Working on the presentation of the project

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Hi,
I'm Miguel Descalzo Pérez and I am going to present the project done as my final's degree work.
A machine used to emit visual stimuli to patients with migraine. It is used in the context of a
psychophysics research.
My tutor for this project has been José Maria Gómez Cama and my advisor in the Vall d’Hebron Institut de Recerca
has been Nara Ikumi.
(PASAR DIAPOSITIVA)
This project is born from the need of the group of Headache and Neurological Pain from the Vall d’Hebron
Institut de Recerca to build a machine to perform an experiment about photophobia in patients with migraine.
Similar experiments have been done in the past by other groups.
The system, will be used with humans, and it has been built with safety concerns because it can emit a high
intensity of light, which could lead to retinal injuries.
In the research, participants are classified in two groups. People who suffer from migraine (the patients), and
people who never suffer from migraine (the controls). They are presented to a series of visual stimuli.
For each stimulus presented they have to respond if they perceived the stimulus as uncomfortable or not.
Using this information a threshold value is calculated, indicating when the stimuli starts being perceived as
unconfortable.
(PASAR DIAPOSITIVA)
Well, about the objectives of the project few things can be said.
The restrictions on the system have been basically two:
- It should be at least as good as the systems used in the previous studies.
- and It must not be able to induce any type of injury to the participants.
This means, the system needs a light source able to emit enough intensity, it should create accurate stimuli, and it
might need to incorporate precautions to prevent the creation of hazardous stimuli, among other things.
(PASAR DIAPOSITIVA)
In regards of the chosen solution for the system, I'd like to highlight the following aspects.
When presenting the stimuli to the participants, it is important to do it in a known and controlled manner.
This system is using the Single Interval Adjustment Matrix method (or SIAM method) to choose which stimulus will be
presented next. The SIAM method is a psycophysichs adaptative method of presenting stimuli for estimating absolute
thresholds, which means the next presented stimulus will depend on the previous answers given by the participant.
There are other methods of presenting stimuli which could be implemented.
As a light soruce the system uses a video projector. The used device is clasified in the Risk Group 2, which
according to the european standard of photobiological safety of lamps and lamp systems it does not pose any hazard
to human vision when exposed to its light beam for 0.25s or less.
To accurately measure the time the stimuli are on screen, the system uses a light sensor and a microcontroller
which comunicates to the main program if the last stimulus was presented for longer than 0.25s or not. If a
hazardous stimulus is detected, the test finishes itself up in order to prevent any retinal injuries.
In order to calibrate the stimuli generated, the system uses a spectrometer to read the light intensity which will
be received by the participants. Using the spectrometer, a transfer function from the stimuli generator function the
the illuminance received is found automatically using a calibration script. With such transfer function the system
then generates the needed stimuli for the test.
(PASAR DIAPOSITIVA)
Finally, in order to controll each of the mentioned parts of the machine, the system uses a MATLAB script.
In the figure we can see the conceptual connections between the computer runing the MATLAB script and the rest of
the system parts. The spectrometer, the light sensor and the projector.
(PASAR DIAPOSITIVA)
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