Progressive degeneration of the right temporal lobe studied with positron emission tomography

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.

Imaging Correlates between Headache and Breast Cancer: An [18F]FDG PET Study

This study aimed to examine brain metabolic patterns on [18F]Fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) in breast cancer (BC), comparing patients with tension-type headache (TTH), migraine (MiG), and those without headache. Further association with BC response to neoadjuvant chemotherapy (NAC) was explored. In this prospective study, BC patients eligible for NAC performed total-body [18F]FDG PET/CT with a dedicated brain scan. A voxel-wise analysis (two-sample t-test) and a multiple regression model were used to compare brain metabolic patterns among TTH, MiG, and no-headache patients and to correlate them with clinical covariates. A single-subject analysis compared each patient's brain uptake before and after NAC with a healthy control group. Primary headache was diagnosed in 39/46 of BC patients (39% TTH and 46% MiG). TTH patients exhibited hypometabolism in specific brain regions before NAC. TTH patients with a pathological complete response (pCR) to NAC showed hypermetabolic brain regions in the anterior medial frontal cortex. The correlation between tumor uptake and brain metabolism varied before and after NAC, suggesting an inverse relationship. Additionally, the single-subject analysis revealed that hypometabolic brain regions were not present after NAC. Primary headache, especially MiG, was associated with a better response to NAC. These findings suggest complex interactions between BC, headache, and hormonal status, warranting further investigation in larger prospective cohorts.

Temporopolar regions of the human brain

Following prolonged neglect during the formative decades of behavioural neurology, the temporopolar region has become a site of vibrant research on the neurobiology of cognition and conduct. This turnaround can be attributed to increasing recognition of neurodegenerative diseases that target temporopolar regions for peak destruction. The resultant syndromes include behavioural dementia, associative agnosia, semantic forms of primary progressive aphasia and semantic dementia. Clinicopathological correlations show that object naming and word comprehension are critically dependent on the language-dominant (usually left) temporopolar region, whereas behavioural control and non-verbal object recognition display a more bilateral representation with a rightward bias. Neuroanatomical experiments in macaques and neuroimaging in humans show that the temporoparietal region sits at the confluence of auditory, visual and limbic streams of processing at the downstream (deep) pole of the 'what' pathway. The functional neuroanatomy of this region revolves around three axes, an anterograde horizontal axis from unimodal to heteromodal and paralimbic cortex; a radial axis where visual (ventral), auditory (dorsal) and paralimbic (medial) territories encircle temporopolar cortex and display hemispheric asymmetry; and a vertical depth-of-processing axis for the associative elaboration of words, objects and interoceptive states. One function of this neural matrix is to support the transformation of object and word representations from unimodal percepts to multimodal concepts. The underlying process is likely to start at canonical gateways that successively lead to generic (superordinate), specific (basic) and unique levels of recognition. A first sign of left temporopolar dysfunction takes the form of taxonomic blurring where boundaries among categories are preserved but not boundaries among exemplars of a category. Semantic paraphasias and coordinate errors in word-picture verification tests are consequences of this phenomenon. Eventually, boundaries among categories are also blurred and comprehension impairments become more profound. The medial temporopolar region belongs to the amygdalocentric component of the limbic system and stands to integrate exteroceptive information with interoceptive states underlying social interactions. Review of the pertinent literature shows that word comprehension and conduct impairments caused by temporopolar strokes and temporal lobectomy are far less severe than those seen in temporopolar atrophies. One explanation for this unexpected discrepancy invokes the miswiring of residual temporopolar neurons during the many years of indolently progressive neurodegeneration. According to this hypothesis, the temporopolar regions become not only dysfunctional but also sources of aberrant outputs that interfere with the function of areas elsewhere in the language and paralimbic networks, a juxtaposition not seen in lobectomy or stroke.

[A case suspected of Alzheimer type dementia showing multimodal (face and voice) person recognition disorder from face and voice]

A 90-year-old woman presented with a multimodal (face and voice) person recognition disorder. Although she had moderate general cognitive impairment, her visual cognitive capacity, other than face recognition, was well preserved. She could identify the faces and voices of family members but could not recall the names and voices of relatives whom she met infrequently, famous individuals, or the medical staff. She could remember the first names and some information about prominent individuals when supplied with their surnames. Therefore, we thought that her person-specific semantic memory was intact but she was unable to access it through their faces and voices. MRI revealed predominantly right-sided bilateral anterior temporal lobe and hippocampal atrophy. SPECT images showed decreased blood flow in the bilateral anterior temporal lobes and inferior parietal lobule (heavily and predominantly right-sided), right posterior cingulate gyrus, and precuneus. Progressive person recognition disorder or prosopagnosia has been considered a right temporal variant of frontotemporal lobar degeneration because abnormal behaviors and psychiatric symptoms frequently coexist. However, no such symptoms were observed in this case, therefore we suspected dementia of the Alzheimer type.

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.

Does the Right Focal Variant of Alzheimer's Disease Really Exist? A Literature Analysis

BACKGROUND

Alzheimer's disease (AD) is a clinically heterogeneous disease. Multiple atypical syndromes, distinct from the usual amnesic phenotype, have been described. In this context, the existence of a right variant of AD (RAD), characterized by enduring visuospatial impairment associated with right-sided asymmetric brain damage, has been proposed. However, to date, this phenotype remains controversial. In particular, its peculiar characteristics and the independence from more prevalent cases (especially the posterior cortical atrophy syndrome) have to be demonstrated.

