal slip and target velocity. We investigate how catch-up saccades are programmed in this condition and how the smooth pursuit system interacts with their execution. 
• Electrophysiological studies. In collaboration with Dr Olivier ( NEFY ), we investigate the oculomotor system of cats using electrophysiological techniques : the role of the superior colliculus and brainstem in the control of saccades and smooth pursuit. 
• Prediction and anticipation in smooth pursuit
• The role of extraretinal signals in the neural control of movement.
  
• Eye - hand coordination.
  
• Clinical applications : our interest in recording patients with oculomotor disturbance is to describe the anomalies of saccades and pursuit in order to understand how pathology of visual & oculomotor system can influence the motor control of eye movements.

Experimental Set-up

To record 3D eye and head movements, we use the scleral search coil technique. Up to 2 Laser spots can be controlled via galvanometers and serve as visual targets projected onto a translucent screen. Inputs and outputs are controlled by a real-time system, allowing closed loop at 0.5 kHz! The user interface is a standard PC on which LabView is running.

For more details, please refer to the experimental set-up and the EyeLab program.

Data Analysis

Generally, we use MatLab and/or Statistica for data analysis. We designed a home made data visualization program (OKULO) able to display behavioral data from different sources: EyeLab , Cambridge Visual Stimulator , Chronos Eye Tracker , etc...

A TIKI knowledge database allows us to exchange standard procedures for data analysis... See "the world of OKULO"

Seminars and Workshops

Articles discussed in the Journal Club with short appreciation (password required!)

Seminars, workshops and conferences

Click here to get an introduction into the neurophysiology of vision.

Selected publications

Coimbra A, Lefèvre P, Missal M, Olivier E (2000). Difference between visually and electrically evoked gaze saccades disclosed by altering the head moment of inertia. Journal of Neurophysiology, 83 , 1103-1107. [ order reprint ]

Missal M, de Brouwer S, Lefèvre P, Olivier E (2000). Activity of mesencephalic vertical burst neurones during saccades and smooth pursuit. Journal of Neurophysiology, 83, 2080-2092. [ order reprint ]

de Brouwer, S, Missal, M, Lefèvre, P (2001). Role of retinal slip in the prediction of target motion during smooth and saccadic pursuit. Journal of Neurophysiology, 86, 550-558. [ order reprint ]

de Brouwer S, Yuksel D, Blohm G, Missal M, Lefèvre P (2002). What triggers catch-up saccades during visual tracking? Journal of Neurophysiology , 87, 1646-50. [ order reprint ]

Missal M., Coimbra A., Lefèvre P., Olivier E. A quantitative analysis of correlations between eye movements and neural activity in the pretectum. Experimental Brain Research (in press). [ order reprint ]

de Brouwer S, Missal M, Barnes G, Lefèvre P (2002). Quantitative analysis of catch-up saccades during sustained pursuit. Journal of Neurophysiology , 87, 1772-80. [ order reprint ]

Blohm G, Missal M, Lefèvre P (2003). Interaction between smooth anticipation and saccades during ocular orientation in darkness. Journal of Neurophysiology 89, pp. 1423-1433  [ order reprint ]

Orban de Xivry JJ, Bennett S.J., Lefevre, P and Barnes GR (2006). Evidence for synergy between saccades and smooth pursuit during transient target disappearance, J Neurophysiol 95: 418-427.  [ order reprint ]

Schreiber C, Missal M, Lefèvre P (2006), Asynchrony Between Position and Motion Signals in the Saccadic System, Journal of Neurophysiology, 95, p.960. [ order reprint ]

Click here for a more complete publication list...