Justice Obiahuba

Agnosia and Neglect

• Introduction• Definitions and Distinctions• Types of Visual Agnosia• Visual Processing Model• Neuroanatomy of Agnosia• Neglect• Neuroanatomy of Neglect• Models• Neuropsychological assessment• Treatment

Overview

• Left Brain Language, Planned movements, Symbolic representation• Right Brain Visual-spatial representation

Hemispheric Specialization

• https://www.youtube.com/watch?v=T1qnPxwalhw

Agnosia is the inability to process sensory information

Visual Agnosia visual disorder of perception and recognition

Neglect: inability of a person to process and perceive stimuli on one side of the body or environment, where that inability is not due to a lack of sensation

Definitions

• Sensation• Perception• Naming• Recognition

Distinctions

• Intact visual acuity and other visual abilities• CANNOT form a whole mental representation of an

object• Can perceive elements of an object but cannot integrate

them• Can recognize objects via different sensory modalities

Apperceptive Agnosia

• Recognition impairment not attributable to decline in intelligence, memory, language or attention• CAN form mental representation of an object• Patients can accurately distinguish between objects• Can’t identify object, its features, or functions

Associative Agnosia

• Superordinate level• Basic Level• Subordinate level

Levels of Knowledge Retrieval

• Differential impairment of categories of objects• Ranges from narrow to broad categories of impairment• Eg. Human faces, living things, non-living things

Category Specificity

• Impaired facial recognition• Not only human faces• Can identify face using different sensory modalities

Prosopagnosia

• Apperceptive Stroke, anoxia, and carbon monoxide poisoning

• Associative damage to the inferior temporo-occipital junction • Infarction of the posterior cerebral artery, tumour,

haemorrhage

Causes

• Generalized category-specific recognition deficits (eg. Living objects) are associated with diffuse hypoxic damage like carbon monoxide poisoning• The more specific category deficits are associated with

isolated damage due to focal stroke

Causes

• Visual agnosia prevalent in Alzheimer’s patients• Neuronal degeneration, via neurofibulary tangles (NFT),

of brain regions involved in vision

Alzheimer’s Disease

• Associative agnosics cannot connect the mental representation of an object to its semantic information• Apperceptive agnosics have impaired formation of the

mental representation of an object• Integrative agnosics have symptoms of both

Differences

MODELS OF OBJECT REPRESENTATION

• Cognitive Psychology• Extract elements/features of visual object Form

mental representation of that object Recognition

Object Recognition Model

• Dense coding All neurons in the visual pathway are involved in the mental representation of a stimulus

• Sparse coding Mental representation of object is encoded by relatively small number of neurons

Neuronal Coding: Sparse vs dense coding

Two Stream Model of Vision

• Bilateral damage along ventral stream of processing• Severe Visual object Agnosia• Perceptive tasks impaired

Size discriminationchoosing larger of two objectsManual estimation Judging size of an object by

shaping hand correctly • Intact parahippocampal place area (PPA)• Region of limbic cortex bordering the ventromedial temporal

lobe• Activated by scenes and backgrounds

Patient DF

Neuroanatomy

• Location of Striate cortex (primary visual cortex)• Areas V1 spared• Areas V2 largely damaged

Occipital lobe

• Perceptual grouping and figure-ground discrimination• Internal substructure that can be visualized by labeling

cytochrome oxidase• 3 functionally distinct compartments:• Thick Stripes disparity- and motion-sensitive cells• Thin stripes unoriented-colour sensitive cells• Pale stripes orientation sensitive cells for form vision

Areas V2

• Highest level of the ventral stream of the visual association cortex• Involved in perception of objects, including people's

bodies and faces

Inferior Temporal Cortex

• Located on the fusiform gyrus, on the base of the temporal lobe• Greater activation for faces than other categories of

visual stimuli• Also selective for objects a person is highly familiar with• Individuals with congenital prosopagnosia have a

smaller fusiform gyrus and a decreased connectivity within the occipital temporal cortex

