Search Results (17)

Background/Objectives: Posterior cortical atrophy, also referred to as Benson’s syndrome, is a presentation of Alzheimer’s disease that occurs in 5–15% of Alzheimer’s patients. Visual processing is the predominantly affected modality in posterior cortical atrophy, and symptoms such as prosopagnosia, simultanagnosia, alexia, optic ataxia, and visual hallucinations may occur, as well as blurred vision and visual distortions. Posterior cortical atrophy is considered to be a disease without a known cause or effective treatment. Methods: Here, we report a patient with posterior cortical atrophy who responded to a personalized, precision medicine protocol. Results: The patient had improved MRI volumetrics, symptoms, and cognitive testing. She regained the ability to read, use a computer, and undertake computer-based brain training, among other cognitive improvements. She has now sustained this improvement for over one year and continues to regain her independence and confidence. Conclusions: These results argue for additional laboratory testing in the evaluation of patients with posterior cortical atrophy, and they support the possibility of utilizing a similar approach in a proof-of-concept trial. Full article

Background and Clinical Significance: Visual agnosia and speech production deficits are well-described sequelae of neurosurgical interventions, but their selective dissociation remains rare. This report presents an unusual combination of postoperative deficits following awake resection of a left frontal low-grade glioma. Case Presentation: We present the case of a right-handed female with left hemisphere language dominance who had a left frontal low-grade glioma. Preoperatively, she exhibited anomia and dysexecutive syndrome, including difficulty completing everyday goal-directed tasks such as sending emails and paying for parking. Following awake tumor resection, she developed two rare, dissociated deficits: (1) speech restricted to infinitive verb forms and (2) selective visual agnosia for static images, with preserved recognition of dynamic stimuli. Conclusions: This uncommon clinical constellation highlights the vulnerability of left frontal language and ventral visual processing networks during surgery and supports the dual-stream model of vision and language production. We describe a selective form of static visual agnosia affecting static images with relative preservation of dynamic and object recognition, for which we use the descriptive label “astatopsia”. This peculiar clinical condition is rarely documented in this particular combination and has not, to the best of our knowledge, previously been denominated in such a manner in the literature. Full article

Background: Gerstmann syndrome (GS) is characterised by the tetrad of agraphia, acalculia, finger agnosia, and right-left disorientation, which was first described by Josef Gerstmann in 1924 and is conventionally linked to lesions of the dominant angular gyrus. Contemporary neuroimaging and lesion mapping research indicates that a more dispersed parietal and occipito-temporal network may be involved. Bilateral parietal lobe infarcts are uncommon and usually arise from embolic events or small artery pathology, frequently resulting in multifocal cognitive and perceptual impairments. Method: This case report describes a 52-year-old male presented with acute confusion, perseverative speech, and an inability to follow commands. The neurological examination indicated the presence of the complete Gerstmann tetrad. The Magnetic Resonance Imaging (MRI brain) revealed bilateral parieto-occipital infarcts, with greater severity on the left, indicative of ischaemia in the territory of the posterior cerebral artery (PCA). The medical team provided supportive care and implemented secondary stroke prevention, leading to partial neurocognitive recovery over a period of three weeks. Results: This case highlights a rare presentation of Gerstmann syndrome due to bilateral parieto-occipital infarcts and emphasises that the syndrome can arise from bilateral or widespread parietal injury rather than lesions limited to the angular gyrus. Conclusions: The prompt identification of the Gerstmann constellation helps localise the lesion, enhances diagnostic accuracy, and aids in rehabilitation planning. Full article

This work argues that there is more than one form of knowledge. By comparing human cognition with Rodney Brooks’ behavior-based robots, which act without representational content, I show that humans interact with the world through contentful representations, while robots rely on contentless, embodied routines. Drawing on empirical cases—spreading activation, object recognition, agnosia, and vision reconstruction—I argue that humans require content and thus face the hard problem of content. I propose that content is internally generated. Ultimately, I defend a pluralistic view: knowledge can be both contentful and contentless and neither form is inherently superior. Full article

