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Jennifer K. E. Steeves, Caitlin Mullin, Jean-François Démonet; Preserved house discrimination in a patient with acquired object agnosia. Journal of Vision 2008;8(6):332. doi: 10.1167/8.6.332.
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© ARVO (1962-2015); The Authors (2016-present)
Is object discrimination a necessary precursor for discrimination houses, whose features might be considered to be objects? For instance, when we manipulate a house by inserting different windows, are the windows within the house an object or are they integrated into the house itself? We compared two different types of discrimination of two visual stimulus classes (houses and faces) in a patient with acquired brain damage to controls. Patient SB is a 38 yr old male who suffered damage to ventral visual areas including the right fusiform gyrus and inferior and middle occipital gyri from meningitis at the age of 4 years. This resulted in profound object agnosia and prosopagnosia but nevertheless SB has previously been shown to have intact scene categorization. Participants performed a same/different discrimination task with stimulus sets of house and face images designed to asses featural and configural processing across these two visual image classes. In the featural set, houses and faces differed only in the features (windows, doors or eyes, mouth). In the configural set, houses and faces differed only in the spacing of the features. Control participants could differentiate featural and configural differences on these two stimulus classes. Patient SB was unable to discriminate the feature spacing or the features of the face stimuli sets, reflecting his prosopagnosia. He also was unable to discriminate the feature spacing of the configural house test, which may be a floor effect. In contrast, SB was able to discriminate houses with different features despite his object agnosia. This implies that the features of the house are not processed as individual objects but rather as integrated components of a global scene. These results suggest that SB discriminates houses using his intact scene processing pathway and further suggests that object and scene processing are independent.
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