What is developmental about developmental prosopagnosia?

Developmental prosopagnosia (DP) is characterised by difficulties recognising face identities and is associated with diverse co-occurring object recognition difficulties. The high co-occurrence rate and heterogeneity of associated difficulties in DP is an intrinsic feature of developmental conditions, where co-occurrence of difficulties is the rule, rather than the exception. However, despite its name, cognitive and neural theories of DP rarely consider the developmental context in which these difficulties occur. This leaves a large gap in our understanding of how DP emerges in light of the developmental trajectory of face recognition. Here, we argue that progress in the field requires re-considering the developmental origins of differences in face recognition abilities, rather than studying the end-state alone. In practice, considering development in DP necessitates a re-evaluation of current approaches in recruitment, design, and analyses.

The anterior fusiform gyrus: The ghost in the cortical face machine

Face-selective regions in the human ventral occipito-temporal cortex (VOTC) have been defined for decades mainly with functional magnetic resonance imaging. This face-selective VOTC network is traditionally divided in a posterior 'core' system thought to subtend face perception, and regions of the anterior temporal lobe as a semantic memory component of an extended general system. In between these two putative systems lies the anterior fusiform gyrus and surrounding sulci, affected by magnetic susceptibility artifacts. Here we suggest that this methodological gap overlaps with and contributes to a conceptual gap between (visual) perception and semantic memory for faces. Filling this gap with intracerebral recordings and direct electrical stimulation reveals robust face-selectivity in the anterior fusiform gyrus and a crucial role of this region, especially in the right hemisphere, in identity recognition for both familiar and unfamiliar faces. Based on these observations, we propose an integrated theoretical framework for human face (identity) recognition according to which face-selective regions in the anterior fusiform gyrus join the dots between posterior and anterior cortical face memories.

Intracerebral electrical stimulation of the face-selective right lateral fusiform gyrus transiently impairs face identity recognition

Neuroimaging and intracranial electrophysiological studies have consistently shown the largest and most consistent face-selective neural activity in the middle portion of the human right lateral fusiform gyrus ('fusiform face area(s)', FFA). Yet, direct evidence for the critical role of this region in face identity recognition (FIR) is still lacking. Here we report the first evidence of transient behavioral impairment of FIR during focal electrical stimulation of the right FFA. Upon stimulation of an electrode contact within this region, subject CJ, who shows typical FIR ability outside of stimulation, was transiently unable to point to pictures of famous faces among strangers and to match pictures of famous or unfamiliar faces presented simultaneously for their identity. Her performance at comparable tasks with other visual materials (written names, pictures of buildings) remained unaffected by stimulation at the same location. During right FFA stimulation, CJ consistently reported that simultaneously presented faces appeared as being the same identity, with little or no distortion of the spatial face configuration. Independent electrophysiological recordings showed the largest neural face-selective and face identity activity at the critical electrode contacts. Altogether, this extensive multimodal case report supports the causal role of the right FFA in FIR.

The role of visual imagery in face recognition and the construction of facial composites. Evidence from Aphantasia

People with aphantasia have a markedly impaired ability to form visual images in the mind's eye. Here, by testing people with and without aphantasia, we examine the relationship between visual imagery and face processing. We show that aphantasics have weaker face recognition than people with visual imagery, using both self-report (Prosopagnosia Index) and behavioural measures (Cambridge Face Memory Test). However, aphantasics nonetheless have a fully intact ability to construct facial composites from memory (i.e., composites produced using EFIT6 by aphantasics and imagers were rated as equally accurate in terms of their resemblance to a target face). Additionally, we show that aphantasics were less able than imagers to see the resemblance between composites and a target face, suggestive of potential issues with face matching (perception). Finally, we show that holistic and featural methods of composite construction using EFIT6 produce equally accurate composites. Our results suggest that face recognition, but not face composite construction, is facilitated by the ability to represent visual properties as 'pictures in the mind'. Our findings have implications for the study of aphantasia, and also for forensic settings, where face composite systems are commonly used to aid criminal investigations.

