vision Flashcards
famous neurological case studies
- Patient Tan for language
- Patient P.G. for Vision (see later)
- Patient H.M. for Memory (covered during the memory lectures)
case reports
- Very important and critical task
- Often performed by a neurologist
- Neurologists will provide a full clinical assessment:
- Neuropsychological nature: psychomotor speed, attention, memory, executive and visuospatial functions
- Motor symptoms severity
- Functional status
- Understand comorbidity
visual agnosia
a condition in which a person can see but cannot recognize or interpret visual information, due to a disorder in the parietal lobes
Neuropsychological Patient Profile: IES
75 year old male with bilateral posterior lesions following a CVA (Cerebrovascular accident).
Scans revealed bilateral PCA stroke involving the ventral occipital lobes including the fusiform and lingual gyrus on the left and fusiform gyrus on the right. There was also damage to the left hippocampus and primary visual cortex.
Clinical diagnosis of visual object agnosia and prosopagnosia without alexia.
achromatopsia
(colour blindness) - No language comprehension or production problems, No loss of semantic knowledge -Upper right quadrant visual field cut (visual field loss).
blindsight
- Impairment to conscious visual experience of stimulus in part of visual field
- Hemianopias
- loss of vision to the left or right side of fixation
- Due to damage in the visual cortex (not the eye itself)
- Blindsight = some patients can respond to stimuli in ‘blind’ part of visual field under certain conditions, even though consciously they do not see anything!
blindsight (cortical blindness)
Persaud and Cowey (2008)
• Patient GY presented with an object in upper or lower part of his “blind” visual field. He had to point to the “opposite” location of object
• They found:
• When in blind area – he responded above chance to the real location of the object
• While being able to do the task fine when in “good” visual field
Agnosia
“Agnosia refers to the inability to recognize people or objects even when basic sensory modalities are intact.”
• Visual agnosia where the person has difficultly recognizing objects, faces and/or words
• Auditory Agnosia which involves the inability to recognize sounds
• Somatosensory Agnosia where the person has difficulty perceiving objects through tactile stimulation
visual agnosia
- A deficit in processing that is restricted to the visual input modality
- Patients may show impaired object recognition with or without Impaired face (proposopagnosia) and/or reading (alexia).
- Lissauer (1890) distinguished between ‘apperceptive’, ‘associative’ and ‘integrative’ visual agnosia
apperceptive agnosia
is a failure in recognition that is due to a failure of perception.
associative agnosia
is a type of agnosia where perception occurs but recognition still does not occur
intergrative
is a disorder in which the patient has symptoms of both apperceptive agnosia and associative agnosia, although their primary visual abilities are intact
Visual Agnosia patients can still do some startling things…
Milner et al (1991)
Patient DF could not identify shapes – Did this effect her movements?
Post card experiment, 2 tasks:
Matching: turn card to match the orientation of the slot
Posting: reach out and “post” the card into the slot
goodale et al 1991
When asked to distinguish blocks perceptually – DF couldn’t do it
When asked to pick the blocks up – she changed the aperture of grip to match the size of the block automatically without problems
But when asked to estimate block size using thumb and forefinger – DF couldn’t do it
dorsal system
involved in object localisation (where system)
Acts in real time
Guides actions
Enables smooth and effective movement
