Transcript Visual-Vestibular Interaction Hypothesis for the Control

Visual-Vestibular Interaction
Hypothesis for the Control of
Orienting Gaze Shifts by Brain
Stem Omnipause Neurons
Mario Prsa and Henrietta L. Galiana
Department of Biomedical Engineering, McGill
University, Montreal, Quebec, Canada
Presented by: Fereshteh Lagzi
Presentation Agenda
• Introduction
• Model Description
• Simulation Results
• Conclusion
Introduction
Gaze =(eye position-in-head + head position-in-space)
orienting movements of the visual axis are
referred to as gaze shifts and are composed of
an initial fast
phase followed by a slow phase.
Introduction
target
attainment
target
fixation
Omnipause Neurons
These two fundamental requirements of gaze
shifts, target attainment and target fixation, are
coordinated by omni-directional pause neurons
(OPNs) located in the nucleus raphe interpositus
of the caudal pontine reticular formation in the
brain stem.
OPNs discharge at a regular rate during
visual fixation and pause for the duration of
the saccadic gaze component.
Gaze Saccade Generation
Robinson’s Model
•The classic local feedback model of eye saccade
generation (Robinson 1975) compares the actual eye
position Theta to the desired target position ThetaT to
produce a motor error signal that drives the burst
cells.
•Improvements of Robinson’s model rely on a dynamic
motor error signal produced by a “comparator” that
drives the burst neurons during the saccadic fast
phase. Most models either attribute its role to the
superior colliculus (SC) or place it downstream of the
SC.
Proposed Switching Strategy
Model Description
Head Velocity & Gaze Position
Error
Gaze Shift Simulation
Head-Fixed Eye Saccades
Simulation
OPN Stimulation
Head Brake Simulation
Conclusion
•The proposed visual-vestibular interaction controlling the
activity of OPNs was shown to accurately reproduce
alternations between fast and slow phases of combined
eye-head gaze movements, which are not controlled
uniquely by a gaze motor error signal.
•Inputs to the OPNs are based on a weighted
premotor fusion of different signals.
•The presentedhypothesis for the neural control of
OPNs can thus provide insight for further
investigations of how the firing activity of these
neurons is modulated during all types of eye-head
movements.
References
• [1] Prsa M, Galiana H.L. VisualVestibular Interaction Hypothesis for the
Control of Orienting Gaze Shifts by Brain
Stem Omnipause Neurons. J Neurophysiol
97: 1149-1162, 2007
،‫ سمينار درس مدلسازي سيستمهاي بيولوژيکي‬.‫ ساره‬،‫[ سعيدي‬2] •
‫ تابستان‬،‫ دانشگاه صنعتي اميرکبير‬،‫دانشکده مهندس ي پزشکي‬
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