Littérature scientifique sur le sujet « Prosopagnosia, Self recognition, Eye movements »

Congenital prosopagnosia (CP), a life-long impairment in face processing that occurs in the absence of any apparent brain damage, provides a unique model in which to explore the psychological and neural bases of normal face processing. The goal of this review is to offer a theoretical and conceptual framework that may account for the underlying cognitive and neural deficits in CP. This framework may also provide a novel perspective in which to reconcile some conflicting results that permits the expansion of the research in this field in new directions. The crux of this framework lies in linking the known behavioral and neural underpinnings of face processing and their impairments in CP to a model incorporating grid cell–like activity in the entorhinal cortex. Moreover, it stresses the involvement of active, spatial scanning of the environment with eye movements and implicates their critical role in face encoding and recognition. To begin with, we describe the main behavioral and neural characteristics of CP, and then lay down the building blocks of our proposed model, referring to the existing literature supporting this new framework. We then propose testable predictions and conclude with open questions for future research stemming from this model.

Incorporation of visual-related self-action signals can help neural networks learn invariance. We describe a method that can produce a network with invariance to changes in visual input caused by eye movements and covert attention shifts. Training of the network is controlled by signals associated with eye movements and covert attention shifting. A temporal perceptual stability constraint is used to drive the output of the network toward remaining constant across temporal sequences of saccadicmotions and covert attention shifts. We use a four-layer neural network model to perform the position-invariant extraction of local features and temporal integration of invariant presentations of local features in a bottom-up structure. We present results on both simulated data and real images to demonstrate that our network can acquire both position and attention shift invariance.

A home-auxiliary robot system based on characteristics of the electrooculogram (EOG) and tongue signal is developed in the current study, which can provide daily life assistance for people with physical mobility disabilities. It relies on five simple actions (blinking twice in a row, tongue extension, upward tongue rolling, and left and right eye movements) of the human head itself to complete the motions (moving up/down/left/right and double-click) of a mouse in the system screen. In this paper, the brain network and BP neural network algorithms are used to identify these five types of actions. The result shows that, for all subjects, their average recognition rates of eye blinks and tongue movements (tongue extension and upward tongue rolling) were 90.17%, 88.00%, and 89.83%, respectively, and after training, the subjects can complete the five types of movements in sequence within 12 seconds. It means that people with physical disabilities can use the system to quickly and accurately complete life self-help, which brings great convenience to their lives.

The study of eye movements and the measurement of the resulting biopotential, referred to as electrooculography (EOG), may find increasing use in applications within the domain of activity recognition, context awareness, mobile human–computer and human–machine interaction (HCI/HMI), and personal medical devices; provided that, seamless sensing of eye activity and processing thereof is achieved by a truly wearable, low-cost, and accessible technology. The present study demonstrates an alternative to the bulky and expensive camera-based eye tracking systems and reports the development of a graphene textile-based personal assistive device for the first time. This self-contained wearable prototype comprises a headband with soft graphene textile electrodes that overcome the limitations of conventional “wet” electrodes, along with miniaturized, portable readout electronics with real-time signal processing capability that can stream data to a remote device over Bluetooth. The potential of graphene textiles in wearable eye tracking and eye-operated remote object interaction is demonstrated by controlling a mouse cursor on screen for typing with a virtual keyboard and enabling navigation of a four-wheeled robot in a maze, all utilizing five different eye motions initiated with a single channel EOG acquisition. Typing speeds of up to six characters per minute without prediction algorithms and guidance of the robot in a maze with four 180° turns were successfully achieved with perfect pattern detection accuracies of 100% and 98%, respectively.

