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

Face naming and recollection represent key memory deficits in developmental prosopagnosia

Previous studies have found that face perception deficits do not fully account for the severity of face recognition deficits in developmental prosopagnosia (DP). Researchers have begun identifying deficient memory mechanisms such as impaired face recollection, but these findings require replication, and further characterization of additional memory deficits is necessary. Our goals were to replicate prior findings of face recollection impairment in DP and extend these findings to assess different types of face associative memory. We had 69 DPs and 99 controls perform a face perception battery as well as three face memory tasks: 1) Old/New task with confidence ratings to calculate recollection and familiarity using ROC analysis, 2) Face/Scene task to examine remember-know judgments and contextual memory for faces, and 3) Face-Name/Occupation task to assess the ability to learn semantic associations with faces. Compared to controls, DPs showed poorer recollection and familiarity across both Old/New and Face/Scene tasks as well as reduced scene accuracy for correct faces. Of these differences, only Old/New recollection remained significant after controlling for group differences in face perception abilities. In the Face-Name/Occupation task, after controlling for face perception, DPs showed poorer recall of names than controls but performed similarly in recalling occupations. Finally, we found that DPs with major, mild, and no face perception deficits showed consistent impairments in Old/New recollection and face-naming, and larger perceptual deficits were associated with larger memory deficits. Together, these results provide several mechanistic insights into the nature of memory deficits in DPs and have diagnostic and treatment implications.

The 2024 Richardson Lecture: Prosopagnosia - A Classic Neurologic Deficit Meets the Modern Era

Acquired prosopagnosia is a rare disorder, but it serves as a model for impairments in expert-level visual processing. This review discusses five key observations made over the past 30 years. First, there are variants, an apperceptive type linked to damage to the inferior occipitotemporal cortex and an amnestic type associated with anterior temporal lesions, both either right or bilateral. Second, these variants are clustered in syndromes with other perceptual deficits, the apperceptive type with field defects, dyschromatopsia and topographagnosia, and the amnestic type with topographagnosia and the auditory disorders of phonagnosia and acquired amusia. Third, extensive testing often shows additional problems with recognizing exemplars of other objects, especially when degrees of expertise are taken into account. Fourth, the prosopagnosic impairment does not affect all facial information. For example, the perception of expression and lip-reading likely depends on other neural substrates than those for processing facial identity. Last, face perception in prosopagnosia is not immutable but can improve with extensive training, though as yet this does not represent a cure for the condition. Continuing work with neural networks and animal models will enhance our understanding of this intriguing condition and what it tells us about how our brains process vision.

The neuropsychological evaluation of face identity recognition

Facial identity recognition (FIR) is arguably the ultimate form of recognition for the adult human brain. Even if the term prosopagnosia is reserved for exceptionally rare brain-damaged cases with a category-specific abrupt loss of FIR at adulthood, subjective and objective impairments or difficulties of FIR are common in the neuropsychological population. Here we provide a critical overview of the evaluation of FIR both for clinicians and researchers in neuropsychology. FIR impairments occur following many causes that should be identified objectively by both general and specific, behavioral and neural examinations. We refute the commonly used dissociation between perceptual and memory deficits/tests for FIR, since even a task involving the discrimination of unfamiliar face images presented side-by-side relies on cortical memories of faces in the right-lateralized ventral occipito-temporal cortex. Another frequently encountered confusion is between specific deficits of the FIR function and a more general impairment of semantic memory (of people), the latter being most often encountered following anterior temporal lobe damage. Many computerized tests aimed at evaluating FIR have appeared over the last two decades, as reviewed here. However, despite undeniable strengths, they often suffer from ecological limitations, difficulties of instruction, as well as a lack of consideration for processing speed and qualitative information. Taking into account these issues, a recently developed behavioral test with natural images manipulating face familiarity, stimulus inversion, and correct response times as a key variable appears promising. The measurement of electroencephalographic (EEG) activity in the frequency domain from fast periodic visual stimulation also appears as a particularly promising tool to complete and enhance the neuropsychological assessment of FIR.

