NEUROBIOLOGY OF LANGUAGE PERCEPTION--FMRI INVESTIGATIONS

University Of California Irvine, Irvine CA

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Abstract

The long range goal of this project is to map the neurobiology of auditory language perception, both in terms of its linguistic sub-components and in terms of its domain specificity. The advent of functional magnetic resonance imaging (fMRI)--a non- invasive, high resolution functional brain imaging technique--has made the realization of this goal a real possibility in the near future. Because optimal methodological procedures for fMR imaging have yet to be worked out satisfactorily we propose a relatively small set of theoretically motivated experiments that we will carry out using protocols that can inform methodological as well as theoretical questions. Aim Concerning the Neural Organization of Language. 1. To map the extent of neural tissue involved in processing auditory language at the sentence level--a level of linguistic analysis which has been prominent in cognitive and linguistic theories but has yet to be investigated thoroughly using functional imaging techniques. 2. To determine the specificity of neural systems involved in linguistic vs. non- linguistic auditory perception. We contrast perception of sentences with perception of a range of non-linguistic auditory stimuli each of which controls for specific aspects of sentence processing such as temporal acoustic processing (backwards sentences), hierarchical structure processing (music), processing meaningful strings of sounds (environmental sound "events"). We also investigate the role of expertise in auditory processing and the neural correlates of hearing a single stimulus as linguistic versus non-linguistic signal. 3. To investigate the extent to which different aspects of the linguistic signal (prosody, lexical-semantic content, syntax) are processed in distinct neural systems. Aims Concerning Methodology. 1. To investigate reliability issues: test-retest reliability, reliability of localization, and reliability as seen in terms of repetition effects. 2. To examine empirically the cognitive basis of task effects in neuroimaging, namely, to answer the question, can task manipulations provide a window on the neural basis of linguistic perception or are we simply measuring task-specific effects. We propose a set of selective attention experiments (a widely used task manipulation) to investigate the issue. 3. Our third goal is to explore the utility of the single trial presentation format. Our prior work has demonstrated that one can present stimuli in single trials (rather than blocks of such stimuli) and obtain reliable activations, perhaps with increased sensitivity. This radically increases the flexibility of experimental design in fMRI. We assess the validity of the technique in several experiments.