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Journal of Neurology, Neurosurgery, and... May 1959"And what is the nature of this knowledge or recollection? I mean to ask, Whether a person, who having seen or heard or in any way perceived anything, knows not only...
"And what is the nature of this knowledge or recollection? I mean to ask, Whether a person, who having seen or heard or in any way perceived anything, knows not only that, but has a conception of something else which is the subject, not of the same but of some other kind of knowledge, may not be fairly said to recollect that of which he has the conception?""And when the recollection is derived from like things, then another consideration is sure to arise, which is, Whether the likeness in any degree falls short or not of that which is recollected?" "The Philosophy of Plato" Phaedo (the Jowett translation).
Topics: Agnosia; Humans; Male; Philosophy; Prosopagnosia
PubMed: 13655102
DOI: 10.1136/jnnp.22.2.124 -
Neuropsychologia Nov 2023We present a comprehensive review of the rare syndrome visual form agnosia (VFA). We begin by documenting its history, including the origins of the term, and the first... (Review)
Review
We present a comprehensive review of the rare syndrome visual form agnosia (VFA). We begin by documenting its history, including the origins of the term, and the first case study labelled as VFA. The defining characteristics of the syndrome, as others have previously defined it, are then described. The impairments, preserved aspects of visual perception, and areas of brain damage in 21 patients who meet these defining characteristics are described in detail, including which tests were used to verify the presence or absence of key symptoms. From this, we note important similarities along with notable areas of divergence between patients. Damage to the occipital lobe (20/21), an inability to recognise line drawings (19/21), preserved colour vision (14/21), and visual field defects (16/21) were areas of consistency across most cases. We found it useful to distinguish between shape and form as distinct constructs when examining perceptual abilities in VFA patients. Our observations suggest that these patients often exhibit difficulties in processing simplified versions of form. Deficits in processing orientation and size were uncommon. Motion perception and visual imagery were not widely tested for despite being typically cited as defining features of the syndrome - although in the sample described, motion perception was never found to be a deficit. Moreover, problems with vision (e.g., poor visual acuity and the presence of hemianopias/scotomas in the visual fields) are more common than we would have thought and may also contribute to perceptual impairments in patients with VFA. We conclude that VFA is a perceptual disorder where the visual system has a reduced ability to synthesise lines together for the purposes of making sense of what images represent holistically.
Topics: Humans; Pattern Recognition, Visual; Visual Perception; Vision, Ocular; Visual Fields; Vision Disorders; Agnosia
PubMed: 37634886
DOI: 10.1016/j.neuropsychologia.2023.108666 -
Current Neurology and Neuroscience... Nov 2023To investigate the neurofunctional correlates of pure auditory agnosia and its varieties (global, verbal, and nonverbal), based on 116 anatomoclinical reports published... (Review)
Review
PURPOSE OF REVIEW
To investigate the neurofunctional correlates of pure auditory agnosia and its varieties (global, verbal, and nonverbal), based on 116 anatomoclinical reports published between 1893 and 2022, with emphasis on hemispheric lateralization, intrahemispheric lesion site, underlying cognitive impairments.
RECENT FINDINGS
Pure auditory agnosia is rare, and observations accumulate slowly. Recent patient reports and neuroimaging studies on neurotypical subjects offer insights into the putative mechanisms underlying auditory agnosia, while challenging traditional accounts. Global auditory agnosia frequently results from bilateral temporal damage. Verbal auditory agnosia strictly correlates with language-dominant hemisphere lesions. Damage involves the auditory pathways, but the critical lesion site is unclear. Both the auditory cortex and associative areas are reasonable candidates, but cases resulting from brainstem damage are on record. The hemispheric correlates of nonverbal auditory input disorders are less clear. They correlate with unilateral damage to either hemisphere, but evidence is scarce. Based on published cases, pure auditory agnosias are neurologically and functionally heterogeneous. Phenotypes are influenced by co-occurring cognitive impairments. Future studies should start from these facts and integrate patient data and studies in neurotypical individuals.
