Eye Movements and Visuo-spatial Perception
Condition: Cerebellum Disease
MeSH terms: Cerebellar Diseases
Study type: Interventional

Summary: 
      This research aims to highlight the key roles of the cerebellar and cortical fronto-parietal
      networks in the coupling of eye movements with visual perception and visuo-spatial attention.
    

Detailed description: 
      The first axe of this research focuses on the role of the cerebellum which has a major
      contribution to sensorimotor adaptation and more precisely in saccadic adaptation but the
      nature of this contribution is still debated. A classical assumption stipulates cerebellum
      has an exclusive action on saccadic burst generator in the brainstem whereas recent data
      increasingly support the view that cerebellum could also modulates cerebral cortex through a
      cerebello-thalamo-cortical pathway. On the other hand, several studies have shown that
      modification of saccade amplitude by saccadic adaptation leads to a distortion of the visual
      localization of briefly flashed spatial probes but no study to date has tested, the
      contribution of the cerebellum in these adaptation-induced mislocalizations. The main
      objective of this axe is to define the role of the cerebellum not only in saccadic
      adaptation, but also in mislocalizations which occur after adaptation. Moreover, in testing
      this assumption, arguments in favour -or in disfavor- of the action of the cerebellum on
      cortical stages dedicated to visuo-spatial perceptual processing will be provided. Besides,
      variability of cerebellar lesion (or cerebellar dysfunction) location in patients can lead to
      different pattern in saccadic adaptation and localization task performances. Identification
      of dissociations between these two abilities in some patients will define more precisely the
      role of the cerebellum in the coupling between saccadic adaptation and visuo spatial
      perception as an oculomotor plasticity territory and / or as a territory underlying the error
      signal coding generating this type of plasticity.

      This second axe of this research aims to apply basic findings in healthy subject on the
      coupling between oculomotor plasticity and spatial attention to patients with parietal
      lesion, in order to evaluate a rehabilitation procedure for neglect patients. Habchi and
      colleagues showed that the adaptation of reactive saccades in the left hemifield has a
      boosting effect on attentional performance in the same hemifield. The coupling between these
      two mechanisms highlighted in healthy subjects can be used as fundamentals in the elaboration
      of a rehabilitation procedure for attentional disorders in the neglect syndrome. This
      syndrome is mainly observed after cerebral lesions in the right hemisphere, and is
      characterized by very disabling cognitive disorders such as an alteration of the spatial
      representation of left hemi-space and/or left hemi-body. stimulation of sensorimotor
      plasticity thanks to prismatic adaptation could be used as a rehabilitation procedure for
      this syndrome. Being another efficient way to stimulate sensorimotor plasticity, the equip
      believe that saccadic adaptation can also be used as a rehabilitation procedure for neglect
      patients. Moreover, due to its tight coupling with visual attention, the benefits of saccadic
      adaptation could be even stronger and longer lasting than the visuo-manual plasticity induced
      by prismatic adaptation.
    

Intervention name(s): Forward adaptation of reactive saccades; Backward adaptation of reactive saccades; Execution of reactive saccades; Generation of reactive saccades
Intervention type(s): Behavioral; Behavioral; Behavioral; Behavioral
Intervention description(s): Protocol of reactive saccade where the target is displaced in the same direction as the saccade in order to induce an adaptive increase of saccade amplitude ('forward adaptation'); Protocol of reactive saccade where the target is displaced in a direction opposite to the saccade in order to induce an adaptive decrease of saccade amplitude ('backward adaptation'); Control protocol of reactive saccade with no displacement of the saccadic target (controlling for non specific factors possibly involved in forward and backward adaptation conditions); Control protocol of reactive saccade with no displacement of the saccadic target (controlling for non specific factors possibly involved in adaptation condition)
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: cerebellar lesion; saccadic adaptation; spatial localization; visuo spatial perception; eye movements