Long-term maintenance of novel vocabulary in persons with chronic aphasia

Abstract

Background: The study of novel word learning in aphasia can shed light on the functionality of patients' learning mechanisms and potentially help in treatment planning. Previous studies have indicated that persons with aphasia are able to learn some new vocabulary. However, these learning outcomes appear short-lived and evidence for the ability to use the newly learned words in the long term is lacking.

Aims: Participants with aphasia and matched controls underwent short training where they were taught to name novel objects with novel names. We studied the participants' word learning and particularly their long-term maintenance. We also examined whether the language and verbal short-term memory impairments of the participants with aphasia related to their ability to acquire and maintain phonological and semantic information on novel words.

Methods & Procedures: Two participants with nonfluent aphasia, LL and AR, and two matched controls took part in the experiment. They were taught to name 20 unfamiliar objects by repeating the names in the presence of the object picture. Half of the items carried a definition that was used to probe incidental semantic learning. There were four training sessions, a post-training test, and follow-up tests up to 6 months post-training. Learning measures included recognition of the trained objects, as well as spontaneous and cued recall in visual confrontation naming. Incidental semantic learning was measured by spontaneous recall of the definitions.

Outcomes & Results: Combining spontaneous and phonologically cued responses, LL acquired 70% and AR 55% of the novel words. With phonological cueing, LL named 50% of the items correctly up to 6 months post-training (vs 95–100% for the controls) and AR 25% up to 8 weeks post-training. AR's lexical-semantic processing, pseudoword repetition and verbal short-term capacity were inferior to those of LL. In line with this, AR learned fewer words and showed more decline in recognition memory for the trained items, and weaker recall of the semantic definitions.

Conclusions: Our results support previous findings that people with aphasia can learn to name novel items. More importantly, the results show for the first time that, with phonological cueing, an individual with aphasia can maintain some of this learning up to 6 months post-training. Moreover the results provide further evidence for the significance of the functional status of lexical-semantic processing on word learning success.

Keywords:

• Aphasia
• Training
• Vocabulary
• Word learning
• Phonological cueing

Acknowledgments

This work was financially supported by the Finnish Graduate School in Language Studies Langnet, the Department of Psychology and Logopedics of Abo Akademi University, and grants from the Research Institute of the Abo Akademi University Foundation. NM was supported by NIDCD grants R01 DC01924-15 and R21 DC008782 awarded to Temple University (PI: N. Martin). ML was supported by a grant from the Academy of Finland (research grant #135688). We would like to thank Petra Grönholm-Nyman PhD for her help in creating the training stimulus sets. In addition we are grateful to Jyrki Tuomainen PhD, Kati Renvall PhD, and Nicholas Gruberg MA for advice and technical help in creating the Finnish adaptation of the Temple Assessment of Language and Short-term Memory in Aphasia (TALSA).

Notes

¹The Temple Assessment of Language and Short-term Memory in Aphasia (TALSA) is a comprehensive test battery designed for evaluating language and verbal short-term memory abilities in aphasia (Martin et al., 2010; Kalinyak-Fliszar et al., 2011). In TALSA, short-term memory load (as number of alternatives to be compared or as different intervals between stimulus and response) are varied systematically across language tasks. The intervals vary from unfilled intervals of 1 or 5 seconds and a filled interval of 5 seconds where phonological rehearsing is impeded by making the participant count aloud numbers that appear on the computer screen in a randomised order. The results of a group of aphasic participants assessed with TALSA indicate that there are two types of processing impairments in aphasia: (i) slowed activation which manifests as superior performance with longer stimulus–response intervals, and (ii) too-fast decay where the participant cannot maintain activation of representations and performance declines as intervals get longer. The impairment profiles are achieved in comparison of performance in tasks that differ only in short-term memory load.

²Both participants with aphasia had item names that they never produced fully correctly during the naming tests. Four of the names were shared between the participants (lihta, kaha, lamuska, lukkaro) and six were difficult only to AR (vidin, käsälä, lisku, junki, mänkki, lippi).