Hulten, A. 1, 2
1 Brain Research Unit, Low Temperature Laboratory, Aalto University, Finland
2 Department of Psychology and Logopedics, Åbo Akademi University, Turku, Finland
The human ability to share novel ideas and thoughts with one another stems from characteristics of human language: the powerful combination of words and syntax enables us to understand and produce an unlimited array of utterances. Applying the rules of syntax, we build up sentences from their lexical constituents and their meanings, arriving to the compositional semantics of the whole sentence. Intriguingly, a person who speaks several languages may shift between different sets of rules as languages may greatly vary in their grammatical structure. The underlying neural implementations of these processes are far from resolved. In the present study, healthy adult volunteers learned a miniature language (Anigram) with a grammar markedly different from that of their mother tongue (Finnish), in four daily training sessions. Thereafter, during magnetoencephalography scanning, participants generated sentence-level description of a pictured event. Sentence vs. word sequence generation was tested separately for each language. The task was divided into a planning phase (picture presentation) and a cloze test (corresponding words overlaid on the picture) that ended with a prompt to generate the final word. Processing of the two languages differed only during the planning stage, as stronger activation for Anigram in the left angular and inferior parietal cortex, interpreted as an increased working memory load for the preparation of novel language output. Production of the sentence-final word, calling for retrieval of rule-based inflectional morphology, was accompanied by increased activation in the left middle superior temporal cortex and did not differ between the languages. Furthermore, the results suggest a prominent role for right hemisphere temporal regions in terms of integrative processing and in discriminating between word sequences and sentences. The study has implications for models of language learning and provides a new approach for the study of the neural mechanisms of sentence-level speech production.