Sherryse Corrow

Developmental prosopagnosia in childhood

Developmental prosopagnosia (DP) is defined by severe face recognition problems resulting from a failure to develop the necessary visual mechanisms for processing faces. While there is a growing literature on DP in adults, little has been done to study this disorder in children. The profound impact of abnormal face perception on social functioning and the general lack of awareness of childhood DP can result in severe social and psychological consequences for children. This review discusses possible aetiologies of DP and summarizes the few cases of childhood DP that have been reported. It also outlines key objectives for the growth of this emerging research area and special considerations for studying DP in children. With clear goals and concerted efforts, the study of DP in childhood will be an exciting avenue for enhancing our understanding of normal and abnormal face perception for all age groups.

Word and text processing in developmental prosopagnosia

ABSTRACT The “many-to-many” hypothesis proposes that visual object processing is supported by distributed circuits that overlap for different object categories. For faces and words the hypothesis posits that both posterior fusiform regions contribute to both face and visual word perception and predicts that unilateral lesions impairing one will affect the other. However, studies testing this hypothesis have produced mixed results. We evaluated visual word processing in subjects with developmental prosopagnosia, a condition linked to right posterior fusiform abnormalities. Ten developmental prosopagnosic subjects performed a word-length effect task and a task evaluating the recognition of word content across variations in text style, and the recognition of style across variations in word content. All subjects had normal word-length effects. One had prolonged sorting time for word recognition in handwritten stimuli. These results suggest that the deficit in developmental prosopagnosia is unlikely to affect visual word processing, contrary to predictions of the many-to-many hypothesis.

Selectivity in acquired prosopagnosia: The segregation of divergent and convergent operations.

Face recognition can be viewed as part of a divergent set of operations in object recognition, in which information from common low-level visual mechanisms feeds forward into increasingly specialized processes for different object types. This divergence may also involve hemispheric specialization, notably for faces in the right and words in the left hemisphere. However, in person recognition, face processing is one of a set of sensory inputs that converge upon access to stored information about people. We review the literature and evidence from a cohort of acquired prosopagnosic subjects, on three issues concerning selectivity. First, we review the data on object recognition in prosopagnosia, and recent evidence that, after adjusting for pre-morbid car expertise, impairments of car identification are common in our cohort, particularly among car experts. Second, we review the data on word processing in prosopagnosia. In our cohort we show that the word-length effect in single word reading is normal after right-sided lesions, but the discrimination of font and handwriting is impaired in most of our subjects, regardless of lesion location. Third, we discuss the status of voice recognition in prosopagnosia, and show that in our cohort, right anterior temporal lesions do not impair this function, but bilateral ones do. Together, these findings suggest that the processes for faces, cars and visual text involve either the same neural resources or parallel processes in close proximity. Voice and face processing remain distinct in our subjects, and confirm that right anterior temporal lesions cause an associative prosopagnosia rather than a multi-modal person recognition syndrome.

Getting lost: Topographic skills in acquired and developmental prosopagnosia

Previous studies report that acquired prosopagnosia is frequently associated with topographic disorientation. Whether this is associated with a specific anatomic subtype of prosopagnosia, how frequently it is seen with the developmental variant, and what specific topographic function is impaired to account for this problem are not known. We studied ten subjects with acquired prosopagnosia from either occipitotemporal or anterior temporal (AT) lesions and seven with developmental prosopagnosia. Subjects were given a battery of topographic tests, including house and scene recognition, the road map test, a test of cognitive map formation, and a standardized self-report questionnaire. House and/or scene recognition were frequently impaired after either occipitotemporal or AT lesions in acquired prosopagnosia. Subjects with occipitotemporal lesions were also impaired in cognitive map formation: an overlap analysis identified right fusiform and parahippocampal gyri as a likely correlate. Only one subject with acquired prosopagnosia had mild difficulty with directional orientation on the road map test. Only one subject with developmental prosopagnosia had difficulty with cognitive map formation, and none were impaired on the other tests. Scores for house and scene recognition correlated most strongly with the results of the questionnaire. We conclude that topographic disorientation in acquired prosopagnosia reflects impaired place recognition, with a contribution from poor cognitive map formation when there is occipitotemporal damage. Topographic impairments are less frequent in developmental prosopagnosia.

Prosopagnosia: Current perspectives

Prosopagnosia is a selective visual agnosia characterized by the inability to recognize the identity of faces. There are both acquired forms secondary to brain damage and developmental forms without obvious structural lesions. In this review, we first discuss the diagnosis of acquired and developmental prosopagnosia, and the challenges present in the latter case. Second, we discuss the evidence regarding the selectivity of the prosopagnosic defect, particularly in relation to the recognition of other objects, written words (another visual object category requiring high expertise), and voices. Third, we summarize recent findings about the structural and functional basis of prosopagnosia from studies using magnetic resonance imaging, functional magnetic resonance imaging, and event-related potentials. Finally, we discuss recent attempts at rehabilitation of face recognition in prosopagnosia.

