EXAM 1 REVIEW Flashcards
Verrey
Right hemiachromatopsia
- normal color vision in LVF
- color perceived as grey in RVF
Shape perception preserved
Conclusions of Verrey’s study
Cortical color center located outside of primary visual cortex
- lingual and fusiform gyri
Strengths of Verrey’s study
Patient had complete loss of color vision in hemifield
-reasonably good testing of form perception
- excellent info about lesion location
What are associated visual symptoms of cerebral achromatopsia?
Scotoma and almost all cases
And often:
Prosopagnosia
reading impairment
cerebral achromatopsia results from damage to and provides evidence for:
A cortical region specialized for color perception
- located in lingual fusiform gyrus
Localization of cortical color area?
Lesion deficit correlation
functional neuroimaging
Zeki et al.
compared brain activation for colored and monchrome stimuli to find brain areas that respond to color
As well as motion
Color afterimages
Staring at one color gives you an after image of the complimentary colors
What do color afterimages show us?
Tells us that there are opponent-receptive color fields
How do you know if a single mechanism for how things work is plausible?
If the deficits consistently occur together
some reason to suppose that the impaired functions might be performed by the same mechanism
how to know if different mechanisms for functions are plausible?
deficits sometimes dissociate
no obvious reason to think impaired functions would be performed by a single mechanism
What are the problems with the single mechanism interpretation for achromatopsia and scotoma?
Dissociations btw achromatopsia and scotomas
when present, scotomas are virtually never limited to the lower visual view
What are the problems with the single mechanism interpretation for achromatopsia and Prosopagnosia?
Dissociation between the two
Bouvier and Engel: normal face recognition in 11/46 achromatopsia cases
Correspondence problem
Match scenes where something changes from one scene to another
Aperture proble
Direction of motion within receptive fields (small window) can be misleading
Basics of motion perception
Detection of motion (distinguishing moving stationary stimuli)
perceiving the direction of motion
LM’s detection of motion:
No impression of motion when cube moved toward or away from LM
Despite clear impression of changes in size and position
Moving vs stationary for LM
Stationary: Lm was substantially slower than the control but could detect the target
Moving:
Much slower than the control to detect movement and often inaccurate in perceiving movement direction
When could LM Never detect direction of motion
In the periphery
Does LM Experience motion aftereffects?
No
Lm’s motion perception:
Impaired detection of motion
impaired perception of motion direction
impaired perception of speed
absence of motion aftereffects
When could LM Perceive motion?
When it was not associated with vision
