Compatibility between auditory and articulatory representations of vowels.

Auditory-articulatory linkage in our brain plays an essential neurobiological role in human speech communication. Speech-specific sensorimotor organization is basically a genetically transmitted program, whereas its ontogenetic outcome may strongly reflect the unique form of human vocal organs. In this study, electromyographic data from the four extrinsic tongue muscles were processed to derive motor targets of vowels in a two-dimensional space representing muscle force equilibrium. The result shows evidence that the motor pattern of tongue muscles in vowel production is compatible with the acoustic pattern of vowels: the distribution of intended targets of tongue movement resembles the vowel distribution in the auditory (F1 vs. F2) space. This coincidence suggests a co-evolution of the human vocal tract and vowel system that facilitates the development of efficient auditory pathway for processing speech sounds.