Modeling and Simulation

1. Vestibulo-Ocular Reflex
Model
PRESENTED TO ENGR. ABDUL HANAN TAQI
PRESENTED BY M. FAISAL MEHMOOD (2021-BME-102)
HUSNAIN ALI (2021-BME-103)
EZZAT FATIMA (2021-BME-126)

2. Objective
Observed eye movement during head rotation.
Simulated eye movement output generated by the model.
In simpler terms, the objective is to make the model of eye
movement.

3. Introduction
It’s conjugate ocular
movement opposite
to head movement
and it’s stimulated by
vestibular system

4. Cont…
VOR is reflex where Activation of vestibular system causes eye
movements.
This Reflex function stabilize image on retina.
During head movements, producing eyes movements in opposite
direction to head movement thus persevering (original state) on the
central visual field.
Vestibular system has sensory system (semicircular canals) which is
located in inner layer of ear which can detect the rotational movement.
Whenever head move the motion receptors activated and vestibular
stimulate the nerves which control extra ocular muscle.

5. Cont….
Semicircular canals act as balance receptors by containing
fluid that moves due to head rotation.
This movement bends hair cells within the canals, sending
signals to the brain about head movement and maintaining
balance.

6. The vestibulo-ocular
reflex (VOR) uses
information from the
vestibular labyrinth
of the inner ear to
generate eye
movements that
stabilize gaze during
head movements.
Left Right

7. Cont…
Cranial Nerve III, IV and VI involves.
CN III called as Oculomotor nerve.
CN IV called as Trochlear nerve.
CN VI called as Abducens nerve.
When head is turned left, both semicircular canals are rotated in opposite
rotational direction, which triggers the eyes to move in opposite direction.
For left cervical rotation, the right lateral rectus and left medial rectus involve.
For right cervical rotation, the left lateral rectus and right medial rectus involve.

8. Example
If head is moving right 30 degree so eye should move 30
degree left to focus the image and vice versa.

9. Model Description
The vestibulo-ocular reflex (VOR) enables the eyes to move at the
same speed and in the opposite direction as the head, so that vision
is not blurred when the head moves during normal activity.
For example, if the head turns in one direction, the eyes turn in the
opposite direction, with the same speed.
The file sdoVOR_Data.mat contains uniformly sampled data of
stimulation and eye movements. Eye data flipped vertically, would
overlay exactly on top of a plot of head motion data.
Such a system would be described by a gain of 1 and a phase of 180
degrees. However, when we plot the data in the file
sdoVOR_Data.mat, the eye movements are close, but not perfectly
compensatory.

11. Output plot
The eye movement data
does not perfectly overlay
the head motion data, and
this can be modeled by
several factors, like:
i. Neural Processing Delay
ii. Gain
iii. Measurement noise
iv. Non-linearity

12. Parameters
There are four parameters in the model:
i. Delay
ii. Gain
iii. Tc
iv. Tp.
The Delay parameter models the fact that there is some delay in
communicating the signals from the inner ear to the brain and the eyes.
This delay is due to the time needed for chemical neurotransmitters to traverse
the synaptic clefts between nerve cells.

13. Cont….
The Gain parameter models the fact that the eyes do not
move quite as much as the head does.
The Tc parameter models the dynamics associated with
the semicircular canals, as well as some additional neural
processing.
The Tp parameter models the dynamics of the oculomotor
plant, i.e. the eye and the muscles and tissues attached to
it.

15. Simulink Model

16. Compare Measured Data to Initial
Simulated Output

17. Output

18. Sensitivity Analysis

20. Benefits of
VOR Model
Understanding Neurological Function
Diagnosing Disorders
Developing Treatments
Educational Tool
Research Development

21. Conclusion
The vestibulo-ocular reflex has provided information about the the
mechanics and dynamics of how the body maintains visual stability during
head movements.
Through the systematic modeling of the VOR, using parameters such as
Delay, Gain, Tc, and Tp, we have been able to simulate and understand the
underlying physiological processes involved in this reflex.
Sensitivity analysis showed that Gain and Tp have the most significant
influence on the model output, while Delay and Tc have minimal impact.
We can fix Delay and Tc during optimization to improve efficiency.

22. References
https://www.sciencedirect.com/topics/neuroscience/vestibulo-ocular-reflex#:
https://www.mathworks.com/help/sldo/ug/identify-key-parameters-for-estimation-code.html
https://youtu.be/r_6y2D-6oDQ?si=4i002BuF_Mc2sbPT
https://apsc450computationalneuroscience.wordpress.com/oculomotor-system/