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.

Investigating the Influence of Autism Spectrum Traits on Face Processing Mechanisms in Developmental Prosopagnosia.

Autism traits are common exclusionary criteria in developmental prosopagnosia (DP) studies. We investigated whether autism traits produce qualitatively different face processing in 43 DPs with high vs. low autism quotient (AQ) scores. Compared to controls (n = 27), face memory and perception were similarly deficient in the high- and low-AQ DPs, with the high-AQ DP group additionally showing deficient face emotion recognition. Task-based fMRI revealed reduced occipito-temporal face selectivity in both groups, with high-AQ DPs additionally demonstrating decreased posterior superior temporal sulcus selectivity. Resting-state fMRI showed similar reduced face-selective network connectivity in both DP groups compared with controls. Together, this demonstrates that high- and low-AQ DP groups have very similar face processing deficits, with additional facial emotion deficits in high-AQ DPs.

Perception of musical pitch in developmental prosopagnosia.

Studies of developmental prosopagnosia have often shown that developmental prosopagnosia differentially affects human face processing over non-face object processing. However, little consideration has been given to whether this condition is associated with perceptual or sensorimotor impairments in other modalities. Comorbidities have played a role in theories of other developmental disorders such as dyslexia, but studies of developmental prosopagnosia have often focused on the nature of the visual recognition impairment despite evidence for widespread neural anomalies that might affect other sensorimotor systems. We studied 12 subjects with developmental prosopagnosia with a battery of auditory tests evaluating pitch and rhythm processing as well as voice perception and recognition. Overall, three subjects were impaired in fine pitch discrimination, a prevalence of 25% that is higher than the estimated 4% prevalence of congenital amusia in the general population. This was a selective deficit, as rhythm perception was unaffected in all 12 subjects. Furthermore, two of the three prosopagnosic subjects who were impaired in pitch discrimination had intact voice perception and recognition, while two of the remaining nine subjects had impaired voice recognition but intact pitch perception. These results indicate that, in some subjects with developmental prosopagnosia, the face recognition deficit is not an isolated impairment but is associated with deficits in other domains, such as auditory perception. These deficits may form part of a broader syndrome which could be due to distributed microstructural anomalies in various brain networks, possibly with a common theme of right hemispheric predominance.

Voice Recognition in Face-Blind Patients.

Right or bilateral anterior temporal damage can impair face recognition, but whether this is an associative variant of prosopagnosia or part of a multimodal disorder of person recognition is an unsettled question, with implications for cognitive and neuroanatomic models of person recognition. We assessed voice perception and short-term recognition of recently heard voices in 10 subjects with impaired face recognition acquired after cerebral lesions. All 4 subjects with apperceptive prosopagnosia due to lesions limited to fusiform cortex had intact voice discrimination and recognition. One subject with bilateral fusiform and anterior temporal lesions had a combined apperceptive prosopagnosia and apperceptive phonagnosia, the first such described case. Deficits indicating a multimodal syndrome of person recognition were found only in 2 subjects with bilateral anterior temporal lesions. All 3 subjects with right anterior temporal lesions had normal voice perception and recognition, 2 of whom performed normally on perceptual discrimination of faces. This confirms that such lesions can cause a modality-specific associative prosopagnosia.

Developmental phonagnosia: Neural correlates and a behavioral marker.

A 20-year old female, AN, with no history of neurological events or detectable lesions, was markedly poorer than controls at identifying her most familiar celebrity voices. She was normal at face recognition and in discriminating which of two speakers uttered a particular sentence. She evidences normal fMRI sensitivity for human speech and non-speech sounds. AN, and two other phonagnosics, were unable to imagine the voices of highly familiar individuals. A region in the ventromedial prefrontal cortex (vmPFC) was differentially activated in controls when imagining familiar celebrity voices compared to imagining non-voice sounds. AN evidenced no differential activation in this area, which has been termed a person identity semantic system. Rather than a deficit in the representation of voice-individuating cues, AN may be unable to associate those cues to the identity of a familiar person. In this respect, the deficit in developmental phonagnosia may bear a striking parallel to developmental prosopagnosia.

Holistic face training enhances face processing in developmental prosopagnosia.

