Effect of Verb Network Strengthening Treatment (VNeST) on lexical retrieval of content words in sentences in persons with aphasia

Background: Verb Network Strengthening Treatment (VNeST) is a semantic treatment that aims to improve lexical retrieval of content words in sentence context by promoting systematic retrieval of verbs (e.g., measure) and their thematic rolesi.e., agent (doer of the action, e.g., carpenter, chef) and patient (receiver of the action, e.g., lumber, sugar). VNeST is influenced by Loverso and colleagues (e.g., Loverso, Selinger, Prescott, 1979) who used verb as core treatment to improve sentence production with encouraging results, and McRae and colleagues who showed that verbs prime typical agents (e.g., pray-nun) and patients (arrest-criminal) (Ferretti, McRae, Hatherell, 2001) and vice-versa (McRae, Hare, Elman, Ferretti, 2005). Aims: There are four specific questions in this study. Does training a set of verbs using VNeST generalise to the ability to produce (1) an agent (carpenter), trained verb (measure), and patient (stairs) in response to novel picture stimuli and (2) an agent (nurse), untrained semantically related verb (weigh), and patient (baby) in response to novel picture stimuli? (3) Are generalisation effects maintained? (4) Does VNeST generalise to the ability to retrieve nouns and verbs not directly related to treatment items in single word naming, picture description, and connected speech tasks? Methods Procedures: Four participants with aphasia participated. Participants received VNeST, which involves retrieval of agent-patient pairs (e.g., chef/sugar, surveyor/land) related to trained verbs (e.g., measure), twice per week. A single-participant, repeated probe, multiple baseline experimental design was used. Generalisation to sentence production for sentences containing trained verbs and untrained semantically related verbs was tested weekly. Outcomes Results: Results demonstrated generalisation to lexical retrieval of content words in sentences with trained and untrained verbs across participants. Additionally, pre- to post-treatment generalisation was observed on single verb and noun naming and lexical retrieval in sentences across a variety of tasks across participants. Generalisation to connected speech was observed for three of four participants. Conclusions: Although preliminary, these results indicate that VNeST may be effective in promoting generalisation from single word naming to connected speech in persons with moderate aphasia. A number of clinical implications related to treatment efficiency are discussed.