The tongue’s vital functionalities are vulnerable to ailments such as stroke, Parkinson’s and Alzheimer’s syndrome, or other neurological events. In cases were the swallowing function is impaired, the condition is referred to as dysphagia. The common devices available to rehabilitation specialist during the dysphagia therapy sessions are hand-held devices that measure the pressure exerted by the tongue. An example of such commonly used devices are the Iowa Oral Pressure Instrument (IOPI) which outputs a single digital number [1] and the Abilex which is completely passive and does not provide a quantitative feedback [2]. If the speech functionality of the tongue is impaired due to an ailment, it could result in various pathologies, such as aphasia, apraxia, and dysarthria. Clinical speech therapy requires monitoring of the tongue’s and the lips’ dynamic motion. To date technologies used for monitoring and quantifying the tongue’s motion include Electromagnetic Articulography (EMA)[3], Palatography [4] and Electropalatography (EPG) [5], [6]. It has been shown that motion visualization and quantification tools reveal pathological markers that are often not fully exposed via the auditory analysis performed by the therapist [7]. These tools also allow for quantification of the rehabilitation progress patterns. However, none of these clinically available tools are wireless, discreet, or portable, and they all require external units. Therefore, in this current work we evaluated the functionalities of two generations of discreet wireless wearable devices developed by our team. The first generation, the O-UIC (Oral-User Interface Controller), was developed with the aim of using it as a typing device and we utilized it for this study. The second generation, the Tongue-Trackpad, was specifically developed for this thesis. The devices developed by our team utilize capacitive sensing technology to detect the contact patterns of the tip of the tongue with the hard palate. This technology is widely used in touchscreens;​ however, in this work we explore the use of this technology in intra-oral wearable devices.

In this work we were interested in identifying the potential presence of a distinct distribution of the tongue’s motion during a free-exploration paradigm. With the big picture being to compare healthy subjects’ motion patterns to potential tongue ailments motion patterns in unhealthy individuals. Previous studies of upper limbs movement have shown that the free-exploration paradigm provides the fullest characterization of the subject’s own motion capabilities [8]. Hence, in order to fully quantify the tongue’s motion capabilities on the hard palate, we instructed a total of eleven healthy subjects to freely move their tongue on the palate, six using the O-UIC device and five using the Tongue-Trackpad.

Our results suggest that the tongue’s frequency of motion is 2 Hz for movements in the mediolateral direction and at 1 Hz for movements in the anteroposterior direction, with the spectrum power going to zero at 6-7 Hz. Our findings suggest that 150-seconds of data are necessary to characterize the tongue’s motion, and we observe distinct patterns of motion amongst subjects under study.