OBJECTIVE

To explore the existence of focal RAD on the basis of existing literature.

METHODS

We performed a literature search for the description of atypical AD presentations, potentially evoking cases of focal RAD. To be considered as affected by RAD, the described cases had to present: 1) well documented right-sided asymmetry at neuroimaging; 2) predominant cognitive deficits localizable on the right hemisphere; 3) no specific diagnosis of a known variant of AD.

RESULTS

Twenty-one cases were found in the literature, but some of them were subsequently excluded because some features of a different clinical syndrome were overlapped with the clinical features of RAD. Thirteen positive cases, three of them with pathologically confirmed AD, remained. A common right clinical-radiological syndrome, characterized by memory and visuospatial impairment with temporal and parietal involvement, consistently emerged. However, the heterogeneity among the reports prevented a definitive and univocal description of the syndrome.

CONCLUSION

Even if sporadic observations strongly support the existence of a focal RAD, no definitive conclusions can still be drawn about it as an independent condition.

Early-stage right temporal lobe variant of frontotemporal dementia: 3 years of follow-up observations

The right temporal lobe variant of frontotemporal dementia (FTD) is an uncommon progressive neurodegenerative disorder. We present the case of a 77-year-old right-handed man who presented with altered behaviour and problems with interpersonal relationships. He had no decline in cognitive function but brain perfusion single-photon emission CT demonstrated distinct hypoperfusion in the right temporal pole. At 2-year follow-up, he could not recognise his wife's relatives; and at 3-year follow-up, he had semantic aphasia. Decreased brain perfusion extended from the right temporal lobe into the contralateral temporal and both frontal lobes. These findings suggest that the right temporal lobe variant of FTD should be considered in elderly patients with altered behaviour and problems with interpersonal relationships, even if dementia is not suspected. The right anterior temporal lobe may play a key role in the onset of the early symptoms of this disease.

Geschwind Syndrome in frontotemporal lobar degeneration: Neuroanatomical and neuropsychological features over 9 years

Geschwind Syndrome, a characteristic behavioral syndrome frequently described in patients affected by temporal lobe epilepsy (TLE), consists of the following features: hyper-religiosity, hypergraphia, hyposexuality, and irritability. Here we report the 9-year-clinical course of a case of Geschwind Syndrome that developed as a first and salient clinical expression of right temporal lobe variant of frontotemporal lobar degeneration (FTLD). Only one patient affected by frontotemporal dementia has previously been shown to present with Geschwind Syndrome. MS presented at age 73 with 3 years of personality and behavioral symptoms. Her early symptoms primarily included hyper-religiosity, hypergraphia, and poor emotional regulation (irritability, impulsivity, disinhibition, egocentric behavior). Over nine years, other cognitive functions (word retrieval, memory coding and recall, set-shifting, famous face and building recognition) became affected; however, hyper-religiosity, hypergraphia, and scarce emotional control remained her most prominent deficits. Longitudinal cortical thickness and volumetric analyses revealed early atrophy in the right temporal pole, right amygdala, and right hippocampus, which progressively affected homologous regions in the left hemisphere. The present case describes an unusual clinical picture associated with frontotemporal dementia (FTD), in which the most salient symptoms originated and remained consistent with Geschwind Syndrome.

Primary Progressive Aphasia and the Left Hemisphere Language Network

Primary progressive aphasia (PPA) is a clinical syndrome diagnosed when three core criteria are met. First, there should be a language impairment (i.e., aphasia) that interferes with the usage or comprehension of words. Second, the neurological work-up should determine that the disease is neurodegenerative, and therefore progressive. Third, the aphasia should arise in relative isolation, without equivalent deficits of comportment or episodic memory. The language impairment can be fluent or non-fluent and may or may not interfere with word comprehension. Memory for recent events is preserved although memory scores obtained in verbally mediated tests may be abnormal. This distinctive clinical pattern is most conspicuous in the initial stages of the disease, and reflects a relatively selective atrophy of the language network, usually located in the left hemisphere. There are different clinical variants of PPA, each with a characteristic pattern of atrophy. Clinicoanatomical correlations in patient with these variants have led to new insights on the organization of the large-scale language network in the human brain. For example, the left anterior temporal lobe, which was not part of the classic language network, has been shown to play a critical role in word comprehension and object naming. Furthermore, patients with PPA have shown that fluency can be dissociated from grammaticality. The underlying neuropathological diseases are heterogeneous and can include Alzheimer's disease as well as frontotemporal lobar degeneration. The clinician's task is to recognize PPA and differentiate it from other neurodegenerative phenotypes, use biomarkers to surmise the nature of the underlying neuropathology, and institute the most fitting multimodal interventions.

Impairments in the Face-Processing Network in Developmental Prosopagnosia and Semantic Dementia

BACKGROUND

Developmental prosopagnosia (DP) and semantic dementia (SD) may be the two most common neurologic disorders of face processing, but their main clinical and pathophysiologic differences have not been established. To identify those features, we compared patients with DP and SD.

METHODS

Five patients with DP, five with right temporal-predominant SD, and ten normal controls underwent cognitive, visual perceptual, and face-processing tasks.