AbstractSensory conflict has been used to explain the way we perceive and control our self-motion, as well as the aetiology of motion sickness. However, recent research on simulated viewpoint jitter provides a strong challenge to one core prediction of these theories — that increasing sensory conflict should always impair visually induced illusions of self-motion (known as vection). These studies show that jittering self-motion displays (thought to generate significant and sustained visual–vestibular conflict) actually induce superior vection to comparable non-jittering displays (thought to generate only minimal/transient sensory conflict). Here we review viewpoint jitter effects on vection, postural sway, eye-movements and motion sickness, and relate them to recent behavioural and neurophysiological findings. It is shown that jitter research provides important insights into the role that sensory interaction plays in self-motion perception.

Our purpose is to allow an autonomous robot to find and to categorise objects in a visual scene according to the actions it performs. The robot information comes from a CCD gray-level camera. The edges are extracted and a simple DOG filter is used to find ‘corner’-like forms in the image. These positions are used as possible focus points. The robot eye performs saccadic movements on the whole visual scene. A log-polar transform of the image is performed in the neighbourhood of the focus points to mimic the projection of the retina on the primary cortical areas. It simplifies object recognition by allowing size and rotation invariance. Those local views are learned on a self-organised topological map according to a vigilance level. At the same time, the robot tries to associate them with a particular action. For instance, we want the robot to learn to turn left when it sees a ‘turn-left’ arrow in the image. The problem is that the robot cannot see only a single object in the visual scene. There are many distractors such as doors, holes, and other objects not significant for the robot behaviour. At the beginning, a probabilistic conditioning rule allows the robot to associate all the seen objects to the performed movement. The robot repeatedly removes or creates new synaptic links to take into account only salient associations. As a result, object categorisation is not performed at the visual level (pure recognition of visual shape), but at the motor level (the action the robot has to perform). Our experiments show that learning and recognition of an object can be greatly simplified if we take into account the sensory-motor loop of the robot in its environment.

Objects along a route can help us to successfully navigate through our surroundings. Previous neuroimaging research has shown that the parahippocampal gyrus (PHG) distinguishes between objects that were previously encountered at navigationally relevant locations (decision points) and irrelevant locations (nondecision points) during simple object recognition. This study aimed at unraveling how this neural marking of objects relevant for navigation is established during learning and postlearning rest. Twenty-four participants were scanned using fMRI while they were viewing a route through a virtual environment. Eye movements were measured, and brain responses were time-locked to viewing each object. The PHG showed increased responses to decision point objects compared with nondecision point objects during route learning. We compared functional connectivity between the PHG and the rest of the brain in a resting state scan postlearning with such a scan prelearning. Results show that functional connectivity between the PHG and the hippocampus is positively related to participants' self-reported navigational ability. On the other hand, connectivity with the caudate nucleus correlated negatively with navigational ability. These results are in line with a distinction between egocentric and allocentric spatial representations in the caudate nucleus and the hippocampus, respectively. Our results thus suggest a relation between navigational ability and a neural preference for a specific type of spatial representation. Together, these results show that the PHG is immediately involved in the encoding of navigationally relevant object information. Furthermore, they provide insight into the neural correlates of individual differences in spatial ability.