Localization and patterns of Cerebral dyschromatopsia: A study of subjects with prospagnosia.

OBJECTIVE Cerebral dyschromatopsia is sometimes associated with acquired prosopagnosia. Given the variability in structural lesions that cause acquired prosopagnosia, this study aimed to investigate the structural correlates of prosopagnosia-associated dyschromatopsia, and to determine if such colour processing deficits could also accompany developmental prosopagnosia. In addition, we studied whether cerebral dyschromatopsia is typified by a consistent pattern of hue impairments. METHODS We investigated hue discrimination in a cohort of 12 subjects with acquired prosopagnosia and 9 with developmental prosopagnosia, along with 42 matched controls, using the Farnsworth-Munsell 100-hue test. RESULTS We found impaired hue discrimination in six subjects with acquired prosopagnosia, five with bilateral and one with a unilateral occipitotemporal lesion. Structural MRI analysis showed maximum overlap of lesions in the right and left lingual and fusiform gyri. Fourier analysis of their error scores showed tritanopic-like deficits and blue-green impairments, similar to tendencies displayed by the healthy controls. Three subjects also showed a novel fourth Fourier component, indicating additional peak deficits in purple and green-yellow regions. No subject with developmental prosopagnosia had impaired hue discrimination. CONCLUSIONS In our subjects with prosopagnosia, dyschromatopsia occurred in those with acquired lesions of the fusiform gyri, usually bilateral but sometimes unilateral. The dyschromatopsic deficit shows mainly an accentuation of normal tritatanopic-like tendencies. These are sometimes accompanied by additional deficits, although these could represent artifacts of the testing procedure.

Perceptual learning of faces: A rehabilitative study of acquired prosopagnosia

Despite many studies of acquired prosopagnosia, there have been only a few attempts at its rehabilitation, all in single cases, with a variety of mnemonic or perceptual approaches, and of variable efficacy. In a cohort with acquired prosopagnosia, we evaluated a perceptual learning program that incorporated variations in view and expression, which was aimed at training perceptual stages of face processing with an emphasis on ecological validity. Ten patients undertook an 11-week face training program and an 11-week control task. Training required shape discrimination between morphed facial images, whose similarity was manipulated by a staircase procedure to keep training near a perceptual threshold. Training progressed from blocks of neutral faces in frontal view through increasing variations in view and expression. Whereas the control task did not change perception, training improved perceptual sensitivity for the trained faces and generalized to new untrained expressions and views of those faces. There was also a significant transfer to new faces. Benefits were maintained over a 3-month period. Training efficacy was greater for those with more perceptual deficits at baseline. We conclude that perceptual learning can lead to persistent improvements in face discrimination in acquired prosopagnosia. This reflects both acquisition of new skills that can be applied to new faces as well as a degree of overlearning of the stimulus set at the level of 3-D expression-invariant representations.

Diagnosing Prosopagnosia: The Utility of Visual Noise in the Cambridge Face Recognition Test

Adding visual noise to facial images has been used to increase reliance on configural processing. Whether this enhances the ability of tests to diagnose prosopagnosia is not known. We examined 15 subjects with developmental prosopagnosia, 13 subjects with acquired prosopagnosia, and 38 control subjects with the Cambridge Face Memory Test. We compared their performance on the second phase, without visual noise, and on the third phase, which adds visual noise. We analyzed the results with signal detection theory methods. The performance of controls worsened more than did that of prosopagnosic subjects when noise was added. The second phase showed better ability to discriminate between prosopagnosic and control subjects than did the third phase. For developmental prosopagnosia, a test using only the 48 trials of the first and second phases yielded sensitivity of 88% and specificity of 91% with a criterion of 33/48 correct, performance characteristics that are similar for a criterion of 43/72 for the whole test. We conclude that a shortened Cambridge Face Memory Test without the noisy images may be a quicker yet equally effective instrument for diagnosing prosopagnosia. The theoretical advantage of noisy images is outweighed by the poorer performance of control subjects with visual noise.

Cross-modal interactions of faces, voices and names in person familiarity

ABSTRACT Person recognition often involves integration of several cues. We asked if familiarity judgments for one cue were influenced by the congruency of pairings with other cues. In a learning phase, subjects studied audiovisual clips of faces, voices and names. A test phase presented uni-modal and bi-modal stimuli. For 10 subjects the bi-modal test stimuli were faces and voices, for 10 faces and names, and for 10 voices and names. In one set of blocks the target was the first modality, and in the other set it was the second. Targets in bi-modal stimuli were paired with either the same or a different identity in the second modality. Face/voice combinations showed congruency effects in reaction time but face/name and voice/name combinations did not. There was no difference between faces modulating target voices and voices modulating target faces. This is consistent with interactions between sensory representations before amodal stages of person recognition.