RESULTS

Although the patients with SD were more cognitively impaired than those with DP, the two groups did not differ statistically on the visual perceptual tests. On the face-processing tasks, the DP group had difficulty with configural analysis and they reported relying on serial, feature-by-feature analysis or awareness of salient features to recognize faces. By contrast, the SD group had problems with person knowledge and made semantically related errors. The SD group had better face familiarity scores, suggesting a potentially useful clinical test for distinguishing SD from DP.

CONCLUSIONS

These two disorders of face processing represent clinically distinguishable disturbances along a right hemisphere face-processing network: DP, characterized by early configural agnosia for faces, and SD, characterized primarily by a multimodal person knowledge disorder. We discuss these preliminary findings in the context of the current literature on the face-processing network; recent studies suggest an additional right anterior temporal, unimodal face familiarity-memory deficit consistent with an "associative prosopagnosia."

The clinical spectrum of sporadic and familial forms of frontotemporal dementia

The term frontotemporal dementia (FTD) describes a clinically, genetically and pathologically diverse group of neurodegenerative disorders. Symptoms of FTD can present in individuals in their 20s through to their 90s, but the mean age at onset is in the sixth decade. The most common presentation is with a change in personality and impaired social conduct (behavioural variant FTD). Less frequently patients present with language problems (primary progressive aphasia). Both of these groups of patients can develop motor features consistent with either motor neuron disease (usually the amyotrophic lateral sclerosis variant) or parkinsonism (most commonly a progressive supranuclear palsy or corticobasal syndrome). In about a third of cases FTD is familial, with mutations in the progranulin, microtubule-associated protein tau and chromosome 9 open reading frame 72 genes being the major causes. Mutations in a number of other genes including TANK-binding kinase 1 are rare causes of familial FTD. This review aims to clarify the often confusing terminology of FTD, and outline the various clinical features and diagnostic criteria of sporadic and familial FTD syndromes. It will also discuss the current major challenges in FTD research and clinical practice, and potential areas for future research. This review clarifies the terminology of frontotemporal dementia (FTD) and summarizes the various clinical features and most recent diagnostic criteria of sporadic and familial FTD syndromes. It also discusses the current major challenges in FTD research and clinical practice, and highlights potential areas for future research.

Right temporal lobe variant of frontotemporal dementia

We present two women with the right temporal lobe variant (RTLV) of frontotemporal dementia (FTD) and analyse the clinical features that are determined by the anatomical distribution of atrophy. Each of our patients displayed different clinical and radiological profiles which were in line with findings reported by other authors. One of two patients carries a novel mutation in the granulin gene. FTD is heterogeneous with regard to clinical manifestation, genetics, distribution of cortical atrophy and underlying disease. Its clinical manifestations are related to the distribution of the cortical atrophy. The RTLV of FTD is an uncommon entity. There is no consensus about its name despite the fact that its clinical and radiological features are well-defined and distinguish it from other types of FTD including semantic dementia.

"The mind is its own place": amelioration of claustrophobia in semantic dementia

Phobias are among the few intensely fearful experiences we regularly have in our everyday lives, yet the brain basis of phobic responses remains incompletely understood. Here we describe the case of a 71-year-old patient with a typical clinicoanatomical syndrome of semantic dementia led by selective (predominantly right-sided) temporal lobe atrophy, who showed striking amelioration of previously disabling claustrophobia following onset of her cognitive syndrome. We interpret our patient's newfound fearlessness as an interaction of damaged limbic and autonomic responsivity with loss of the cognitive meaning of previously threatening situations. This case has implications for our understanding of brain network disintegration in semantic dementia and the neurocognitive basis of phobias more generally.

Cognitive and anatomical underpinnings of the conceptual knowledge for common objects and familiar people: a repetitive transcranial magnetic stimulation study

Several studies have addressed the issue of how knowledge of common objects is organized in the brain, whereas the cognitive and anatomical underpinnings of familiar people knowledge have been less explored. Here we applied repetitive transcranial magnetic stimulation (rTMS) over the left and right temporal poles before asking healthy individuals to perform a speeded word-to-picture matching task using familiar people and common objects as stimuli. We manipulated two widely used semantic variables, namely the semantic distance and the familiarity of stimuli, to assess whether the semantic organization of familiar people knowledge is similar to that of common objects. For both objects and faces we reliably found semantic distance and familiarity effects, with less accurate and slower responses for stimulus pairs that were more closely related and less familiar. However, the effects of semantic variables differed across categories, with semantic distance effects larger for objects and familiarity effects larger for faces, suggesting that objects and faces might share a partially comparable organization of their semantic representations. The application of rTMS to the left temporal pole modulated, for both categories, semantic distance, but not familiarity effects, revealing that accessing object and face concepts might rely on overlapping processes within left anterior temporal regions. Crucially, rTMS of the left temporal pole affected only the recognition of pairs of stimuli that could be discriminated at specific levels of categorization (e.g., two kitchen tools or two famous persons), with no effect for discriminations at either superordinate or individual levels. Conversely, rTMS of the right temporal pole induced an overall slowing of reaction times that positively correlated with the visual similarity of the stimuli, suggesting a more perceptual rather than semantic role of the right anterior temporal regions. Results are discussed in the light of current models of face and object semantic representations in the brain.