Inflammatory pseudotumor (IPT) is a rarely occurring lesion with no identifiable local or systemic cause. First described in 1905 by Birch-Hirschfield,1 it remains somewhat of an enigmatic disease entity despite multiple otolaryngologic, radiologic, and pathologic reports. The term “pseudotumor” was used because these lesions mimic invasive malignant tumors, both clinically and radiologically. IPT most commonly involves the lung and orbit, but has also been reported to occur at sites that make biopsy or excision difficult or potentially disfiguring.2 Its diagnosis and prompt recognition may help avoid radical surgery for this benign lesion. CASE A 27-year-old male was seen at our outpatient department due to a progressively enlarging left infraorbital mass. Two years prior, the patient noted a swelling over his left infraorbital area. The swelling was somewhat painful and rapidly grew in size so that it measured almost 2.5x2.5cm after a week. Still tender, it became firm and violaceous in color. He sought medical attention at a local hospital after one more week of persistent swelling and increasing cheek pain, but denied excessive lacrimation, blurring of vision, orbital pain, eye discharge or numbness. Incision and drainage of the left infraorbital mass drained purulent material with resolution of the swelling and associated symptoms, but a pea-sized mass was still palpable over the post operative site. Over the months that followed, the mass gradually increased in size, with occasional serosanguinous discharge from the incision site. There was no pain, numbness or blurring of vision. He self-medicated with Cefalexin, taken irregularly for 8 months without any improvement, before finally consulting again. An orbital CT scan requested by the referring Ophthalmology service showed an expansile, mildly enhancing soft tissue mass with few peripheral foci of calcifications measuring 8.2 x 4.4 x 6.4 cm (Figures 1 A, B) completely occupying the left maxillary sinus and extending up to the infero-lateral aspect of the left orbital cavity. There was erosion of the lateral portion of the left orbital floor and disruption of the frontal process of the left zygomatic bone with obliteration and effacement of the left pterygopalatine fossa. Our physical examination revealed a firm, fixed, nontender 4x4cm left inferior orbital mass with serosanguinous discharge, and a bulging lateral nasal wall. Epiphora from the left eye suggested nasolacrimal duct obstruction, but vision and extraocular movements were intact. Caldwell-Luc biopsy surprisingly yielded only necrotic and inflammatory tissues despite generous samples from multiple sections of the maxillary portion, and inflammatory polyps from the intranasal component. At surgery after a few weeks, the mass still occupied the entire left maxillary sinus despite the previous biopsy which had removed a significant amount of tumor. Furthermore, the mass now extended beyond the maxillary sinus into the left upper gingivobuccal area thru the previous maxillary window. The entire clinically aggressive maxillary sinus mass was removed under endoscopic guidance, but the final histopathology report was still similar to the previous findings of necrotic and inflammatory tissues. A month after surgery, the patient was seen at the Emergency room for left infraorbital swelling and discharge. Contrast-enhanced MRI of the nasopharynx showed a large expansile left maxillary sinus lesion bulging into the nasal cavity, extending into adjacent lateral orbital soft tissue and extending into the buccal space through an apparently disrupted left inferolateral maxillary wall. Intravenous antibiotics and a high-dose steroid trial resulted in complete disappearance of the left infraorbital mass and discharge within a week, and the patient was discharged on a tapering steroid dose. DISCUSSION Inflammatory pseudotumor is a quasi-neoplastic lesion that has been reported to occur in nearly every site in the body, most commonly involving the lung and the orbit, and rarely the maxillary sinus1. Its diagnosis is usually by exemption since clinical and histopathologic findings are sometimes vague and inconsistent. The exact etiology of these lesions is not clear. It has been postulated that they might be the result of a post-inflammatory repair process, a metabolic disturbance, or an antigen-antibody interaction with an agent that was no longer identifiable in aspiration or biopsy material.3 The clinical findings in a patient with an inflammatory pseudotumor are variable, depending on the growth rate of the lesion and the specific structures that have been affected. Inflammatory pseudotumors have been reported to cause chronic cough (as a result of endobronchial growth), dry cough, fever, pleuritic pain, right upper quadrant or epigastric pain, and several constitutional symptoms, such as malaise, weight loss, fatigue, and syncope. Inflammatory pseudotumors have been found incidentally during imaging examinations for other reasons.3 Extraorbital inflammatory pseudotumor of head and neck can occur in the nasal cavity, nasopharynx, maxillary sinus, larynx and trachea. Perineural spread along maxillary, mandibular and hypoglossal nerves had been described. Sinonasal inflammatory psuedotumors do not affect a particular age group and cause no systemic symptoms. However, they have a more aggressive appearance than those of the orbit, with bony changes such as erosion, remodelling and sclerosis usually seen on radiographic studies.4 On CAT scans, a moderately enhancing soft tissue mass is usually seen, accompanied by bony changes common among malignant processes.5 On cut sections, inflammatory cells dominate as well as necrotic tissues. In some patients, laboratory findings are normal; in others, there might be an elevated erythrocyte sedimentation rate and C-reactive protein level and sometimes a high white blood cell count3. However, none of the published reports on inflammatory pseudotumor have mentioned any presence of positive tumor markers. Complete surgical resection if possible is the treatment of choice for sinonasal inflammatory pseudotumors, followed by corticosteroids in cases of incomplete excision. Response to steroids is often unpredictable, but these drugs are the primary treatment method for orbital inflammatory pseudotumor. The only cases in which radiation therapy is indicated are those patients for whom surgery or corticosteroid therapy is unsuccessful or contraindicated.6

