Prosopagnosia can be associated with damage confined to the right hemisphere--an MRI and PET study and a review of the literature

Does the right hemisphere retain functional characteristics typical of the emotional adaptive system? An evolutionary approach to the problem of brain asymmetries

The right and left hemispheres host two complementary adaptive systems with a right-sided prevalence of automatic and unconscious processing modes, typical of the 'emotional system', and a left-sided prevalence of propositional and conscious processing modes typical of the 'cognitive system' The principal right hemispheric syndromes (and the functioning modes typical of this hemisphere) are, indeed, characterized by automatic and unconscious processing modalities. Thus, the unilateral neglect syndrome discloses a defective automatic (and spared intentional) spatial orienting of attention; face and voice recognition disorders are due to disruption of mechanisms that automatically generate familiarity feelings and anosognosia seems due to the unconscious loss of personal significance attributed by the patient to the pathological event. Since emotions were the only adaptive system existing before the development of language (which is provided of a strong capacity to develop and shape cognition), the persistence in the right hemisphere of mechanisms typical of the emotional system strongly supports an evolutionary model of brain laterality. (160 words).

Prosopagnosia: face blindness and its association with neurological disorders

Loss of facial recognition or prosopagnosia has been well-recognized for over a century. It has been categorized as developmental or acquired depending on whether the onset is in early childhood or beyond, and acquired cases can have degenerative or non-degenerative aetiologies. Prosopagnosia has been linked to involvement of the fusiform gyri, mainly in the right hemisphere. The literature on prosopagnosia comprises case reports and small case series. We aim to assess demographic, clinical and imaging characteristics and neurological and neuropathological disorders associated with a diagnosis of prosopagnosia in a large cohort. Patients were categorized as developmental versus acquired; those with acquired prosopagnosia were further subdivided into degenerative versus non-degenerative, based on neurological aetiology. We assessed regional involvement on [18F] fluorodeoxyglucose-PET and MRI of the right and left frontal, temporal, parietal and occipital lobes. The Intake and Referral Center at the Mayo Clinic identified 487 patients with possible prosopagnosia, of which 336 met study criteria for probable or definite prosopagnosia. Ten patients, 80.0% male, had developmental prosopagnosia including one with Niemann-Pick type C and another with a forkhead box G1 gene mutation. Of the 326 with acquired prosopagnosia, 235 (72.1%) were categorized as degenerative, 91 (27.9%) as non-degenerative. The most common degenerative diagnoses were posterior cortical atrophy, primary prosopagnosia syndrome, Alzheimer's disease dementia and semantic dementia, with each diagnosis accounting for >10% of this group. The most common non-degenerative diagnoses were infarcts (ischaemic and haemorrhagic), epilepsy-related and primary brain tumours, each accounting for >10%. We identified a group of patients with non-degenerative transient prosopagnosia in which facial recognition loss improved or resolved over time. These patients had migraine-related prosopagnosia, posterior reversible encephalopathy syndrome, delirium, hypoxic encephalopathy and ischaemic infarcts. On [18F] fluorodeoxyglucose-PET, the temporal lobes proved to be the most frequently affected regions in 117 patients with degenerative prosopagnosia, while in 82 patients with non-degenerative prosopagnosia, MRI revealed the right temporal and right occipital lobes as most affected by a focal lesion. The most common pathological findings in those with degenerative prosopagnosia were frontotemporal lobar degeneration with hippocampal sclerosis and mixed Alzheimer's and Lewy body disease pathology. In this large case series of patients diagnosed with prosopagnosia, we observed that facial recognition loss occurs across a wide range of acquired degenerative and non-degenerative neurological disorders, most commonly in males with developmental prosopagnosia. The right temporal and occipital lobes, and connecting fusiform gyrus, are key areas. Multiple different pathologies cause degenerative prosopagnosia.

Is Anosognosia for Left-Sided Hemiplegia Due to a Specific Self-Awareness Defect or to a Poorly Conscious Working Mode Typical of the Right Hemisphere?

This review aimed to evaluate whether the association between 'anosognosia for hemiplegia' and lesions of the right hemisphere points to a special self-awareness role of the right side of the brain, or could instead be due to a working mode typical of the right hemisphere. This latter viewpoint is consistent with a recently proposed model of human brain asymmetries that assumes that language lateralization in the left hemisphere might have increased the left hemisphere's level of consciousness and intentionality in comparison with the right hemisphere's less conscious and more automatic functioning. To assess these alternatives, I tried to ascertain whether anosognosia is greater for left-sided hemiplegia than for other disorders provoked by right brain lesions, or whether unawareness prevails in tasks more clearly related to the disruption of the right hemisphere's more automatic (and less conscious) functioning. Data consistent with the first alternative would support the existence of a specific link between anosognosia for hemiplegia and self-awareness, whereas data supporting the second option would confirm the model linking anosognosia to a poorly conscious working mode typical of the right hemisphere. Analysis results showed that the incidence of anosognosia of the highly automatic syndrome of unilateral neglect was greater than that concerning the unawareness of left hemiplegia, suggesting that anosognosia for left-sided hemiplegia might be due to the poorly conscious working mode typical of the right hemisphere.

Why can people with developmental prosopagnosia recognise some familiar faces? Insights from subjective experience

Developmental prosopagnosia is a relatively common visuo-cognitive condition, characterised by impaired facial identity recognition. Impairment severity appears to reside on a continuum, however, it is unknown whether instances of milder deficits reflect the successful use of spontaneous (typical) face recognition strategies, or the application of extraneous compensatory cues to recognition. Here, we explore this issue in two studies. First, 23 adults with developmental prosopagnosia were asked about their use of spontaneous versus compensatory face recognition techniques in everyday life, using a series of closed- and open-ended questions. Second, the same participants performed a computerised famous face recognition task where they were asked to provide reasons why they could make any successful identifications. Findings from both studies suggest that people with developmental prosopagnosia can successfully, and quite frequently, use compensatory strategies to recognition, and that these cues support the majority of instances of preserved familiar face recognition. In contrast, 16 of the 23 participants were able to spontaneously recognise familiar faces on at least some occasions, but there were vast individual differences in frequencies of success. These findings have important implications for our conceptualisation of the condition, as well as for diagnostic practice.