Decoding representations of face identity that are tolerant to rotation

In order to recognize the identity of a face we need to distinguish very similar images (specificity) while also generalizing identity information across image transformations such as changes in orientation (tolerance). Recent studies investigated the representation of individual faces in the brain, but it remains unclear whether the human brain regions that were found encode representations of individual images (specificity) or face identity (specificity plus tolerance). In the present article, we use multivoxel pattern analysis in the human ventral stream to investigate the representation of face identity across rotations in depth, a kind of transformation in which no point in the face image remains unchanged. The results reveal representations of face identity that are tolerant to rotations in depth in occipitotemporal cortex and in anterior temporal cortex, even when the similarity between mirror symmetrical views cannot be used to achieve tolerance. Converging evidence from different analysis techniques shows that the right anterior temporal lobe encodes a comparable amount of identity information to occipitotemporal regions, but this information is encoded over a smaller extent of cortex.

Words and objects at the tip of the left temporal lobe in primary progressive aphasia

Eleven of 69 prospectively enrolled primary progressive aphasics were selected for this study because of peak atrophy sites located predominantly or exclusively within the anterior left temporal lobe. Cortical volumes in these areas were reduced to less than half of control values, whereas average volume elsewhere in the left hemisphere deviated from control values by only 8%. Failure to name objects emerged as the most consistent and severe deficit. Naming errors were attributed to pure retrieval failure if the object could not be named even when the denoting word was understood, the object recognized and the two accurately matched. Surprisingly many of the naming errors reflected pure retrieval failures, without discernible semantic or associative component. The remaining set of errors had associative components. These errors reflected the inability to define the word denoting the object more often than the inability to define the nature of the pictured object. In a separate task where the same object had to be linked to verbal or non-verbal associations, performance was abnormal only in the verbal format. Excessive taxonomic interference was observed for picture-word, but not picture-picture, matching tasks. This excessive interference reflected a blurring of intra- rather than inter-category distinctions as if the acuity of word-object associations had been diminished so that correspondences were easier to recognize at generic than specific levels. These dissociations between verbal and non-verbal markers of object knowledge indicate that the reduced neural mass at peak atrophy sites of the left temporal tip, accounting for half or more of the presumed premorbid volume, was unlikely to have contained domain-independent semantic representations of the type that would be expected in a strictly amodal hub. A more likely arrangement entails two highly interactive routes--a strongly left lateralized temporosylvian language network for verbal concepts, and a presumably more bilateral or right-sided inferotemporal/fusiform object recognition network, which remained relatively spared because peak atrophy sites were concentrated on the left. The current results also suggest that the left anterior temporal neocortex should be inserted into the language network where it is likely to play a major role in selecting verbal labels for objects and mediating the progression of word comprehension from generic to specific levels of precision.

Neuropsychological, behavioral, and anatomical evolution in right temporal variant frontotemporal dementia: a longitudinal and post-mortem single case analysis

We describe a patient with semantic variant of frontotemporal dementia who received longitudinal clinical evaluations and structural MRI scans and subsequently came to autopsy. She presented with early behavior changes and semantic loss for foods and people and ultimately developed a pervasive semantic impairment affecting social-emotional as well as linguistic domains. Imaging revealed predominant atrophy of the right temporal lobe, with later involvement of the left, and pathology confirmed bilateral temporal involvement. Findings support the view that left and right anterior temporal lobes serve as semantic hubs that may be affected differentially in semantic variant by early, relatively unilateral damage.

Agnosia for global patterns: When the cross-talk between grouping and visual selective attention failS

We present a single case study of a 72-year-old mild AD patient, MC, with a highly specific deficit in deriving the global pattern of visual stimuli, in the absence of visuospatial neglect. MC shows a specific difficulty in segregating overlapping figures, in object decision, and in all neuropsychological tasks requiring perception of a global structure from local cues, such as the Street Completion Test and the perception of illusory contours and of the global level of hierarchical stimuli. The detailed neuropsychological assessment prompted a psychophysical experiment aiming to quantify the limits of perceptual grouping in MC. We measured the thresholds of integration for a closed chain of Gabor Patches as a function of background noise using stimuli with different values of the distance between the local elements. When compared to normal controls, the patient displays a statistically significant drop of performance for stimuli with the larger interelement distance. The data are interpreted in the context of the "association field" theory (Field, Hayes, & Hess, 1993). As MC presents with a marked atrophy of the right temporoparietal junction, we interpret our data as providing further evidence of a neuromodulatory role of the right temporoparietal junction over the occipital cortices, in line with recent functional evidence (Fink et al., 1997a). The study also highlights the benefits of complementing classical neuropsychological investigations with more quantitative psychophysical procedures.

C rossmodal agnosia for familiar people as a consequence of right infero polar temporal atrophy

A 60-year-old, right-handed woman, with no focal brain lesions, suffered from a progressive impairment in recognising people of personal relevance and public figures familiar to her in the premorbid period. The patient did not suffer from general cognitive deterioration. There was no ecological or clear psychometric evidence of visuoperceptual or visuospatial deficits. Her defective person recognition was not overcome by extra-facial (e.g., observing animated people in their usual surroundings) or extra-visual information (e.g., listening to the voice). Moreover, presenting the correct name in the presence of an unrecognised familiar person failed to prompt her familiarity judgement, or retrieval of the relevant biographical knowledge. The patient also had some recognition difficulties with famous buildings and songs as well as with some common objects. It is argued that the patient's difficulty in identifying familiar people was the consequence of progressive loss of stored exemplars of familiar persons and perhaps also of some other "unique items" (famous songs and monuments) in an independent subsystem of semantics that we term "exemplar semantics." We discuss the associative (semantic) nature and specificity of the deficit in person knowledge, the possible top-down negative influences of the loss of exemplars in the person recognition system, and the link between the disorders and the right/left temporal lobe.

