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Hybrid model of the context dependent vestibulo-ocular reflex: implications for vergence-version interactions.

Ranjbaran M, Galiana HL - Front Comput Neurosci (2015)

Bottom Line: By simply assigning proper nonlinear neural computations at the premotor level, the model replicates all reported experimental observations.This work sheds light on potential underlying neural mechanisms driving the context dependent AVOR and explains contradictory results in the literature.Moreover, context-dependent behaviors in more complex motor systems could also rely on local nonlinear neural computations.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, McGill University Montreal, QC, Canada.

ABSTRACT
The vestibulo-ocular reflex (VOR) is an involuntary eye movement evoked by head movements. It is also influenced by viewing distance. This paper presents a hybrid nonlinear bilateral model for the horizontal angular vestibulo-ocular reflex (AVOR) in the dark. The model is based on known interconnections between saccadic burst circuits in the brainstem and ocular premotor areas in the vestibular nuclei during fast and slow phase intervals of nystagmus. We implemented a viable switching strategy for the timing of nystagmus events to allow emulation of real nystagmus data. The performance of the hybrid model is evaluated with simulations, and results are consistent with experimental observations. The hybrid model replicates realistic AVOR nystagmus patterns during sinusoidal or step head rotations in the dark and during interactions with vergence, e.g., fixation distance. By simply assigning proper nonlinear neural computations at the premotor level, the model replicates all reported experimental observations. This work sheds light on potential underlying neural mechanisms driving the context dependent AVOR and explains contradictory results in the literature. Moreover, context-dependent behaviors in more complex motor systems could also rely on local nonlinear neural computations.

No MeSH data available.


Related in: MedlinePlus

VOR in response to sinusoidal head rotation recorded with EOG. (A) Conjugate eye position and scaled head position (degree). (B) Conjugate eye velocity and scaled head velocity (degree/s). Sample slow and fast phase segments are marked with gray and dashed-gray rectangles, respectively.
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Figure 1: VOR in response to sinusoidal head rotation recorded with EOG. (A) Conjugate eye position and scaled head position (degree). (B) Conjugate eye velocity and scaled head velocity (degree/s). Sample slow and fast phase segments are marked with gray and dashed-gray rectangles, respectively.

Mentions: VOR nystagmus consists of compensatory (slow phase) and reorienting (fast phase) segments. The slow phases of the VOR stabilize gaze in space by moving the eyes in the opposite direction to the head movement, while the fast phases redirect the gaze at high speeds in the direction of the head velocity. We focus on the angular VOR (AVOR), tested with passive whole-body rotation in the dark while recording conjugate (eye movements in the same direction) or monocular horizontal eye movements. Figure 1 shows an example of the VOR during sinusoidal head rotations using electrooculography (EOG) in the dark: some slow and fast phase segments are marked. The sawtooth-like pattern of the eye movement is a characteristic of most types of eye movements and is known as ocular nystagmus. In clinical tests, the VOR is characterized by its gain defined as the ratio of peak eye velocity to peak head velocity during harmonic testing or short pulse perturbations.


Hybrid model of the context dependent vestibulo-ocular reflex: implications for vergence-version interactions.

Ranjbaran M, Galiana HL - Front Comput Neurosci (2015)

VOR in response to sinusoidal head rotation recorded with EOG. (A) Conjugate eye position and scaled head position (degree). (B) Conjugate eye velocity and scaled head velocity (degree/s). Sample slow and fast phase segments are marked with gray and dashed-gray rectangles, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321407&req=5

Figure 1: VOR in response to sinusoidal head rotation recorded with EOG. (A) Conjugate eye position and scaled head position (degree). (B) Conjugate eye velocity and scaled head velocity (degree/s). Sample slow and fast phase segments are marked with gray and dashed-gray rectangles, respectively.
Mentions: VOR nystagmus consists of compensatory (slow phase) and reorienting (fast phase) segments. The slow phases of the VOR stabilize gaze in space by moving the eyes in the opposite direction to the head movement, while the fast phases redirect the gaze at high speeds in the direction of the head velocity. We focus on the angular VOR (AVOR), tested with passive whole-body rotation in the dark while recording conjugate (eye movements in the same direction) or monocular horizontal eye movements. Figure 1 shows an example of the VOR during sinusoidal head rotations using electrooculography (EOG) in the dark: some slow and fast phase segments are marked. The sawtooth-like pattern of the eye movement is a characteristic of most types of eye movements and is known as ocular nystagmus. In clinical tests, the VOR is characterized by its gain defined as the ratio of peak eye velocity to peak head velocity during harmonic testing or short pulse perturbations.

Bottom Line: By simply assigning proper nonlinear neural computations at the premotor level, the model replicates all reported experimental observations.This work sheds light on potential underlying neural mechanisms driving the context dependent AVOR and explains contradictory results in the literature.Moreover, context-dependent behaviors in more complex motor systems could also rely on local nonlinear neural computations.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, McGill University Montreal, QC, Canada.

ABSTRACT
The vestibulo-ocular reflex (VOR) is an involuntary eye movement evoked by head movements. It is also influenced by viewing distance. This paper presents a hybrid nonlinear bilateral model for the horizontal angular vestibulo-ocular reflex (AVOR) in the dark. The model is based on known interconnections between saccadic burst circuits in the brainstem and ocular premotor areas in the vestibular nuclei during fast and slow phase intervals of nystagmus. We implemented a viable switching strategy for the timing of nystagmus events to allow emulation of real nystagmus data. The performance of the hybrid model is evaluated with simulations, and results are consistent with experimental observations. The hybrid model replicates realistic AVOR nystagmus patterns during sinusoidal or step head rotations in the dark and during interactions with vergence, e.g., fixation distance. By simply assigning proper nonlinear neural computations at the premotor level, the model replicates all reported experimental observations. This work sheds light on potential underlying neural mechanisms driving the context dependent AVOR and explains contradictory results in the literature. Moreover, context-dependent behaviors in more complex motor systems could also rely on local nonlinear neural computations.

No MeSH data available.


Related in: MedlinePlus