Fusiform Face Area (FFA)

• https://www.youtube.com/watch?v=VdIC-x6UZg0

Neglect

• Lack of attention on one side of the world• Can affect sensory modules such as visual, auditory,

somatosensory, etc

Neglect

• Sensory Neglect• Motor neglect• Representational neglect

Input or Output

Allocentric vs. Egocentric

• Strokes• Unilateral brain damage• 80% of visual neglect on the left-hand side

• Right-sided spatial neglect is rare• Memory and recall perception affected

Neglect - Causes

Theories of Neglect

• Caused by damage to structures involved in arousal and transmission of sensory information to the cortex• Leads to decreased attention to the contralateral side of

lesion

Attention Arousal Theory

• Right hemisphere specialized for attention to both left and right visual fields• Left hemisphere only attends to the left• Thus, damage to right leads to loss of control of left-side

attention

Hemispheric Specialization

• Difficulty in detaching or disengaging attention from right-sided stimuli• Stimulus on right side appears sufficient to inhibit a

similar stimulus on the left side

Disengagement Theory

• Imbalance in brain activation with each hemisphere having specific cognitive and perceptual functions• Left hemisphere activated by language• Right hemisphere activated by spatial tasks• Both act mutually to achieve inhibitory inbalance• Damage to the right causes increased activity of the left

and decreased spatial functioning

Interhemispheric Interaction and Inhibition

• Occurs more commonly and with greater severity after right- than left hemisphere-lesions• Right hemisphere involved in attention and spatial

representations Temporo-parietal junction• Posterior parietal cortex

Parietal Lobe

• 12/18 patients at acute stage of neglect had lesions at middle temporal gyrus and/or the temporo-parietal paraventricular white matter• high correlation between persisting neglect and a lesion

involving the paraventricular white matter in the temporal lobe

Temporal Lobe

Frontal lobe

• Planning, organization, problem solving, selective attention• Mesial and dorsolateral portions of frontal lobe

• Relay of sensory information

Thalamus

Basal Ganglia

• Coordination of voluntary motor movements and eye movements

• Usually elderly patients• Use of fMRI and/or diffusion tensor imaging (DTI) for

localization of brain damage • Patients usually have cortical damage not exclusive to

visual processing areas• No two cases of Agnosia are the same (Symptoms or

localization of brain damage)

Case Studies

• Ability to name drawings of living things impaired, while ability to name man-made things intact• Early visual processes of shapes intact• Ability to identify overlapping man-made objects intact

Patient ELM

Agnosia ASSESSMENT

1. Rule out other conditions that might lead to recognition impairment

2. Scope and specificity of recognition impairment• Specific sensory modality• Specific category of stimuli• Conditions which recognition is possible

3. Associative or Apperceptive agnosia

Goals of Assessment

Ghent’s overlapping figure test (APP)

• figure-ground discrimination

Gottschaldt’s hidden figure test (APP)

Columbia Mental Maturity Test (ASP)

Neglect Assessment

Line Bisection Test

Line Cancellation Test

Drawing

TREATMENTS

• Awareness of patient’s deficits• Repetitive training of impaired ability• Coping strategies• Use of other sensory modalities• Take more time on tasks

• Visual Tracing

Compensatory Treatment Approaches

• Involves large team of professionals• Progressive incremental use of neglected side

Neglect Treatments

• Job loss• More likely to Depend on others (eating, getting around)

Changes in Lifestyle

• https://www.youtube.com/watch?v=cP6hfLJq8ng

Charnallet, A., Carbonnel, S., David, D., & Moreaud, O. (2008). Associative visual agnosia: A case study. Behavioural Neurology,19(1-2), 41-44. doi:http://dx.doi.org/10.1155/2008/241753

Damasio, A. R., Damasio, H., & Chui, H. C. (1980). Neglect following damage to frontal lobe or basal ganglia. Neuropsychologia,18(2), 123-132. Retrieved from http://ezproxy.library.yorku.ca/login?url=http://search.proquest.com/docview/616500759?accountid=15182

de Schotten, M. T., Urbanski, M., Duffau, H., Volle, E., Lévy, R., Dubois, B., & Bartolomeo, P. (2005). Direct evidence for a parietal-frontal pathway subserving spatial awareness in humans. Science, 309(5744), 2226-2228. Retrieved from http://ezproxy.library.yorku.ca/login?url=http://search.proquest.com/docview/620935825?accountid=15182E.K. Warrington and T. Shallice, Category specific semantic impairments,Brain107(1984), 829–854.

