Articles CME Covert recognition in acquired and developmental prosopagnosia Jason J.S. Barton, MD, PhD, FRCPC; Mariya Cherkasova, BA; and Margaret O’Connor, PhD Article abstract—Background: Some patients with prosopagnosia have covert recognition, meaning that they retain some familiarity or knowledge of facial identity of which they are not aware. Objective: To test the hypothesis that prosopagnosic patients with right occipitotemporal lesions and impaired face perception lack covert processing, whereas patients with associative prosopagnosia and bilateral anterior temporal lesions possess it. Methods: Eight patients with prosopagnosia were tested with a battery of four face recognition tests to determine their ability to discriminate between famous and unknown faces. Results: Measures of overt familiarity revealed better residual discrimination in patients with acquired prosopagnosia than in those with the developmental form. With forced-choice methods using famous faces paired with unknown faces, no patient demonstrated covert familiarity. However, when the semantic cue of the name of the famous face was provided, covert processing was present in all five patients with acquired prosopagnosia, including the three with extensive right-sided lesions and impaired perceptual discrimination of facial configuration. Sorting unrecog- nized faces by occupation was also performed above chance in three of these five patients. In contrast, none of the three patients with developmental prosopagnosia had covert processing, even though two demonstrated flawless performance on similar tests of name (rather than face) recognition. Overt familiarity correlated highly with the degree of covert recognition. Conclusions: Extensive right occipitotemporal lesions with significant deficits in face perception are not incompatible with covert face processing. Covert processing is absent in developmental prosopagnosia, because this condition likely precludes the establishment of a store of accurate facial memories. The presence of covert processing correlates with the degree of residual overt familiarity, indicating that these are related phenomena. NEUROLOGY 2001;57:1161–1168 Prosopagnosic patients deny familiarity with and cannot identify faces of people known to them. How- ever, a range of physiologic and behavioral techniques have shown in at least 12 patients that some retain “covert recognition” of these faces. 1 Two different co- vert phenomena can be shown: covert familiarity, or distinguishing known from unknown faces, and co- vert knowledge, or retained information about name, occupation, and other facts associated with a face. For covert familiarity, differences between familiar and unfamiliar faces have been shown with physiologic measurements such as the electrodermal skin conduc- tance test 2 and the P300 evoked potential. 3 Behavioral methods can also show covert familiarity. The se- quence of eye fixations of two prosopagnosic patients was less stereotyped when they viewed familiar rather than unfamiliar faces. 4 Judging whether two different pictures portray the same person was more rapid and dependent on internal facial features with familiar faces in normal subjects and also one prosopagnosic patient. 5 Matching the old and young faces of individu- als across a 30-year span was easier with famous faces for another prosopagnosic patient. 6 The classification of a target name as familiar or unfamiliar was affected by whether a simultaneously shown face was related to the name, indicating the presence of covert “priming.” 7 For covert knowledge, greater electrodermal re- sponses were found in two patients when a name read aloud belonged to a famous face than when it did not. 8,9 When forced to choose between a correct and incorrect name, one patient guessed better than chance, 6 though another did not for occupation. 5 Several prosopagnosic patients were better at learning to associate a famous face with a correct name than with an incorrect one. 5,6,10,11 Covert processing has also been shown with a “facial interference” task in one patient. 12 In this, the speed to classify a name by occupation was faster if a simultaneously shown face was that of either the named person or someone with the same occupation than if the face was of an unrelated person. Conversely, some studies have shown lack of co- vert recognition in at least some prosopagnosic See also pages 1151 and 1168 From the Departments of Neurology (Drs. Barton and O’Connor, and M. Cherkasova) and Ophthalmology (Dr. Barton), Beth Israel Deaconess Medical Center and Harvard Medical School; and Department of Biomedical Engineering, Boston University (Dr. Barton), MA. Supported by a grant from the National Institute of Neurological Disorders and Stroke (J.J.S.B.). Presented at the 53rd annual meeting of the American Academy of Neurology; Philadelphia, PA; May 9, 2001. Received December 28, 2000. Accepted in final form May 12, 2001. Address correspondence and reprint requests to Dr. J.J.S. Barton, Department of Neurology, KS 452, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215; e-mail: jbarton@caregroup.harvard.edu Copyright © 2001 by AAN Enterprises, Inc. 1161