Evidence for a Classical Dissociation between Face and Object Recognition in Developmental Prosopagnosia

It is still a matter of debate whether developmental prosopagnosia is a disorder selective to faces or whether object recognition is also affected. In a previous study, based on a small sample of developmental prosopagnosics (DPs; N = 10), we found impairments in both domains although the difficulties were most pronounced for faces. Importantly, impairments with faces and objects were systematically related. We suggested that that the seemingly disproportional impairment for faces in DP was likely to reflect differences between stimulus categories in visual similarity. Here, we aimed to replicate these findings in a larger, independent sample of DPs (N = 21) using the same experimental paradigms. Contrary to our previous results, we found no disproportional effect of visual similarity on performance with faces or objects in the new DP group when compared to controls (N = 21). The new DP group performed within the control range, and significantly better than the old DP-group, on sensitive and demanding object recognition tasks, and we can demonstrate a classical dissociation between face and object recognition at the group level. These findings are perhaps the strongest evidence yet presented for a face-specific deficit in developmental prosopagnosia.

Face processing in the temporal lobe

Face perception is a socially important but complex process with many stages and many facets. There is substantial evidence from many sources that it involves a large extent of the temporal lobe, from the ventral occipitotemporal cortex and superior temporal sulci to anterior temporal regions. While early human neuroimaging work suggested a core face network consisting of the occipital face area, fusiform face area, and posterior superior temporal sulcus, studies in both humans and monkeys show a system of face patches stretching from posterior to anterior in both the superior temporal sulcus and inferotemporal cortex. Sophisticated techniques such as fMRI adaptation have shown that these face-activated regions show responses that have many of the attributes of human face processing. Lesions of some of these regions in humans lead to variants of prosopagnosia, the inability to recognize the identity of a face. Lesion, imaging, and electrophysiologic data all suggest that there is a segregation between identity and expression processing, though some suggest this may be better characterized as a distinction between static and dynamic facial information.

Selective defects of face familiarity associated to a left temporo-occipital lesion

Acquired prosopagnosia is usually a consequence of bilateral or right hemisphere lesions and is often associated with topographical disorientation and dyschromatopsia. Left temporo-occipital lesions sometimes result in a face recognition disorder but in a context of visual object agnosia with spared familiarity feelings for faces, usually in left-handers. We describe a patient with a left temporo-occipital hemorrhagic lesion unexpectedly resulting in a deficit of face familiarity, which could represent a mild form of associative prosopagnosia. Our patient failed to feel familiarity feelings even with very well-known famous faces but had neither visual object agnosia nor defects with semantics or naming of celebrities. This was confirmed even when the patient was re-tested a year later. We speculate that a graded lateralization of face processing could be at the basis of occasional cases of prosopagnosia.

Voice gender categorization in the connected and disconnected hemispheres

The role of the left and right hemispheres in processing the gender of voices is controversial, some evidence suggesting a bilateral involvement, some others suggesting a right-hemispheric superiority. We investigated this issue in a gender categorization task involving healthy participants and a male split-brain patient: female or male natural voices were presented in one ear during the simultaneous presentation of white noise in the other ear (dichotic listening paradigm). Results revealed faster responses by the healthy participants for stimuli presented in the left than in the right ear, although no asymmetries emerged between the two ears in the accuracy of both the patient and the control group. Healthy participants were also more accurate at categorizing female than male voices, and an opposite-gender bias emerged - at least in females - showing faster responses in categorizing voices of the opposite gender. The results support a bilateral hemispheric involvement in voice gender categorization, without asymmetries in the patient, but with a faster categorization when voices are directly presented to the right hemisphere in the healthy sample. Moreover, when the two hemispheres directly interact with one another, a faster categorization of voices of the opposite gender emerges, and it can be an evolutionary grounded bias.

