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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

Simulated conjugate eye position (top) and conjugate velocity (bottom) in response to sinusoidal head velocity rotation (amplitude = 180 degree/s). (A,B) input frequency is 1/6 Hz. (C,D) input frequency is 1/2 Hz. solid-black → top: conjugate position(degree)- bottom: conjugate eye velocity (degree/s), dashed-gray → top: head velocity/5 (degree/s)- bottom: head velocity (degree/s).
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Figure 3: Simulated conjugate eye position (top) and conjugate velocity (bottom) in response to sinusoidal head velocity rotation (amplitude = 180 degree/s). (A,B) input frequency is 1/6 Hz. (C,D) input frequency is 1/2 Hz. solid-black → top: conjugate position(degree)- bottom: conjugate eye velocity (degree/s), dashed-gray → top: head velocity/5 (degree/s)- bottom: head velocity (degree/s).

Mentions: Figure 3 depicts the response of the hybrid model with Tconj = 5 s at two different rotation frequencies: 1/6 Hz (A,B) and 1/2 Hz (C,D) with velocity peaks of 180 degree/s. As in experimental observations, the number of fast phases per cycle decreases for higher frequency sinusoidal head rotations. In other words, fast phases are triggered more often during low frequency head rotations. This is due to the band pass characteristics of the central neurons in the VOR pathway. At lower frequencies the gain of central neurons is higher which increases the possibility of exceeding their firing thresholds and triggering a fast phase. Furthermore, at a given rotation frequency, fast phases are more frequent at the higher head velocity levels; consistent with experimental observations (Buettner et al., 1978).


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

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

Simulated conjugate eye position (top) and conjugate velocity (bottom) in response to sinusoidal head velocity rotation (amplitude = 180 degree/s). (A,B) input frequency is 1/6 Hz. (C,D) input frequency is 1/2 Hz. solid-black → top: conjugate position(degree)- bottom: conjugate eye velocity (degree/s), dashed-gray → top: head velocity/5 (degree/s)- bottom: head velocity (degree/s).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Simulated conjugate eye position (top) and conjugate velocity (bottom) in response to sinusoidal head velocity rotation (amplitude = 180 degree/s). (A,B) input frequency is 1/6 Hz. (C,D) input frequency is 1/2 Hz. solid-black → top: conjugate position(degree)- bottom: conjugate eye velocity (degree/s), dashed-gray → top: head velocity/5 (degree/s)- bottom: head velocity (degree/s).
Mentions: Figure 3 depicts the response of the hybrid model with Tconj = 5 s at two different rotation frequencies: 1/6 Hz (A,B) and 1/2 Hz (C,D) with velocity peaks of 180 degree/s. As in experimental observations, the number of fast phases per cycle decreases for higher frequency sinusoidal head rotations. In other words, fast phases are triggered more often during low frequency head rotations. This is due to the band pass characteristics of the central neurons in the VOR pathway. At lower frequencies the gain of central neurons is higher which increases the possibility of exceeding their firing thresholds and triggering a fast phase. Furthermore, at a given rotation frequency, fast phases are more frequent at the higher head velocity levels; consistent with experimental observations (Buettner et al., 1978).

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