Alexander A. Stevens
Research Assistant Professor, Department of Psychiatry,
Assistant Professor, Behavioral Neuroscience, OHSU
e-mail: stevenal@ohsu.edu
Functional Brain Imaging Website
Major Areas
Neural basis of language and audition, functional magnetic resonance imaging of cortical reorganization in the blind, language abnormalities in schizophrenia
Previous Positions
Postdoctoral Associate, Department of Diagnostic Radiology, Yale University School of Medicine.
NIMH Postdoctoral Fellow, Departments of Neurobiology and Psychiatry, Yale University School of Medicine.
Lecturer - Department of Psychology, University of New Hampshire
Education
Ph.D. (1995) Experimental Psychology, University of New Hampshire
M.A. (1991) Experimental Psychology, University of New Hampshire
License (C2) (1989) Physiological Psychology, University of Paris V
B.A. (1986) Psychology. University of Rochester
Research Interests
The research in this lab focuses on the study of the neural basis of language, auditory processing and memory, primarily using functional magnetic resonance imaging (fMRI), psychophysics and cognitive testing. We are interested in understanding the relationships between behavior, and the organization of the neural systems underlying these functions. We are using brain mapping techniques to study the organization of sound recognition, sound localization and speech processing in the human cortex in normal individuals as well as in psychiatric groups and the blind.
Our current focus is using fMRI to study how occipital, temporal and parietal cortical areas that usually are involved in visual processes in sighted people are reorganized in the blind. A growing body of research indicates that blind individuals have greater auditory perceptual abilities than sighted individuals. What is unclear is if these perceptual abilities translate into better performance on auditory tasks of attention and memory. Furthermore, it is unknown how these abilities are related to the reorganization of occipito-temporal brain regions that are involved in visual processing in sighted individuals. We are attempting to determine the extent of these superior auditory abilities and if they relate to the reorganization of occipitotemporal and occipitoparietal cortex. We are examining the relationship of neural reorganization and auditory processing skills in early and late onset blind individuals as well as sighted controls using fMRI in concert with psychophysical and cognitive testing procedures.
A second project is examining the neural basis of language comprehension and voice recognition. Unlike the visual system, the organization of cortical auditory systems is poorly understood in primates. Voice recognition appears to be processed by right lateralized brain regions that are dissociable from the classic left hemisphere speech areas. Different aspects of voice processing are critical to identifying speakers, and, speech prosody and intonation also provide important information regarding affective and syntactic information critical to interpreting the content of speech. This distinction is particularly interesting because previous work has suggested that individuals with schizophrenia have language processing abnormalities (e.g. verbal memory impairments, auditory hallucinations in the form of voices) but their auditory non-verbal abilities appear to be relatively normal. We are further characterizing the verbal and nonverbal auditory memory using fMRI to map the neural systems involved in these functions in healthy subjects.
Selected Recent Publications
Stevens AA (2004) Dissociating the cortical basis of memory for voices, words and tones. Brain Res Cogn Brain Res. Jan;18(2):162-71.
Wexler BE, Donegan N, Stevens AA, Jacob SA (2002) Deficits in language-mediated mental operations in patients with schizophrenia. Schizophr Res. Jan 15;53(3):171-9.
Stevens AA, Skudlarski P., Gatenby JC., Gore JC. (2000) fMRI reveals event-related activation during auditory and visual oddball tasks. Magnetic Resonance Imaging . 18 (5), 495-502.
Stevens AA, Donegan, N, Anderson M, Goldman-Rakic PS, Wexler BE. (2000) Proactive interference and modality effects on auditory verbal working memory in schizophrenia. Journal of Abnormal Psychology , 109(2).
Stevens AA, Goldman-Rakic PS, Gore JC, Fulbright RK, Wexler BE (1998). Functional magnetic resonance imaging reveals frontal lobe dysfunction during verbal working memory in schizophrenia. Archives of General Psychiatry , 55, 1097-1103.
Wexler BE, Stevens AA, Bowers S, Goldman-Rakic PS. (1998). Differentiating auditory verbal deficits in working memory from spared non-verbal memory function in schizophrenia. Archives of General Psychiatry . 55, 1093-1096.
Stevens AA & Mair RG. (1998). Auditory conditional discrimination impairments without an imposed delay following thalamic and prefrontal cortical lesions in the rat. Psychobiology , 26, 205-215.