Three-dimensional visualization of electropalatography

Abstract

Electropalatography (EPG) is a widely used noninvasive technique for monitoring dynamic tongue-palate contact patterns in speech research and speech clinics. However, the conventional two-dimensional (2D) visualization system is incapable of informing individual characteristics of three-dimensional (3-D) palatal shape or the relationship between electrode positions and anatomical landmarks (e.g., teeth). This paper reports a method for visualizing tongue-palate contact patterns on the 3-D palatal shape display. A convex palatal shape model was formed by silicone impression material from an individual dental cast, and electrode positions on the individual-specific artificial palate (RION SP-01, 63 electrodes) were marked on the surface of the convex model. The 3-D geometry and the surface texture information of the convex model were extracted by a laser beam scanner (Cyberware 4020). Then, palatographic data were collected through the EPG system (RION DP-20) and the tongue-palate contact patterns were mapped on the 3-D graphical display of the palate. Preliminary observation of Japanese fricatives revealed vertical differences in constriction between [s] and [■]. Its application to speech production research and speech training will be discussed.