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.

Understanding face matching

Many security settings rely on the identity matching of unfamiliar people, which has led this task to be studied extensively in Cognitive Psychology. In these experiments, observers typically decide whether pairs of faces depict one person (an identity match) or two different people (an identity mismatch). The visual similarity of the to-be-compared faces must play a primary role in how observers accurately resolve this task, but the nature of this similarity-accuracy relationship is unclear. The current study investigated the association between accuracy and facial similarity at the level of individual items (Experiments 1 and 2) and facial features (Experiments 3 and 4). All experiments demonstrate a strong link between similarity and matching accuracy, indicating that this forms the basis of identification decisions. At a feature level, however, similarity exhibited distinct relationships with match and mismatch accuracy. In matches, similarity information was generally shared across the features of a face pair under comparison, with greater similarity linked to higher accuracy. Conversely, features within mismatching face pairs exhibited greater variation in similarity information. This indicates that identity matches and mismatches are characterised by different similarity profiles, which present distinct challenges to the cognitive system. We propose that these identification decisions can be resolved through the accumulation of convergent featural information in matches and the evaluation of divergent featural information in mismatches.

Which components of famous people recognition are lateralized? A study of face, voice and name recognition disorders in patients with neoplastic or degenerative damage of the right or left anterior temporal lobes

We administered to large groups of patients with neoplastic or degenerative damage affecting the right or left ATL, the 'Famous People Recognition Battery' (FPRB), in which subjects are required to recognize the same 40 famous people through their faces, voices and names, to clarify which components of famous people recognition are lateralized. At the familiarity level, we found, as expected, a dissociation between a greater impairment of patients with right ATL lesions on the non-verbal (face and voice) recognition modalities and of those with left ATL lesions on name familiarity. Equally expected were results obtained at the naming level, because the worse naming scores for faces and voices were observed in left-sided patients. Less foregone were, for two reasons, results obtained at the semantic level. First, no difference was found between the two hemispheric groups when scores obtained on the verbal (name) and non-verbal (face and voice) recognition modalities were account for. Second, the face and voice recognition modalities showed a different degree of right lateralization. All groups of patients showed, indeed, both at the familiarity and at the semantic level, a greater difficulty in the recognition of voices regarding faces, but this difference reached significance only in patients with right ATL lesions, suggesting a greater right lateralization of the more complex task of voice recognition. A model aiming to explain the greater right lateralization of the more perceptually demanding voice modality of person recognition is proposed.

Neural dissociation of the acoustic and cognitive representation of voice identity

Recognising a speaker's identity by the sound of their voice is important for successful interaction. The skill depends on our ability to discriminate minute variations in the acoustics of the vocal signal. Performance on voice identity assessments varies widely across the population. The neural underpinnings of this ability and its individual differences, however, remain poorly understood. Here we provide critical tests of a theoretical framework for the neural processing stages of voice identity and address how individual differences in identity discrimination mediate activation in this neural network. We scanned 40 individuals on an fMRI adaptation task involving voices drawn from morphed continua between two personally familiar identities. Analyses dissociated neuronal effects induced by repetition of acoustically similar morphs from those induced by a switch in perceived identity. Activation in temporal voice-sensitive areas decreased with acoustic similarity between consecutive stimuli. This repetition suppression effect was mediated by the performance on an independent voice assessment and this result highlights an important functional role of adaptive coding in voice expertise. Bilateral anterior insulae and medial frontal gyri responded to a switch in perceived voice identity compared to an acoustically equidistant switch within identity. Our results support a multistep model of voice identity perception.

Social gaze in preterm infants may act as an early indicator of atypical lateralization

Visual field biases have been identified as markers of atypical lateralization in children with developmental conditions, but this is the first investigation to consider early lateralized gaze behaviors for social stimuli in preterm infants. Eye-tracking methods with 51 preterm (33 male, 92.1% White) and 61 term-born (31 male, 90.1% White) infants aged 8-10 months from Edinburgh, UK, captured the development of visual field biases, comparing gaze behavior to social and non-social stimuli on the left versus right of the screen. Preterm infants showed a significantly reduced interest to social stimuli on the left versus right compared to term children (d = .58). Preterm children exhibit early differential orienting preferences that may be an early indicator of atypical lateralized function.

Twenty years of investigation with the case of prosopagnosia PS to understand human face identity recognition. Part II: Neural basis

Patient PS sustained her dramatic brain injury in 1992, the same year as the first report of a neuroimaging study of human face recognition. The present paper complements the review on the functional nature of PS's prosopagnosia (part I), illustrating how her case study directly, i.e., through neuroimaging investigations of her brain structure and activity, but also indirectly, through neural studies performed on other clinical cases and neurotypical individuals, inspired and constrained neural models of human face recognition. In the dominant right hemisphere for face recognition in humans, PS's main lesion concerns (inputs to) the inferior occipital gyrus (IOG), in a region where face-selective activity is typically found in normal individuals ('Occipital Face Area', OFA). Her case study initially supported the criticality of this region for face identity recognition (FIR) and provided the impetus for transcranial magnetic stimulation (TMS), intracerebral electrical stimulation, and cortical surgery studies that have generally supported this view. Despite PS's right IOG lesion, typical face-selectivity is found anteriorly in the middle portion of the fusiform gyrus, a hominoid structure (termed the right 'Fusiform Face Area', FFA) that is widely considered to be the most important region for human face recognition. This finding led to the original proposal of direct anatomico-functional connections from early visual cortices to the FFA, bypassing the IOG/OFA (lulu), a hypothesis supported by further neuroimaging studies of PS, other neurological cases and neuro-typical individuals with original visual stimulation paradigms, data recordings and analyses. The proposal of a lack of sensitivity to face identity in PS's right FFA due to defective reentrant inputs from the IOG/FFA has also been supported by other cases, functional connectivity and cortical surgery studies. Overall, neural studies of, and based on, the case of prosopagnosia PS strongly question the hierarchical organization of the human neural face recognition system, supporting a more flexible and dynamic view of this key social brain function.