No increased prevalence of prosopagnosia in aphantasia: Visual recognition deficits are small and not restricted to faces

Aphantasia and prosopagnosia are both rare conditions with impairments in visual cognition. While prosopagnosia refers to a face recognition deficit, aphantasics exhibit a lack of mental imagery. Current object recognition theories propose an interplay of perception and mental representations, making an association between recognition performance and visual imagery plausible. While the literature assumes a link between aphantasia and prosopagnosia, other impairments in aphantasia have been shown to be rather global. Therefore, we assumed that aphantasics do not solely exhibit impairments in face recognition but rather in general visual recognition performance, probably moderated by stimulus complexity. To test this hypothesis, 65 aphantasics were compared to 55 controls in a face recognition task, the Cambridge Face Memory Test, and a corresponding object recognition task, the Cambridge Car Memory Test. In both tasks, aphantasics performed worse than controls, indicating mild recognition deficits without face-specificity. Additional correlations between imagery vividness and performance in both tasks were found, suggesting that visual imagery influences visual recognition not only in imagery extremes. Stimulus complexity produced the expected moderation effect but only for the whole imagery-spectrum and only with face stimuli. Overall, the results imply that aphantasia is linked to a general but mild deficit in visual recognition.

Dissociations between face identity and face expression processing in developmental prosopagnosia

Individuals with developmental prosopagnosia (DPs) experience severe and lifelong deficits recognising faces, but whether their deficits are selective to the processing of face identity or extend to the processing of face expression remains unclear. Clarifying this issue is important for understanding DP impairments and advancing theories of face processing. We compared identity and expression processing in a large sample of DPs (N = 124) using three different matching tasks that each assessed identity and expression processing with identical experimental formats. We ran each task in upright and inverted orientations and we measured inversion effects to assess the integrity of upright-specific face processes. We report three main results. First, DPs showed large deficits at discriminating identity but only subtle deficits at discriminating expression. Second, DPs showed a reduced inversion effect for identity but a normal inversion effect for expression. Third, DPs' performance on the expression tasks were linked to autism traits, but their performance on the identity tasks were not. These results constitute several dissociations between identity and expression processing in DP, and they are consistent with the view that the core impairment in DP is highly selective to identity.

Provoked overt recognition in acquired prosopagnosia using multiple different images of famous faces

Provoked overt recognition refers to the fact that patients with acquired prosopagnosia can sometimes recognize faces when presented in arrays of individuals from the same category (e.g., actors or politicians). We ask whether a prosopagnosic patient might experience recognition when presented with multiple different images of the same face simultaneously. Over two sessions, patient Herschel, a 66-year-old British man with acquired prosopagnosia, viewed face images individually or in arrays. On several occasions he failed to recognize single photos of an individual but successfully identified that person when the same photos were presented together. For example, Herschel failed to recognize any individual images of King Charles or Paul McCartney but recognised both in arrays of the same photos. Like reports based on category membership, overt recognition was transient and inconsistent. These findings are discussed in terms of models of covert recognition, alongside more recent research on within-person variability for face perception.

Contrasting domain-general and domain-specific accounts in cognitive neuropsychology: An outline of a new approach with developmental prosopagnosia as a case

The backbone of cognitive neuropsychology is the observation of (double) dissociations in performance between patients, suggesting some degree of independence between cognitive processes (domain specificity). In comparison, observations of associations between disorders/deficits have been deemed less evidential in neuropsychological theorizing about cognitive architecture. The reason is that associations can reflect damage to independent cognitive processes that happen to be mediated by structures commonly affected by the same brain disorder rather than damage to a shared (domain-general) mechanism. Here we demonstrate that it is in principle possible to discriminate between these alternatives by means of a procedure involving large unbiased samples. We exemplify the procedure in the context of developmental prosopagnosia (DP), but the procedure is in principle applicable to all neuropsychological deficits/disorders. A simulation of the procedure on a dataset yields estimates of dissociations/associations that are well in line with existing DP-studies, and also suggests that seemingly selective disorders can reflect damage to both domain-general and domain-specific cognitive processes. However, the simulation also highlights some limitations that should be considered if the procedure is to be applied prospectively. The main advantage of the procedure is that allows for examination of both associations and dissociations in the same sample. Hence, it may help even the balance in the use of associations and dissociations as grounds for neuropsychological theorizing.

Normal gaze processing in developmental prosopagnosia

Two key functions in human face perception are gaze discrimination and identity recognition. Here we examine whether gaze discrimination can be intact when identity recognition is impaired in developmental prosopagnosia (DP). We ran a large sample of developmental prosopagnosics (DPs) with a series of gaze discrimination tasks that assess various mechanisms in gaze processing. Experiment 1 (N = 101 DP participants) investigates spatial processing using an abnormal eye gaze detection task and a Wollaston illusion task that measures perceptual integration of eye and head direction. Experiment 2 (N = 45 DP participants) investigates temporal processing using an adaptation task and a serial dependence task. Despite their deficits with identity recognition, DPs performed in the normal range across both experiments. These results demonstrate that gaze discrimination can be normal in DP, and that various mechanisms of gaze processing can be spared when identity recognition is impaired. Our findings clarify the highly selective nature of impairments in DP and provide support for neurocognitive models of face perception with distinct mechanisms for gaze and identity processing.

