Separable processing of consonants and vowels

There are two views about the nature of consonants and vowels. One view hol ds that they are categorically distinct objects that play a fundamental rol e in the construction of syllables in speech production(1-3). The other vie w is that they are convenient labels for distinguishing between peak (vowel ) and non-peak (consonant) parts of a continuous stream of sound that varie s in sonority (roughly the degree of openness of the vocal apparatus during speech)(4-6), or that they are summary labels for bundles of feature segme nts(7,8). Taking the latter view, consonants and vowels do not have an inde pendent status in language processing. Here we provide evidence for the pos sible categorical distinction between consonants and vowels in the brain. W e report the performance of two Italian-speaking aphasics who show contrast ing, selective difficulties in producing vowels and consonants. Their perfo rmance in producing individual consonants is independent of the sonority va lue and feature properties of the consonants. This pattern of results sugge sts that consonants and vowels are processed by distinct neural mechanisms, thereby providing evidence for their independent status in language produc tion.