.. include:: ../links.inc Eye-tracker =========== The MEG is equipped with an `EyeLink 1000 Plus`_ eye-tracker from `SR Research`_. The eye-tracker can be used in all positions: - upright, 60° or 68°, camera below the projection screen - supine, 0°, camera above the projection screen Setup ----- .. tab-set:: .. tab-item:: Upright position .. image:: ../_static/eye-tracker/upright.png :align: center :class: img-with-border :width: 600 .. tab-item:: Supine position .. image:: ../_static/eye-tracker/supine.png :align: center :class: img-with-border :width: 600 Standalone vs integrated mode ----------------------------- The eye-tracker can be controlled from the :ref:`stimulation PC `. This is the recommended approach, as it allows to customize the eye-tracker settings, calibration and visual for every experiment. However, it is also possible to use the eye-tracker in standalone mode, either without the :ref:`stimulation PC ` or through a simple calibration and recording application on the :ref:`stimulation PC `. .. tab-set:: .. tab-item:: Integrated mode Every paradigm should be designed to communicate with the eye-tracker directly. Bindings and examples for different software and programming languages are available on the `SR Research`_ website. Mainly, this method increases control on the visual window displayed for calibration and recording and allows a tight integration of the calibration in the paradigm. With this method, a monitoring window can be opened during the experiment displaying a live view of the gaze position super-imposed on the paradigm. .. tab-item:: Standalone mode In standalone mode, the eye-tracker can be controlled from the EyeLink PC or through a simple calibration and recording application on the :ref:`stimulation PC `, such as `eyelink-track`_. Triggers -------- Triggers delivered to the MEG (see the section about :ref:`triggers from the stimulation PC `) are automatically duplicated and delivered to the eye tracker on the ``DIN`` channel. Alternatively, triggers can be delivered as a "message" via the ethernet link between the :ref:`stimulation PC ` and the EyeLink PC. .. image:: ../_static/eye-tracker/triggers-light.png :align: center :class: only-light :width: 600 .. image:: ../_static/eye-tracker/triggers-dark.png :align: center :class: only-dark :width: 600 .. note:: Both hardware trigger through the DB25 (parallel port) of the :ref:`stimulation PC ` and through the `Chronos`_ are duplicated and sent to the eye-tracker. Analogical outputs ------------------ The eye tracker is capable of sending some analogical output directly into the ``misc`` channels of the MEG, thus recording core information as part of the FIF file. In total, 6 channels are available. .. tab-set:: .. tab-item:: Gaze (default) In this mode, the channels correspond to the actual gaze position on the display screen. This mode requires a calibration. - ``0``: :math:`X_{pos}` (eye A) - ``1``: :math:`Y_{pos}` (eye A) - ``2``: Pupil size (eye A) - ``3``: :math:`X_{pos}` (eye B) - ``4``: :math:`Y_{pos}` (eye B) - ``5``: Pupil size (eye B) By default, the 3 first channels are connected to the 3 first MEG miscellaneous channels: ``MISC001``, ``MISC002``, and ``MISC003``. The information is encoded linearly on the voltage range ``(-5, 5) Volts``. For the :math:`X` and :math:`Y` position: - ``(-5, -5)`` corresponds to the top-left corner. - ``(0, 0)`` corresponds to the center of the screen. - ``(5, 5)`` corresponds to the bottom-right corner. .. image:: ../_static/eye-tracker/analogic-coordinates-light.png :align: center :class: only-light :width: 600 .. image:: ../_static/eye-tracker/analogic-coordinates-dark.png :align: center :class: only-dark :width: 600 .. warning:: When tracking of the eye is lost, e.g. during a blink, the analogical output drops to the minimum ``-5V`` value. .. tab-item:: Raw This measurement is the raw pupil-center position (or pupil minus corneal if run in pupil-CR mode) and does not require a calibration. .. tab-item:: HREF This measurement is related to the tangent of the rotation angle of the eye relative to the head. For the ``-5V`` to ``5V`` range, it's :math:`5V * tan(angle)`, measured separately for vertical and horizontal rotations. This mode requires a calibration.