Functional anatomy of derivational morphology

Lexical morphology involves two types of suffixes: inflectional suffixes, which have a grammatical function, and derivational suffixes with a word formation function. In this study, functional magnetic resonance imaging (fMRI) was used during processing of Italian derived and inflected words. In the derivational task, subjects were asked to produce nouns derived from verbs and from adjectives (e.g., to observe - observation; kind - kindness). After the presentation of the derived noun, they had to generate the corresponding verb (e.g., failure - to fail: generation task). In the inflectional task, subjects had to produce the past participle of the verb or the plural form of the adjective or the derived noun. Behavioural data were collected in separate sessions in two different conditions. In the first experiment, as in the fMRI study, vocal reaction times (RTs) were measured from the offset of the auditory stimulus to the onset of the participant's response. In the second experiment, run with a different group of participants, RTs were recorded starting from the onset of the auditory stimulus to the onset of the response. The fMRI results showed that, relative to the inflectional task and to a repetition task, the derivational task, but not the verb generation task, brought about an activation of left fronto-parietal regions, documenting a specific involvement of these areas in the processing of derived words. Although less extended, similar activation was found for verb inflection but was absent for noun and adjective plural forms. Analysis of behavioral data indicated that an explanation in terms of task difficulty was unlikely related to the imaging results.