Looking beyond the face area: lesion network mapping of prosopagnosia

Damage to the right fusiform face area can disrupt the ability to recognize faces, a classic example of how damage to a specialized brain region can disrupt a specialized brain function. However, similar symptoms can arise from damage to other brain regions, and face recognition is now thought to depend on a distributed brain network. The extent of this network and which regions are critical for facial recognition remains unclear. Here, we derive this network empirically based on lesion locations causing clinically significant impairments in facial recognition. Cases of acquired prosopagnosia were identified through a systematic literature search and lesion locations were mapped to a common brain atlas. The network of brain regions connected to each lesion location was identified using resting state functional connectivity from healthy participants (n = 1000), a technique termed lesion network mapping. Lesion networks were overlapped to identify connections common to lesions causing prosopagnosia. Reproducibility was assessed using split-half replication. Specificity was assessed through comparison with non-specific control lesions (n = 135) and with control lesions associated with symptoms other than prosopagnosia (n = 155). Finally, we tested whether our facial recognition network derived from clinically evident cases of prosopagnosia could predict subclinical facial agnosia in an independent lesion cohort (n = 31). Our systematic literature search identified 44 lesions causing prosopagnosia, only 29 of which intersected the right fusiform face area. However, all 44 lesion locations fell within a single brain network defined by connectivity to the right fusiform face area. Less consistent connectivity was found to other face-selective regions. Surprisingly, all 44 lesion locations were also functionally connected, through negative correlation, with regions in the left frontal cortex. This connectivity pattern was highly reproducible and specific to lesions causing prosopagnosia. Positive connectivity to the right fusiform face area and negative connectivity to left frontal regions were independent predictors of prosopagnosia and predicted subclinical facial agnosia in an independent lesion cohort. We conclude that lesions causing prosopagnosia localize to a single functionally connected brain network defined by connectivity to the right fusiform face area and to left frontal regions. Implications of these findings for models of facial recognition deficits are discussed.

Perceptual Function and Category-Selective Neural Organization in Children with Resections of Visual Cortex

The consequences of cortical resection, a treatment for humans with pharmaco-resistant epilepsy, provide a unique opportunity to advance our understanding of the nature and extent of cortical (re)organization. Despite the importance of visual processing in daily life, the neural and perceptual sequellae of occipitotemporal resections remain largely unexplored. Using psychophysical and fMRI investigations, we compared the neural and visuoperceptual profiles of 10 children or adolescents following unilateral cortical resections and their age- and gender-matched controls. Dramatically, with the exception of two individuals, both of whom had relatively greater cortical alterations, all patients showed normal perceptual performance on tasks of intermediate- and high-level vision, including face and object recognition. Consistently, again with the exception of the same two individuals, both univariate and multivariate fMRI analyses revealed normal selectivity and representational structure of category-selective regions. Furthermore, the spatial organization of category-selective regions obeyed the typical medial-to-lateral topographic organization albeit unilaterally in the structurally preserved hemisphere rather than bilaterally. These findings offer novel insights into the malleability of cortex in the pediatric population and suggest that, although experience may be necessary for the emergence of neural category-selectivity, this emergence is not necessarily contingent on the integrity of particular cortical structures.SIGNIFICANCE STATEMENT One approach to reduce seizure activity in patients with pharmaco-resistant epilepsy involves the resection of the epileptogenic focus. The impact of these resections on the perceptual behaviors and organization of visual cortex remain largely unexplored. Here, we characterized the visuoperceptual and neural profiles of ventral visual cortex in a relatively large sample of post-resection pediatric patients. Two major findings emerged. First, most patients exhibited preserved visuoperceptual performance across a wide-range of visual behaviors. Second, normal topography, magnitude, and representational structure of category-selective organization were uncovered in the spared hemisphere. These comprehensive imaging and behavioral investigations uncovered novel evidence concerning the neural representations and visual functions in children who have undergone cortical resection, and have implications for cortical plasticity more generally.

Object recognition in acquired and developmental prosopagnosia

Whether face and object recognition are dissociated in prosopagnosia continues to be debated: a recent review highlighted deficiencies in prior studies regarding the evidence for such a dissociation. Our goal was to study cohorts with acquired and developmental prosopagnosia with a complementary battery of tests of object recognition that address prior limitations, as well as evaluating for residual effects of object expertise. We studied 15 subjects with acquired and 12 subjects with developmental prosopagnosia on three tests: the Old/New Tests, the Cambridge Bicycle Memory Test, and the Expertise-adjusted Test of Car Recognition. Most subjects with developmental prosopagnosia were normal on the Old/New Tests: for acquired prosopagnosia, subjects with occipitotemporal lesions often showed impairments while those with anterior temporal lesions did not. Ten subjects showed a putative classical dissociation between the Cambridge Face and Bicycle Memory Tests, seven of whom had normal reaction times. Both developmental and acquired groups showed reduced car recognition on the expertise-adjusted test, though residual effects of expertise were still evident. Two subjects with developmental prosopagnosia met criteria for normal object recognition across all tests. We conclude that strong evidence for intact object recognition can be found in a few subjects but the majority show deficits, particularly those with the acquired form. Both acquired and developmental forms show residual but reduced object expertise effects.