The rehabilitation of object agnosia and prosopagnosia: A systematic review

BACKGROUND

Agnosia for objects is often overlooked in neuropsychology, especially with respect to rehabilitation. Prosopagnosia has been studied more extensively, yet there have been few attempts at training it. The lack of training protocols may partially be accounted for by their relatively low incidence and specificity to sensory modality. However, finding effective rehabilitations for such deficits may help to reduce their impact on the social and psychological functioning of individuals.

OBJECTIVE

Our aim in this study was to provide clinicians and researchers with useful information with which to conduct new studies on the rehabilitation of object agnosia and prosopagnosia. To accomplish this, we performed a systematic and comprehensive review of the effect of neuropsychological rehabilitation on visual object and prosopagnosia.

METHODS

The Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed. In addition, the Single-Case Experimental Design (SCED) and the Critical Appraisal Skills Programme (CASP) scales were used to assess the quality of reporting.

RESULTS

Seven articles regarding object agnosia, eight articles describing treatments for prosopagnosia, and two articles describing treatments for both deficits were included.

CONCLUSIONS

In the light of the studies reviewed, treatments based on analysis of parts seem effective for object agnosia, while prosopagnosia appears to benefit most from treatments relying on holistic/configural processing. However, more attempts at rehabilitation of face and object agnosia are needed to clarify the mechanisms of these processes and possible rehabilitations. Moreover, a publication bias could mask a broader attempt to find effective treatments for visual agnosia and leaving out studies that are potentially more informative.

Is There a Causal Link between the Left Lateralization of Language and Other Brain Asymmetries? A Review of Data Gathered in Patients with Focal Brain Lesions

This review evaluated if the hypothesis of a causal link between the left lateralization of language and other brain asymmetries could be supported by a careful review of data gathered in patients with unilateral brain lesions. In a short introduction a distinction was made between brain activities that could: (a) benefit from the shaping influences of language (such as the capacity to solve non-verbal cognitive tasks and the increased levels of consciousness and of intentionality); (b) be incompatible with the properties and the shaping activities of language (e.g., the relations between language and the automatic orienting of visual-spatial attention or between cognition and emotion) and (c) be more represented on the right hemisphere due to competition for cortical space. The correspondence between predictions based on the theoretical impact of language on other brain functions and data obtained in patients with lesions of the right and left hemisphere was then assessed. The reviewed data suggest that different kinds of hemispheric asymmetries observed in patients with unilateral brain lesions could be subsumed by common mechanisms, more or less directly linked to the left lateralization of language.

Lesion-behaviour mapping reveals multifactorial neurocognitive processes in recognition memory for unfamiliar faces

Face recognition abilities, which play a critical role in social interactions, involve face processing and identifying familiar faces, but also remembering one-off encounters with previously unfamiliar faces. Previous functional imaging and lesion studies have found evidence for temporal, frontal, and parietal contributions to episodic recognition memory for previously unfamiliar faces. However, the functional contributions of these regions remain unclear. We, therefore, conducted a systematic group analysis of this memory function using lesion-behavior mapping. 95 first-event stroke patients (53 with right- and 42 with left-hemisphere damage) in the sub-acute phase performed the Wechsler Memory Scale (WMS-III) face recognition memory subtest. We analyzed their performance relative to 75 healthy controls, using signal detection measures. To identify brain lesions specifically implicated in face recognition deficits, we used voxel-based lesion-behavior mapping (VLBM; an analysis comparing the performance of participants with and without damage affecting a given voxel). Behavioral analysis disclosed a pronounced impairment in the performance of patients with right hemisphere damage. Frontal damage was associated with an increased amount of false alarms (i.e., failed rejection of new face items) and overly liberal criterion setting, without affecting the recognition of studied faces. In contrast, parietal damage was associated with impaired recognition of studied faces, which was more pronounced in immediate than in delayed retrieval. These findings suggest the existence of multifactorial neurocognitive processes in recognition memory for unfamiliar faces.

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.

Application of Empirical Mode Decomposition for Decoding Perception of Faces Using Magnetoencephalography

Neural decoding is useful to explore the timing and source location in which the brain encodes information. Higher classification accuracy means that an analysis is more likely to succeed in extracting useful information from noises. In this paper, we present the application of a nonlinear, nonstationary signal decomposition technique—the empirical mode decomposition (EMD), on MEG data. We discuss the fundamental concepts and importance of nonlinear methods when it comes to analyzing brainwave signals and demonstrate the procedure on a set of open-source MEG facial recognition task dataset. The improved clarity of data allowed further decoding analysis to capture distinguishing features between conditions that were formerly over-looked in the existing literature, while raising interesting questions concerning hemispheric dominance to the encoding process of facial and identity information.

Prosopagnosia following nonlanguage dominant inferior temporal lobe low-grade glioma resection in which the inferior longitudinal fasciculus was disrupted preoperatively: illustrative case

BACKGROUND

Prosopagnosia is a rare neurological condition characterized by the impairment of face perception with preserved visual processing and cognitive functioning and is associated with injury to the fusiform gyrus and inferior longitudinal fasciculus (ILF). Reports of this clinical impairment following resection of right temporal lobe diffuse gliomas in the absence of contralateral injury are exceedingly scarce and not expected as a complication of surgery.

OBSERVATIONS

The authors describe the case of a young female patient found to have an incidental diffuse glioma in the right inferior temporal lobe despite evidence of preoperative ILF disruption by the tumor. Following resection of the lesion, despite the preoperative disruption to the ILF by the tumor, the patient developed prosopagnosia. There was no evidence of contralateral, left-sided ILF injury.

LESSONS

Given the significant functional impairment associated with prosopagnosia, neurosurgeons should be aware of the exceedingly rare possibility of a visual-processing deficit following unilateral and, in this case, right-sided inferior temporal lobe glioma resections. More investigation is needed to determine whether preoperative testing can determine dominance of facial-processing networks for patients with lesions in the right inferior posterior temporooccipital lobe and whether intraoperative mapping could help prevent this complication.

