Congenital prosopagnosia is associated with a genetic variation in the oxytocin receptor (OXTR) gene: An exploratory study.

Face-recognition deficits, referred to with the term prosopagnosia (i.e., face blindness), may manifest during development in the absence of any brain injury (from here the term congenital prosopagnosia, CP). It has been estimated that approximately 2.5% of the population is affected by face-processing deficits not depending on brain lesions, and varying a lot in severity. The genetic bases of this disorder are not known. In this study we tested for genetic association between single-nucleotide polymorphisms (SNPs) in the oxytocin receptor gene (OXTR) and CP in a restricted cohort of Italian participants. We found evidence of an association between the common genetic variants rs53576 and rs2254298 OXTR SNPs and prosopagnosia. This association was also found when including an additional group of German individuals classified as prosopagnosic in the analysis. Our preliminary data provide initial support for the involvement of genetic variants of OXTR in a relevant cognitive impairment, whose genetic bases are still largely unexplored.

Guidelines for studying developmental prosopagnosia in adults and children.

Developmental prosopagnosia (DP) is a neurodevelopmental condition characterized by severe face identity recognition problems that results from a failure to develop the mechanisms necessary for adequate face processing (Duchaine BC, Nakayama K. Developmental prosopagnosia: a window to content-specific face processing. Curr Opin Neurobiol 2006, 16:166-173.). It occurs in children and adults with normal visual acuity, and without intellectual impairments or known brain injuries. Given the importance of face recognition in daily life, and the detrimental effects of impaired face recognition, DP is an important area of study. Yet conventions for classifying individuals as DP for research purposes are poorly defined. In this focus paper, we discuss: (1) criteria for an operational definition of DP; 2) tests of face recognition and conventions for classifying individuals as DP; and 3) important considerations regarding common associations and dissociations, and cognitive heterogeneity in DP. We also highlight issues unique to studying DP in children, a relatively new endeavor that is proving to be an important complement to the work with adults. Ultimately, we hope to identify challenges researchers face when studying DP, and offer guidelines for others to consider when embarking on their own research pursuits on the topic. For further resources related to this article, please visit the WIREs website.

Deficits in long-term recognition memory reveal dissociated subtypes in congenital prosopagnosia.

The study investigates long-term recognition memory in congenital prosopagnosia (CP), a lifelong impairment in face identification that is present from birth. Previous investigations of processing deficits in CP have mostly relied on short-term recognition tests to estimate the scope and severity of individual deficits. We firstly report on a controlled test of long-term (one year) recognition memory for faces and objects conducted with a large group of participants with CP. Long-term recognition memory is significantly impaired in eight CP participants (CPs). In all but one case, this deficit was selective to faces and didn't extend to intra-class recognition of object stimuli. In a test of famous face recognition, long-term recognition deficits were less pronounced, even after accounting for differences in media consumption between controls and CPs. Secondly, we combined test results on long-term and short-term recognition of faces and objects, and found a large heterogeneity in severity and scope of individual deficits. Analysis of the observed heterogeneity revealed a dissociation of CP into subtypes with a homogeneous phenotypical profile. Thirdly, we found that among CPs self-assessment of real-life difficulties, based on a standardized questionnaire, and experimentally assessed face recognition deficits are strongly correlated. Our results demonstrate that controlled tests of long-term recognition memory are needed to fully assess face recognition deficits in CP. Based on controlled and comprehensive experimental testing, CP can be dissociated into subtypes with a homogeneous phenotypical profile. The CP subtypes identified align with those found in prosopagnosia caused by cortical lesions; they can be interpreted with respect to a hierarchical neural system for face perception.

Not all patients labeled as "prosopagnosia" have a real prosopagnosia.

Since face recognition is the most powerful source of information for identifying familiar people, patients showing a multimodal defect in people recognition have been sometimes considered as affected by "prosopagnosia"-namely, by a form of visual agnosia, specifically affecting face recognition. In this note we report two anatomoclinical observations and a neuroanatomical study in which an inappropriate use of the term "prosopagnosia" was made, because the person recognition defect was not confined to the visual (face) modality, but also concerned voice and/or name of the target person. The dangers of this inappropriate use of the term prosopagnosia are briefly discussed.

The delusional misidentification syndromes: strange, fascinating, and instructive.

The delusional misidentification syndromes (Capgras' syndrome, Frégoli syndrome, intermetamorphosis syndrome, syndrome of subjective doubles) are rare psychopathologic phenomena that occur primarily in the setting of schizophrenic illness, affective disorder, and organic illness. They are grouped together because they often co-occur and interchange, and their basic theme is the concept of the double (sosie). They are distinguished as hypoidentifications (Capgras' syndrome) and hyperidentifications (the other three syndromes). In this review, we present the basic hypotheses that have been put forward to explain these syndromes and propose that the appearance of these syndromes must alert physicians to investigate the existence of possible organic contributions.

Hereditary prosopagnosia: the first case series.

Prosopagnosia is defined as a specific type of visual agnosia characterised by a discernible impairment in the capacity to recognise familiar people by their faces. We present seven family pedigrees with 38 cases in two to four generations of suspected hereditary prosopagnosia, detected using a screening questionnaire. Men and women are impaired and the anomaly is regularly transmitted from generation to generation in all pedigrees studied. Segregation is best explained by a simple autosomal dominant mode of inheritance, suggesting that loss of human face recognition can occur by the mutation of a single gene. Eight of the 38 affected persons were tested on the Warrington Recognition Memory Test for Faces (RMF; Warrington, 1984), famous and family faces tests, learning tests for internal and external facial features and a measure of mental imagery for face and non-face images. As a group, the eight participants scored significantly below an age- and education-matched comparison group on the most relevant test of face recognition; and all were impaired on at least one of the tests. The results provide compelling evidence for significant genetic contribution to face recognition skills and contribute to the promise offered by the emerging field of cognitive neurogenetics.