Topics: Humans; Agnosia; Auditory Perception
PubMed: 37747655
DOI: 10.1007/s11910-023-01302-1 -
Neurologia (Barcelona, Spain) Oct 2014Patients who have difficulties recognising visual form stimuli are usually labelled as having visual agnosia. However, recent studies let us identify different clinical... (Review)
Review
INTRODUCTION
Patients who have difficulties recognising visual form stimuli are usually labelled as having visual agnosia. However, recent studies let us identify different clinical manifestations corresponding to discrete diagnostic entities which reflect a variety of deficits along the continuum of cortical visual processing.
DEVELOPMENT
We reviewed different clinical cases published in medical literature as well as proposals for classifying deficits in order to provide a global perspective of the subject. Here, we present the main findings on the neuroanatomical basis of visual form processing and discuss the criteria for evaluating processing which may be abnormal. We also include an inclusive diagram of visual form processing deficits which represents the different clinical cases described in the literature. Lastly, we propose a boosted decision tree to serve as a guide in the process of diagnosing such cases.
CONCLUSIONS
Although the medical community largely agrees on which cortical areas and neuronal circuits are involved in visual processing, future studies making use of new functional neuroimaging techniques will provide more in-depth information. A well-structured and exhaustive assessment of the different stages of visual processing, designed with a global view of the deficit in mind, will give a better idea of the prognosis and serve as a basis for planning personalised psychostimulation and rehabilitation strategies.
Topics: Agnosia; Decision Support Techniques; Female; Humans; Neuropsychological Tests; Vision Disorders; Visual Perception
PubMed: 22652145
DOI: 10.1016/j.nrl.2012.03.006 -
Current Biology : CB Jan 2007
Topics: Cerebral Cortex; Humans; Prosopagnosia; Visual Perception
PubMed: 17208177
DOI: 10.1016/j.cub.2006.11.043 -
Quarterly Journal of Experimental... Feb 2017Over the last 20 years much attention in the field of face recognition has been directed towards the study of developmental prosopagnosia (DP), with some authors...
Over the last 20 years much attention in the field of face recognition has been directed towards the study of developmental prosopagnosia (DP), with some authors investigating the behavioural characteristics of the condition, and many others using these individuals to further our theoretical understanding of the typical face-processing system. It is broadly agreed that the term "DP" refers to people who have failed to develop the ability to recognize faces in the absence of neurological illness or injury, yet more precise terminology in relation to potential subtypes of the population are yet to be confirmed. Furthermore, specific diagnostic techniques and inclusion and exclusion criteria have yet to be uniformly accepted across the field, making cross-paper comparisons and meta-analyses very difficult. This paper presents an overview of the current challenges that face research into DP and introduces a series of papers that attempt to further our understanding of the condition's characteristics. It is hoped that this special issue will provide a springboard for further research addressing these issues, improving the current state of the art by ensuring the quality of theoretical investigations into DP, and by posing advances that will assist those who have the condition.
Topics: Humans; Prosopagnosia
PubMed: 27251859
DOI: 10.1080/17470218.2016.1195414 -
Journal of Neurology, Neurosurgery, and... Feb 2002From a series of glimpses, we perceive a seamless and richly detailed visual world. Cerebral damage, however, can destroy this illusion. In the case of Bálint's... (Review)
Review
OBJECTIVES
From a series of glimpses, we perceive a seamless and richly detailed visual world. Cerebral damage, however, can destroy this illusion. In the case of Bálint's syndrome, the visual world is perceived erratically, as a series of single objects. The goal of this review is to explore a range of psychological and anatomical explanations for this striking visual disorder and to propose new directions for interpreting the findings in Bálint's syndrome and related cerebral disorders of visual processing.
METHODS
Bálint's syndrome is reviewed in the light of current concepts and methodologies of vision research.