Is this a new type of primary prosopagnosia, both progressive and apperceptive?

Prosopagnosia, the inability to recognize faces, has a history going back to Charcot and Hughlings-Jackson, but was first named by Bodamer in 1947. Its anatomical loci are still unclear. However, progressive prosopagnosia is normally linked to right dominant temporal lobe atrophy, and diagnosed as part of frontotemporal lobar degeneration. Here we report a case of prosopagnosia linked to posterior cortical atrophy. Although case reports of posterior cortical atrophy-prosopagnosia do already exist, it is normally described as an accessory symptom. The interest of our own posterior cortical atrophy patient, possibly the first such case, is that he had a rare apperceptive type of prosopagnosia unrelated to the associative, frontotemporal lobar degeneration-type.

Asymmetric cortical degenerative syndromes: an integrated approach to clinical and imaging review

BACKGROUND

The term asymmetric cortical degenerative syndromes (ACDSs) refers to any brain afflictions that result in selective atrophy, particularly with an asymmetric pattern. Regardless of the etiology, the resulting compromised profile reflects the affected topography, which correlates with the clinical findings, more than any specific neuropathologic entity.

REVIEW SUMMARY

ACDS can represent a diagnostic challenge, because of an overlap of clinical manifestations, especially in the early stages. Magnetic resonance techniques are useful to understand nuclear medicine studies and to confirm areas of focal atrophy by providing anatomic details and allowing an accurate correlation with several different clinical settings.

CONCLUSIONS

This article demonstrates a practical neuroradiologic approach for ACDS, including optimized imaging analysis (magnetic resonance and nuclear medicine studies), which correlates their patterns with clinical and pathologic findings of the most relevant disorders.

Progressive associative phonagnosia: a neuropsychological analysis

There are few detailed studies of impaired voice recognition, or phonagnosia. Here we describe two patients with progressive phonagnosia in the context of frontotemporal lobar degeneration. Patient QR presented with behavioural decline and increasing difficulty recognising familiar voices, while patient KL presented with progressive prosopagnosia. In a series of neuropsychological experiments we assessed the ability of QR and KL to recognise and judge the familiarity of voices, faces and proper names, to recognise vocal emotions, to perceive and discriminate voices, and to recognise environmental sounds and musical instruments. The patients were assessed in relation to a group of healthy age-matched control subjects. QR exhibited severe impairments of voice identification and familiarity judgments with relatively preserved recognition of difficulty-matched faces and environmental sounds; recognition of musical instruments was impaired, though better than recognition of voices. In contrast, patient KL exhibited severe impairments of both voice and face recognition, with relatively preserved recognition of musical instruments and environmental sounds. Both patients demonstrated preserved ability to analyse perceptual properties of voices and to recognise vocal emotions. The voice processing deficit in both patients could be characterised as associative phonagnosia: in the case of QR, this was relatively selective for voices, while in the case of KL, there was evidence for a multimodal impairment of person knowledge. The findings have implications for current cognitive models of voice recognition.

Right anterior temporal lobe atrophy and person-based semantic defect: a detailed case study

We report a new case of a right temporal pole variant of frontotemporal dementia (Rtv-FTLD), MD, who presented a slowly progressive deterioration of the recognition of familiar and famous people. We thoroughly investigated MD's face processing and semantic abilities, including a neuroimaging investigation. This analysis revealed a cross-modal person-based deficit together with a more general semantic alteration. However, there was no evidence of impairment in face perception, including holistic processing, or of an abnormal pattern of brain activation in face-sensitive cortical areas. We discuss the nature of face processing in the Rtv-FTLD and the context of a person-based semantic defect.

Structure and function in acquired prosopagnosia: lessons from a series of 10 patients with brain damage

Acquired prosopagnosia varies in both behavioural manifestations and the location and extent of underlying lesions. We studied 10 patients with adult-onset lesions on a battery of face-processing tests. Using signal detection methods, we found that discriminative power for the familiarity of famous faces was most reduced by bilateral occipitotemporal lesions that involved the fusiform gyri, and better preserved with unilateral right-sided lesions. Tests of perception of facial structural configuration showed severe deficits with lesions that included the right fusiform gyrus, whether unilateral or bilateral. This deficit was most consistent for eye configuration, with some patients performing normally for mouth configuration. Patients with anterior temporal lesions had better configuration perception, though at least one patient showed a more subtle failure to integrate configural data from different facial regions. Facial imagery, an index of facial memories, was severely impaired by bilateral lesions that included the right anterior temporal lobe and marginally impaired by fusiform lesions alone; unilateral right fusiform lesions tended to spare imagery for facial features. These findings suggest that (I) prosopagnosia is more severe with bilateral than unilateral lesions, indicating a minor contribution of the left hemisphere to face recognition, (2) perception of facial configuration critically involves the right fusiform gyrus and (3) access to facial memories is most disrupted by bilateral lesions that also include the right anterior temporal lobe. This supports assertions that more apperceptive variants of prosopagnosia are linked to fusiform damage, whereas more associative variants are linked to anterior temporal damage. Next, we found that behavioural indices of covert recognition correlated with measures of overt familiarity, consistent with theories that covert behaviour emerges from the output of damaged neural networks, rather than alternative pathways. Finally, to probe the face specificity of the prosopagnosic defect, we tested recognition of fruits and vegetables: While face specificity was not found in most of our patients, the data of one patient suggested that this may be possible with more focal lesions of the right fusiform gyrus.

