What is the prevalence of developmental prosopagnosia? An empirical assessment of different diagnostic cutoffs.

The prevalence of developmental prosopagnosia (DP), lifelong face recognition deficits, is widely reported to be 2-2.5%. However, DP has been diagnosed in different ways across studies, resulting in differing prevalence rates. In the current investigation, we estimated the range of DP prevalence by administering well-validated objective and subjective face recognition measures to an unselected web-based sample of 3116 18-55 year-olds and applying DP diagnostic cutoffs from the last 14 years. We found estimated prevalence rates ranged from .64-5.42% when using a z-score approach and .13-2.95% when using a percentile approach, with the most commonly used cutoffs by researchers having a prevalence rate of .93% (z-score, .45% when using percentiles). We next used multiple cluster analyses to examine whether there was a natural grouping of poorer face recognizers but failed to find consistent grouping beyond those with generally above versus below average face recognition. Lastly, we investigated whether DP studies with more relaxed diagnostic cutoffs were associated with better performance on the Cambridge Face Perception Test. In a sample of 43 studies, there was a weak nonsignificant association between greater diagnostic strictness and better DP face perception accuracy (Kendall's tau-b correlation, τb =.18 z-score; τb = .11 percentiles). Together, these results suggest that researchers have used more conservative DP diagnostic cutoffs than the widely reported 2-2.5% prevalence. We discuss the strengths and weaknesses of using more inclusive cutoffs, such as identifying mild and major forms of DP based on DSM-5.

The definition and diagnosis of developmental prosopagnosia.

Over the last 20 years much attention in the field of face recognition has been directed towards the study of developmental prosopagnosia (DP), with some authors investigating the behavioural characteristics of the condition, and many others using these individuals to further our theoretical understanding of the typical face-processing system. It is broadly agreed that the term "DP" refers to people who have failed to develop the ability to recognize faces in the absence of neurological illness or injury, yet more precise terminology in relation to potential subtypes of the population are yet to be confirmed. Furthermore, specific diagnostic techniques and inclusion and exclusion criteria have yet to be uniformly accepted across the field, making cross-paper comparisons and meta-analyses very difficult. This paper presents an overview of the current challenges that face research into DP and introduces a series of papers that attempt to further our understanding of the condition's characteristics. It is hoped that this special issue will provide a springboard for further research addressing these issues, improving the current state of the art by ensuring the quality of theoretical investigations into DP, and by posing advances that will assist those who have the condition.

Prevalence of face recognition deficits in middle childhood.

Approximately 2-2.5% of the adult population is believed to show severe difficulties with face recognition, in the absence of any neurological injury-a condition known as developmental prosopagnosia (DP). However, to date no research has attempted to estimate the prevalence of face recognition deficits in children, possibly because there are very few child-friendly, well-validated tests of face recognition. In the current study, we examined face and object recognition in a group of primary school children (aged 5-11 years), to establish whether our tests were suitable for children and to provide an estimate of face recognition difficulties in children. In Experiment 1 (n = 184), children completed a pre-existing test of child face memory, the Cambridge Face Memory Test-Kids (CFMT-K), and a bicycle test with the same format. In Experiment 2 (n = 413), children completed three-alternative forced-choice matching tasks with faces and bicycles. All tests showed good psychometric properties. The face and bicycle tests were well matched for difficulty and showed a similar developmental trajectory. Neither the memory nor the matching tests were suitable to detect impairments in the youngest groups of children, but both tests appear suitable to screen for face recognition problems in middle childhood. In the current sample, 1.2-5.2% of children showed difficulties with face recognition; 1.2-4% showed face-specific difficulties-that is, poor face recognition with typical object recognition abilities. This is somewhat higher than previous adult estimates: It is possible that face matching tests overestimate the prevalence of face recognition difficulties in children; alternatively, some children may "outgrow" face recognition difficulties.

Face recognition in patients with migraine.

OBJECTIVES: Prosopagnosia is a rare dysfunction seen during the aura phase of migraine. We aimed to evaluate the face recognition, which has not previously been investigated in migraineurs during the interictal period, and its relationships with clinical features. METHODS: Seventy-four migraineurs, with or without aura, diagnosed according to the International Headache Society criteria and 37 healthy control subjects were included. Benton face recognition test (BFRT) and judgment of line orientation test (LOT) for complex visual perception were applied to all participants. RESULTS: Migraineurs showed significantly lower performance in both of the BFRT and LOT scores (P = 0.027; P = 0.014, respectively), indicating impaired visuospatial perception. In the subgroup analysis, these impairments were more pronounced in the group with migraine without aura. CONCLUSION: Migraineurs had poorer performance in both face recognition and visuospatial perception. These findings could be based on functional differences in the migraineurs' brain or genetic changes.

Low scores on the Benton Facial Recognition Test associated with vertebrobasilar insufficiency.