Prosopagnosia has largely been regarded as an untreatable disorder. However, recent case studies using cognitive training have shown that it is possible to enhance face recognition abilities in individuals with developmental prosopagnosia. Our goal was to determine if this approach could be effective in a larger population of developmental prosopagnosics. We trained 24 developmental prosopagnosics using a 3-week online face-training program targeting holistic face processing. Twelve subjects with developmental prosopagnosia were assessed before and after training, and the other 12 were assessed before and after a waiting period, they then performed the training, and were then assessed again. The assessments included measures of front-view face discrimination, face discrimination with view-point changes, measures of holistic face processing, and a 5-day diary to quantify potential real-world improvements. Compared with the waiting period, developmental prosopagnosics showed moderate but significant overall training-related improvements on measures of front-view face discrimination. Those who reached the more difficult levels of training ('better' trainees) showed the strongest improvements in front-view face discrimination and showed significantly increased holistic face processing to the point of being similar to that of unimpaired control subjects. Despite challenges in characterizing developmental prosopagnosics' everyday face recognition and potential biases in self-report, results also showed modest but consistent self-reported diary improvements. In summary, we demonstrate that by using cognitive training that targets holistic processing, it is possible to enhance face perception across a group of developmental prosopagnosics and further suggest that those who improved the most on the training task received the greatest benefits.

Functional connectivity between face-movement and speech-intelligibility areas during auditory-only speech perception.

It has been proposed that internal simulation of the talking face of visually-known speakers facilitates auditory speech recognition. One prediction of this view is that brain areas involved in auditory-only speech comprehension interact with visual face-movement sensitive areas, even under auditory-only listening conditions. Here, we test this hypothesis using connectivity analyses of functional magnetic resonance imaging (fMRI) data. Participants (17 normal participants, 17 developmental prosopagnosics) first learned six speakers via brief voice-face or voice-occupation training (<2 min/speaker). This was followed by an auditory-only speech recognition task and a control task (voice recognition) involving the learned speakers' voices in the MRI scanner. As hypothesized, we found that, during speech recognition, familiarity with the speaker's face increased the functional connectivity between the face-movement sensitive posterior superior temporal sulcus (STS) and an anterior STS region that supports auditory speech intelligibility. There was no difference between normal participants and prosopagnosics. This was expected because previous findings have shown that both groups use the face-movement sensitive STS to optimize auditory-only speech comprehension. Overall, the present findings indicate that learned visual information is integrated into the analysis of auditory-only speech and that this integration results from the interaction of task-relevant face-movement and auditory speech-sensitive areas.

Galactose uncovers face recognition and mental images in congenital prosopagnosia: the first case report.

A woman in her early 40s with congenital prosopagnosia and attention deficit hyperactivity disorder observed for the first time sudden and extensive improvement of her face recognition abilities, mental imagery, and sense of navigation after galactose intake. This effect of galactose on prosopagnosia has never been reported before. Even if this effect is restricted to a subform of congenital prosopagnosia, galactose might improve the condition of other prosopagnosics. Congenital prosopagnosia, the inability to recognize other people by their face, has extensive negative impact on everyday life. It has a high prevalence of about 2.5%. Monosaccharides are known to have a positive impact on cognitive performance. Here, we report the case of a prosopagnosic woman for whom the daily intake of 5 g of galactose resulted in a remarkable improvement of her lifelong face blindness, along with improved sense of orientation and more vivid mental imagery. All these improvements vanished after discontinuing galactose intake. The self-reported effects of galactose were wide-ranging and remarkably strong but could not be reproduced for 16 other prosopagnosics tested. Indications about heterogeneity within prosopagnosia have been reported; this could explain the difficulty to find similar effects in other prosopagnosics. Detailed analyses of the effects of galactose in prosopagnosia might give more insight into the effects of galactose on human cognition in general. Galactose is cheap and easy to obtain, therefore, a systematic test of its positive effects on other cases of congenital prosopagnosia may be warranted.

A laboratory analogue of mirrored-self misidentification delusion: the role of hypnosis, suggestion, and demand characteristics.

Mirrored-self misidentification is the delusional belief that one's own reflection in the mirror is a stranger. In two experiments, we tested the ability of hypnotic suggestion to model this condition. In Experiment 1, we compared two suggestions based on either the delusion's surface features (seeing a stranger in the mirror) or underlying processes (impaired face processing). Fifty-two high hypnotisable participants received one of these suggestions either with hypnosis or without in a wake control. In Experiment 2, we examined the extent to which social cues and role-playing could account for participants' behaviour by comparing the responses of 14 hypnotised participants to the suggestion for impaired face processing (reals) with those of 14 nonhypnotised participants instructed to fake their responses (simulators). Overall, results from both experiments confirm that we can use hypnotic suggestion to produce a compelling analogue of mirrored-self misidentification that cannot simply be attributed to social cues or role-playing.

Holistic processing of the mouth but not the eyes in developmental prosopagnosia.

