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Prosopagnosia: when all faces look the same
No full textThis book provides readers with a simplified and comprehensive account of the cognitive and neural bases of face perception in humans. Faces are ubiquitous in our environment and we rely on them during social interactions. The human face processing system allows us to extract information about the identity, gender, age, mood, race, attractiveness and approachability of other people in about a fraction of a second, just by glancing at their faces. By introducing readers to the most relevant research on face recognition, this book seeks to answer the questions: “Why are humans so fast at recognizing faces?”, “Why are humans so efficient at recognizing faces?”, “Do faces represent a particular category for the human visual system?”, What makes face perception in humans so special?, “Can our face recognition system fail”? This book presents the author’s findings on face perception during his research studies on both normal subjects and subjects with prosopagnosia, a neurological disorder characterized by the inability to recognize faces. The book describes two known forms of prosopagnosia: acquired prosopagnosia, which is the result of a brain lesion, and congenital prosopagnosia, which refers to a lifelong, developmental impairment of face recognition. Written in a comprehensive and accessible style, this book addresses both experts (cognitive scientists, psychologists, neuroscientists and computer scientists) and the general public, and aims at raising awareness for a debilitating face recognition disorder, such as prosopagnosia, which is often ignored or misdiagnosed as autism, with serious consequences for the affected persons and their families
Prosopagnosia. Un mondo di facce uguali
No full textIn questo libro l'autore racconta le basi cognitive e neurali del processamento dei volti. In particolare descrive la ricerca effettuata in persone normali ed in persone con Prosopagnosia, una condizione per cui, chi ne soffre, e’ incapace di utilizzare i volti per riconoscere le persone, riportando i risultati più importanti che coinvolgono le due forme conosciute di prosopagnosia, quella acquisita (conseguenza di un danno cerebrale) e quella congenita (condizione che si riferisce all’incapacità’ di riconoscere i volti dalla nascita)
More than just a problem with faces: altered body perception in a group of congenital prosopagnosics
Full text linkIt has been estimated that one out of 40 people in the general population suffer from congenital prosopagnosia (CP), a neurodevelopmental disorder characterized by difficulty identifying people by their faces. CP involves impairment in recognizing faces, although the perception of non-face stimuli may also be impaired. Given that social interaction depends not only on face processing, but also on the processing of bodies, it is of theoretical importance to ascertain whether CP is also characterized by body perception impairments. Here, we tested 11 CPs and 11 matched control participants on the Body Identity Recognition Task (BIRT), a forced-choice match-to-sample task, using stimuli that require processing of body-specific, not clothing-specific, features. Results indicated that the group of CPs were as accurate as controls on the BIRT, which is in line with the lack of body perception complaints by CPs. However, the CPs were slower than controls, and when accuracy and response times were combined into inverse efficiency scores (IESs), the group of CPs were impaired, suggesting that the CPs could be using more effortful cognitive mechanisms to be as accurate as controls. In conclusion, our findings demonstrate that CP may not generally be limited to face processing difficulties, but may also extend to body perception
Stimulus Inversion and Emotional Expressions Independently Affect Face and Body Perception: An ERP Study
No full textFaces and bodies provide critical cues for social interaction and communication. Their structural encoding depends on configural processing, as suggested by the detrimental effect of stimulus inversion for both faces (i.e., face inversion effect - FIE) and bodies (body inversion effect - BIE). An occipito-temporal negative event-related potential (ERP) component peaking around 170 ms after stimulus onset (N170) is consistently elicited by human faces and bodies and is affected by the inversion of these stimuli. Albeit it is known that emotional expressions can boost structural encoding (resulting in larger N170 components for emotional than for neutral faces), little is known about body emotional expressions. Thus, the current study investigated the effects of different emotional expressions on structural encoding in combination with FIE and BIE. Three ERP components (P1, N170, P2) were recorded using a 128-channel electroencephalogram (EEG) when participants were presented with (upright and inverted) faces and bodies conveying four possible emotions (happiness, sadness, anger, fear) or no emotion (neutral). Results demonstrated that inversion and emotional expressions independently affected the Accuracy and amplitude of all ERP components (P1, N170, P2). In particular, faces showed specific effects of emotional expressions during the structural encoding stage (N170), while P2 amplitude (representing top-down conceptualisation) was modified by emotional body perception. Moreover, the task performed by participants (i.e., implicit vs. explicit processing of emotional information) differently influenced Accuracy and ERP components. These results support integrated theories of visual perception, thus speaking in favour of the functional independence of the two neurocognitive pathways (one for structural encoding and one for emotional expression analysis) involved in social stimuli processing. Results are discussed highlighting the neurocognitive and computational advantages of the independence between the two pathways
I’ll have this salad on the left, and I’ll have it now! The influence of hunger on healthy-left nudge
No full textDisplaying foods congruently with the healthy-left/unhealthy-right (HL/UR) horizontal mental representation could, through self-control facilitation, lead to healthier food choices. Here, by using two versions of the same on-line menu, we tested whether the healthy-left nudge was influenced by the hunger of our participants. A total of 192 participants filled the HL/UR version whereas 194 filled the specular version (unhealthy-left/healthy-right; UL/HR) of the same survey. We did not find a significant difference in healthy (vs unhealthy) item choices when displayed on the left vs the right page of the menu: this null result can be attributed to sated participants that decided to eat the product later. On the opposite, hungry participants who preferred to eat the product immediately were nudged toward healthy (vs unhealthy) products when they were listed on the left page as compared to the right. The implications of these findings are discussed in the context of healthy nudge
Semantic information can facilitate covert face recognition in congenital prosopagnosia
No full textPeople with congenital prosopagnosia have never developed the ability to accurately recognize faces. This single case investigation systematically investigates covert and overt face recognition in C., a 69 year-old woman with congenital prosopagnosia. Specifically, we: (a) describe the first assessment of covert face recognition in congenital prosopagnosia using multiple tasks; (b) show that semantic information can contribute to covert recognition; and (c) provide a theoretical explanation for the mechanisms underlying covert face recognition. © 2010 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business
What is overt and what is covert in congenital prosopagnosia?
