Associative visual agnosia resulting from a disconnection between intact visual memory and semantic systems

Clinical and structural disconnectome evaluation in a case of optic aphasia

Optic Aphasia (OA) and Associative Visual Agnosia (AVA) are neuropsychological disorders characterized by impaired naming on visual presentation. From a cognitive point of view, while stimulus identification is largely unimpaired in OA (where access to semantic knowledge is still possible), in AVA it is not. OA has been linked with right hemianopia and disconnection of the occipital right-hemisphere (RH) visual processing from the left hemisphere (LH) language areas.In this paper, we describe the case of AA, an 81-year-old housewife suffering from a deficit in naming visually presented stimuli after left occipital lesion and damage to the interhemispheric splenial pathway. AA has been tested through a set of tasks assessing different levels of visual object processing. We discuss behavioral performance as well as the pattern of lesion and disconnection in relation to a neurocognitive model adapted from Luzzatti and colleagues (1998). Despite the complexity of the neuropsychological picture, behavioral data suggest that semantic access from visual input is possible, while a lesion-based structural disconnectome investigation demonstrated the splenial involvement.Altogether, neuropsychological and neuroanatomical findings support the assumption of visuo-verbal callosal disconnection compatible with a diagnosis of OA.

AGO-Net: Association-Guided 3D Point Cloud Object Detection Network

The human brain can effortlessly recognize and localize objects, whereas current 3D object detection methods based on LiDAR point clouds still report inferior performance for detecting occluded and distant objects: The point cloud appearance varies greatly due to occlusion, and has inherent variance in point densities along the distance to sensors. Therefore, designing feature representations robust to such point clouds is critical. Inspired by human associative recognition, we propose a novel 3D detection framework that associates intact features for objects via domain adaptation. We bridge the gap between the perceptual domain, where features are derived from real scenes with sub-optimal representations, and the conceptual domain, where features are extracted from augmented scenes that consist of non-occlusion objects with rich detailed information. A feasible method is investigated to construct conceptual scenes without external datasets. We further introduce an attention-based re-weighting module that adaptively strengthens the feature adaptation of more informative regions. The network's feature enhancement ability is exploited without introducing extra cost during inference, which is plug-and-play in various 3D detection frameworks. We achieve new state-of-the-art performance on the KITTI 3D detection benchmark in both accuracy and speed. Experiments on nuScenes and Waymo datasets also validate the versatility of our method.

Object recognition and visual object agnosia

The term visual agnosia is used to refer to recognition disorders that are confined to the visual modality, that are not due to an impairment in sensory functions, and that cannot be explained by other cognitive deficits or by general reduction in intellectual ability. Here, we describe the different types of visual agnosia that have been reported (form agnosia, integrative agnosia, associative agnosia, transformational and orientation agnosia as well as category-specific impairments such as pure alexia and prosopagnosia) and how they relate to the current understanding of visual object recognition. Together with related disorders such as simultanagnosia, texture agnosia, aphantasia, and optic aphasia, these visual perceptual impairments can have severe consequences for those affected. We suggest how in-depth assessment can be carried out to determine the type and the extent of these impairments. In the context of clinical assessment, a step-by-step approach reflecting a posterior to anterior gradient in visual object recognition, from more perceptual to more memory-related processes, is suggested. Individually tailored interventions targeting the identified impairments can be initiated based on the results of the assessment.

Declining object recognition performance in semantic dementia: A case for stored visual object representations

The role of the semantic system in recognizing objects is a matter of debate. Connectionist theories argue that it is impossible for a participant to determine that an object is familiar to them without recourse to a semantic hub; localist theories state that accessing a stored representation of the visual features of the object is sufficient for recognition. We examine this issue through the longitudinal study of two cases of semantic dementia, a neurodegenerative disorder characterized by a progressive degradation of the semantic system. The cases in this paper do not conform to the "common" pattern of object recognition performance in semantic dementia described by Rogers, T. T., Lambon Ralph, M. A., Hodges, J. R., & Patterson, K. (2004). Natural selection: The impact of semantic impairment on lexical and object decision. Cognitive Neuropsychology, 21, 331-352., and show no systematic relationship between severity of semantic impairment and success in object decision. We argue that these data are inconsistent with the connectionist position but can be easily reconciled with localist theories that propose stored structural descriptions of objects outside of the semantic system.