Individual differences in face identity processing

We investigated the relationships between individual differences in different aspects of face-identity processing, using the Glasgow Face Matching Test (GFMT) as a measure of unfamiliar face perception, the Cambridge Face Memory Test (CFMT) as a measure of new face learning, and the Before They Were Famous task (BTWF) as a measure of familiar face recognition. These measures were integrated into two separate studies examining the relationship between face processing and other tasks. For Study 1 we gathered participants' subjective ratings of their own face perception abilities. In Study 2 we used additional measures of perceptual and cognitive abilities, and personality factors to place individual differences in a broader context. Performance was significantly correlated across the three face-identity tasks in both studies, suggesting some degree of commonality of underlying mechanisms. For Study 1 the participants' self-ratings correlated poorly with performance, reaching significance only for judgements of familiar face recognition. In Study 2 there were few associations between face tasks and other measures, with task-level influences seeming to account for the small number of associations present. In general, face tasks correlated with each other, but did not show an overall relation with other perceptual, cognitive or personality tests. Our findings are consistent with the existence of a general face-perception factor, able to account for around 25% of the variance in scores. However, other relatively task-specific influences are also clearly operating.

Tests of whole upright face processing in prosopagnosia: A literature review

Prosopagnosia refers to an acquired or developmental deficit in face recognition. This neuropsychological impairment has received increasing attention over the last decade, in particular because of an increased scientific interest in developmental prosopagnosia. Studies investigating prosopagnosia have used a variety of different clinical and experimental tests to assess face processing abilities. With such a large variety of assessment methods available, test selection can be challenging. Some previous works have aimed to provide an overview of tests used to diagnose prosopagnosia. However, no overview that is based on a structured review of the literature is available. We review the literature to identify tests that have been used to assess the processing of whole upright faces in acquired and developmental prosopagnosia over the last five years (2013-2017). We not only review tests that have been used for diagnostic purposes, but also tests that have been used for experimental purposes. Tests are categorised according to i) their experimental designs and, ii) the stage of face processing that they assess. On this basis, we discuss considerations regarding test designs for future studies. A visual illustration providing a structured overview of paradigms available for testing the processing of whole upright faces is provided. This visual illustration can be used to inform test selection when designing a study and to apply a structured approach to interpreting findings from the literature. The different approaches to assessment of face processing in prosopagnosia have been necessary and fruitful in generating data and hypotheses about the cause of face processing deficits. However, impairments at different levels of face processing have often been interpreted as reflecting a deficit in the recognition stage of face processing. Based on the data now available on prosopagnosia, we advocate for a more structured approach to assessment, which may facilitate a better understanding of the key deficits in prosopagnosia and of the level(s) of face processing that are impaired.

Damasio's error - Prosopagnosia with intact within-category object recognition

The sudden inability to recognize individual faces following brain damage was first reported in a scientific journal 150 years ago and termed 'prosopagnosia' 70 years ago. While the term originally identified a face-selective neurological condition, it is now obscured by a sequence of imprecisions. First, prosopagnosia is routinely used to define symptoms of individual face recognition (IFR) difficulties in the context of visual object agnosia or other neurological conditions, or even in the normal population. Second, this over-expansive definition has lent support to a long-standing within-category recognition account of prosopagnosia, that is, that the impairment of IFR reflects a general impairment in recognizing within-category objects. However, stringent experimental studies of classical cases of prosopagnosia following brain damage show that their core impairment is not in recognizing physically similar exemplars within non-face object categories. Instead, the impairment presents specifically for recognizing exemplars of the category of faces. Moreover, compared to typical observers, the impairment appears even more severe for recognizing individual faces against physically dissimilar than similar distractors. Here, I argue that we need to limit accordingly our definition of prosopagnosia to a clinical (i.e., neurological) condition in which there is no basic-level object recognition impairment. Other criteria for prosopagnosia are proposed, with the hope that this conservative definition enables the study of human IFR processes in isolation, and supports progress in understanding the nature of these processes.

