Assessment of explicit and implicit linguistic impairments in patients with aphasia after resection of tumour of the left cerebral hemisphere. Preliminary results.

Background And Purpose: Classical definitions of aphasia des-cribe deficits of different language levels (syntactic, semantic, phonologic) hindering the ability to communicate. Recent studies indicate, however, that impairment of particular aspects of linguistic competencies in aphasia differs in severity. Contemporary approach to the aphasic symptoms presents them as disturbed access of linguistic representations to the awareness system. Accordingly, such an approach requires different types of tasks: direct, involving explicit language processes, and indirect, based on implicit language representations. The aim of our study was to examine explicit and implicit language processes in patients with aphasia after resection of the tumour of left cerebral hemisphere along with characterization of relationships between explicit and implicit language processes.

Material And Methods: Our cohort included 28 right-handed patients who were divided into four equal groups: two clinical (brain tumours) and two control (lumbar disc disease). Four tasks that assess and compare language processes: lexical decisions (at explicit and implicit levels), sorting of picture captions and word monitoring were implemented.

Results: In direct tasks, patients with aphasia provided less correct lexical decisions at word level, but did not show deficits in sentence comprehension. In both groups, no priming effect was observed in tasks requiring implicit lexical decisions. The longest time was found in non-primed words, the shortest in pseudowords. The differences between groups regarding word monitoring were also observed. Patients with aphasia obtained longer reaction times in all types of sentences (of different grade of language correctness), with respect to low- and high- frequency words.

Conclusions: Patients with aphasia after brain tumour resection show more pronounced impairments of explicit than implicit linguistic behavior; the same effect was found in studies on forgetting in amnestic syndrome.