The anatomic correlate of prosopagnosia in semantic dementia

OBJECTIVE

To determine the anatomic correlate of prosopagnosia in subjects with semantic dementia.

METHODS

We identified all subjects who had been evaluated by an experienced behavioral neurologist, met criteria for semantic dementia, and had completed a volumetric head MRI scan. In all subjects, historical records were reviewed and subjects in which the presence (n = 15) or absence (n = 12) of prosopagnosia was specifically ascertained by the neurologist were identified. Voxel-based morphometry was used to assess patterns of gray matter atrophy in subjects with and without prosopagnosia compared to a group of age and gender-matched normal controls, and compared to each other.

RESULTS

Compared to controls, both groups showed prominent temporal lobe volume loss. Those with prosopagnosia showed bilateral loss but with greater involvement of the right temporal lobe, while those without prosopagnosia showed predominantly left anterior temporal lobe loss. On direct comparison, subjects with prosopagnosia showed greater loss predominantly in the right amygdala, hippocampus, fusiform gyrus, and anterior temporal pole than those without prosopagnosia. No regions were involved to a greater degree in those without prosopagnosia, compared to those with prosopagnosia.

CONCLUSIONS

Prosopagnosia appears to be associated with volume loss of the right temporal lobe, particularly medial temporal lobe, fusiform gyrus, and anterior temporal pole, although in semantic dementia it is occurring in the context of bilateral temporal lobe volume loss.

A reappraisal of person recognition and identification

In the last years an increasing number of cases (Gainotti et al., 2008, this issue) have been reported in whom difficulty to recognise and identify familiar people occurs in everyday multimodal settings, differently from unimodal face-specific impairments (i.e., prosopagnosia). A reappraisal of current person processing models is presented in order to account for such deficits as well as for the common slips of recognition occurring in healthy subjects. The model we propose is based upon three main modifications of current models, namely: (1) the role of PINs as stores of multimodal perceptual knowledge; (2) the richness of perceptual nuances characterizing PINs of most familiar people; (3) the PINs' addressing of Exemplar Semantics by a provisional Gestalt guessing and an analytical check, to be negotiated whenever a conflict arises. A single case report of Capgras delusion is presented as a crossmodal person processing disorder in everyday settings for whom the proposed model allows a cognitive interpretation.

Face familiarity feelings, the right temporal lobe and the possible underlying neural mechanisms

A comprehensive review was made of the relationships between right hemisphere and face familiarity feelings, taking separately into account: (a) studies of patients with unilateral lesions of the anterior or the posterior parts of the right and left temporal lobes, who showed a familiar people recognition disorder, (b) studies of right and left brain-damaged patients, presenting an increased familiarity for unknown persons or abnormal familiarity feelings for well known people, (c) results of studies conducted in normal subjects to evaluate the lateralization of face familiarity feelings. In this last section, we separately reviewed: results obtained by means of separate presentation of familiar and unfamiliar faces to the right and left visual fields; lateralization of event-related potentials evoked by familiar vs unfamiliar faces; results of activation studies presenting familiar and unfamiliar faces. Taken together, results of this review have shown that face familiarity feelings are specifically generated by the right hemisphere. Clinical and neurophysiological data suggest that familiarity feelings: (1) are probably due to a lateralized subcortical route, allowing a first, unconscious, global recognition of familiar faces and (2) facilitate the subsequent distinction of known faces (unconsciously detected) from unfamiliar faces. Results of the review have also shown that the right frontal areas play an important role in the production or monitoring of inappropriate familiarity decisions.

Different patterns of famous people recognition disorders in patients with right and left anterior temporal lesions: a systematic review

Selective disorders in recognition of familiar people have been described in patients with right and left anterior temporal lesions, but the exact nature of these cognitive impairments remains controversial. A clarification of this issue could have theoretical implications, because, according to Snowden et al. [Snowden, J. S., Thompson, J. C., & Neary, D. (2004). Knowledge of famous faces and names in semantic dementia. Brain, 127, 860-872], the pattern of impairment shown by patients with right and left anterior temporal atrophy is inconsistent with unitary, abstract, amodal models of semantic memory. This pattern could, on the contrary suggest a multimodal network, in which the right and left temporal lobes would mainly process and store visual and, respectively, verbal information. I tried to clarify this issue by systematically reviewing: (a) all published individual cases of patients showing a prevalent damage of the anterior parts of the right or left temporal lobes and a selective disorder of famous people recognition; (b) all group studies of patients with right or left temporal lobe epilepsy, which had investigated aspects of famous people recognition impairment. Results of these reviews consistently showed that different patterns of impaired recognition of familiar people can be observed in patients with right and left anterior temporal pathology. These patterns consist of a loss of familiarity feelings and of person specific information retrieval from face stimuli, when the right temporal lobe is damaged and of a prevalent impairment in finding their names when the anterior parts of the left temporal lobe are selectively damaged.