Goodale, MA., Jakobson, LS., Milner, AD., Perrett, DI., Benson, PJ., Hietanen, JK.(1994) The nature and limits of orientation and pattern processing supporting visuoniotor control in a visual form agnosic. Journal of Cognitive Neuroscience, 6: 46-S6.

Grossman, M., Galetta, S., Ding, X., & Morrison, D. (1996). Clinical and positron emission tomography studies of visual apperceptive agnosia. Neuropsychiatry, Neuropsychology, & Behavioral Neurology, 9(1), 70-77. Retrieved from http://ezproxy.library.yorku.ca/login?url=http://search.proquest.com/docview/618815909?accountid=15182

Heider, B. (2000). Visual form agnosia: Neural mechanisms and anatomical foundations. Neurocase, 6(1), 1-12. doi:http://dx.doi.org/10.1080/13554790008402753

Heilman, K. M., Valenstein, E., & Watson, R. T. (1994). The what and how of neglect. Neuropsychological Rehabilitation, 4(2), 133-139. Retrieved from http://ezproxy.library.yorku.ca/login?url=http://search.proquest.com/docview/57564545?accountid=15182

Hliro, 0., Ciiwleniont, J., Barrientos, A., Urbanomarquez, A., Cardellach, F. (1998).Mitochondria1 cytochrome c oxidase inhibition during acute carbon monoxide poisoning. Pharmacology and Toxicology, 82, 199-202.

References

Marsh, E. B., & Hillis, A. E. (2008). Dissociation between egocentric and allocentric visuospatial and tactile neglect in acute stroke.Cortex: A Journal Devoted to the Study of the Nervous System and Behavior, 44(9), 1215-1220. doi:http://dx.doi.org/10.1016/j.cortex.2006.02.002

Marotta, J. J., McKeeff, T. J., & Behrmann, M. (2003). Hemispatial neglect: Its effect on visual perception and visually guided grasping. Neuropsychologia, 41(9), 1262-1271. doi:http://dx.doi.org/10.1016/S0028-3932(03)00038-1

Mesulam, M. -. (1992). A cortical network for directed attention and unilateral neglect The MIT Press, Cambridge, MA. Retrieved from http://ezproxy.library.yorku.ca/login?url=http://search.proquest.com/docview/618233684?accountid=1518

M.J. Farah and J.L. McClelland, A computational model ofsemantic memory impairment: Modality specificity and emergent category specificity,Journal of Experimental Psychology: General120(1991), 339–357.

Samuelsson, H., Jensen, C., Ekholm, S., Naver, H., & Blomstrand, C. (1997). Anatomical and neurological correlates of acute and chronic visuospatial neglect following right hemisphere stroke. Cortex: A Journal Devoted to the Study of the Nervous System and Behavior, 33(2), 271-285. Retrieved from http://ezproxy.library.yorku.ca/login?url=http://search.proquest.com/docview/619095755?accountid=15182

Shulman, G. L., Pope, D. L. W., Astafiev, S. V., McAvoy, M. P., Snyder, A. Z., & Corbetta, M. (2010). Right hemisphere dominance during spatial selective attention and target detection occurs outside the dorsal frontoparietal network. The Journal of Neuroscience, 30(10), 3640-3651. doi:http://dx.doi.org/10.1523/JNEUROSCI.4085-09.2010

Z. Mehta, F. Newcombe and E. De Haan, Selective loss ofimagery in a case of visual agnosia, Neuropsychologia30(1992), 645–655

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