No full textThe term covert recognition refers to recognition without awareness. In the context of face recognition, it refers to the fact that some individuals show behavioural, electrophysiological or autonomic indices of recognition in the absence of overt, conscious recognition. Originally described in cases of people that have lost their ability to overtly recognize faces (acquired prosopagnosia, AP), covert face recognition has more recently also been described in cases of congenital prosopagnosia (CP), who never develop typical overt face recognition skills. The presence of covert processing in a developmental disorder such as CP is a particularly intriguing phenomenon, and its investigation is relevant for a variety of reasons. From a theoretical point of view, it is useful to help shed light on the cognitive and neural underpinnings of face recognition deficits. From a clinical point of view, it has the potential to aid the design of rehabilitation protocols aimed at improving face recognition skills in this population. In the current review we selectively summarize the recent literature on covert face recognition in CP, highlight its main findings, and provide a theoretical interpretation for them. © 2012 Springer Science+Business Media New York
Anodal-tDCS over the human right occipital cortex enhances the perception and memory of both faces and objects
Full text linkAccurate face processing skills are pivotal for typical social cognition, and impairments in this ability characterise various clinical conditions (e.g., prosopagnosia). No study to date has investigated whether transcranial direct current stimulation (tDCS) can causally enhance face processing. In addition, the category- and the process-specificity of tDCS effects, as well as the role of the timing of neuromodulation with respect to the execution of cognitive tasks are still unknown. In this single-blind, sham-controlled study, we examined whether the administration of anodal-tDCS (a-tDCS) over the right occipital cortex of healthy volunteers (N=64) enhances performance on perceptual and memory tasks involving both face and object stimuli. Neuromodulation was delivered in two conditions: online (a-tDCS during task execution) and offline (a-tDCS before task execution). The results demonstrate that offline a-tDCS enhances the perception and memory performance of both faces and objects. There was no effect of online a-tDCS on behaviour. Furthermore, the offline effect was site-specific since a-tDCS over the sensory-motor cortex did not lead to behavioural changes. Our results add relevant information about the breadth of cognitive processes and visual stimuli that can be modulated by tDCS, and about the design of effective neuromodulation protocols, which have implications for advancing theories in cognitive neuroscience and clinical applications
Deep learning applied to EEG source-data reveals both ventral and dorsal visual stream involvement in holistic processing of social stimuli
Full text linkAbstract Perception of social stimuli (faces and bodies) relies on “holistic” (i.e., global) mechanisms, as supported by picture-plane inversion: perceiving inverted faces/bodies is harder than perceiving their upright counterpart. Albeit neuroimaging evidence suggested involvement of face-specific brain areas in holistic processing, their spatiotemporal dynamics and selectivity for social stimuli is still debated. Here, we investigate the spatiotemporal dynamics of holistic processing for faces, bodies and houses (adopted as control non-social category), by applying deep learning to high-density electroencephalographic signals (EEG) at source-level. Convolutional neural networks were trained to classify cortical EEG responses to stimulus orientation (upright/inverted), separately for each stimulus type (faces, bodies, houses), resulting to perform well above chance for faces and bodies, and close to chance for houses. By explaining network decision, the 150–200 ms time interval and few visual ventral-stream regions were identified as mostly relevant for discriminating face and body orientation (lateral occipital cortex, and for face only, precuneus cortex, fusiform and lingual gyri), together with two additional dorsal-stream areas (superior and inferior parietal cortices). Overall, the proposed approach is sensitive in detecting cortical activity underlying perceptual phenomena, and by maximally exploiting discriminant information contained in data, may reveal spatiotemporal features previously undisclosed, stimulating novel investigations
Covert face recognition in congenital prosopagnosia: A group study
No full textIntroduction: Even though people with congenital prosopagnosia (CP) never develop a normal ability to "overtly" recognize faces, some individuals show indices of "covert" (orimplicit) face recognition. The aim of this study was to demonstrate covert face recognition in CP when participants could not overtly recognize the faces. Methods: Eleven people with CP completed three tasks assessing their overt face recognition ability, and three tasks assessing their "covert" face recognition: a Forced choice familiarity task, a Forced choice cued task, and a Priming task. Results: Evidence of covert recognition was observed with the Forced choice familiarity task, but not the Priming task. In addition, we propose that the Forced choice cued task does not measure covert processing as such, but instead "provoked-overt" recognition. Conclusions: Our study clearly shows that people with CP demonstrate covert recognition for faces that they cannot overtly recognize, and that behavioural tasks vary in their sensitivity to detect covert recognition in CP. © 2011 Elsevier Srl
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