A detailed investigation of facial expression processing in congenital prosopagnosia as compared to acquired prosopagnosia.

Whether the ability to recognize facial expression can be preserved in the absence of the recognition of facial identity remains controversial. The current study reports the results of a detailed investigation of facial expression recognition in three congenital prosopagnosic (CP) participants, in comparison with two patients with acquired prosopagnosia (AP) and a large group of 30 neurologically normal participants, including individually age- and gender-matched controls. Participants completed a fine-grained expression recognition paradigm requiring a six-alternative forced-choice response to continua of morphs of six different basic facial expressions (e.g. happiness and surprise). Accuracy, sensitivity and reaction times were measured. The performance of all three CP individuals was indistinguishable from that of controls, even for the most subtle expressions. In contrast, both individuals with AP displayed pronounced difficulties with the majority of expressions. The results from the CP participants attest to the dissociability of the processing of facial identity and of facial expression. Whether this remarkably good expression recognition is achieved through normal, or compensatory, mechanisms remains to be determined. Either way, this normal level of performance does not extend to include facial identity.

[Prosopagnosia: is it a single or a multiple entity?]. / Prosopagnosia: ¿entidad unica o multiple?

INTRODUCTION: The prosopagnosia has generally been defined as an incapacity to recognize familiar faces, or faces previously known, due to certain lesions to certain areas of the cerebral cortex. Yet it seems that there is no universal consensus neither on its definition nor in relation to the specific lesions that might cause it. There seems to be no consensus either around the criteria that might enable us to identify different types of prosopagnosia. OBJECTIVE: We make an attempt to revise the definition of prosopagnosia and to see if it is appropriate to consider it as a single entity or, on the contrary, we are able to differentiate specific types of prosopagnosia according to its origin, brain lesion associated with it or the patients characteristics. On the other hand, we questioned ourselves whether different exams usually utilized for the identification of prosopagnosia in fact measure the same concept. CONCLUSIONS: We propose that we could distinguish different types of prosopagnosia with different clinical characteristics. Then we went on to differentiate between developed prosopagnosias and acquired prosopagnosias by bilateral brain lesion as opposed with those associated with a fundamentally aperceptive deficit, as opposed to those linked with a fundamentally associative deficit. Lastly, we propose that different types of exams of recognition and identification can measure distinct aspects linked to prosopagnosia.

Covert recognition and the neural system for face processing.

In this viewpoint, we discuss the new evidence on covert face recognition in prosopagnosia presented by Bobes et al. (2003, this issue) and by Sperber and Spinnler (2003, this issue). Contrary to earlier hypotheses, both papers agree that covert and overt face recognition are based on the same mechanism. In line with this suggestion, an analysis of reported cases with prosopagnosia indicates that a degree of successful encoding of facial representations is a prerequisite for covert recognition to occur. While we agree with this general conclusion as far as Bobes et al.'s and Sperber and Spinnler's data are concerned, we also discuss evidence for a dissociation between different measures of covert recognition. Specifically, studies in patients with Capgras delusion and patients with prosopagnosia suggest that skin conductance and behavioural indexes of covert face recognition are mediated by partially different mechanisms. We also discuss implications of the new data for models of normal face recognition that have been successful in simulating covert recognition phenomena (e.g., Young and Burton, 1999, and O'Reilly et al., 1999). Finally, in reviewing recent neurophysiological and brain imaging evidence concerning the neural system for face processing, we argue that the relationship between ERP components (specifically, N170, N250r, and N400) and different cognitive processes in face recognition is beginning to emerge.

[Prosopagnosia]. / Prosopagnosie.

True prosopagnosy preserves the perception of human faces. However, the latter faces cannot be identified even by patients who have kept an intact implicit recognition. After a thorough examination of the visual recognition disorder, other kinds of information may be involved like, on one hand, those of places, landscapes and building constructions or, on the other hand, those of animals. We observed that a transitorily prosopagnosic farmer was definitively unable to recognize his cows. Arguments for a right hemisphere dominance are discussed.

[Impaired recognition of faces: implicit recognition, feeling of familiarity, role of each hemisphere]. / Troubles de la reconnaissance des visages: reconnaissance implicite, sentiment de familiarité, rôle de chaque hémisphère.

We report three observations of patients who suffered from impaired face recognition following cerebral lesions. Two had classical prosopagnosia, resulting from bilateral in one case and right unilateral occipito-temporal in the other. They could not differentiate famous face from unknown ones, and did not feel any familiarity. The third patient has a normal feeling of knowing, could distinguish between familiar and unfamiliar faces, but was unable to evoke any biographical information about the personalities. Prosopagnosic patients demonstrated, in an experimental condition of learning face-name pairs, implicit knowledge. We assume that these capacities were dependent of the activation of networks coding familiar faces in memory. Mental imagery of faces were normal in theses two cases. In addition, stimulation of mental imagery in the first patient improved implicit knowledge in forced choice tasks. These cases throws a light on the respective role of each hemisphere in face recognition. The right hemisphere is advantaged in perceptual analysis, and activates, from the perceived faces, mnestic systems which codes for previously encountered faces. It generates feeling of familiarity, probably by the way of specific systems which differs from, and completes, those allowing identification. The left hemisphere enable access to semantic-biographic knowledge in a conscious, verbal and explicit way.