Reorganization of the Social Brain in Individuals with Only One Intact Cerebral Hemisphere

Social cognition and emotion are ubiquitous human processes that recruit a reliable set of brain networks in healthy individuals. These brain networks typically comprise midline (e.g., medial prefrontal cortex) as well as lateral regions of the brain including homotopic regions in both hemispheres (e.g., left and right temporo-parietal junction). Yet the necessary roles of these networks, and the broader roles of the left and right cerebral hemispheres in socioemotional functioning, remains debated. Here, we investigated these questions in four rare adults whose right (three cases) or left (one case) cerebral hemisphere had been surgically removed (to a large extent) to treat epilepsy. We studied four closely matched healthy comparison participants, and also compared the patient findings to data from a previously published larger healthy comparison sample (n = 33). Participants completed standardized socioemotional and cognitive assessments to investigate social cognition. Functional magnetic resonance imaging (fMRI) data were obtained during passive viewing of a short, animated movie that distinctively recruits two social brain networks: one engaged when thinking about other agents’ internal mental states (e.g., beliefs, desires, emotions; so-called Theory of Mind or ToM network), and the second engaged when thinking about bodily states (e.g., pain, hunger; so-called PAIN network). Behavioral assessments demonstrated remarkably intact general cognitive functioning in all individuals with hemispherectomy. Social-emotional functioning was somewhat variable in the hemispherectomy participants, but strikingly, none of these individuals had consistently impaired social-emotional processing and none of the assessment scores were consistent with a psychiatric disorder. Using inter-region correlation analyses, we also found surprisingly typical ToM and PAIN networks, as well as typical differentiation of the two networks (in the intact hemisphere of patients with either right or left hemispherectomy), based on idiosyncratic reorganization of cortical activation. The findings argue that compensatory brain networks can process social and emotional information following hemispherectomy across different age levels (from 3 months to 20 years old), and suggest that social brain networks typically distributed across midline and lateral brain regions in this domain can be reorganized, to a substantial degree.

Does face-selective cortex show a left visual field bias for centrally-viewed faces?

The left half of a centrally-viewed face contributes more strongly to recognition performance than the right. This left visual field (LVF) advantage is typically attributed to an untested assumption that face-selective cortex in the right hemisphere (RH) exhibits a contralateral bias, even for centrally-viewed faces. We tested the validity of this assumption using a behavioral measure of the LVF advantage and an fMRI experiment that measured laterality of face-selective cortex and neural contralateral bias. In the behavioral experiment, participants performed a chimeric face-matching task (Harrison and Strother, 2019). In the fMRI experiment, participants viewed chimeric faces comprised of face halves that either repeated or changed simultaneously in both hemifields, or repeated in one hemifield and changed in the other. This enabled us to measure lateralization of fMRI face-repetition suppression and hemifield-specific half-face sensitivity in face-selective cortex. We found that LVF bias in the fusiform face area (FFA) and right-lateralization of the FFA for changing versus repeated faces were both positively correlated with a behavioral measure of the LVF advantage for upright (but not inverted) faces. Results from regression analyses showed that LVF bias in the right FFA and FFA laterality make separable contributions to the prediction of our behavioral measure of the LVF bias for upright faces. Our results confirm a ubiquitous but previously untested assumption that RH superiority combined with contralateral bias in face-selective cortex explains the LVF advantage in face recognition. Specifically, our results show that neural LVF bias in the right FFA is sufficient to explain the relationship between FFA laterality and the perceptual LVF bias for centrally-viewed faces.

Personality in Autism Spectrum Disorder: Associations With Face Memory Deficit and Theory of Mind

OBJECTIVE

To examine the personality profiles of adults with autism spectrum disorder (ASD) using a standard personality assessment and to investigate the association between personality, ASD-related face memory deficit (FMD), and theory of mind (ToM). In a broader context, to examine whether there are distinct clinical phenotypes in the ASD population that have implications for personality development and treatment.

METHOD

Fifty-five adults with ASD and 22 neurotypical (NT) adults underwent a battery of neuropsychological tests, including measures of personality, face memory, and ToM. We compared ASD and NT groups in terms of their Personality Assessment Inventory (PAI) profiles. Additional analyses focused on the association between specific PAI scales and FMD. Performance on the Eyes Test was compared across groups and was examined in relation to FMD.

RESULTS

Adults with ASD demonstrated significant elevations on several PAI scales compared with NT adults. The presence of FMD was associated with differing PAI profiles among the ASD adults. The ASD adults with FMD scored significantly higher on scales that are sensitive to positive impression management and treatment rejection and significantly lower on scales that are sensitive to borderline personality, anxiety, depression, schizophrenia, and stress. There was a significant association between performance on the Eyes Test and FMD in the ASD group.

CONCLUSION

Adults with ASD have a unique personality profile. Further, ASD adults with FMD have reduced insight into their difficulties with emotional processing and may not be as sensitive as ASD adults without FMD to the emotions of others.

Visual input to the left versus right eye yields differences in face preferences in 3-month-old infants

From birth, infants prefer looking at faces over scrambled faces. This face input is important for the development of face processing: individuals who experienced early visual deprivation due to congenital cataracts have long-lasting face processing deficits. Interestingly, the deficits are eye-specific such that left eye cataracts disrupt the development of face processing, whereas right eye cataracts do not. This raises the question of whether infant face preferences are driven primarily by faces observed through the left eye. To investigate this, we presented 3-month-old infants with intact faces paired with scrambled faces. Infants viewed the moving stimuli binocularly, only with their left eye, or only with their right eye. Infants viewing stimuli binocularly or with only the left eye spent significantly more time looking at intact faces than scrambled faces, but this effect was equivocal in infants viewing stimuli through only their right eye. Infants in the binocular group had the greatest preference for faces, and this preference was greater than the right eye group's preference for faces. The left eye group's preference for faces was not statistically different from the other two groups' preference for faces, but additional analyses revealed a correlation between preference for faces and age for the right eye group only, indicating that preference for faces seen with the right eye increase from 3 to 4 months of age. These results indicate that the left eye plays a special role in face processing at, or before 3 months of age, but a preference for faces through the right eye emerges soon after.

