Movement patterns are shown for 2 sensors mounted on the tongue: One on
the tongue-tip and one on the tongue dorsum. The tongue-tip sensor is
oriented with its main axis at right-angles to the mid-line of the tongue,
the tongue-dorsum sensor is oriented along the midline.
(In this experiment we also monitored 2 sensors attached to the head, but
these are not shown here.)
Four movement examples are available here as QuickTime movies. All movies
show the movement in both sagittal and transversal (e.g as if viewing from
above) views. The sagittal view is always on the left, the transversal
view on the right.
For the sagittal view the x-axis is labelled "a-p" (=
"anterior-posterior") and the y-axis is labelled "lon" (= "longitudinal").
For the transversal view the x-axis is the same as in the sagittal view
while the y-axis is labelled "lat" (= "lateral").
On the a-p axis more anterior locations are (unfortunately) to the RIGHT,
i.e the opposite way round to the way we have normally displayed 2D EMMA
data. Thus in all plots the tongue-tip coil is on the right and the
tongue-dorsum on the left.
In all plots the trajectories are colour-coded by time.
The white lines at the sensor locations show the orientation of the
sensors. The basic length of these lines was abitrarily chosen to give a
clear display. Considered in 3 dimensions the length of these lines is
constant. However, in the 2D sagittal and transversal views the length
changes whenever there is a change in the orientation of the sensor with
respect to these planes.
In order for the movie to run in real time the movements have been downsampled from the orignal rate of 200 Hz to 25Hz.
The transversal view clearly shows the expected strong lateral motion of the sensors as the head rotates. The observed change in the orientation of the sensors is also clearly consistent with a rotational movement of the head, i.e the orientation of the tongue-tip sensor as seen in the transversal view stays more or less tangential to the curved movement trajectory.
This example (as well as most of the other examples shown here) helps to emphasize that this is really a 5D system. In other words, even with a single sensor it would have been possible in this example to distinguish between translational and rotational components in a curved trajectory. In a system that only monitors spatial but not rotational coordinates one sensor would not have been sufficient for this.
As would be expected, most of the movement is now in the sagittal plane. The observed change in the orientation of the tongue-dorsum sensor in the sagittal view is consistent with the rotational movement of the head that emerges from the change in relative position of the two sensors.
Two versions of the movie are available.
In the first version the movement has been downsampled to run in real time
(with sound).
The second version shows a slow-motion display which retains the full
temporal resolution (200Hz) of the original recording).
This example (refer to the sagittal view) confirms that the system is capable of recovering subtle but consistent movement patterns well-known from the old 2D system, namely the phenomenon that the tongue-dorsum sensor moves forward during the closure phase of the velar stop /k/ (even though it then has to backtrack to move to the following vowel /u/).
Quicktime (0.15MB) Real Time
Quicktime (1.2MB) Slow Motion
As for /aku/ both real-time and slow-motion versions are available.
This example shows an example of a movement pattern that could well have resulted in unreliable data in the old 2D system: As the tongue tip raises to form the closure for /l/ it also shows considerable lateral movement (i.e it moves about 5 mm away from the midline) and also shows considerable change in its orientation (both these effects are clearly visible in the transversal view).
Quicktime (0.2MB) Real Time
Quicktime (1.4MB) Slow Motion