Object decision: the interaction of semantic information and structural description system

In the neuropsychological literature, visual object recognition is deemed to be subserved by structural information that is functionally independent from semantic memory. According to this view, the perceptual representation of the stimulus is compared with representations of objects previously seen and stored in the so-called “Structural Description System”, or SDS; when matching between representations occurs, the corresponding conceptual knowledge is activated. Recently, the functional independence of SDS has been challenged based on the evidence that patients affected by Semantic Dementia, a neurodegenerative condition characterized by a selective disruption of semantic memory with sparing of the early stages of object recognition, are impaired at Object Decision tasks. In the present dissertation, we aimed at investigating whether object recognition could be achieved on the basis of structural features alone, or whether semantic knowledge about the object is also involved. To this aim we created two different Object Decision tasks and administered them to healthy young subjects, elderly normal controls and neurodegenerative patients. Our findings suggest that conceptual knowledge plays a crucial role in visual object recognition, and that semantic memory and the SDS are highly interactive.