Background/Objectives: As high-acuity vision is limited to a very small visual angle, examination of a scene requires multiple fixations. Simultanagnosia, a disorder wherein elements of a scene can be perceived correctly but cannot be integrated into a coherent whole, has been parsed into dorsal and ventral forms. In ventral simultanagnosia, limited visual integration is possible. This case study was the first to record gaze during the presentation of a series of visual stimuli, which required the processing of local and global elements. We hypothesised that gaze patterns would differ with successful processing and that feature integration could be disrupted by distractors. Methods: The patient received a neuropsychological assessment and underwent CT and MRI. Eye movements were recorded during the following tasks: (1) famous face identification, (2) facial emotion recognition, (3) identification of Ishihara colour plates, and (4) identification of both local and global letters in Navon composite letters, presented either alone or surrounded by filled black circles, which we hypothesised would impair global processing by disrupting fixation. Results: The patients identified no famous faces but scanned them qualitatively normally. The only emotion to be consistently recognised was happiness, whose scanpath differed from the other emotions. She identified none of the Ishihara plates, although her colour vision was normal on the FM-15, even mapping an unseen digit with fixations and tracing it with her finger. For plain Navon figures, she correctly identified 20/20 local and global letters; for the “dotted” figures, she was correct 19/20 times for local letters and 0/20 for global letters (chi-squared NS for local, p < 0.0001, global), with similar fixation of salient elements for both. Conclusions: Contrary to our hypothesis, gaze behaviour was largely independent of the ability to process global stimuli, showing for the first time that normal acquisition of visual information did not ensure its integration into a percept. The core defect lay in processing, not acquisition. In the novel Navon task, adding distractors abolished feature integration without affecting the fixation of the salient elements, confirming for the first time that distractors could disrupt the processing, not the acquisition, of visual information in this disorder. Full article

Background/Objectives: Vestibular agnosia is characterized by a reduced or absent self-motion perception while demonstrating the presence of normal peripheral vestibular function following stimulation. This condition has previously been reported by previous authors in different populations and more recently in traumatic brain injury patients. However, the underlying mechanisms responsible for vestibular agnosia remain a matter of debate. The objective of this manuscript is to review and compare the behavioral and neuroanatomical findings in populations where vestibular agnosia has been demonstrated to better understand the underlying mechanism. Methods: A review of the literature was conducted using four databases: Medline, Embase, Google Scholar, and PubMed. A normal vestibulo-ocular reflex function with an impaired self-motion perception following vestibular stimulation represented the inclusion criteria used. Results: Behavioral data reviewed in the studies revealed a clear association with postural instability. However, no consensus can be drawn from neuroanatomical data due to variability in brain impairments in those populations even though impairments in the parietal cortex are often reported. Conclusions: In general, behavioral data and neuroanatomical data regarding vestibular agnosia have been poorly documented throughout the literature. However, vestibular agnosia can be observed in different populations and is present in concomitant postural control deficits, an important predictor of falls. Finally, even though the parietal cortex has been associated with vestibular agnosia, future studies are required to adequately identify the underlying mechanism. Indeed, the parietal cortex could be part of a larger network mediating vestibular agnosia. This review proposes various methods that future studies should use to overcome the present limitations. Full article

The recent publication of Merleau-Ponty’s work from the late Forties contributes valuable material for those interested in reconstructing a specifically Merleau-Pontian theory of value. In this paper, I examine how, in these texts, Merleau-Ponty’s political concerns show themselves to expand upon the famous analysis of the case of Schneider in Phenomenology of Perception. This retroactively offers an opportunity for a normative reading of the case of Schneider and for identifying Merleau-Ponty’s practical philosophy as concerned with preventing and healing agnosia in politics and ethics. On the basis of this negative hypothesis—that the ethical project is to oppose agnosia—it becomes possible to formulate a positive ethics. There, the unpublished texts also expand upon the Phenomenology of Perception: they propose a humanism which relies on the notion of hermeneutic freedom as the chief practical virtue and elaborate, somewhat unexpectedly, an analysis of play as the existential attitude that corresponds to this virtue. I conclude with a meta-ethical assessment of the merits of this ethical construction. Full article