AbstractPrevious studies showed that (a) performing pointing movements towards to-be-remembered locations enhanced their later recognition, and (b) in a joint-action condition, experimenter-performed pointing movements benefited memory to the same extent as self-performed movements. The present study replicated these findings and additionally recorded participants’ fixations towards studied arrays. Each trial involved the presentation of two consecutive spatial arrays, where each item occupied a different spatial location. The item locations of one array were encoded by mere visual observation (the no-move array), whereas the locations of the other array were encoded by observation plus pointing movements (the move array). Critically, in Experiment 1, participants took turns with the experimenter in pointing towards the move arrays (joint-action condition), while in Experiment 2 pointing was performed only by the experimenter (passive condition). The results showed that the locations of move arrays were recognized better than the locations of no-move arrays in Experiment 1, but not in Experiment 2. The pattern of eye-fixations was in line with behavioral findings, indicating that in Experiment 1, fixations to the locations of move arrays were higher in number and longer in duration than fixations to the locations of no-move arrays, irrespective of the agent who performed the movements. In contrast, no differences emerged in Experiment 2. We propose that, in the joint-action condition, self- and other-performed pointing movements are coded at the same representational level and their functional equivalency is reflected in a similar pattern of eye-fixations.

Congenital prosopagnosia consists of the failure to develop normal face recognition ability despite intact low-level perceptual and intellectual functioning, and in the context of normal exposure to faces throughout the individual’s life. Typically, these individuals are able to perceive facial stimuli as faces but fail to identify a face as familiar or unfamiliar and to identify it. Despite the large amount of studies that have investigated face recognition in individuals with typical development and in congenital prosopagnosics over the last twenty years, we are still far from a complete understanding of the mechanisms underlying typical and atypical face recognition, and some research questions are still open. For this reason, the present dissertation investigates some perceptual effects in individuals with a selective deficit in face recognition processing in order to reach a better understanding of what happens during a successful and unsuccessful face recognition process. In particular, by using a combination of behavioural and eye-tracking methods, I investigated whether the left perceptual bias and the self-face advantage are shown by individuals with congenital prosopagnosia and are truly face-specific or not. My results demonstrate that, whereas the left perceptual bias seems to characterize the recognition of unfamiliar faces in good recognizers, individuals with congenital prosopagnosia seem to show an opposite bias (i.e., a right perceptual bias) during the recognition of the self-face. Moreover, despite their face recognition impairment, congenital prosopagnosics consistently show high accuracy in recognizing their own face (i.e., a self-face advantage). Furthermore, some of the studies I conducted on the visual scanning strategies of this population demonstrated that the self-face advantage phenomenon is not associated with a different exploration of the face stimuli, suggesting that it could reflect a more general self-advantage and not be face-specific. Finally, the evidence presented in this dissertation also highlights that individuals with face impairment from birth show some difficulties in recognizing stimuli with high degree of similarity (such as objects belonging to the same class), and that these difficulties are associated with a different pattern of visual exploration. Overall, the evidence illustrated in the present thesis helps to shed light on the mechanisms characterizing face recognition and to expand our knowledge on the impairment affecting individuals with congenital prosopagnosia.