Visual Neuropsychology Flashcards
1
Q
What is neuropsychology?
A
- Neuropsychology is the study of behavioural problems of people with brain damage (for eg. stroke, trauma and cancer).
- Behavioural experiments are used to understand what brain areas show the deficits associated with these problems
2
Q
What does damage to prefrontal & orbitofrontal cortex cause?
A
Damage here causes social behaviour problems
3
Q
Describe the frontal lobe and its disorders?
A
- Represents large area of brain
- 3 general anatomical divisions of frontal cortex: the limbic, the precentral and the prefrontal cortices.
- Brain centers within the frontal lobe interconnected with other parts of the brain.
- Emotion and Mood centres lesion in frontal lobe – may not trigger feedback to visual cortex e.g. see car coming but have no fear of it & so don’t move out way
- Cognitive centres.
- Interconnected complexity results in a number of syndromes associated with lesions of this area
Aphasia: inability to speak
Acalculia: inability to calculate
4
Q
What is Body Schema Disruption?
A
Lesions of Parietal lobes may produce characteristic disturbances of cognitive model representing knowledge about arrangement of body parts & their spatial relationship to objects in environment
5
Q
What is the initial visual pathway?
A
Eyes, Optic Nerve, Optic Chiasm: Fibre crossover: separation of R & L VFs instead of R&L eyes
6
Q
What is the middle visual pathway?
A
- Middle Visual Path I: Geniculostriate Path
- Optic chiasm
- Lateral geniculate body of thalamus
- Optic radiations
- Calcarine fissure: primary visual cortex
- Purpose is pattern analysis and colour perception
7
Q
What problems are caused by damge to different parts of the visual pathway?
A
- Retinal or other eye damage (e.g. macular degeneration, retinal stroke)
- Monocular blindness: field cuts
- Homonymous hemianopsias: bitemporal, nasal
- Quadrantinopsias
- Macular sparing – central vision unaffected
- L optic nerve cut – no vision in LE but RE sees L VF
- L optic tract cut – R VF loss in each eye
- Optic chiasm split in middle – BEs lose peripheral vision – problems w/ binocularity as each eye seeing differently
8
Q
What are the dorsal and ventral streams? (brief description)
A
- Dorsal stream is pathway for visual info involved in spatial awareness: recognising where objects are in space.
- Ventral stream is associated with object recognition & form representation. Has strong connections to the medial temporal lobe, the limbic system and the dorsal stream
9
Q
Describe the problems which arise due to damage to the dorsal or ventral stream?
A
- Visual Agnosias: Inability to recognise people or objects even when basic sensory modalities, such as vision, are intact.
- Prosopagnosia: issue with faces
- Agnostic Alexia: issue with reading material
- Colour Agnosia: issue with colours (even if cones intact)
- Object Agnosia: issue with objects (‘man who mistook wife for hat’)
- Simultanagnosia: Inability to recognise a whole image although individual details are recognised
10
Q
Describe prosopagnosia?
A
- Inability to perceive faces, or face blindness.
- Perceptual problem that stops people from being able to put the image of the face together as a whole.
- Px will often try to use other clues e.g. clothes of the person
- If test px’s VA it will be fine – they do not have issue recognising letters
- Rare disorder & varies in intensity – one person with the disorder may not be able to recognise whether two pictures are of the same face or not, while in another patient recognition of one’s own family members is affected.
- A most severe example of prosopagnosia is when one cannot recognise oneself in a photograph or in the mirror.
- These skills do not improve with practice or familiarity. Usually it is not limited to the recognition of individuals, but also of more basic facts such as gender and facial expression.
- An extreme form of both object agnosia and prosopagnosia was described by Oliver Sacks in his book ‘The man who mistook his wife for a hat.’
11
Q
Describe Central Achromatopsia?
A
- Refers to a loss of colour perception as a result of lesions of the optic nerve or occipital lobe.
- The disorder can affect both VFs or a single hemi-field.
- Patients are usually aware of the deficit and report the world as “grey”, or “dirty”.
- Patients will correctly answer questions pertaining to colour concepts or descriptions of objects that include colour (e.g., “what is the colour of blood?).
- Central achromatopsia may also affect one colour more than another may. Lesions of the fusiform gyrus of the medial occipital lobe are associated with this syndrome.
12
Q
Describe simultanagnosia?
A
- Simultanagnosia refers to inability to recognise two or more things at the same time.
- Identification of some parts of an object helps patients to make inferences about the whole object
- Dorsal Simultanagnosics may seem to be “blind” since they bump into objects that are close together. Motion may further impair their ability to perceive objects. They find it difficult to read or count because it involves more than one object at a time. Common cause: bilateral damage to the bilateral parieto-occipito region
- Ventral simultanagnosia: inability to identify more than one object at a time. They can see more than one object at a time but cannot read or describe pictures. Common cause: damage to the left inferior temporo-occipital region
13
Q
Describe the Visual Spatial Disorders Spatial Localisation?
A
- Patients with visual spatial impairment have difficulty localising objects in 2 & 3D space. For e.g. patients with spatial disorder cannot determine if a pattern of dots presented on a card are the same or different than another pattern. They have difficulty judging distance from themselves to objects in space.
- Stereopsis (binocular depth perception) is often impaired.
- They also have difficulty matching directional orientation of objects. For e.g., it is difficult for these patients to judge whether two lines on a page have the same angular orientation.
- These difficulties in judging direction and distance are maintained even when the information about the objects is presented by touch as well as vision.
o Integration problem of >1 sensory problem
14
Q
Describe visual spatial construction?
A
- Patients have difficulty w/ construction activities that require spatial abilities. Include drawing, both copying as well as drawing to verbal command, and assembling 2 and 3D objects. This latter ability is usually examined with block puzzles.
- The deficit extends to everyday activities that require assembling objects from basic elements: e.g. laying out a place setting at the table, assembling furniture or drawing a map to one’s house.
- Although patients with visual spatial impairment show impairment on these tasks, the activities all require substantial motor skill and praxis.
- Consequently, patients with lesions of other parts of the brain that subsume these functions will also have difficulty with spatial construction tasks –> feedforward & feedback
15
Q
Describe visual neglect & hemineglect?
A
- Pxs w/ Hemineglect syndrome can accurately perceive sensory information but behave as if it does not exist.
- Since lesion usually affects only one hemisphere most neglect syndromes only involve sensory information on one side (i.e.. hemi).
- Their primary sensory systems (e.g., vision) are intact, but they do not attend to or behave consistent with perception.
- They behave as if they only perceive information from the unaffected side.
- Patients with severe forms of hemi-neglect may even refuse to accept that the affected limbs even belong to them.
- They may even complain that someone else’s leg is in bed with them. Patients with Hemineglect who are touched on the affected side may report being touched on the intact side. This error is called allesthesia.
- Allesthesia may be present in any sensory modality (not just vision)
- Common in stroke pxs
- Speech & comprehension may be fine but vision affected
