Reacquisition of semantic knowledge by errorless learning in a patient with a semantic deficit and anterograde amnesia

Abstract

Background: So far 11 therapy studies have been reported which aimed to re‐teach semantic knowledge in brain‐damaged patients presenting with a semantic deficit consecutive to stroke, herpes encephalitis, or semantic dementia. All these semantic therapy studies but one recorded a significant improvement in the patients' performance on tasks requiring semantic processing. The exception to this pattern was the semantic therapy study by Sartori, Miozzo, and Job (1994), which yielded negative results. Because the study concerned two patients with anterograde amnesia associated with the semantic deficit, Sartori et al. concluded that reacquiring semantic knowledge was not possible when such association of deficits was present. Aims: Sartori et al.'s study, like all the other semantic therapy studies, applied an errorful learning procedure during the therapy. However, the question can be raised of whether such procedure is appropriate when amnesia is associated with the semantic deficit. Because error elimination is likely a function of explicit memory, which is impaired in amnesic patients, wrong stimulus–response associations would be repeatedly retrieved and strengthened in (spared) implicit memory, thus preventing the patient from learning novel semantic knowledge. In the present single‐case study we addressed this issue by using an errorless learning procedure during semantic therapy in a post‐encephalitis patient (DL) who suffered both a semantic deficit and anterograde amnesia. Methods & Procedures: The therapy aimed at re‐teaching semantic attributes of 16 items. The design included, further to these 16 target items, 16 contrast and 16 control items, which were semantic coordinates of the target items. Both shared (category) and distinctive (non‐category) attributes were included in the learning set. Learning was based on an attribute classification task in which the properties of the target items had to be contrasted with those of coordinate items, within a paradigm that greatly reduced the chance of making errors. A pre‐ and post‐therapy picture naming and an attribute verification task allowed us to assess the therapy effects at the end of therapy and 1 year later. Outcomes & Results: Significant therapy effects were observed in the attribute verification task and were still present 1 year afterwards. Thus, the patient's performance significantly improved for the category (i.e., shared) attributes of the target, contrast, and control items, and for the non‐category (i.e., distinctive) attributes of the target items. Conclusions: This finding showed that, contrary to Sartori et al.'s claim, re‐acquiring semantic knowledge was possible in a patient with anterograde amnesia associated with her semantic deficit.