Congenital prosopagnosia without object agnosia? A literature review

A longstanding controversy concerns the functional organization of high-level vision, and the extent to which the recognition of different classes of visual stimuli engages a single system or multiple independent systems. We examine this in the context of congenital prosopagnosia (CP), a neurodevelopmental disorder in which individuals, without a history of brain damage, are impaired at face recognition. This paper reviews all CP cases from 1976 to 2016, and explores the evidence for the association or dissociation of face and object recognition. Of the 238 CP cases with data permitting a satisfactory evaluation, 80.3% evinced an association between impaired face and object recognition whereas 19.7% evinced a dissociation. We evaluate the strength of the evidence and correlate the face and object recognition behaviour. We consider the implications for theories of functional organization of the visual system, and offer suggestions for further adjudication of the relationship between face and object recognition.

Drawing a distinction between familiar and unfamiliar voice processing: A review of neuropsychological, clinical and empirical findings

Thirty years on from their initial observation that familiar voice recognition is not the same as unfamiliar voice discrimination (van Lancker and Kreiman, 1987), the current paper reviews available evidence in support of a distinction between familiar and unfamiliar voice processing. Here, an extensive review of the literature is provided, drawing on evidence from four domains of interest: the neuropsychological study of healthy individuals, neuropsychological investigation of brain-damaged individuals, the exploration of voice recognition deficits in less commonly studied clinical conditions, and finally empirical data from healthy individuals. All evidence is assessed in terms of its contribution to the question of interest - is familiar voice processing distinct from unfamiliar voice processing. In this regard, the evidence provides compelling support for van Lancker and Kreiman's early observation. Two considerations result: First, the limits of research based on one or other type of voice stimulus are more clearly appreciated. Second, given the demonstration of a distinction between unfamiliar and familiar voice processing, a new wave of research is encouraged which examines the transition involved as a voice is learned.

The problem of being bad at faces

Developmental prosopagnosia has received increased attention in recent years, but as yet has no confirmed genetic or structural markers. It is not certain whether this condition reflects simply the low-end of the spectrum of normal face recognition, an 'under-development', or a pathologic failure to develop such mechanisms, a 'mal-development'. This difference in views creates challenges for the diagnosis of developmental prosopagnosia by behavioural criteria alone, which also vary substantially between studies, with secondary effects on issues such as determining its prevalence. After review of the literature and the problems inherent to diagnoses based solely on behavioural data, we propose as a starting discussion point a set of two primary and four secondary criteria for the diagnosis of developmental prosopagnosia.

Do people have insight into their face recognition abilities?

Diagnosis of developmental or congenital prosopagnosia (CP) involves self-report of everyday face recognition difficulties, which are corroborated with poor performance on behavioural tests. This approach requires accurate self-evaluation. We examine the extent to which typical adults have insight into their face recognition abilities across four experiments involving nearly 300 participants. The experiments used five tests of face recognition ability: two that tap into the ability to learn and recognize previously unfamiliar faces [the Cambridge Face Memory Test, CFMT; Duchaine, B., & Nakayama, K. (2006). The Cambridge Face Memory Test: Results for neurologically intact individuals and an investigation of its validity using inverted face stimuli and prosopagnosic participants. Neuropsychologia, 44(4), 576-585. doi:10.1016/j.neuropsychologia.2005.07.001; and a newly devised test based on the CFMT but where the study phases involve watching short movies rather than viewing static faces-the CFMT-Films] and three that tap face matching [Benton Facial Recognition Test, BFRT; Benton, A., Sivan, A., Hamsher, K., Varney, N., & Spreen, O. (1983). Contribution to neuropsychological assessment. New York: Oxford University Press; and two recently devised sequential face matching tests]. Self-reported ability was measured with the 15-item Kennerknecht et al. questionnaire [Kennerknecht, I., Ho, N. Y., & Wong, V. C. (2008). Prevalence of hereditary prosopagnosia (HPA) in Hong Kong Chinese population. American Journal of Medical Genetics Part A, 146A(22), 2863-2870. doi:10.1002/ajmg.a.32552]; two single-item questions assessing face recognition ability; and a new 77-item meta-cognition questionnaire. Overall, we find that adults with typical face recognition abilities have only modest insight into their ability to recognize faces on behavioural tests. In a fifth experiment, we assess self-reported face recognition ability in people with CP and find that some people who expect to perform poorly on behavioural tests of face recognition do indeed perform poorly. However, it is not yet clear whether individuals within this group of poor performers have greater levels of insight (i.e., into their degree of impairment) than those with more typical levels of performance.