ABSTRACT
Early stages in visual object recognition are likely to involve the independent coding of primitive visual features at a number of spatial scales. The term visual agnosia refers to patients who, following brain damage, having problems in recognizing visually presented objects. It seems likely that problems in visual object recognition can reflect a number of functionally different impairments, possibly also including a selective problem in grouping image features. Over the past ten years, the authors have been able to study a patient with severe visual agnosia, HJA, who also seemed to have some problems in grouping visual elements in a spatially parallel manner. This chapter presents a more extensive investigation into HJA's ability to code and group image features. The results suggest that the search for a form conjunction amongst homogeneous distractors depends upon the particular processes that can be selectively impaired after brain damage.