In neuropsychology and clinical psychology, the efficacy of virtual reality (VR) experiences for knowledge acquisition and the potential for modifying conduct are well documented. Consequently, the scope of VR experiences for educational purposes has expanded in the health field in recent years. In this study, we sought to assess the effectiveness of ViveDe in a psychoeducational caregiver program. ViveDe is a VR application that presents users with possible daily life situations from the perspective of individuals with dementia. These situations can be experienced in immersive mode through 360° video. This research aimed to ascertain the associations between the sense of presence that can be achieved in VR and some users’ psychological characteristics, such as distress and empathetic disposition. The study involved 36 informal caregivers of individuals with Alzheimer’s disease. These participants were assessed using scales of anxiety and depression, perceived stress, empathy, and emotional regulation. They were asked to participate in a six-session psychoeducation program conducted online on dementia topics, in addition to experiencing the ViveDe application. The immersive VR sessions enabled the caregivers to directly experience the symptoms of dementia (e.g., spatial disorientation, agnosia, difficulty in problem-solving, and anomia) in everyday and social settings. The results indicated that although the experience in ViveDe (evaluated using the XRPS scale and five questions about emotional attunement) showed efficacy in producing a sense of first-person participation in the symptoms of dementia, further research is needed to confirm this. The structural equation model provided evidence that the characteristics of individuals who enjoy the VR experience play a determining role in the perceived sense of presence, which in turn affects the efficacy of the VR experience as a psychoeducational tool. Further research will be conducted to ascertain the potential role of these elements in conveying change in the caregivers of people with dementia. This will help us study the long-term effectiveness of a large-scale psychoeducation program in VR. Full article

The non-dual path—which runs through the undercurrent of all the great traditions and religions at their esoteric and initiatory level—is underpinned by the doctrine of Unity, namely the fact that the ultimate Reality is one. In this respect, negation is neither local nor tied to a positive content (simple negation), nor does it affirm elsewhere the existence of what it denies (presuppositional negation), but it presents itself, in a more original way, as the neutralization of all determination and dualism, i.e., of false assumptions on what there is that prevent us from accessing to that which, being unqualifiable, really is. In order to grasp the meaning of the via negativa as a path of deconstruction and disidentification (Neti-Neti) and of the apparent obscurity of non-knowledge (Agnosia), which is expressed in the lexicon proper to negative theology (silence, abyss, inexpressible, unrepresentable, non-manifest), the questioning about the Being-in-itself must not be separated from that about one’s own Self. This original negativity, which proceeds from the metaphysical ignorance of the truth of the self and the truth of what is (Avidyā), once lifted, opens the way to the subjective apprehension of Reality, i.e., the perspective of transcendental interiority: the Supreme Identity between the Being-in-itself and Oneself. Full article

Visuo-motor adaptation to optical prisms (Prism Adaptation, PA), displacing the visual scene laterally, is a behavioral method used for the experimental investigation of visuomotor plasticity, and, in clinical settings, for temporarily ameliorating and rehabilitating unilateral spatial neglect. This study investigated the building up of PA, and the presence of the typically occurring subsequent Aftereffects (AEs) in a brain-damaged patient (TMA), suffering from apperceptive agnosia and a right visual half-field defect, with bilateral atrophy of the parieto-occipital cortices, regions involved in PA and AEs. Base-Right prisms and control neutral lenses were used. PA was achieved by repeated pointing movements toward three types of stimuli: visual, auditory, and bimodal audio-visual. The presence and the magnitude of AEs were assessed by proprioceptive, visual, visuo-proprioceptive, and auditory-proprioceptive straight-ahead pointing tasks. The patient’s brain connectivity was investigated by Diffusion Tensor Imaging (DTI). Unlike control participants, TMA did not show any adaptation to prism exposure, but her AEs were largely preserved. These findings indicate that AEs may occur even in the absence of PA, as indexed by the reduction of the pointing error, showing a dissociation between the classical measures of PA and AEs. In the PA process, error reduction, and its feedback, may be less central to the building up of AEs, than the sensorimotor pointing activity per se. Full article

Dementia is a neurodegenerative disease that leads to the development of cognitive deficits, such as aphasia, apraxia, and agnosia. It is currently considered one of the most significant major medical problems worldwide, primarily affecting the elderly. This condition gradually impairs the patient’s cognition, eventually leading to the inability to perform everyday tasks without assistance. Since dementia is an incurable disease, early detection plays an important role in delaying its progression. Because of this, tools and methods have been developed to help accurately diagnose patients in their early stages. State-of-the-art methods have shown that the use of syntactic-type linguistic features provides a sensitive and noninvasive tool for detecting dementia in its early stages. However, these methods lack relevant semantic information. In this work, we propose a novel methodology, based on the semantic features approach, by using sentence embeddings computed by Siamese BERT networks (SBERT), along with support vector machine (SVM), K-nearest neighbors (KNN), random forest, and an artificial neural network (ANN) as classifiers. Our methodology extracted 17 features that provide demographic, lexical, syntactic, and semantic information from 550 oral production samples of elderly controls and people with Alzheimer’s disease, provided by the DementiaBank Pitt Corpus database. To quantify the relevance of the extracted features for the dementia classification task, we calculated the mutual information score, which demonstrates a dependence between our features and the MMSE score. The experimental classification performance metrics, such as the accuracy, precision, recall, and F1 score (77, 80, 80, and 80%, respectively), validate that our methodology performs better than syntax-based methods and the BERT approach when only the linguistic features are used. Full article