A clinical-radiological framework of the right temporal variant of frontotemporal dementia

The concept of the right temporal variant of frontotemporal dementia (rtvFTD) is still equivocal. The syndrome accompanying predominant right anterior temporal atrophy has previously been described as memory loss, prosopagnosia, getting lost and behavioural changes. Accurate detection is challenging, as the clinical syndrome might be confused with either behavioural variant FTD (bvFTD) or Alzheimer’s disease. Furthermore, based on neuroimaging features, the syndrome has been considered a right-sided variant of semantic variant primary progressive aphasia (svPPA). Therefore, we aimed to demarcate the clinical and neuropsychological characteristics of rtvFTD versus svPPA, bvFTD and Alzheimer’s disease. Moreover, we aimed to compare its neuroimaging profile against svPPA, which is associated with predominant left anterior temporal atrophy. Of 619 subjects with a clinical diagnosis of frontotemporal dementia or primary progressive aphasia, we included 70 subjects with a negative amyloid status in whom predominant right temporal lobar atrophy was identified based on blinded visual assessment of their initial brain MRI scans. Clinical symptoms were assessed retrospectively and compared with age- and sex-matched patients with svPPA (n = 70), bvFTD (n = 70) and Alzheimer’s disease (n = 70). Prosopagnosia, episodic memory impairment and behavioural changes such as disinhibition, apathy, compulsiveness and loss of empathy were the most common initial symptoms, whereas during the disease course, patients developed language problems such as word-finding difficulties and anomia. Distinctive symptoms of rtvFTD compared to the other groups included depression, somatic complaints, and motor/mental slowness. Aside from right temporal atrophy, the imaging pattern showed volume loss of the right ventral frontal area and the left temporal lobe, which represented a close mirror image of svPPA. Atrophy of the bilateral temporal poles and the fusiform gyrus were associated with prosopagnosia in rtvFTD. Our results highlight that rtvFTD has a unique clinical presentation. Since current diagnostic criteria do not cover specific symptoms of the rtvFTD, we propose a diagnostic tree to be used to define diagnostic criteria and call for an international validation.

Unconscious processing of emotions and the right hemisphere

Many influential authors maintain that, even if emotions are conscious experiences, the processing of information that produces emotions is usually unconscious. This chapter discusses the nonconscious aspects of emotional processing and the critical role played in them by the right hemisphere. This chapter first reviews the studies that have demonstrated the existence of unconscious or subconscious forms of emotional processing and then discusses the data supporting the hypothesis that the right hemisphere is dominant for the processing of emotions. After these topics are reviewed, the chapter will discuss investigations that have shown that the right and left amygdala have different roles in the processing of emotional stimuli, the former being involved in nonconscious and the latter in conscious forms of emotional learning. This chapter will also address the distinction proposed by Freud between "removed" and "nonremoved" forms of unconscious processing and will consider whether "nonremoved preverbal implicit memories" have a preferential link with the right hemisphere. The possibility that the right hemisphere may play a critical role not only in the formation of nonremoved subconscious memories but also in the development of denial phenomena, resulting from dynamic processes of unconscious repression, will also be discussed.

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.

Higher Cortical Visual Disorders

PURPOSE OF REVIEW

This article reviews the disorders that result from disruption of extrastriate regions of the cerebral cortex responsible for higher visual processing. For each disorder, a historical perspective is offered and relevant neuroscientific studies are reviewed.

RECENT FINDINGS

Careful analysis of the consequences of lesions that disrupt visual functions such as facial recognition and written language processing has improved understanding of the role of key regions in these networks. In addition, modern imaging techniques have built upon prior lesion studies to further elucidate the functions of these cortical areas. For example, functional MRI (fMRI) has identified and characterized the response properties of ventral regions that contribute to object recognition and dorsal regions that subserve motion perception and visuospatial attention. Newer network-based functional imaging studies have shed light on the mechanisms behind various causes of spontaneous visual hallucinations.

SUMMARY

Understanding the regions and neural networks responsible for higher-order visual function helps the practicing neurologist to diagnose and manage associated disorders of visual processing and to identify and treat responsible underlying disease.

Learning face perception without vision: Rebound learning effect and hemispheric differences in congenital vs late-onset blindness

To address the longstanding questions of whether the blind-from-birth have an innate face-schema, what plasticity mechanisms underlie non-visual face learning, and whether there are interhemispheric face processing differences in face processing in the blind, we used a unique non-visual drawing-based training in congenitally blind (CB), late-blind (LB) and blindfolded-sighted (BF) groups of adults. This Cognitive-Kinesthetic Drawing approach previously developed by Likova (e.g., 2010, 2012, 2013) enabled us to rapidly train and study training-driven neuroplasticity in both the blind and sighted groups. The five-day two-hour training taught participants to haptically explore, recognize, memorize raised-line images, and draw them free-hand from memory, in detail, including the fine facial characteristics of the face stimuli. Such drawings represent an externalization of the formed memory. Functional MRI was run before and after the training. Tactile-face perception activated the occipito-temporal cortex in all groups. However, the training led to a strong, predominantly left-hemispheric reorganization in the two blind groups, in contrast to right-hemispheric in blindfolded-sighted, i.e., the post-training response-change was stronger in the left hemisphere in the blind, but in the right in the blindfolded. This is the first study to discover interhemispheric differences in non-visual face processing. Remarkably, for face perception this learning-based change was positive in the CB and BF groups, but negative in the LB-group. Both the lateralization and inversed-sign learning effects were specific to face perception, but absent for the control nonface categories of small objects and houses. The unexpected inversed-sign training effect in CB vs LB suggests different stages of brain plasticity in the ventral pathway specific to the face category. Importantly, the fact that only after a very few days of our training, the totally-blind-from-birth CB manifested a very good (haptic) face perception, and even developed strong empathy to the explored faces, implies a preexisting face schema that can be "unmasked" and "tuned up" by a proper learning procedure. The Likova Cognitive-Kinesthetic Training is a powerful tool for driving brain plasticity, and providing deeper insights into non-visual learning, including emergence of perceptual categories. A rebound learning model and a neuro-Bayesian economy principle are proposed to explain the multidimensional learning effects. The results provide new insights into the Nature-vs-Nurture interplay in rapid brain plasticity and neurorehabilitation.

