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

Advances in semantic dementia: Neuropsychology, pathology & neuroimaging

Semantic dementia is a kind of neurodegenerative disorder, characterized by prominent semantic impairments and anterior temporal lobe atrophy. Since 2010, more studies have devoted to this rare disorder, revealing that it is more complex than we think. Clinical advances include more specific findings of semantic impairments and other higher order cognitive deficits. Neuroimaging techniques can help revealing the different brain networks affected (both structurally and functionally) in this condition. Pathological and genetic studies have also found more complex situations of semantic dementia, which might explain the huge variance existing in semantic dementia. Moreover, the current diagnosis criteria mainly focus on semantic dementia's classical prototype. We further delineated the features of three subtypes of semantic dementia based on atrophy lateralization with three severity stages. In a broader background, as a part of the continuum of neurodegenerative disorders, semantic dementia is commonly compared with other resembling conditions. Therefore, we summarized the differential diagnosis between semantic dementia and them. Finally, we introduced the challenges and achievements of its diagnosis, treatment, care and cross cultural comparison. By providing a comprehensive picture of semantic dementia on different aspects of advances, we hope to deepen the understanding of semantic dementia and promote more inspirations on both clinical and theoretical studies about it.

Perceptual and semantic deficits in face recognition in semantic dementia

State of the art

Semantic dementia (SD) patients including semantic variant primary progressive aphasia (svPPA) and semantic behavioral variant frontotemporal dementia (sbvFTD) patients show semantic difficulties identifying faces and known people related to right anterior temporal lobe (ATL) atrophy. However, it remains unclear whether they also have perceptual deficits in face recognition.

Methodology

We selected 74 SD patients (54 with svPPA and predominant left ATL atrophy and 20 with sbvFTD and predominant right ATL atrophy) and 36 cognitively healthy controls (HC) from UCSF Memory and Aging Center. They underwent a perceptual face processing test (Benton facial recognition test-short version; BFRT-S), and semantic face processing tests (UCSF Famous people battery - Recognition, Naming, Semantic associations - pictures and words subtests), as well as structural magnetic resonance imaging (MRI). Neural correlates with the task's performance were conducted with a Voxel-based morphometry approach using CAT12.

Results

svPPA and sbvFTD patients were impaired on all semantic face processing tests, with sbvFTD patients performing significantly lower on the famous faces' recognition task in comparison to svPPA, and svPPA performing significantly lower on the naming task in comparison to sbvFTD. These tasks predominantly correlated with gray matter (GM) volumes in the right and left ATL, respectively. Compared to HC, both svPPA and sbvFTD patients showed preserved performance on the perceptual face processing test (BFRT-S), and performance on the BFRT-S negatively correlated with GM volume in the right posterior superior temporal sulcus (pSTS).

Conclusion

Our results suggest that early in the disease, with the atrophy mostly restricted to the anterior temporal regions, SD patients do not present with perceptual deficits. However, more severe SD cases with atrophy in right posterior temporal regions might show lower performance on face perception tests, in addition to the semantic face processing deficits. Early sparing of face perceptual deficits in SD patients, regardless of hemispheric lateralization, furthers our understanding of clinical phenomenology and therapeutical approaches of this complex disease.

Disentangling developmental prosopagnosia: A scoping review of terms, tools and topics

The goal of this preregistered scoping review is to create an overview of the research on developmental prosopagnosia (DP). Through analysis of all empirical studies of DP in adults, we investigate 1) how DP is conceptualized and defined, 2) how individuals are classified with DP and 3) which aspects of DP are investigated in the literature. We reviewed 224 peer-reviewed studies of DP. Our analysis of the literature reveals that while DP is predominantly defined as a lifelong face recognition impairment in the absence of acquired brain injury and intellectual/cognitive problems, there is far from consensus on the specifics of the definition with some studies emphasizing e.g., deficits in face perception, discrimination and/or matching as core characteristics of DP. These differences in DP definitions is further reflected in the vast heterogeneity in classification procedures. Only about half of the included studies explicitly state how they classify individuals with DP, and these studies adopt 40 different assessment tools. The two most frequently studied aspects of DP are the role of holistic processing and the specificity of face processing, and alongside a substantial body of neuroimaging studies of DP, this paints a picture of a research field whose scientific interests and aims are rooted in cognitive neuropsychology and neuroscience. We argue that these roots - alongside the heterogeneity in DP definition and classification - may have limited the scope and interest of DP research unnecessarily, and we point to new avenues of research for the field.