The aim of this article is to discuss the logic and assumptions behind the concept of neural reuse, to explore its biological advantages and to discuss the implications for the cognition of a brain that reuses existing circuits and resources. We first address the requirements that must be fulfilled for neural reuse to be a biologically plausible mechanism. Neural reuse theories generally take a developmental approach and model the brain as a dynamic system composed of highly flexible neural networks. They often argue against domain-specificity and for a distributed, embodied representation of knowledge, which sets them apart from modular theories of mental processes. We provide an example of reuse by proposing how a phylogenetically more modern mental capacity (mental rotation) may appear through the reuse and recombination of existing resources from an older capacity (motor planning). We conclude by putting arguments into context regarding functional modularity, embodied representation, and the current ontology of mental processes. Full article

Background: Stroke is the leading cause of cortical deafness (CD), the most severe form of central hearing impairment. CD remains poorly characterized and perhaps underdiagnosed. We perform a systematic review to describe the clinical and radiological features of stroke-associated CD. Methods: PubMed and the Web of Science databases were used to identify relevant publications up to 30 June 2021 using the MeSH terms: “deafness” and “stroke”, or “hearing loss” and “stroke” or “auditory agnosia” and “stroke”. Results: We found 46 cases, caused by bilateral lesions within the central auditory pathway, mostly located within or surrounding the superior temporal lobe gyri and/or the Heschl’s gyri (30/81%). In five (13.51%) patients, CD was caused by the subcortical hemispheric and in two (0.05%) in brainstem lesions. Sensorineural hearing loss was universal. Occasionally, a misdiagnosis by peripheral or psychiatric disorders occurred. A few (20%) had clinical improvement, with a regained oral conversation or evolution to pure word deafness (36.6%). A persistent inability of oral communication occurred in 43.3%. A full recovery of conversation was restricted to patients with subcortical lesions. Conclusions: Stroke-associated CD is rare, severe and results from combinations of cortical and subcortical lesions within the central auditory pathway. The recovery of functional hearing occurs, essentially, when caused by subcortical lesions. Full article

Dementia comprises a collection of cognitive and sensory symptoms, including memory loss, communication difficulties, difficulty in planning and problem solving, disorientation and confusion, compromised olfaction, loss of visual perception, agnosia; and psychological symptoms, including personality and behavioral changes, depression, anxiety, hallucination, mood swings, agitation, and apathy [...] Full article

Visual recognition deficits are the hallmark symptom of visual agnosia, a neuropsychological disorder typically associated with damage to the visual system. Most research into visual agnosia focuses on characterizing the deficits through detailed behavioral testing, and structural and functional brain scans are used to determine the spatial extent of any cortical damage. Although the hierarchical nature of the visual system leads to clear predictions about the temporal dynamics of cortical deficits, there has been little research on the use of neuroimaging methods with high temporal resolution to characterize the temporal profile of agnosia deficits. Here, we employed high-density electroencephalography (EEG) to investigate alterations in the temporal dynamics of the visual system in two individuals with visual agnosia. In the context of a steady state visual evoked potential paradigm (SSVEP), individuals viewed pattern-reversing checkerboards of differing spatial frequency, and we assessed the responses of the visual system in the frequency and temporal domain. JW, a patient with early visual cortex damage, showed impaired SSVEP response relative to a control group and to the second patient (SM) who had right temporal lobe damage. JW also showed lower decoding accuracy for early visual responses (around 100 ms). SM, whose lesion is more anterior in the visual system, showed good decoding accuracy initially but low decoding after 500 ms. Overall, EEG and multivariate decoding methods can yield important insights into the temporal dynamics of visual responses in individuals with visual agnosia. Full article