The right temporal lobe variant of frontotemporal dementia

The right temporal variant of frontotemporal lobar degeneration (Rtv-FTLD) is a focal degenerative condition affecting predominantly the right temporal lobe. The aim of this study was to further characterize the profile of cognitive impairment and the neuroanatomical basis of Rtv-FTLD patients without behavioural disturbances. A group of three patients with this syndrome had a detailed neuropsychological assessment, along with Voxel-Based Morphometry (VBM) of their brain to determine location of cortical atrophy. VBM analyses showed a pattern of atrophy that was predominant in the right hemisphere and concerned primarily the right anterior temporal lobe region. Patients carried out a test of famous people in which their ability to recognize, name and provide semantic information about famous persons from their faces, their voices and their names was investigated. They all showed a severe defect in recognizing, naming and identifying famous people irrespective of modality. Therefore, their inability to recognize famous people resulted from a multimodal defect (semantic). These results highlight the semantic nature of the defect, and suggest that the anterior right temporal lobe may have a prominent role in processing person-based semantic knowledge. This study helps in further understanding the neuropsychological profile of patients with Rtv-FTLD.

Hyperfamiliarité stéréotypée pour les visages au cours d’une démence fronto-temporale avec prosopagnosie

INTRODUCTION

The association of prosopagnosia and false recognition of faces is unusual and contributes to our understanding of the generation of facial familiarity.

METHOD

A 67-year-old man with a left prefrontal traumatic lesion, developed a temporal variety of fronto-temporal dementia (semantic dementia) with amyotrophic lateral sclerosis. Cerebral imagery demonstrated a bilateral, temporal anterior atrophy predominating in the right hemisphere. The main cognitive signs consisted in severe difficulties to recognize faces of familiar people (prosopagnosia), associated with systematic false recognition of unfamiliar people.

RESULT

Neuropsychological testing indicated that the prosopagnosia probably resulted from the association of an associative/mnemonic mechanism (inability to activate the Face Recognition Units (FRU) from the visual input) and a semantic mechanism (degradation of semantic/biographical information or deconnexion between FRU and this information). At the early stage of the disease, the patient could activate residual semantic information about individuals from their names, but after a 4-year course, he failed to do so. This worsening could be attributed to the extension of the degenerative lesions to the left temporal lobe. Familiar and unfamiliar faces triggered a marked feeling of knowing. False recognition concerned all the unfamiliar faces, and the patient claimed spontaneously that they corresponded to actors, but he could not provide any additional information about their specific identities. The coexistence of prosopagnosia and false recognition suggests the existence of different interconnected systems processing face recognition, one intended to identification of individuals, and the other producing the sense of familiarity. Dysfunctions at different stages of one or the other of these two processes could result in distortions in the feeling of knowing.

CONCLUSION

From this case and others reported in literature, we propose to complete the classical model of face processing by adding a pathway linked to limbic system and frontal structures. This later pathway could normally emit signals for familiarity, essentially autonomic, in response to the familiar faces. These signals, primitively unconscious, secondly reach consciousness and are then integrated by a central supervisor system which evaluates and verifies identity-specific biographical information in order to make a decision about the sense of familiarity.

Distribution of cerebral cortical lesions in diffuse neurofibrillary tangles with calcification: a clinicopathological study of four autopsy cases showing prominent parietal lobe involvement

We investigated clinicopathologically four Japanese autopsy cases of diffuse neurofibrillary tangles with calcification (DNTC), which has been believed to be characterized by temporal or temporofrontal circumscribed lobar atrophy, and examined the distribution of their cerebral cortical lesions using hemisphere specimens. The lesions were classified into three categories (slight, moderate, and severe). Severe lesions were present in the temporal lobes and insular gyri of all four cases, consistent with the studies reported to date. In contrast, severe lesions were encountered in the parietal lobe of case 1 and moderate lesions were found in the parietal lobes of cases 2-4. Furthermore, moderate lesions of the precentral gyrus were present in cases 2-4, and moderate lesions of the postcentral gyrus were encountered in all four cases. We postulate that the distribution of cerebral cortical lesions in DNTC is more widespread than previously assumed. Our data also indicate that the unusual clinical signs of DNTC reported by several Japanese researchers, including parietal signs such as apraxia and agnosia, are roughly consistent with the topographic distribution of cerebral cortical lesions in DNTC elucidated in this study.

Dementia as a window to the neurology of art

Art is an expression of neurological function and how it organizes and interprets perception. Recent reports of changes in art performance among patients with frontotemporal dementia have provided an unexpected window to the neurology of art. They confirm that visual art is predominantly in the right hemisphere and suggest a neuroanatomical schema for artistic creativity. The right parietal region is critical for the visuospatial prerequisites of art, and the right temporal lobe integrates and interprets these percepts. The right temporal lobe appears necessary for extracting and exaggerating the essential features of an artistic composition. In contrast, the left parietal region and the left temporal lobe have inhibitory effects on artistic expression through attention to visuospatial detail and semantic labeling, respectively. Frontal-executive functions are also required for artistic expression, particularly right dorsolateral frontal initiation of a network for novelty-seeking behavior. Further study of art in dementia can profitably evaluate this proposed schema for the mechanisms of art in the brain.

