INTRODUCTION

Damage to the left inferior frontal lobe typically results in a pattern of performance characterized by agrammatic production and asyntactic comprehension, suggesting that this brain area is implicated in morphosyntactic processing (e.g., Caramazza and Zurif, 1976) Recently, Ullman et al. (1997) have challenged this position and have argued that this brain area is only implicated in rule-based processes of all types. This proposal predicts that damage to the left inferior frontal lobe would result in: a) agrammatic speech production and b) poor performance with only those
morphophonological process that are rule-based. Accordingly, damage to this brain area would lead to poorer performance when applying regular morphophonological transformations than irregular morphophonological transformations, despite the fact that both processes involve morphosyntactic operations. We tested this hypothesis by exploring the performance of two Catalan-Spanish bilingual agrammatic patients in a morphological transformation task. Patients were asked to complete aurally presented sentences using the appropriate verb tense form. For example, given the sentence frame “Ayer yo comía, Hoy yo….” (Yesterday I ate, today I ….), the patients were required to produce the verb form “como” (I eat). Regular and Irregular verbs were presented randomly in the same testing session. The patients were tested in their two languages: Catalan and Spanish. According to Ullman et al.’s hypothesis, the two agrammatic patients with damage to the left inferior frontal lobe should perform more poorly with regular than irregular verbs.