Alec Marantz - US grants

This project will investigate the comprehension of morphologically complex words, words like "knowable" that can be broken down into pieces. Linguists and psycholinguists disagree on whether all words that consist of a possibly independent stem ("know" is a verb by itself) and an identifiable suffix ("-able" generally creates adjectives from verbs) are analyzed as complex by speakers and whether all or any such words are recognized via decomposition into their parts. The issue is particularly controversial for words like "tolerable" apparently built from roots that do not appear on their own ("toler-" is also seen in "tolerate" but not elsewhere). This project uses magnetoencephalographic (MEG) brain monitoring methods to test a theory about the interaction of linguistic representations and neural computations. The theory demands that every decomposition motivated by linguistic theory is a necessary computational step in recognizing a word and that each computation maps to neural activity of a set of brain regions at particular time latencies during word recognition. For this project, subjects will read or listen to individual words and non-words, judging their word status, while the electrical activity in their brains is monitored with MEG. A novel analysis technique will be developed that correlates the brain responses of each subject for each word with continuous stimulus variables such as word frequency, suffix frequency, and the probability of having a particular suffix following a particular stem. Given sufficient numbers of subjects and stimuli, this technique can provide meaningful data about individual words and individual subjects. For example, is a word like "vulnerable", whose root "vulner-" does not appear elsewhere in English, recognized in the same way as "knowable" or "tolerable"?

The project should elucidate the connections among linguistic theory, psycholinguistic models, and brain activity while testing hypotheses about the comprehension of morphologically complex words. Since for the theories of morphology being tested, the structure of words involves the same computations and representations as the structure of sentences, support for full decomposition to the root for words like "knowable" and "tolerable" will have implications for language processing at all levels of linguistic analysis. The single trial MEG analysis techniques developed by the project should aid greatly in the diagnosis of language-impaired populations and in the evaluation of remediation. Exploiting the results and techniques of this project, future research can ask, for example, how the brain responses of an individual dyslexic or autistic subject differ from the norm along various dimensions, and if any of these responses approach group norms after intervention. Progress in understanding and treating these deficits should come from an understanding of how neural systems perform linguistic computations and store and manipulate linguistic representations.

The advent of non-invasive brain imaging at high spatial and temporal resolution in awake, behaving human beings has had a profound impact on the study of language in the brain. It is now the ten-year anniversary of the first international conference on the Neurobiology of Language, a field that has grown substantially since then and continues to blossom. Studying the neurobiology of language requires highly specialized skills (e.g., brain imaging) and broad multidisciplinary knowledge (e.g., psychology, linguistics, neuroscience). In order to promote scientific inquiry of the highest quality, it is vital to promote dialogue and interaction among the relevant disciplines. This project explores how to facilitate this interaction.

The "neurobiology of language" is the biological implementation for representations and processes involved in the production and understanding of speech, sign, and language in context. Previously, brain structures and functions for language could only be inferred from studying humans with brain injury. By monitoring the anatomical encodings and physiological dynamics of language processing in awake, behaving human beings, researchers can now study human language at a biological precision previously possible only in animal models (of functions other than language). Concomitant with these new approaches has been a dramatic increase in the number of investigators dedicating their effort to understanding the biological basis of language. The growth in the number of investigators and the use of expanded techniques and theoretical perspectives have driven the need for enhanced transparency, integrity, and robust and rapid research dissemination. The PIs will explore these topics while developing systems and operations for open science, facilitating reproducibility and replicability of research, and dissemination of new findings.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.