PhD, Brown University
Speech Science and Neurolinguistics
I am a professor in the University of Texas at Dallas' School of Behavioral and Brain Sciences. After receiving my Ph.D. in linguistics from Brown University (1987), I spent four years as a post-doctorate fellow at the University of California San Diego. I have also served as a visiting scientist at the Universities of Goettingen and Konstanz, Germany.
My research interests focus on how humans represent and use speech and language. I approach this topic within the theoretical framework of neurolinguistics: a discipline concerned with how the brain represents language, how this process develops throughout life, and how it is affected by disease. Within the discipline of neurolinguistics, I have concentrated on phonology (sound systems and rules) and phonetics (the nature of speech sounds). An important method for understanding the phonology/phonetics of language is to study the speech of subjects whose linguistic systems are impaired as the result of brain injury. These subjects may serve as experiments in nature in that their impaired linguistic systems often fractionate in highly specific ways, revealing underlying patterns of language structure and processing.
In particular, I have investigated the speech production capability of individuals with aphasia and apraxia of speech (AOS). Aphasia refers to disorders of language resulting from brain injury occurring in individuals who have acquired language prior to the injury. With damage to the anterior left hemisphere of the brain, patients typically suffer from a nonfluent or Broca's aphasia in which speech production is greatly impaired while auditory comprehension is relatively spared. The slow, halting, nonfluent speech, which generally accompanies Broca's aphasia, may also be termed apraxia of speech, difficulties with motor output during volitional speech. By carefully comparing aphasic/apraxic subjects' speech capabilities with their neurological profiles it is possible to build detailed models of the neural representation of speech production.
My independent contribution to the field of neurolinguistics has been to integrate kinematic and acoustic/perceptual data in order to examine language breakdown in terms of linguistic organization principles. This work has led to new insights concerning the functional organization of language and how motor-speech processes may be represented in the brain. I am currently working on projects investigating (1) the role of the cerebellum in adult speech production, (2) kinematic biofeedback as a means of remediating stroke-related speech disorders, (3) the development of coarticulation in children's speech, and (4) adults' perception of children's vowels.
My research is on compensatory articulation in normal and impaired speech. 'Compensatory articulation' refers to the fact that normal speakers immediately compensate for the displacement of an articulator during vowel production. This form of motor equivalence is an important feature of the human speech production system. By examining how normal and brain-damaged subjects speak while holding a small 'bite block' between the teeth, it is possible to learn more about the neurological and functional organization of speech motor control.
Assmann, P. and Katz, W.F. (2005). Synthesis fidelity and time-varying spectral change in vowels. Journal of the Acoustical Society of America, 117, 886-895.
Gabbert, G.J., Dewey, R., and Katz, W.F. (2004). Compensatory articulation in individuals with Parkinson’s disease. Brain and Language 91, 19-20.
Yoshida, M. and Katz, W.F. (2004). Children’s use of prosody to identify ambiguous sets of compound nouns. Journal of the Acoustical Society of America, 116, 2645.