The Neural Correlates of Object Familiarity and Domain Specificity in the Human Visual Cortex: An fMRI Study

Ventral occipito-temporal cortex is known to play a major role in visual object recognition. Still unknown is whether object familiarity and semantic domain are critical factors in its functional organization. Most models assume a functional locus where exemplars of familiar categories are represented: the structural description system. On the assumption that familiarity should modulate the effect of visual noise on form recognition, we attempted to individualize the structural description system by scanning healthy subjects while they looked at familiar (living and nonliving things) and novel 3-D objects, either with increasing or decreasing visual noise. Familiarity modulated the visual noise effect (particularly when familiar items were living things), revealing a substrate for the structural description system in right occipito-temporal cortex. These regions also responded preferentially to living as compared to nonliving items. Overall, these results suggest that living items are particularly reliant on the structural description system.

Differential contribution of right and left temporo-occipital and anterior temporal lesions to face recognition disorders

In the study of prosopagnosia, several issues (such as the specific or non-specific manifestations of prosopagnosia, the unitary or non-unitary nature of this syndrome and the mechanisms underlying face recognition disorders) are still controversial. Two main sources of variance partially accounting for these controversies could be the qualitative differences between the face recognition disorders observed in patients with prevalent lesions of the right or left hemisphere and in those with lesions encroaching upon the temporo-occipital (TO) or the (right) anterior temporal cortex. Results of our review seem to confirm these suggestions. Indeed, they show that (a) the most specific forms of prosopagnosia are due to lesions of a right posterior network including the occipital face area and the fusiform face area, whereas (b) the face identification defects observed in patients with left TO lesions seem due to a semantic defect impeding access to person-specific semantic information from the visual modality. Furthermore, face recognition defects resulting from right anterior temporal lesions can usually be considered as part of a multimodal people recognition disorder. The implications of our review are, therefore, the following: (1) to consider the components of visual agnosia often observed in prosopagnosic patients with bilateral TO lesions as part of a semantic defect, resulting from left-sided lesions (and not from prosopagnosia proper); (2) to systematically investigate voice recognition disorders in patients with right anterior temporal lesions to determine whether the face recognition defect should be considered a form of "associative prosopagnosia" or a form of the "multimodal people recognition disorder."

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.

Associative (prosop)agnosia without (apparent) perceptual deficits: A case-study

In associative agnosia early perceptual processing of faces or objects are considered to be intact, while the ability to access stored semantic information about the individual face or object is impaired. Recent claims, however, have asserted that associative agnosia is also characterized by deficits at the perceptual level, which are too subtle to be detected by current neuropsychological tests. Thus, the impaired identification of famous faces or common objects in associative agnosia stems from difficulties in extracting the minute perceptual details required to identify a face or an object. In the present study, we report the case of a patient DBO with a left occipital infarct, who shows impaired object and famous face recognition. Despite his disability, he exhibits a face inversion effect, and is able to select a famous face from among non-famous distractors. In addition, his performance is normal in an immediate and delayed recognition memory for faces, whose external features were deleted. His deficits in face recognition are apparent only when he is required to name a famous face, or select two faces from among a triad of famous figures based on their semantic relationships (a task which does not require access to names). The nature of his deficits in object perception and recognition are similar to his impairments in the face domain. This pattern of behavior supports the notion that apperceptive and associative agnosia reflect distinct and dissociated deficits, which result from damage to different stages of the face and object recognition process.

Multiregional cell assemblies, temporal binding and the representation of conceptual knowledge in cortex: a modern theory by a "classical" neurologist, Carl Wernicke

A contemporary view of conceptual representation in the brain holds that conceptual knowledge is distributed throughout the cerebral cortex, localized to cortical regions involved in their initial processing, and functionally interconnected through synchronized associative processes that are mediated through "convergence zones". The primary goal of the present paper is to point out that Carl Wernicke proposed a theory of how concepts are acquired and represented in cortex which is strikingly similar to contemporary views. Wernicke sketched his ideas on this topic in his earliest writings on aphasia. But his theory is developed most fully in the Grundriss der Psychiatrie (Outlines of Psychiatry), published in 1900 and never translated into English. We describe Wernicke's views on the distributed nature of conceptual knowledge in the brain using select quotes from his early work, and by providing a translation of relevant sections of the Grundriss der Psychiatrie.

