Purpose: The primary purpose of this study was to identify the brain bases of phonological working memory (the shortterm maintenance of speech sounds) using behavioral tasks analogous to clinically sensitive assessments of nonword repetition. The secondary purpose of the study was to identify how individual differences in brain activation were related to participants' nonword repetition abilities. Method: We used functional magnetic resonance imaging to measure neurophysiological response during a nonword discrimination task derived from standard clinical assessments of phonological working memory. Healthy adult control participants (N = 16) discriminated pairs of real words or nonwords under varying phonological working memory load, which we manipulated by parametrically varying the number of syllables in target (non)words. Participants' cognitive and phonological abilities were also measured using standardized assessments. Results: Neurophysiological responses in bilateral superior temporal gyrus, inferior frontal gyrus, and supplementary motor area increased with greater phonological working memory load. Activation in left superior temporal gyrus during nonword discrimination correlated with participants' performance on standard clinical nonword repetition tests. Conclusion: These results suggest that phonological working memory is related to the function of cortical structures that canonically underlie speech perception and production. T he cognitive processes that underlie the short-term maintenance of language sounds are known collectively as phonological working memory. Phonological working memory is thought to support a wide range of linguistic behaviors, including novel word learning and vocabulary development, maintenance of information during sentence and discourse processing, and the acquisition of reading skill

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Purpose Child language acquisition is marked by an optional infinitive period (ages 2–4 years) during which children use nonfinite (infinitival) verb forms and finite verb forms interchangeably in grammatical contexts that require finite forms. In English, children's errors include omissions of past tense /– ed / and 3rd-person singular /– s /. This language acquisition period typically ends by the age of 4 years, but it persists in children with language impairments. It is unknown if adults still process optional infinitives differently than other kinds of morphosyntax errors. Method We compared behavior and functional brain activation during grammaticality judgments across sentences with developmental optional infinitive tense/agreement errors (“Yesterday I play the song”), nondevelopmental agreement errors (“He am tall”) that do not occur in typical child language acquisition, and grammatically correct sentences. Results Adults ( N = 25) were significantly slower and less accurate in judging sentences with developmental errors relative to other sentences. Sentences with developmental errors yielded greater activation in bilateral inferior frontal gyri relative to nondevelopmental error sentences in both auditory and visual modalities. Conclusions These findings suggest that the heightened computational demands for finiteness extend well beyond early childhood and continue to exert their influence on grammatical mental and brain function in adulthood.