Attending to What and Where: Background Connectivity Integrates Categorical and Spatial Attention

Top-down attention prioritizes the processing of goal-relevant information throughout visual cortex based on where that information is found in space and what it looks like. Whereas attentional goals often have both spatial and featural components, most research on the neural basis of attention has examined these components separately. Here we investigated how these attentional components are integrated by examining the attentional modulation of functional connectivity between visual areas with different selectivity. Specifically, we used fMRI to measure temporal correlations between spatially selective regions of early visual cortex and category-selective regions in ventral temporal cortex while participants performed a task that benefitted from both spatial and categorical attention. We found that categorical attention modulated the connectivity of category-selective areas, but only with retinotopic areas that coded for the spatially attended location. Similarly, spatial attention modulated the connectivity of retinotopic areas only with the areas coding for the attended category. This pattern of results suggests that attentional modulation of connectivity is driven both by spatial selection and featural biases. Combined with exploratory analyses of frontoparietal areas that track these changes in connectivity among visual areas, this study begins to shed light on how different components of attention are integrated in support of more complex behavioral goals.

The left cradling bias: An evolutionary facilitator of social cognition?

A robust left side cradling bias (LCB) in humans is argued to reflect an evolutionarily old left visual field bias and right hemisphere dominance for processing social stimuli. A left visual field bias for face processing, invoked via the LCB, is known to reflect a human population-level right cerebral hemisphere specialization for processing social stimuli. We explored the relationship between cradling side biases, hand dominance and socio-communicative abilities. Four and five year old typically-developing children (N = 98) participated in a battery of manual motor tasks interspersed by cradling trials comprising a(n): infant human doll, infant primate doll, proto-face pillow and no-face pillow. Mean social and communication ability scores were obtained via a survey completed by each child's key teacher. We found a population-level LCB for holding an infant human doll that was not influenced by hand dominance, sex, age or experience of having a younger sibling. Children demonstrating a LCB, did however, obtain a significantly higher mean social ability score compared with their right side cradling counterparts. Like the infant human doll, the proto-face pillow's schematic face symbol was sufficient to elicit a population-level LCB. By contrast, the infant primate doll elicited a population-level right side cradling bias, influenced by both hand dominance and sex. The findings suggest that the LCB is present and visible early in development and is likely therefore, to represent evolutionarily old domain-specific organization and function of the right cerebral hemisphere. Additionally, results suggest that a LCB requires minimal triggering but can be reversed in some situations, possibly in response to species-type or levels of novelty or stress as perceived by the viewer. Patterns of behavioral biases within the context of social stimuli and their associations with cognitive ability are important for understanding how socio-communication abilities emerge in developing children.

Social neuroscience: undoing the schism between neurology and psychiatry

Multiple disorders once jointly conceived as "nervous diseases" became segregated by the distinct institutional traditions forged in neurology and psychiatry. As a result, each field specialized in the study and treatment of a subset of such conditions. Here we propose new avenues for interdisciplinary interaction through a triangulation of both fields with social neuroscience. To this end, we review evidence from five relevant domains (facial emotion recognition, empathy, theory of mind, moral cognition, and social context assessment), highlighting their common disturbances across neurological and psychiatric conditions and discussing their multiple pathophysiological mechanisms. Our proposal is anchored in multidimensional evidence, including behavioral, neurocognitive, and genetic findings. From a clinical perspective, this work paves the way for dimensional and transdiagnostic approaches, new pharmacological treatments, and educational innovations rooted in a combined neuropsychiatric training. Research-wise, it fosters new models of the social brain and a novel platform to explore the interplay of cognitive and social functions. Finally, we identify new challenges for this synergistic framework.

Lingual Gyrus Surface Area Is Associated with Anxiety-Depression Severity in Young Adults: A Genetic Clustering Approach

Here we aimed to identify cortical endophenotypes for anxiety-depression. Our data-driven approach used vertex-wise genetic correlations (estimated from a twin sample: 157 monozygotic and 194 dizygotic twin pairs) to parcellate cortical thickness (CT) and surface area (SA) into genetically homogeneous regions (Chen et al., 2013). In an overlapping twin and sibling sample (n = 834; aged 15–29, 66% female), in those with anxiety-depression Somatic and Psychological Health Report (SPHERE) scores (Hickie et al., 2001) above median, we found a reduction of SA in an occipito-temporal cluster, which comprised part of the right lingual, fusiform and parahippocampal gyrii. A similar reduction was observed in the Human Connectome Project (HCP) sample (n = 890, age 22–37, 56.5% female) in those with Adult Self Report (ASR) DSM-oriented scores (Achenbach et al., 2005) in the 25–95% quantiles. A post hoc vertex-wise analysis identified the right lingual and, to a lesser extent the fusiform gyrus. Overall, the surface reduction explained by the anxiety-depression scores was modest (r = −0.10, 3rd order spline, and r = −0.040, 1st order spline in the HCP). The discordant results in the top 5% of the anxiety-depression scores may be explained by differences in recruitment between the studies. However, we could not conclude whether this cortical region was an endophenotype for anxiety-depression as the genetic correlations did not reach significance, which we attribute to the modest effect size (post hoc statistical power <10%).

Face Processing Systems: From Neurons to Real-World Social Perception

Primate face processing depends on a distributed network of interlinked face-selective areas composed of face-selective neurons. In both humans and macaques, the network is divided into a ventral stream and a dorsal stream, and the functional similarities of the areas in humans and macaques indicate they are homologous. Neural correlates for face detection, holistic processing, face space, and other key properties of human face processing have been identified at the single neuron level, and studies providing causal evidence have established firmly that face-selective brain areas are central to face processing. These mechanisms give rise to our highly accurate familiar face recognition but also to our error-prone performance with unfamiliar faces. This limitation of the face system has important implications for consequential situations such as eyewitness identification and policing.

Development of social systems neuroscience using macaques

This paper reviews the literature on social neuroscience studies using macaques in the hope of encouraging as many researchers as possible to participate in this field of research and thereby accelerate the system-level understanding of social cognition and behavior. We describe how different parts of the primate brain are engaged in different aspects of social information processing, with particular emphasis on the use of experimental paradigms involving more than one monkey in laboratory settings. The description begins with how individual neurons are used for evaluating socially relevant information, such as the identity, face, and focus of attention of others in various social contexts. A description of the neural bases of social reward processing and social action monitoring follows. Finally, we provide several perspectives on novel experimental strategies to help clarify the nature of interacting brains under more socially and ecologically plausible conditions.