When two fields collide: Identifying "super-recognisers" for neuropsychological and forensic face recognition research

In the last decade, a novel individual differences approach has emerged across the face recognition literature. While the field has long been concerned with prosopagnosia (the inability to recognise facial identity), it has more recently become clear that there are vast differences in face recognition ability within the typical population. "Super-recognisers" are those individuals purported to reside at the very top of this spectrum. On one hand, these people are of interest to cognitive neuropsychologists who are motivated to explore the commonality of the face recognition continuum, whereas on the other hand, researchers from the forensic face matching field evaluate the implementation of super-recognisers into real-world police and security settings. These two rather different approaches have led to discrepancies in the definition of super-recognisers, and perhaps more fundamentally, the approach to identifying them, resulting in a lack of consistency that prohibits theoretical progress. Here, we review the protocols used in published work to identify super-recognisers, and propose a common definition and screening recommendations that can be adhered to across fields.

Characterizing developmental prosopagnosia beyond face perception: Impaired recollection but intact familiarity recognition

Converging lines of research suggests that many developmental prosopagnosics (DPs) have impairments beyond face perception, but currently no framework exists to characterize these impaired mechanisms. One potential extra-perceptual deficit is that DPs encode/retrieve faces in a distinct manner from controls that does not sufficiently support individuation. To test this possibility, 30 DPs and 30 matched controls performed an old/new face recognition task while providing confidence ratings, to which a model-based ROC analysis was applied. DPs had significantly reduced recollection compared to controls, driven by fewer 'high-confidence target' responses, but intact familiarity. Recollection and face perception ability uniquely predicted objective and subjective prosopagnosia symptoms, together explaining 51% and 56% of the variance, respectively. These results suggest that a specific deficit in face recollection in DP may represent a core aspect of the difficulty in confidently identifying an individual by their face.

Rapid forgetting of faces in congenital prosopagnosia

Congenital prosopagnosia (CP) is a life-long impairment in face recognition that occurs in the absence of any known brain damage. It is still unclear whether this disorder is related to a visual deficit, or to an impairment in encoding, maintaining or retrieving a face from memory. We tested CPs and matched neurotypical controls using a delayed estimation task in which a target face was shown either upright or inverted. Participants were asked to select the target face out of a cyclic space of morphed faces that could either resemble the target face, or not. The inclusion of upright and inverted faces enabled to examine the extent of the face inversion effect, a well-known face specific effect often associated with holistic processing. To enable disentangling visual from mnemonic processing, reports were required either following 1 and 6 sec retention interval, or simultaneously while the target face was still visible. Controls showed slower forgetting of upright compared to inverted faces. In contrast, CPs exhibited rapid forgetting of upright faces that was comparable to their performance and to performance of controls on inverted faces. Such forgetting was evident in random errors in which the selected faces did not resemble the face in memory, implying a time related decrease in the probability to access the correct face in memory. Importantly, CPs exhibited no inversion effect across all retention intervals, including the simultaneous one, suggesting that their abnormal rapid forgetting could be explained by an impairment in holistic visual processing of upright faces.

Meanings in motion and faces: developmental associations between the processing of intention from geometrical animations and gaze detection accuracy

Aspects of face processing, on the one hand, and theory of mind (ToM) tasks, on the other hand, show specific impairment in autism. We aimed to discover whether a correlation between tasks tapping these abilities was evident in typically developing children at two developmental stages. One hundred fifty-four normal children (6-8 years and 16-18 years) and 13 high-IQ autistic children (11-17 years) were tested on a range of face-processing and IQ tasks, and a ToM test based on the attribution of intentional movement to abstract shapes in a cartoon. By midchildhood, the ability accurately and spontaneously to infer the locus of attention of a face with direct or averted gaze was specifically associated with the ability to describe geometrical animations using mental state terms. Other face-processing and animation descriptions failed to show the association. Autistic adolescents were impaired at both gaze processing and ToM descriptions, using these tests. Mentalizing and gaze perception accuracy are associated in typically developing children and adolescents. The findings are congruent with the possibility that common neural circuitry underlies, at least in part, processing implicated in these tasks. They are also congruent with the possibility that autism may lie at one end of a developmental continuum with respect to these skills, and to the factor(s) underpinning them.

Recognition of famous faces in the medial temporal lobe: An invasive ERP study

OBJECTIVE

To investigate the involvement of the rhinal cortex and the hippocampus in the processing of famous faces in contrast to nonfamous faces using intracranial event-related potentials (ERPs), and to analyze repetition effects for famous and nonfamous faces.