BACKGROUND: Decreased posterior cerebral circulation has been observed in patients with vertebrobasilar insufficiency (VBI). Reduced cerebral perfusion may have an impact on mental performance as measured by the Benton Facial Recognition Test (BFRT). We evaluated the usefulness of BFRT in identifying cognitive decline in patients with VBI by correlating test performance with total blood flow in the vertebrobasilar system and other variables such as educational level and gender. MATERIALS AND METHODS: Thirty-three participants without dementia (mini-mental state examination; MMSE >27) and cranial magnetic resonance imaging abnormality, but with atherosclerotic risk factors were involved in the study. Nineteen subjects had a total vertebrobasilar flow volume less than 200 ml/min (Group I), and 14 subjects had a flow volume more than 200 ml/min (Group II). RESULTS: The groups were similar in regard to gender, age, and educational level. BFRT results were 19.53 ± 3.12 and 22.36 ± 2.73 for Groups I and II, respectively (p=0.01). The educational level was the main factor affecting the BFRT score in Group I (p=0.04). DISCUSSION: BFRT is clearly impaired in VBI as measured by Doppler ultrasound examination. We concluded that the test appears to adequately distinguish cognitive levels between VBI and other patients. Additionally, our results suggest that education is associated with BFRT results, and for normative purposes, gender consideration is unnecessary. Further studies are needed to investigate the association between VBI and memory dysfunction in early dementia.

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Comment on prevalence of hereditary prosopagnosia (HPA) in Hong Kong Chinese population.

Kennerknecht et al. [Kennerknecht et al. (2008); Am J Med Genet Part A 146A] estimate that 1.9% of the Chinese population are hereditary prosopagnosics. I discuss concerns about their assumption that the great majority of prosopagnosia resulting from developmental problems are heritable and present data from my laboratory that suggests that a considerable proportion of developmental prosopagnosics do not have relatives who share their face recognition deficits.

Prevalence of hereditary prosopagnosia (HPA) in Hong Kong Chinese population.

Prosopagnosia (PA), or the inability to recognize a familiar person by the face alone, had been considered to be a rare dysfunction mainly acquired by trauma to the brain. Recently we have shown that the congenital form of PA, which was considered to be even rarer, is common in Caucasians, with a prevalence of 2.5%. As these cases were familial we coined the term Hereditary Prosopagnosia (HPA). The present study is the first systematic screening for HPA in a defined population of ethnic Chinese. In 2004-2005, 533 out of around 750 medical students of The University of Hong Kong took part in a questionnaire-based screening. The responses of 133 students indicated that they were likely to be candidates for PA. One hundred twenty agreed for diagnostic interview. Finally we made the clinical diagnosis of PA in 10 subjects. A prevalence of 1.88% (95% CI, 1.05-2.71) is established which is in the same range as in Caucasians. We took a detailed family history of four index prosopagnosic persons and were able to further investigate the families of four probands. Each had other first-degree relatives with the same visual cognitive dysfunction. Thus, as in the Caucasians, regular autosomal dominant inheritance might best explain the segregation pattern.

Impaired medial temporal repetition suppression is related to failure of parietal deactivation in Alzheimer disease.

OBJECTIVES: Neural networks supporting encoding of new information are affected early in the course of Alzheimer disease (AD). Functional magnetic resonance imaging (fMRI) studies in AD have reported decreased medial temporal lobe (MTL) activation when comparing novel versus repeated stimuli. It is, however, unclear whether this finding is related to a failure of normal suppression of MTL activity to repeated stimuli in AD. DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS: Twenty-nine healthy older subjects comprising a comparison group (OC) and 15 mild AD patients underwent fMRI during an associative memory paradigm in an academic medical center. The task consisted of blocks of Novel and Repeated face-name pairs and visual Fixation. To reveal neural correlates of processing repeatedly presented stimuli, Repeated blocks were contrasted to Fixation. RESULTS: AD patients demonstrated greater activation during Repeated stimuli in the MTL and in prefrontal and superior parietal cortices, compared with OC. In contrast, OC showed greater parietal task-induced deactivation than AD. Increased MTL activity during Repeated was correlated with more impaired parietal deactivation and poorer performance of the postscan recognition memory test of encoding the face-name pairs. CONCLUSION: Reduction of MTL activity to repeated stimuli, which become highly familiarized to healthy OC, was impaired in AD. This abnormal increased MTL activation was related to disrupted parietal deactivation and to poor recognition memory performance. These preliminary results suggest that the typical episodic memory impairment seen in mild AD may manifest as a failure of normal repetition suppression and loss of "beneficial" deactivation in the MTL-parietal memory networks.

Migraine aura and related phenomena: beyond scotomata and scintillations.

Migraine affects the cortical physiology and may induce dysfunction both ictally and interictally. Although visual symptoms predominate during aura, other contiguous cortical areas related to less impressive symptoms are also impaired in migraine. Answers from 72.2% migraine with aura and 48.6% of migraine without aura patients on human faces and objects recognition, colour perception, proper names recalling and memory in general showed dysfunctions suggestive of prosopagnosia, dyschromatopsia, ideational apraxia, alien hand syndrome, proper name anomia or aphasia, varying in duration and severity. Symptoms frequently occurred in a successively building-up pattern fitting with the geographical distribution of the various cortical functions. When specifically inquired, migraineurs reveal less evident symptoms that are not usually considered during routine examination. Spreading depression most likely underlies the aura symptoms progression. Interictal involvement indicates that MWA and MWoA are not completely silent outside attacks, and that both subforms of migraine may share common mechanisms.