RESULTS
The syndrome affects visual perception (causing simultanagnosia/visual disorientation) and visual control of eye and hand movement (causing ocular apraxia and optic ataxia). Although it has been generally construed as a biparietal syndrome causing an inability to see more than one object at a time, other lesions and mechanisms are also possible. Key syndrome components are dissociable and comprise a range of disturbances that overlap the hemineglect syndrome. Inouye's observations in similar cases, beginning in 1900, antedated Bálint's initial report. Because Bálint's syndrome is not common and is difficult to assess with standard clinical tools, the literature is dominated by case reports and confounded by case selection bias, non-uniform application of operational definitions, inadequate study of basic vision, poor lesion localisation, and failure to distinguish between deficits in the acute and chronic phases of recovery.
CONCLUSIONS
Studies of Bálint's syndrome have provided unique evidence on neural substrates for attention, perception, and visuomotor control. Future studies should address possible underlying psychoanatomical mechanisms at "bottom up" and "top down" levels, and should specifically consider visual working memory and attention (including object based attention) as well as systems for identification of object structure and depth from binocular stereopsis, kinetic depth, motion parallax, eye movement signals, and other cues.
Topics: Agnosia; Attention; Brain Mapping; Cerebrovascular Disorders; Dominance, Cerebral; Humans; Occipital Lobe; Perceptual Disorders; Psychomotor Disorders; Visual Cortex; Visual Perception
PubMed: 11796765
DOI: 10.1136/jnnp.72.2.162 -
The Permanente Journal 2016
Topics: Adult; Agnosia; Anomia; Color Perception; Dyslexia; Female; Humans
PubMed: 27352419
DOI: 10.7812/TPP/15-165 -
F1000Research 2019Prosopagnosia is an impairment in the ability to recognize faces and can be acquired after a brain lesion or occur as a developmental variant. Studies of prosopagnosia... (Review)
Review
Prosopagnosia is an impairment in the ability to recognize faces and can be acquired after a brain lesion or occur as a developmental variant. Studies of prosopagnosia make important contributions to our understanding of face processing and object recognition in the human visual system. We review four areas of advances in the study of this condition in recent years. First are issues surrounding the diagnosis of prosopagnosia, including the development and evaluation of newer tests and proposals for diagnostic criteria, especially for the developmental variant. Second are studies of the structural basis of prosopagnosia, including the application of more advanced neuroimaging techniques in studies of the developmental variant. Third are issues concerning the face specificity of the defect in prosopagnosia, namely whether other object processing is affected to some degree and in particular the status of visual word processing in light of recent predictions from the "many-to-many hypothesis". Finally, there have been recent rehabilitative trials of perceptual learning applied to larger groups of prosopagnosic subjects that show that face impairments are not immutable in this condition.
Topics: Facial Recognition; Humans; Learning; Neuroimaging; Prosopagnosia
PubMed: 31231507
DOI: 10.12688/f1000research.18492.1 -
Philosophical Transactions of the Royal... Jun 2016Stereoscopic depth perception requires considerable neural computation, including the initial correspondence of the two retinal images, comparison across the local... (Review)
Review
Stereoscopic depth perception requires considerable neural computation, including the initial correspondence of the two retinal images, comparison across the local regions of the visual field and integration with other cues to depth. The most common cause for loss of stereoscopic vision is amblyopia, in which one eye has failed to form an adequate input to the visual cortex, usually due to strabismus (deviating eye) or anisometropia. However, the significant cortical processing required to produce the percept of depth means that, even when the retinal input is intact from both eyes, brain damage or dysfunction can interfere with stereoscopic vision. In this review, I examine the evidence for impairment of binocular vision and depth perception that can result from insults to the brain, including both discrete damage, temporal lobectomy and more systemic diseases such as posterior cortical atrophy.This article is part of the themed issue 'Vision in our three-dimensional world'.
Topics: Agnosia; Alzheimer Disease; Animals; Depth Perception; Hemianopsia; Humans; Macaca; Perceptual Disorders; Vision, Binocular; Visual Cortex
PubMed: 27269597
DOI: 10.1098/rstb.2015.0254