Improving fMRI in signal drop-out regions at 7 T by using tailored radio-frequency pulses: application to the ventral occipito-temporal cortex

OBJECTIVE

Signal drop-off occurs in echo-planar imaging in inferior brain areas due to field gradients from susceptibility differences between air and tissue. Tailored-RF pulses based on a hyperbolic secant (HS) have been shown to partially recover signal at 3 T, but have not been tested at higher fields.

MATERIALS AND METHODS

The aim of this study was to compare the performance of an optimized tailored-RF gradient-echo echo-planar imaging (TRF GRE-EPI) sequence with standard GRE-EPI at 7 T, in a passive viewing of faces or objects fMRI paradigm in healthy subjects.

RESULTS

Increased temporal-SNR (tSNR) was observed in the middle and inferior temporal lobes and orbitofrontal cortex of all subjects scanned, but elsewhere tSNR decreased relative to the standard acquisition. In the TRF GRE-EPI, increased functional signal was observed in the fusiform, lateral occipital cortex, and occipital pole, regions known to be part of the visual pathway involved in face-object perception.

CONCLUSION

This work highlights the potential of TRF approaches at 7 T. Paired with a reversed-gradient distortion correction to compensate for in-plane susceptibility gradients, it provides an improved acquisition strategy for future neurocognitive studies at ultra-high field imaging in areas suffering from static magnetic field inhomogeneities.

Intracranial markers of conscious face perception in humans

Investigations of the neural basis of consciousness have greatly benefited from protocols that involve the presentation of stimuli at perceptual threshold, enabling the assessment of the patterns of brain activity that correlate with conscious perception, independently of any changes in sensory input. However, the comparison between perceived and unperceived trials would be expected to reveal not only the core neural substrate of a particular conscious perception, but also aspects of brain activity that facilitate, hinder or tend to follow conscious perception. We take a step towards the resolution of these confounds by combining an analysis of neural responses observed during the presentation of faces partially masked by Continuous Flash Suppression, and those responses observed during the unmasked presentation of faces and other images in the same subjects. We employed multidimensional classifiers to decode physical properties of stimuli or perceptual states from spectrotemporal representations of electrocorticographic signals (1071 channels in 5 subjects). Neural activity in certain face responsive areas located in both the fusiform gyrus and in the lateral-temporal/inferior-parietal cortex discriminated seen vs. unseen faces in the masked paradigm and upright faces vs. other categories in the unmasked paradigm. However, only the former discriminated upright vs. inverted faces in the unmasked paradigm. Our results suggest a prominent role for the fusiform gyrus in the configural perception of faces, and possibly other objects that are holistically processed. More generally, we advocate comparative analysis of neural recordings obtained during different, but related, experimental protocols as a promising direction towards elucidating the functional specificities of the patterns of neural activation that accompany our conscious experiences.

Neural correlates of the eye dominance effect in human face perception: the left-visual-field superiority for faces revisited

Faces are processed best when they are presented in the left visual field (LVF), a phenomenon known as LVF superiority. Although one eye contributes more when perceiving faces, it is unclear how the dominant eye (DE), the eye we unconsciously use when performing a monocular task, affects face processing. Here, we examined the influence of the DE on the LVF superiority for faces using event-related potentials. Twenty left-eye-dominant (LDE group) and 23 right-eye-dominant (RDE group) participants performed the experiments. Face stimuli were randomly presented in the LVF or right visual field (RVF). The RDE group exhibited significantly larger N170 amplitudes compared with the LDE group. Faces presented in the LVF elicited N170 amplitudes that were significantly more negative in the RDE group than they were in the LDE group, whereas the amplitudes elicited by stimuli presented in the RVF were equivalent between the groups. The LVF superiority was maintained in the RDE group but not in the LDE group. Our results provide the first neural evidence of the DE’s effects on the LVF superiority for faces. We propose that the RDE may be more biologically specialized for face processing.

How does reading direction modulate perceptual asymmetry effects?

Left-side bias effects refer to a bias towards the left side of the stimulus/space in perceptual/visuospatial judgments, and are argued to reflect dominance of right hemisphere processing. It remains unclear whether reading direction can also account for the bias effect. Previous studies comparing readers of languages read from left to right with those read from right to left (e.g., French vs. Hebrew) have obtained inconsistent results. As a language that can be read from left to right or from right to left, Chinese provides a unique opportunity for a within-culture examination of reading direction effects. Chinese participants performed a perceptual judgment task (with both face and Chinese character stimuli; Experiment 1) and two visuospatial attention tasks (the greyscales and line bisection tasks; Experiment 2) once before and once after a reading task, in which they read Chinese passages either from left to right or from right to left for about 20 min. After reading from right to left, participants showed significantly reduced left-side bias in Chinese character perceptual judgments but not in the other three tasks. This effect suggests that the role of reading direction on different forms of left-side bias may differ, and its modulation may be stimulus-specific.

Binocular rivalry after right-hemisphere stroke: Effects of attention impairment on perceptual dominance patterns

Binocular rivalry is when perception fluctuates while the stimuli, consisting of different images presented to each eye, remain unchanged. The fluctuation rate and predominance ratio of these images are regarded as information source for understanding properties of consciousness and perception. We administered a binocular rivalry task to 26 right-hemisphere stroke patients and 26 healthy control participants, using stimuli such as simple Gabor anaglyphs. Each single Gabor image was of unequal spatial frequency compared to its counterpart, allowing assessment of the effect of relative spatial frequency on rivalry predominance. Results revealed that patients had significantly decreased alternation rate compared to healthy controls, with severity of patients' attention impairment predicting alternation rates. The patient group had higher predominance ratio for high compared to low relative spatial frequency stimuli consistent with the hypothesis that damage to the right hemisphere may disrupt processing of relatively low spatial frequencies. Degree of attention impairment also predicted the effect of relative spatial frequencies. Lastly, both groups showed increased predominance rates in the right eye compared to the left eye. This right eye dominance was more pronounced in patients than controls, suggesting that right hemisphere stroke may additionally affect eye predominance ratios.