Because holistic processing is a hallmark of normal face recognition, we ask whether such processing is reduced in developmental prosopagnosia (DP), and, if so, what the sources are of this deficit. Existing literature provides a mixed picture, with face inversion effects showing consistent holistic processing deficits but unable to locate their source and with some composite face studies showing reduced holistic processing and some not. We addressed this issue more thoroughly with a very large sample of DPs (N = 38) performing the part-whole task, a well-accepted measure of holistic processing that allows for the separate evaluation of individual face parts. Contrary to an expected overall reduction in holistic processing, we found an intact holistic advantage for the mouth and a complete absence of a holistic advantage for the eye region. Less severely impaired prosopagnosics showed significantly more holistic processing of the mouth, suggesting that holistic processing can aid them in recognizing faces.

Perceptual separability of featural and configural information in congenital prosopagnosia.

The deficit in face recognition in individuals with prosopagnosia has often been attributed to an underlying impairment in holistic processing. Exactly what constitutes holistic processing has remained controversial, however. Here, we compare how configural information and featural information interact during face processing in a group of individuals with congenital prosopagnosia (CP) and matched controls. We adopted Amishav and Kimchi's version of Garner's speeded classification task, in which observers classify upright faces based on configural (intereyes and nose-mouth spacing) or featural (shape of eyes, nose, and mouth) information while the other dimension remains constant or varied randomly. We replicated the finding that normal observers evince symmetric Garner interference--failure to selectively attend to features without being influenced by irrelevant variation in configuration, and vice versa--indicating that featural and configural information are integral in normal face processing. In contrast, the CPs showed no Garner interference: They were able to attend to configural information without interference from irrelevant variation in featural information, and they were able to attend to featural information without interference from irrelevant variation in configural information. The absence of Garner interference in CP provides strong evidence that featural information and configural information are perceptually separable in CP's face processing. These findings indicate that CPs do not perceive faces holistically; rather, they process featural and configural information independently.

Visual body recognition in a prosopagnosic patient.

Conspicuous deficits in face recognition characterize prosopagnosia. Information on whether agnosic deficits may extend to non-facial body parts is lacking. Here we report the neuropsychological description of FM, a patient affected by a complete deficit in face recognition in the presence of mild clinical signs of visual object agnosia. His deficit involves both overt and covert recognition of faces (i.e. recognition of familiar faces, but also categorization of faces for gender or age) as well as the visual mental imagery of faces. By means of a series of matching-to-sample tasks we investigated: (i) a possible association between prosopagnosia and disorders in visual body perception; (ii) the effect of the emotional content of stimuli on the visual discrimination of faces, bodies and objects; (iii) the existence of a dissociation between identity recognition and the emotional discrimination of faces and bodies. Our results document, for the first time, the co-occurrence of body agnosia, i.e. the visual inability to discriminate body forms and body actions, and prosopagnosia. Moreover, the results show better performance in the discrimination of emotional face and body expressions with respect to body identity and neutral actions. Since FM's lesions involve bilateral fusiform areas, it is unlikely that the amygdala-temporal projections explain the relative sparing of emotion discrimination performance. Indeed, the emotional content of the stimuli did not improve the discrimination of their identity. The results hint at the existence of two segregated brain networks involved in identity and emotional discrimination that are at least partially shared by face and body processing.

Direct structural connections between voice- and face-recognition areas.

Currently, there are two opposing models for how voice and face information is integrated in the human brain to recognize person identity. The conventional model assumes that voice and face information is only combined at a supramodal stage (Bruce and Young, 1986; Burton et al., 1990; Ellis et al., 1997). An alternative model posits that areas encoding voice and face information also interact directly and that this direct interaction is behaviorally relevant for optimizing person recognition (von Kriegstein et al., 2005; von Kriegstein and Giraud, 2006). To disambiguate between the two different models, we tested for evidence of direct structural connections between voice- and face-processing cortical areas by combining functional and diffusion magnetic resonance imaging. We localized, at the individual subject level, three voice-sensitive areas in anterior, middle, and posterior superior temporal sulcus (STS) and face-sensitive areas in the fusiform gyrus [fusiform face area (FFA)]. Using probabilistic tractography, we show evidence that the FFA is structurally connected with voice-sensitive areas in STS. In particular, our results suggest that the FFA is more strongly connected to middle and anterior than to posterior areas of the voice-sensitive STS. This specific structural connectivity pattern indicates that direct links between face- and voice-recognition areas could be used to optimize human person recognition.

Impaired holistic processing in congenital prosopagnosia.