Can 'football-team color-code' compensate for anomia? The case study of FN, a patient with color anomia

A case study is reported on large ischemic infracts involving cortical and subcortical areas of the parietal lobes bilaterally, especially left temporo-parietal and right parietal. On examination, the diagnosis of vascular dementia with color anomia, optic aphasia for colors, was established. The patient (FN) showed great difficulty in understanding a scene as a whole and in describing complex scenes. FN's oral comprehension skills at word and sentence level were satisfactory and he exhibited communicative effectiveness during conversation. He could read letter by letter, but could not make simple judgments of shapes. FN exhibited a marked inability to name colors presented to him visually and to indicate or point to the color requested from the examiner. The most interesting of all the patient's characteristics was the strategy--a football-team color-code--he had developed for compensating for his inability to name colors.

Larger Interregional Synchrony is Associated with Greater Behavioral Success in a Complex Sensory Integration Task in Humans

Successful behavior depends on effective communication between distant brain regions. Moreover, disturbance of effective communication can cause neurological symptoms like apraxia, dyslexia or object agnosia. Interregional communication can be assessed by coherence analysis of synchronized neuronal oscillations, and has been referred to as synchrony or "binding". The concept of synchrony as a means of information coding is attractive, but its functional relevance has been challenged. We hypothesized that if synchrony is functionally relevant in humans, then more synchrony should determine better behavioral performance. Here, we show in a visuotactile integration task that the amount of low-frequency (7-13Hz), long-range electroencephalographic coherence between visual and sensorimotor cortex is significantly correlated with the level of performance. Trials with highest coherences were the most successful ones and vice versa in the absence of differences in regional activation measured as task-related spectral power. In summary, quantitatively linking the amount of long-range synchrony with the degree of behavioral success in humans, the present data suggest that the ability to generate topographically specific synchrony of high amplitude is functionally relevant for behavioral success. They also raise the possibility that the magnitude of regional activation is less representative of the efficacy of brain functioning than interregional synchrony.

Visual agnosia in a child with non-lesional occipito-temporal CSWS

In this paper we describe a case of severe visual agnosia in a child with an electrophysiological pattern of continuous spike-wave discharges in slow sleep (CSWS) in the occipito-temporal regions. The neuropsychological spectrum related to this phenomenon is discussed. Published paediatric reports associate visual agnosia (i.e. an inability to recognize objects without impairment of visual acuity) mainly with symptomatic occipito-temporal aetiology (e.g. cortical dysplasia, vascular insults) and other neurological symptoms (e.g. autism). We describe a detailed 2 year electrophysiological and neuropsychological follow-up of an 8-year-old boy with sporadic seizures, occipito-temporal CSWS and visual agnosia. The growth and neurological development of the child had been considered as normal, neurological examination did not reveal any focal signs, visual acuity was intact and MRI was normal. First EEG and six consecutive 24 h video EEG recordings during the follow-up of 22 months showed continuous spike-and-wave activity covering over 85% of the non-REM sleep. According to structured neuropsychological tests (Wechsler Intelligence Scale for Children--Third Edition, A Developmental Neuropsychological Assessment (NEPSY), Test of Visual-Perceptual Skills, Corsi block, Hooper Visual Organization Test) the boy had normal verbal intelligence but major deficits in visual perception, especially in object recognition, impaired shape discrimination and detection, and poor copying skills. Attention and executive functions were intact. There were no difficulties in short- or long-term memory. Verbal cues and naming the objects improved visual memory. Tracing the objects with a finger or by moving the head improved object recognition. Currently the boy attends a special school with a rehabilitation plan including neuropsychological and occupational therapies. This case adds a new facet to the spectrum of neuropsychological deficits in children with CSWS. Sleep EEG should be included in the etiological studies of children with specific neuropsychological problems and detailed neuropsychological assessment is needed for diagnostic and rehabilitation purposes.

Disorders of higher visual function and hemi-spatial neglect

Lesions of the extrastriate cerebral cortex result in disorders of vision, which reveal two cortical processing streams extending ventrally and dorsally from the primary visual cortex. Current theories emphasize the visual perceptual and visuomotor specialization of the ventral and dorsal streams, respectively. Recent investigations of hemi-spatial neglect suggest that the inferior parietal region may lie at the junction of the visual and motor processing pathways.