Increased diffusivity in gray matter in recent onset schizophrenia is associated with clinical symptoms and social cognition

INTRODUCTION

Diffusion weighted MRI (dMRI) is a method sensitive to pathological changes affecting tissue microstructure. Most dMRI studies in schizophrenia, however, have focused solely on white matter. There is a possibility, however, that subtle changes in diffusivity exist in gray matter (GM). Accordingly, we investigated diffusivity in GM in patients with recent onset schizophrenia.

METHODS

We enrolled 45 patients and 21 age and sex-matched healthy controls. All subjects were evaluated using the short form of the Wechsler Adult Intelligence Scale, the Positive and Negative Syndrome Scale (PANSS), and the video based social cognition scale. DMRI and T1W images were acquired on a 3 Tesla magnet, and mean Fractional Anisotropy (FA), Trace (TR) and volume were calculated for each of the 68 cortical GM Regions of Interest parcellated using FreeSurfer.

RESULTS

There was no significant difference of FA and GM volume between groups after Bonferroni correction. For the dMRI measures, however, patients evinced increased TR in the left bank of the superior temporal sulcus, the right inferior parietal, the right inferior temporal, and the right middle temporal gyri. In addition, higher TR in the right middle temporal gyrus and the right inferior temporal gyrus, respectively, was associated with decreased social function and higher PANSS score in patients with schizophrenia.

CONCLUSION

This study demonstrates high sensitivity of dMRI to subtle pathology in GM in recent onset schizophrenia, as well as an association between increased diffusivity in temporal GM regions and abnormalities in social cognition and exacerbation of psychiatric symptoms.

A face-selective ventral occipito-temporal map of the human brain with intracerebral potentials

Human neuroimaging studies have identified a network of distinct face-selective regions in the ventral occipito-temporal cortex (VOTC), with a right hemispheric dominance. To date, there is no evidence for this hemispheric and regional specialization with direct measures of brain activity. To address this gap in knowledge, we recorded local neurophysiological activity from 1,678 contact electrodes implanted in the VOTC of a large group of epileptic patients (n = 28). They were presented with natural images of objects at a rapid fixed rate (six images per second: 6 Hz), with faces interleaved as every fifth stimulus (i.e., 1.2 Hz). High signal-to-noise ratio face-selective responses were objectively (i.e., exactly at the face stimulation frequency) identified and quantified throughout the whole VOTC. Face-selective responses were widely distributed across the whole VOTC, but also spatially clustered in specific regions. Among these regions, the lateral section of the right middle fusiform gyrus showed the largest face-selective response by far, offering, to our knowledge, the first supporting evidence of two decades of neuroimaging observations with direct neural measures. In addition, three distinct regions with a high proportion of face-selective responses were disclosed in the right ventral anterior temporal lobe, a region that is undersampled in neuroimaging because of magnetic susceptibility artifacts. A high proportion of contacts responding only to faces (i.e., "face-exclusive" responses) were found in these regions, suggesting that they contain populations of neurons involved in dedicated face-processing functions. Overall, these observations provide a comprehensive mapping of visual category selectivity in the whole human VOTC with direct neural measures.

Behaviorally Relevant Abstract Object Identity Representation in the Human Parietal Cortex

The representation of object identity is fundamental to human vision. Using fMRI and multivoxel pattern analysis, here we report the representation of highly abstract object identity information in human parietal cortex. Specifically, in superior intraparietal sulcus (IPS), a region previously shown to track visual short-term memory capacity, we found object identity representations for famous faces varying freely in viewpoint, hairstyle, facial expression, and age; and for well known cars embedded in different scenes, and shown from different viewpoints and sizes. Critically, these parietal identity representations were behaviorally relevant as they closely tracked the perceived face-identity similarity obtained in a behavioral task. Meanwhile, the task-activated regions in prefrontal and parietal cortices (excluding superior IPS) did not exhibit such abstract object identity representations. Unlike previous studies, we also failed to observe identity representations in posterior ventral and lateral visual object-processing regions, likely due to the greater amount of identity abstraction demanded by our stimulus manipulation here. Our MRI slice coverage precluded us from examining identity representation in anterior temporal lobe, a likely region for the computing of identity information in the ventral region. Overall, we show that human parietal cortex, part of the dorsal visual processing pathway, is capable of holding abstract and complex visual representations that are behaviorally relevant. These results argue against a "content-poor" view of the role of parietal cortex in attention. Instead, the human parietal cortex seems to be "content rich" and capable of directly participating in goal-driven visual information representation in the brain.

SIGNIFICANCE STATEMENT

The representation of object identity (including faces) is fundamental to human vision and shapes how we interact with the world. Although object representation has traditionally been associated with human occipital and temporal cortices, here we show, by measuring fMRI response patterns, that a region in the human parietal cortex can robustly represent task-relevant object identities. These representations are invariant to changes in a host of visual features, such as viewpoint, and reflect an abstract level of representation that has not previously been reported in the human parietal cortex. Critically, these neural representations are behaviorally relevant as they closely track the perceived object identities. Human parietal cortex thus participates in the moment-to-moment goal-directed visual information representation in the brain.

Right inferior longitudinal fasciculus lesions disrupt visual-emotional integration

The mechanism by which the brain integrates visual and emotional information remains incompletely understood, and can be studied through focal lesions that selectively disrupt this process. To date, three reported cases of visual hypoemotionality, a vision-specific form of derealization, have resulted from lesions of the temporo-occipital junction. We present a fourth case of this rare phenomenon, and investigate the role of the inferior longitudinal fasciculus (ILF) in the underlying pathophysiology. A 50-year-old right-handed male was found to have a right medial temporal lobe tumor following new-onset seizures. Interstitial laser ablation of the lesion was complicated by a right temporo-parieto-occipital intraparenchymal hemorrhage. The patient subsequently experienced emotional estrangement from visual stimuli. A lesion overlap analysis was conducted to assess involvement of the ILF by this patient's lesion and those of the three previously described cases, and diffusion tensor imaging was acquired in our case to further investigate ILF disruption. All four lesions specifically overlapped with the expected trajectory of the right ILF, and diminished structural integrity of the right ILF was observed in our case. These findings implicate the ILF in visual hypoemotionality, suggesting that the ILF is critical for integrating visual information with its emotional content.