Associated impairment of the categories of conspecifics and biological entities: Cognitive and neuroanatomical aspects of a new case

Abstract

Case A.C.A. presented an associated impairment of visual recognition and semantic knowledge for celebrities and biological objects. This case was relevant for (a) the neuroanatomical correlations, and (b) the relationship between visual recognition and semantics within the biological domain and the conspecifics domain. A.C.A. was not affected by anterior temporal damage. Her bilateral vascular lesions were localized on the medial and inferior temporal gyrus on the right and on the intermediate fusiform gyrus on the left, without concomitant lesions of the parahippocampal gyrus or posterior fusiform. Data analysis was based on a novel methodology developed to estimate the rate of stored items in the visual structural description system (SDS) or in the face recognition unit. For each biological object, no particular correlation was found between the visual information accessed through the semantic system and that tapped by the picture reality judgement. Findings are discussed with reference to whether a putative resource commonality is likely between biological objects and conspecifics, and whether or not either category may depend on an exclusive neural substrate.

Keywords:

• Prosopagnosia
• Biological categories
• Semantics
• Fusiform gyrus

Acknowledgments

We are grateful to A.C.A. for her patience and collaboration during the long testing sessions that were necessary for this study. We are also indebted to Ilaria Bizzozero and her colleagues for having made available to us the original records of their studies in order to find the controls matched to A.C.A. for parts of the tests.

This project was partly supported by grants from Milan University and MIUR (Ministry of Education, Universities and Research) to E.C.

Rosemary Allpress revised the English text, and Ada Patriarca assisted with the figure preparation.

Notes

¹ Throughout the paper we use the terms (a) “early perception” for the processing stages that permit the assembly of an object-centred representation of the stimulus; (b) “visual recognition” for the successful matching between an object-centred representation and the visual information stored in a presemantic channel-specific system; and (c) “identification” for the ability, for each stimulus, to successfully access the semantic system and wide-scope information not limited to a given input channel. This is not always consistent with the meaning given to these terms by other authors, and we point out this discrepancy where relevant.

² As the demographic variables can influence performance, the scores of a control group were previously adjusted for demographic variables, and thresholds for pathological and normal performance were set using nonparametric, one-sided tolerance limits (Barbarotto et al., 2002). With biological items the rate of correct responses (71.7%) was adjusted to 73.9%, which was pathological (pathology threshold = 75.9%). Similarly with artefacts the rate of correct responses (68.3%) was adjusted to 74.5%, which was pathological (pathology threshold = 76.9%).

³ In this case the experimental conditions prevented us from following the signal detection theory (SDT) approach. SDT assumes that the number of really presented stimuli (“signal present”) is known with certainty, whereas in the picture reality decision test, and especially in the face familiarity judgement, we are not sure whether the visual representation corresponding to a given stimulus was really stored in the patient's cognitive system before the occurrence of her brain damage. We do not discuss here further violations of the basic SDS assumptions—for instance, the need for a signal uniformity during the detection experiment.