The neuropsychological evaluation of face identity recognition

Facial identity recognition (FIR) is arguably the ultimate form of recognition for the adult human brain. Even if the term prosopagnosia is reserved for exceptionally rare brain-damaged cases with a category-specific abrupt loss of FIR at adulthood, subjective and objective impairments or difficulties of FIR are common in the neuropsychological population. Here we provide a critical overview of the evaluation of FIR both for clinicians and researchers in neuropsychology. FIR impairments occur following many causes that should be identified objectively by both general and specific, behavioral and neural examinations. We refute the commonly used dissociation between perceptual and memory deficits/tests for FIR, since even a task involving the discrimination of unfamiliar face images presented side-by-side relies on cortical memories of faces in the right-lateralized ventral occipito-temporal cortex. Another frequently encountered confusion is between specific deficits of the FIR function and a more general impairment of semantic memory (of people), the latter being most often encountered following anterior temporal lobe damage. Many computerized tests aimed at evaluating FIR have appeared over the last two decades, as reviewed here. However, despite undeniable strengths, they often suffer from ecological limitations, difficulties of instruction, as well as a lack of consideration for processing speed and qualitative information. Taking into account these issues, a recently developed behavioral test with natural images manipulating face familiarity, stimulus inversion, and correct response times as a key variable appears promising. The measurement of electroencephalographic (EEG) activity in the frequency domain from fast periodic visual stimulation also appears as a particularly promising tool to complete and enhance the neuropsychological assessment of FIR.

Behavioral Variant Frontotemporal Dementia and Social and Criminal Transgressions

OBJECTIVE

Behavioral variant frontotemporal dementia (bvFTD) is associated with social and criminal transgressions; studies from countries around the world have documented such behavior in persons with this condition. An overview and analysis of social and criminal transgressions in bvFTD and their potential neurobiological mechanisms can provide a window for understanding the relationship of antisocial behavior and the brain.

METHODS

This review evaluated the literature on the frequency of social and criminal transgressions in bvFTD and the neurobiological disturbances that underlie them.

RESULTS

There is a high frequency of transgressions among patients with bvFTD due to impairments in neurocognition, such as social perception, behavioral regulation, and theory of mind, and impairments in social emotions, such as self-conscious emotions and empathy. Additionally, there is significant evidence for a specific impairment in an innate sense of morality. Alterations in these neurobiological processes result from predominantly right-hemisphere pathology in frontal (ventromedial, orbitofrontal, inferolateral frontal), anterior temporal (amygdala, temporal pole), limbic (anterior cingulate, amygdala), and insular regions.

CONCLUSIONS

Overlapping disturbances in neurocognition, social emotions, and moral reasoning result from disease in the mostly mesial and right-sided frontotemporal network necessary for responding emotionally to others and for behavioral control. With increased sophistication in neurobiological interventions, future goals may be the routine evaluation of these processes among individuals with bvFTD who engage in social and criminal transgressions and the targeting of these neurobiological mechanisms with behavioral, pharmacological, and other interventions.

Frontotemporal dementia: A unique window on the functional role of the temporal lobes

Frontotemporal dementia (FTD) is an umbrella term covering a plethora of progressive changes in executive functions, motor abilities, behavior, and/or language. Different clinical syndromes have been described in relation to localized atrophy, informing on the functional networks that underlie these specific cognitive, emotional, and behavioral processes. These functional declines are linked with the underlying neurodegeneration of frontal and/or temporal lobes due to diverse molecular pathologies. Initially, the accumulation of misfolded proteins targets specifically susceptible cell assemblies, leading to relatively focal neurodegeneration that later spreads throughout large-scale cortical networks. Here, we discuss the most recent clinical, neuropathological, imaging, and genetics findings in FTD-spectrum syndromes affecting the temporal lobe. We focus on the semantic variant of primary progressive aphasia and its mirror image, the right temporal variant of FTD. Incipient focal atrophy of the left anterior temporal lobe (ATL) manifests with predominant naming, word comprehension, reading, and object semantic deficits, while cases of predominantly right ATL atrophy present with impairments of socioemotional, nonverbal semantic, and person-specific knowledge. Overall, the observations in FTD allow for crucial clinical-anatomic inferences, shedding light on the role of the temporal lobes in both cognition and complex behaviors. The concerted activity of both ATLs is critical to ensure that percepts are translated into concepts, yet important hemispheric differences should be acknowledged. On one hand, the left ATL attributes meaning to linguistic, external stimuli, thus supporting goal-oriented, action-related behaviors (e.g., integrating sounds and letters into words). On the other hand, the right ATL assigns meaning to emotional, visceral stimuli, thus guiding socially relevant behaviors (e.g., integrating body sensations into feelings of familiarity).

Impaired visual search in posterior cortical atrophy vs. typical Alzheimer's disease

BACKGROUND

Posterior cortical atrophy (PCA) is a neurocognitive disorder characterized by difficulty localizing in space. Recognizing PCA is important because it is usually missed early in its course and may result from a number of neurological disorders other than Alzheimer's disease (AD).

