chapter 13: the occipital lobe and its functions Flashcards
What is the anatomical name of the primary visual cortex? Which Brodmann Area is it?
Calcarine sulcus, BA 17.
What are ‘blobs’? What do they do?
Structures (different cell types) within V1 that process colour information.
What structures in V1 process form and motion?
Interblobs.
What function is each stripe in V2 responsible for processing?
Thin stripes: colour perception
Thick stripes: form information
Pale stripes: motion perception
What are the three streams projecting from V2 to major visual areas? What are functions are they responsible for?
Dorsal stream: visual guidance of movement
Superior temporal sulcus (STS) stream: object perception and motion perception
Ventral stream: object perception and motion perception
What are higher visual areas (V3-V5) responsible for processing?
V3: dynamic form, shapes in motion
V4: colour information
V5: motion processing; MT
Which disorder is caused by damage to V4?
Achromatopsia.
Which disorder is caused by damage to V5?
Akinetopsia.
Damage to __ results in blindness, damage to __________ __________ results in deficits in specific functions.
V1, higher areas
In patients with V1 damage, smaller projections from subcortical areas provide some limited vision. This is an example of what phenomenon?
Blindsight.
The dorsal and ventral pathways are responsible for (perception/action) and (perception/action) accordingly.
action, perception
The lateral occipital, fusiform face area, and extrastriate body area, are all regions belonging to the (dorsal/ventral) stream.
ventral
the lateral intraparietal sulcus, ventral intraparietal sulcus, and parietal reach region, are al regions belonging to the (dorsal/ventral) stream.
dorsal
What is egocentric space vs allocentric space? Which does/do the visual system guide movements by?
Egocentric space: objects organized in relation to the observer
Allocentric space: objects organized in relation to each other
Visual system encodes both perspectives to guide movement and to remember scenes.
Visually guided movements project from __ to __________ __________ via __________ stream.
V1, parietal areas, dorsal
Patients with damage to __________ occipital area could shape hand, could not consciously see.
patients with damage to __________ __________ can see objects, could not accurately reach.
lateral, dorsal stream
Parietal lesions that impact visual areas typically characterized as __________ or __________.
visuospatial, visuomotor
Posterior parietal visual neurons are only active when brain is __________, not __________.
acting, looking
Comparison of faces is processed by the __________ __________ area in __________ lobe.
fusiform face area, temporal
Imaging studies show increased activity in __ when subjects asked to detect motion, __ when asked to detect colour.
V4, V5
What is the name of the site at which visual inputs (optic nerves) cross?
The optic chiasm.
Where in the brain are binocular visual inputs combined?
V1, calcarine sulcus
What is macular sparing?
The phenomenon of information in central part of visual field being spared in cases of visual cortex damage.
What are scotomas?
Small blind spots in visual fields; are often unnoticed due eyes constantly moving, and brain performing compensation via previous inputs.
H.M.’s bilateral lobotomy indicated the function of which brain region? What was the is the function of the region?
Hippocampus, memory.
B.K.’s damage to their V1 resulted in what symptom(s)?
Temporary loss of vision in left visual field, permanent loss in lower-left field; blindsight in affected areas.
D.B.’s damage to V1 resulted in what symptom(s)?
Blindsight: no conscious awareness of visual stimuli, but can accurately indicate descriptors.
What is significant about B.I.’s childhood occipital lobe damage?
By age 6, not blind; can recognize faces and colours, navigate environment.
Plasticity to rearrange visual system and strengthen pathways from subcortical areas to V5.
Describe J.I.’s achromatopsia.
World appeared in greyscale following accident. Lost ability to remember or imagine colours, even in dreams.
Implication that imagination is tied to perceptive capabilities.
What is significant about P.B.’s blindness compared to J.I.?
Despite blindness, retained ability to imagine colour. Likely due different mechanism/location of damage.
Describe L.M’s akinetopsia.
Lost ability to detect motion due damage to V5. Vision otherwise normal.
Describe D.F.’s visual agnosia.
Inability to recognize objects, pictures of objects; inability to draw copy of objects. Due carbon monoxide poisoning damaging lateral occipital (LO).
D.F’s visual agnosia affected which occipital stream? Which functions were retained?
Damage to ventral stream (visual recognition).
Dorsal stream reaching/grasping left intact.
Describe V.K.’s optic ataxia. Which functions were retained?
Deficit in visually-guided movements, such as reaching due bilateral stroke in occipito-parietal regions.
Ventral stream visual recognition left intact.
Describe D’s prosopagnosia.
Inability to recognize familiar faces due lesion to right occipitotemporal region.
Describe T’s alexia.
Loss of ability to read due lesion to left occipitotemporal region.
What is the significance of D and T’s lesions compared to each other?
Both have lesions to occiptotemporal regions, retention of each others’ lost functions indicates full lateralization of reading and facial recognition.
Describe apperceptive agnosia.
Failure to recognize basic feature of object (e.g. colour or motion).
Describe simultagnosia.
Inability to perceive more than one object at a time despite ability to perceive individual objects.
Apperceptive agnosia and simultagnosia often result from damage to what areas?
Bilateral damage to lateral occipital.
Describe associative agnosia.
Inability to recognize object despite ability to perceive it. Typically due damage to ventral stream (e.g. D.F.)
Alexia is caused by damage to which areas?
Left fusiform gyrus and lingual area.
Which area is responsible for mental rotation of visual images?
Right-hemisphere dorsal stream areas.