It has long been argued that face processing requires disproportionate reliance on holistic or configural processing, relative to that required for non-face object recognition, and that a disruption of such holistic processing may be causally implicated in prosopagnosia. Previously, we demonstrated that individuals with congenital prosopagnosia (CP) did not show the normal face inversion effect (better performance for upright compared to inverted faces) and evinced a local (rather than the normal global) bias in a compound letter global/local (GL) task, supporting the claim of disrupted holistic processing in prosopagnosia. Here, we investigate further the nature of holistic processing impairments in CP, first by confirming, in a large sample of CP individuals, the absence of the normal face inversion effect and the presence of the local bias on the GL task, and, second, by employing the composite face paradigm, often regarded as the gold standard for measuring holistic face processing. In this last task, we show that, in contrast with controls, the CP group perform equivalently with aligned and misaligned faces and was impervious to (the normal) interference from the task-irrelevant bottom part of faces. Interestingly, the extent of the local bias evident in the composite task is correlated with the abnormality of performance on diagnostic face processing tasks. Furthermore, there is a significant correlation between the magnitude of the local bias in the GL and performance on the composite task. These results provide further evidence for impaired holistic processing in CP and, moreover, corroborate the critical role of this type of processing for intact face recognition.

Training with own-race faces can improve processing of other-race faces: evidence from developmental prosopagnosia.

Faces of one's own race are discriminated and recognized more accurately than faces of an other race (other-race effect - ORE). Studies have employed several methods to enhance individuation and recognition of other-race faces and reduce the ORE, including intensive perceptual training with other-race faces and explicitly instructing participants to individuate other-race faces. Unfortunately, intensive perceptual training has shown to be specific to the race trained and the use of explicit individuation strategies, though applicable to all races, can be demanding of attention and difficult to consistently employ. It has not yet been demonstrated that a training procedure can foster the automatic individuation of all other-race faces, not just faces from the race trained. Anecdotal evidence from a training procedure used with developmental prosopagnosics (DPs) in our lab, individuals with lifelong face recognition impairments, suggests that this may be possible. To further test this idea, we had five Caucasian DPs perform ten days of configural face training (i.e. attending to small spacing differences between facial features) with own-race (Caucasian) faces to see if training would generalize to improvements with other-race (Korean) faces. To assess training effects and localize potential effects to parts-based or holistic processing, we used the part-whole task using Caucasian and Korean faces (Tanaka, J. W., Kiefer, M., & Bukach, C. M. (2004). A holistic account of the own-race effect in face recognition: evidence from a cross-cultural study. Cognition, 93(1), B1-9). Results demonstrated that after training, DPs showed a disproportionate improvement in holistic processing of other-race faces compared to own-race faces, reducing their ORE. This suggests that configural training with own-race faces boosted DPs' general configural/holistic attentional resources, which they were able to apply to other-race faces. This provides a novel method to reduce the ORE and supports more of an attentional/social-cognitive model of the ORE rather than a strictly expertise model.

Superior voice recognition in a patient with acquired prosopagnosia and object agnosia.

Anecdotally, it has been reported that individuals with acquired prosopagnosia compensate for their inability to recognize faces by using other person identity cues such as hair, gait or the voice. Are they therefore superior at the use of non-face cues, specifically voices, to person identity? Here, we empirically measure person and object identity recognition in a patient with acquired prosopagnosia and object agnosia. We quantify person identity (face and voice) and object identity (car and horn) recognition for visual, auditory, and bimodal (visual and auditory) stimuli. The patient is unable to recognize faces or cars, consistent with his prosopagnosia and object agnosia, respectively. He is perfectly able to recognize people's voices and car horns and bimodal stimuli. These data show a reverse shift in the typical weighting of visual over auditory information for audiovisual stimuli in a compromised visual recognition system. Moreover, the patient shows selectively superior voice recognition compared to the controls revealing that two different stimulus domains, persons and objects, may not be equally affected by sensory adaptation effects. This also implies that person and object identity recognition are processed in separate pathways. These data demonstrate that an individual with acquired prosopagnosia and object agnosia can compensate for the visual impairment and become quite skilled at using spared aspects of sensory processing. In the case of acquired prosopagnosia it is advantageous to develop a superior use of voices for person identity recognition in everyday life.

Face and object imagery in congenital prosopagnosia: a case series.

It has been reported that congenital prosopagnosics may have a general imagery deficit or an imagery deficit specific to faces. However, much of this evidence is based on self-report questionnaires, rather than experimentally based testing (Grüter et al., 2007, 2009). This study tested face and non-face based imagery in a case series of congenital prosopagnosics, utilising both questionnaire based and forced choice accuracy measures. Our findings indicate that all the prosopagnosics showed impaired face based imagery, which contrasted with normal performance on imagery of objects and colours - a pattern that is consistent with reports of acquired prosopagnosia (Barton, 2008; Michelon and Biederman, 2003). Given all our experimentally based testing indicated face imagery impairments, despite no such problems being seen on self-report questionnaires, we would argue that testing based only on the latter must be interpreted with some caution. Overall, we would advocate that our findings demonstrate a category specific visual imagery impairment in congenital prosopagnosia, such that general imagery skill can be intact in such cases.