Introduction

We describe five different impairments in verb retrieval, focusing on alternating-verbs in Hebrew (e.g., “closed” in 'Dan closed the door’ and 'the door closed'). Hebrew alternating verbs share a consonantal-root but differ in their verbal-pattern, each with a separate argument structure. E.g., sagar and nisgar ('closed _[Transitive]' and 'closed _{[Intransitive]}' respectively).

Methods

We designed a battery of seven tasks assessing the production of alternating and non-alternating verbs, tested 34 Hebrew-speakiers with various types of aphasia or developmental language-impairments, and compared their performance to each other and to control groups of non-impaired individuals. Finally, we inferred the function of each cognitive component in the production of morphologically-complex verbs based on the different error patterns.

Results

We identified 5 error-patterns, consistent with 5 loci of impairment: 1. Conceptual system: Alternant substitutions, without argument structure errors 2. Syntactic lexicon: Alternant substitutions, with argument structure errors 3. Phonological lexicon, stems: Impairment in retrieving roots, but not patterns in alternating and non-alternating verbs 4. Phonological lexicon, stems and affixes: Impairment in retrieving roots and patterns, in alternating and non-alternating verbs  5. Phonological buffer: Impairments in retrieving roots, patterns, tense and agreement in alternating and non-alternating verbs. We propose a sentence production model that can account for these patterns.

Conclusion

There is not one but many morphological impairments, and production errors that may seem similar on the surface stem from different underlying impairments in functional components that are usually not considered as involved in morphological processes. This has clinical implications for diagnosis and treatment.