OBJECTIVE

This study aimed to clarify whether impaired visual search tasks of spatial localization distinguished patients with PCA from those with other more typical dementias as well as from healthy control (HC) subjects.

METHODS

Twelve patients meeting neuroimaging-supported Consensus Criteria for PCA, 12 comparably advanced patients with amnestic-predominant typical AD (tAD), and 24 HC participants were compared on tests of untimed and timed visual search, spatial neglect, mental rotation, environmental orientation, visuospatial construction, and face recognition.

RESULTS

Only abnormalities in untimed and timed visual search and environmental orientation distinguished the PCA patients from both the tAD group and the HC group without also distinguishing the tAD patients from HC's. The PCA patients also had a tendency to greater difficulty scanning left hemispace compared to HC's. Visuospatial constructions, although worse in PCA, and face recognition were impaired in both dementia groups.

CONCLUSIONS

These findings support the concept of PCA as a disorder of spatial processing and localization, indicating that visual search tasks are particularly sensitive and specific for detecting PCA and distinguishing it from more typical dementia syndromes.

Evaluating a Maintenance-Based Treatment Approach to Preventing Lexical Dropout in Progressive Anomia

Purpose Primary progressive aphasia (PPA) and the amnestic variant of Alzheimer's disease (AD) are neurodegenerative conditions characterized by a profound loss of functional communication abilities. Communicative impairment in AD and PPA is especially apparent in the domain of naming common objects and familiar faces. We evaluated the effectiveness of a language intervention targeting maintenance of an individualized core vocabulary in a longitudinal cohort of older adults experiencing either PPA or AD. Method PPA (n = 9) and AD (n = 1) patients were administered a semantically based language treatment for up to 2 years. Patients repeatedly named and generated semantic features for a personalized lexicon consisting of 100 words. We evaluated naming accuracy and off-line neuropsychological measures at four successive timepoints. Naming accuracy was assessed in patients (n = 7) who completed at least three recurrent evaluations. Off-line neuropsychological performance was assessed across timepoints in all patients. Results Patients demonstrated relative preservation of naming trained words relative to a steep decline for untrained (control) words. The greatest decrements were observed for naming people relative to objects. Conclusion These results suggest that consistent training of a finite set of words can protect a core lexicon composed of crucial target concepts (e.g., a spouse's name). We discuss potential benefits and clinical implications of maintenance-based approaches to promoting language functioning in the context of neurodegeneration.

The sampling precision of research in five major areas of psychology

After obtaining a sample of published, peer-reviewed articles from journals with high and low impact factors in social, cognitive, neuro-, developmental, and clinical psychology, we used a priori equations recently derived by Trafimow (Educational and Psychological Measurement, 77, 831-854, 2017; Trafimow & MacDonald in Educational and Psychological Measurement, 77, 204-219, 2017) to compute the articles' median levels of precision. Our findings indicate that developmental research performs best with respect to precision, whereas cognitive research performs the worst; however, none of the psychology subfields excelled. In addition, we found important differences in precision between journals in the upper versus lower echelons with respect to impact factors in cognitive, neuro-, and clinical psychology, whereas the difference was dramatically attenuated for social and developmental psychology. Implications are discussed.

Tests of whole upright face processing in prosopagnosia: A literature review

Prosopagnosia refers to an acquired or developmental deficit in face recognition. This neuropsychological impairment has received increasing attention over the last decade, in particular because of an increased scientific interest in developmental prosopagnosia. Studies investigating prosopagnosia have used a variety of different clinical and experimental tests to assess face processing abilities. With such a large variety of assessment methods available, test selection can be challenging. Some previous works have aimed to provide an overview of tests used to diagnose prosopagnosia. However, no overview that is based on a structured review of the literature is available. We review the literature to identify tests that have been used to assess the processing of whole upright faces in acquired and developmental prosopagnosia over the last five years (2013-2017). We not only review tests that have been used for diagnostic purposes, but also tests that have been used for experimental purposes. Tests are categorised according to i) their experimental designs and, ii) the stage of face processing that they assess. On this basis, we discuss considerations regarding test designs for future studies. A visual illustration providing a structured overview of paradigms available for testing the processing of whole upright faces is provided. This visual illustration can be used to inform test selection when designing a study and to apply a structured approach to interpreting findings from the literature. The different approaches to assessment of face processing in prosopagnosia have been necessary and fruitful in generating data and hypotheses about the cause of face processing deficits. However, impairments at different levels of face processing have often been interpreted as reflecting a deficit in the recognition stage of face processing. Based on the data now available on prosopagnosia, we advocate for a more structured approach to assessment, which may facilitate a better understanding of the key deficits in prosopagnosia and of the level(s) of face processing that are impaired.