No global processing deficit in the Navon task in 14 developmental prosopagnosics.

Faces are represented in a more configural or holistic manner than other objects. Substantial evidence indicates that this representation results from face-specific mechanisms, but some have argued that it is produced by configural mechanisms that can be applied to many objects including words. The face-specific hypothesis predicts that non-face configural processes will often be normal in prosopagnosic subjects, whereas the domain-general configural hypothesis predicts they will be deficient on all configural tasks. Although the weight of the evidence favors the face-specific hypothesis, a recent study reopened this issue when it was found that three out of five developmental prosopagnosics showed a larger local processing bias than controls in a global-local task (i.e. a Navon task). To examine this issue more thoroughly we tested a significantly larger sample of prosopagnosics (14 participants) who had severe face memory and face perception deficits. In contrast to the previous report, the developmental prosopagnosics performed normally in the global-local task. Like controls, they showed a typical global advantage and typical global-to-local consistency effects. The results demonstrate that the configural processing required by the Navon task is dissociable from face configural processing.

Hereditary prosopagnosia (HPA): the first report outside the Caucasian population.

Prosopagnosia (PA) or face blindness is characterized by a deficiency in identifying familiar faces. Almost all reports are single cases or collections of unrelated patients who acquired prosopagnosia after brain injuries, strokes or atrophy of at least the right occipito-temporal cortex. Until 2001, the inborn form - in the absence of any brain lesions - was described in fewer than 20 probands exclusively of Caucasian origin. We recently found that in the German Caucasian population, congenital prosopagnosia has a very high prevalence of at least 2.5% and that it is genetically determined. It is best described by autosomal-dominant inheritance in the more than 50 families investigated. We therefore introduced the term non-syndromic hereditary PA for the congenital form of a monosymptomatic or isolated PA. This surprisingly high frequency in the Caucasian population prompted us to extend our search to other ethnic groups. We performed a questionnaire-based screening among 198 native Indian students at Banaras Hindu University in Varanasi. In a then selected subset, we found after further detailed diagnostic interviews one Bengali female student with visual agnosia for face recognition only. Several other members of her large family reported the same impairment of face recognition. The segregation pattern of PA in this family is also compatible with autosomal-dominant inheritance.

First report of prevalence of non-syndromic hereditary prosopagnosia (HPA).

Acquired prosopagnosia (PA) is a rare condition after, for example, a stroke or brain injury. The congenital form of PA is generally considered to be even less common. Beside a few single case reports and anecdotal mentioning of familial cases no data on the epidemiology exists. Following a questionnaire-based screening in local secondary schools and at our medical faculty, candidates suspicious for PA underwent a semi-structured interview followed by examinations of first degree relatives. Among 689 local pupils and medical students of our university we found 17 with congenital PA. This corresponds to a prevalence rate of 2.47% (95% CI 1.31-3.63). The frequency is among the highest known for a monogenic disorder. All those index subjects (n = 14) of the target group who agreed to further examinations of their family members had other first degree relatives with the same cognitive disorder. This study provides epidemiological evidence that congenital PA is a very common cognitive disorder which almost always runs in families. The segregation pattern of this hereditary prosopagnosia (HPA) is fully compatible with autosomal dominant inheritance.

Prevalence and correlates of face recognition impairments after acquired brain injury.

Impairments of face recognition after acquired brain injury (ABI) are not restricted to prosopagnosia but commonly arise in association with other cognitive deficits and can be psychosocially debilitating. Despite this, the prevalence and cognitive concomitants of such impairments after ABI have not been systematically investigated. We tested 91 adults with ABI on a range of cognitive measures including several indices of face recognition and learning. The proportion of patients who show impaired performance varied across face learning/recognition tests between 21% and 80%. Principal components analyses indicated orthogonality between impairments of "directed facial processing", associated with memory and visuoperceptual deficits and manifest in slow learning and matching of previously unfamiliar faces, and of "face identification", associated with deficits on verbal tests and manifest in difficulty in naming famous faces. Theoretical and rehabilitative implications are considered.

Covert processing of faces in prosopagnosia is restricted to facial expressions: evidence from cross-modal bias.

We present a single case study of a brain-damaged patient, AD, suffering from visual face and object agnosia, with impaired visual perception and preserved mental imagery. She is severely impaired in all aspects of overt recognition of faces as well as in covert recognition of familiar faces. She shows a complete loss of processing facial expressions in recognition as well as in matching tasks. Nevertheless, when presented with a task where face and voice expressions were presented concurrently, there was a clear impact of face expressions on her ratings of the voice. The cross-modal paradigm used here and validated previously with normal subjects (de Gelder & Vroomen, 1995, 2000), appears as a useful tool in investigating spared covert face processing in a neuropsychological perspective, especially with prosopagnosic patients. These findings are discussed against the background of different models of the covert recognition of face expressions.