METHODS

ERPs were elicited by pictures of famous and nonfamous faces and recorded from rhinal and hippocampal sites of intracranial electrodes in 10 presurgical patients with unilateral medial temporal lobe epilepsy. Famous and nonfamous faces were presented twice and mixed with distorted faces serving as targets. There was no instruction for an overt discrimination between famous and nonfamous faces. In contrast to nonfamous faces, famous faces stimulate processes related with access and retrieval of semantic memory.

RESULTS

All faces evoked anterior medial temporal lobe N400-like (AMTL-N400) potentials in the rhinal cortex and P600-like potentials in the hippocampus. The AMTL-N400 and the hippocampal P600 amplitudes were larger for famous faces than for nonfamous faces. Mean amplitudes of the first and second presentation of famous faces suggest a repetition effect for the rhinal sites; however, they are significant only in the later signal components. No repetition effect was found for nonfamous faces and for potentials from the hippocampus.

CONCLUSION

The anterior medial temporal lobe N400 and the hippocampal P600 may be related to the access and retrieval of person-specific semantic memory.

The effect of trimethoprim on potassium and uric acid metabolism in normal human subjects

BACKGROUND

Trimethoprim used in combination with other antibiotics, has been implicated in causing hyperkalemia and hypouricemia in patients with acquired immune deficiency syndrome (AIDS). In experimental animal models, trimethoprim has been demonstrated to block sodium channels and Na+-K+-ATPase in the distal nephron and thus impair potassium excretion. Although the data from the experimental models suggest that trimethoprim reduces urinary potassium excretion, the retrospective clinical studies have confounding factors that prevent a rigorous demonstration that the hyperkalemia and hypouricemia are due solely to the effects of trimethoprim on solute excretion.

AIM

The purpose of this study was to evaluate the effect of trimethoprim on potassium and uric acid balance in normal human subjects.

METHODS

Five normal human subjects were admitted to the general clinical research center and placed on a fixed metabolic diet. After a 4-day control period, the subjects were given trimethoprim (15 mg/kg/day) orally for 5-7 days followed by a 4-day recovery period. Free-flow blood samples and 24-hour urine collections were obtained daily.

RESULTS

Treatment with trimethoprim resulted in a significant increase in plasma potassium concentration (4.5 +/- 0.1 versus 3.7 +/- 0.1 mmol/l, p < 0.005) and significant decrease in serum uric acid concentration (3.8 +/- 0.4 versus 5.6 +/- 0.5 mg/dl, p < 0.001). Treatment with trimethoprim significantly increased the urinary excretion of uric acid, but did not significantly decrease potassium excretion during the 7-day treatment period. There was, however, a significant decrease in potassium excretion observed during the first 48 hours of trimethoprim treatment. In one subject where repeat studies were performed using different dosages, the effect on potassium and uric acid levels appeared to be dose-dependent.

CONCLUSIONS

Trimethoprim increases plasma potassium concentration probably by reducing urinary potassium excretion. Trimethoprim decreases serum uric acid levels by augmenting urinary uric acid excretion. This uricosuric effect may be due to the ability of trimethoprim to impair urate reabsorption by the urate-anion exchanger in the proximal tubule.

Cognitive intervention in Alzheimer disease: a randomized placebo-controlled study

The efficacy of a cognitive intervention consisting of training in face-name associations, spaced retrieval, and cognitive stimulation was tested in a sample of 37 patients (16 men, 21 women) with probable Alzheimer disease (AD). Patients with AD were randomly assigned to receive either the cognitive intervention or a mock (placebo) intervention for 5 weeks. The placebo group then crossed over to receive the intervention. During the intervention, AD patients showed significant improvement in recall of personal information, face-name recall, and performance on the Verbal Series Attention Test. Improvement did not generalize to additional neuropsychologic measures of dementia severity, verbal memory, visual memory, word generation, or motor speed, or to caregiver-assessed patient quality of life. Results suggest that although face-name training, spaced retrieval, and cognitive stimulation may produce small gains in learning personal information and on a measure of attention, improvement does not generalize to overall neuropsychologic functioning or patient quality of life.

Prosopagnosia

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Prosopagnosia

"And what is the nature of this knowledge or recollection? I mean to ask, Whether a person, who having seen or heard or in any way perceived anything, knows not only that, but has a conception of something else which is the subject, not of the same but of some other kind of knowledge, may not be fairly said to recollect that of which he has the conception?""And when the recollection is derived from like things, then another consideration is sure to arise, which is, Whether the likeness in any degree falls short or not of that which is recollected?" "The Philosophy of Plato" Phaedo (the Jowett translation).