Woorden en Objecten

Abstract

The semantic system has a central position in the language processing system as the intermediate between language production and language comprehension. The system itself may be separated into distinctive components: visual and lexical semantics. Their is much discussion about the interference between the visual and lexical semantic system and about the quality of the processing routes. Some authors propose a unitary amodal system, other authors plead for modality-specific semantic systems. The stage of perceptual categorization is considered both as optional and as obligatory. The objective of this study is: to investigate visual and lexical semantic processing in aphasic patients (n=74) (control groups: right- hemispheric patients (n=10) and normals (n=96)) (i), to examine the relation between semantic deficits and aphasia type and severity (ii) and to explore the relation between presemantic and semantic visual processing. Instruments to measure presemantic and semantic processing: Object Decision (Riddoch & Humphreys, 1987) and the verbal and visual Semantic Association Test (Visch-Brink e.a.., 1993). Results: aphasie patients as a group were significantly impaired both in Object Decision and visual and verbal semantic processing. Some patients appeared to have a selective deficit in visual or verbal semantic processing (1). No correlation was found between the performance on the visual or verbal Semantic Association Test and the aphasia type or severity (ii). In some patients a dissociation was found between presemantic and semantic visual processing (iii). Conclusions: Visual and lexical semantic processing in aphasia may selectively disturbed, which pleads rather for a multiple than for a unitary semantic processing system. Aphasia type and the severity of aphasia do not function as indicators for the presence of a visual and/or lexical semantic disorder. For the interpretation of the meaning of a picture, the stage of perceptual categorization can be bypassed.