Alterations of the Sense of “Humanness” in Right Hemisphere Predominant Frontotemporal Dementia Patients

OBJECTIVE

To evaluate the sense of "humanness" in frontotemporal dementia (FTD) patients with right hemispheric involvement.

BACKGROUND

Early in the course, FTD is often asymmetric, and those with predominant right frontotemporal disease have disproportionate disturbances in social behavior and empathy. A disruption in a sense of humanness may underlie these behavioral disturbances.

METHOD

Sixteen patients with asymmetric FTD on functional neuroimaging underwent recognition tests of facial masking, human-animal morphing, and facial distortion. Additional tests evaluated facial discrimination and the recognition of famous faces, facial emotions, and animate-inanimate differences.

RESULTS

On the distorted and morphed face tasks, 8 FTD patients with predominant right hemisphere involvement were significantly more likely to call morphed and distorted faces "human" as compared with both 8 FTD patients with predominant left hemisphere involvement and normal controls. The FTD groups did not differ on thresholds for recognizing masked faces or on other face recognition measures.

CONCLUSIONS

In FTD, right hemispheric involvement may alter the threshold for judging someone as human independent of the recognition of faces or facial affect. These results suggest that a specific sense of humanness facilitates a person recognition network in the right frontotemporal region of the brain.

Cognitive and Behavioral Profile in a Case of Right Anterior Temporal Lobe Neurodegeneration

Semantic dementia (SD) is a clinical variant of frontotemporal lobar degeneration (FTLD) characterized by progressive deterioration of semantic memory with relative sparing of other cognitive functions. It is associated with mainly left anterior temporal atrophy, and is also referred to as "left-temporal lobe variant" of FTLD. Recently, patients with mainly right-sided atrophy, or "right-temporal lobe variant"(RTLV), have been described. While some authors have reported that the initial and most significant deficit in these right-sided cases is a difficulty in recognizing famous people, others have observed that major behavioral abnormalities are the presenting symptoms. Here we report a detailed neuropsychological, language, behavioral and neuroimaging assessment of JT, a case of right temporal lobe variant of FTLD. JT showed early and prominent behavioral changes accompanied by a severe impairment in recognizing foods by their look, flavor or name. Later she also developed a difficulty in recognizing familiar people and objects. Standardized caregiver questionnaires of JT's pre- and post-morbid personality and interpersonal functioning showed that she went from being a flexible, dominant, extraverted, person to showing rigid, submissive and introverted behaviors. Her levels of neuroticism significantly increased, while her scores on agreeableness and cognitive and emotional empathy dropped. Voxel-based morphometry (VBM) showed most significant atrophy in the right amygdala/anterior hippocampal complex and collateral sulcus, extending to the right insula. We discuss the atypical cognitive and behavioral features of this case of RTLV of FTLD and stress the importance of behavioral changes and atypical semantic deficits for early diagnosis.

[Confirmation of cortical lesions of progressive prosopagnosia by cerebral SPECT]

We present the case of a 78 year old man admitted to the hospital with progressive memory disorder. Neuropsychological examination showed inability to recognize familiar faces (prosopagnosia). MRI documented cortical atrophy, which did not explain the neurological deficit. CT did not show abnormalities. Most patients with prosopagnosia present brain atrophy, as they are more than 65 years old. Scanning by SPECT revealed hypoperfusion in the right parietotemporal region, which was worse in a later examination.

Slowly progressive pure dysgraphia with late apraxia of speech: a further variant of the focal cerebral degeneration

We report a longitudinal neuropsychological investigation of a patient with slowly progressive pure dysgraphia. Cognitive analysis of writing errors suggested a selective impairment of the graphemic buffer. After about seven years, the patient developed an apraxia of speech. No other linguistic or generalized cognitive impairment occurred subsequently, so that, twelve years after the beginning of the disease, the patient showed complete independence in daily life and still remained professionally active. Functional neuroimaging revealed hypoperfusion confined to left fronto-temporal lobe. This well-recognizable syndrome does not fit any of the cases described previously in the literature. This report therefore, adds another variant to heterogeneous clinical spectrum of focal neurodegenerative disorders, further suggesting the opportunity of their distinction from pathological processes leading to dementia.

Agnosia for scenes in topographagnosia

Topographagnosia is most commonly attributed to an agnosia for landmarks. In order to define the nature of this agnosia, we studied a patient with isolated topographic disorientation (TD) after a stroke in the right medial occipitotemporal region. The patient got lost in familiar environments but could readily read and draw maps, describe familiar routes, and provide correct directions. He had normal perceptual test performance and met criteria for topographagnosia rather than for other forms of topographic disorientation. Two ecologically valid route tests assessed the nature of his agnosia. On a familiar route, he could recognize major landmarks. He could not, however, recognize route configurations made up of combinations of visual features each lacking individual distinctiveness. On a test of route learning, he learned landmarks that differed in minor details and could use them to orient himself along a route. He had difficulty, however, recognizing and learning scenes lacking salient landmarks. This agnosia for scenes was worse for semantically-related environments, but improved with semantic knowledge such as street names. In addition, the patient lacked overt prosopagnosia but tended toward semantic errors in the recognition of famous faces. Together these findings suggest that this patient's inability to recognize a route resulted from an inability of intact perceptual units for scenes, composed of specific visual configurations of individually indefinite features, from accessing stored representations.