Selective impairment of semantic memory in dementia: A case study

Progressive neuropsychological impairments (non aphasic language deficits, gnosic and face recognition disturbances, semantic memory impairments and comportemental disorders) were observed in a 65 year old woman. Bi-temporal cortico-sub-cortical atrophia and right frontal lobe damages were demonstrated by morphological and functional investigations (CT scan, MNR and SPECT). In spite of agnosia without aphasia or apraxia, the diagnostic of DTA was initially suggested. This unusual observation was discussed on three points. I) As the clinical assessment revealed ''living/non living'' item dissociation, the gnosic disturbances were explained with regard to asemantic agnosia. 2) Following the cognitive perspective, the organization of semantic memory was discussed on the base of the visual/auditive modality impairments. From this discussion, the ''prosopagnosic symptoms'' were understood as disturbances which specifically involved the ''living'' category in semantic memory. 3) The diagnostic of Semantic Dementia was argued. In conclusion, this observation could be characterized by a core deficit of semantic memory, disorders of which could suggest a crossed multimodal organization (specific modalities and semantic categories).