L10/11 - occipital lobes - object recognition, disorder of perception Flashcards
3 clear landmarks on the medial surface of occipital lobe
parieto-occipital sulcus (most superior) collateral sulus ( middle) calcarine sulcus ( most inferior
where is V1 located?
in the calcarine sulcus. - separated as upper and lower visual fields.
- upper sulcus = lower VF
- lower sulcus = upper VF
2 landmarks of the ventral surface of the occipital lobe
lingual gyrus - houses V2/VP
fusiform gyrus - houses v4
subdivisions of the occipital cortex
v1, v2 - more complex moving forward. temporal extent intraparietal lateral occipital fusiform face area
division in vision - 2 streams
lesions cause?
dorsal = where. make assoc based on things in space.
D lesion: cant assoc target w spatial position
ventral - what * inferior temporal lobe path*. difference between objects and naming.
areas involved = anterior inferior temporal & posterior inferior temporal. lesion = cant tell difference between objects.
more complex - engage where?
engage further downstream areas = more anterior with complexity.
where are biological features interpreted?
v4/v5
- functional specificity for complexity of environment
primary job of v4
colour vision. (also distributed through occipital cortex tho)
- plays role in detection of movement, depth and position.
connections of the visual cortex.
V1 input, output?
v2 - output
after v2 - output paths?
- V1 - input from lateral geniculate nucleus. output to all levels.
v2 - output to all levels.
v2 paths: - to parietal = dorsal stream
- to inferior temporal lobe - ventral steram
- to superior temporal sulcus = superior temporal sulcus stream.
function of 3 pathways
dorsal - visual guidance of movement
vental - object perception
STS - visuospatial functions, movement perception.
5 categories of vision - list
vision for action action for vision visual recognition visual space visual attention
what is vision for action?
- parietal visual areas in the dorsal stream used to prep body for interacting w moving objects & to know where to move
action for vision - what stream?
dorsal stream because deals with movement - maybe some interplay with ventral stream
invovled with visual scanning & eye movements
action for vision - normal vs agnosic patient
- normal: eye movement tracked around face, eye and mouth = focus. focus on left side of pic/right side of face = maybe important for recognizing.
- agnosic = can’t ID object - random eye movements. brain cant direct eyes in meaningful way
what is visual recognition? what area related?
temporal lobes invovled in object recognition
what is visual space? brain area related?
parietal and temporal lobes encode for spatial location
- egocentric (object relative to person)
- allocentric (object relative to other person
- what is visual attention
selective attention for specific visual input.
parietal lobes guide movement, temporal in object recognition.
3 important ventral regions
lateral occipital cortex
fusiform face area
superior temporall sulcus
function of LOC
object analysis
- perceptual constancy (same objects regardless of size, location viewpoint, illumination)
- form-cue invariance: recognize object regardless of how it is depicted.
- sensitive to visual illusion
function of fusiform face area
face analysis
funciton of superior temporal sulcus
analysis of biological motion
important dorsal region
anterior intraparietal sulcus
- object-directed grasping.
david marr - scaffolding
low level info gets scaffolded upon.
edges, regions -> texture, depth -> scene is visualized (allo/ego-centric)
what are geons?
volumetric properties - specific and limited set. can be put together to build larger thing with meaning.
goodale & milner model of vision for percepiton & vision for action
- object recognition/perception? what stream? which brain areas?
- action? what stream? brain areas.
reco = ventral.
v1, v2, v3 (dynamic form), v4 (colour form), LOC - temporal visual areas
act = dorsal.
v1, v5 (motion), v3a (form), parietal areas - AIP
name disorders of visual pathways
- monocular blindness
- bitemporal hemianopia
- nasal hemianopia
- homonymous hemianopia
- macular sparing
- quadrantoanopa or hemianopia
- field defects: scotoma
monocular blindness
loss of sight in one eye
- results from destruction of retina or optic nerve
bitemporal hemianopia
loss of vision from both temporal fields (extend to nasal hemi-retina)
- lesion to the medial region of the optic chiasm
nasal hemianopia
loss of vision of one nasal field - due to one temporal retina.
lesion of lateral region of optic chiasm
- need 2 lesions for bi-nasal hemianopia.
homonymous hemianopia
blindness of one entire visual field
- cut of optic tract, LGN or V1.
macular sparing
sparing of the central or macular region of the visual field.
- results from lesion ot occipital lobe. - redundant blood supply to that area
quadrantoanopia/hemianopia.
complete loss of vision in 1/4 of fovea or 1/2 of fovea.
results from lesion to occiipital lobe.
hemianopia has larger lesion to v1(calcarine sulcus) than quadrantoanopia.
field defects
scotoma - small blind spots. often unnoticed due to nystagmus
- reult from small lesion to occipital lobe
what is nystagmus
tiny, involuntary eye movements
disorders of cortical function
- BK - v1 damage and scotoma
- lesion?
- symptoms?
right infarct in occipital lobe.
- blindight. could perceive motion, location without perceiving content.
.- could detect light, had feeling but couldnt see object.
- slow facial recognition- face area in right hemisphere correspond to lesion.
disorders of cortical function
- DB v1 damage and blindsight
lesion?
symptoms? due to what stream?
angioma in right calcarine fissure
- cortical blindness: could report mvoement and location, but no conscious awareness of seeing = due to dorsal stream: see when not consciously seeing. = automatic process.
disorder of cortical function
case JI: V4 damage and loss of colour vision
accident? damage where?
better acuity when?
concussion resulted in loss of colour vision.
- damage in occipital cortex.
= improved acuity at twilight, bc rods worked in dark, cones at night.
disorder of cortical function
case PB: conscious colour perception in a blind patient
damage?
symptom?
suffered ischemia that destroyed large area of posterior cortex & visual cortex
- can only detect presence or absence of light. could see colour.
disorder of cortical function
case of LM: V5damage and perception of movement
- lesion:
vascular abormality produced bilateral posterior damage.
- loss of movement/snapshot vision.
- couldnt intercept moving object.
disorder of cortical function- case DF: where is damage? what are sympotms? caused by?
occipital damage = visual form agnosia due to CO poisoning.
bilateral damage to LO region and tissue between parietal and occipital lobes
what is visual form agnosia?
inability to recognize line drawings of objects.
- can use visual info to guide movement, not for recognizing objects
3 types of visual agnosia
apperceptive agnosia
associative agnosia
specific agnosia
what is apperceptive agnosia .
problem is probably where?
perceptual categorization - cannot form a whole. recognize local aspect, cant put together
- issue probably in ventral stream
what is associative agnosia?
maybe issue with?
- lesions where?
- can describe with detail, cant put a name to it.
- maybe recall, memory access disorder.
- more medial lesions of temporal or hippocampus
what is specific agnosia?
- issue with?
know all object except those linked to specific category
memory access disorder
face processing and prosopagnosia
- monkey studies: inferior temporal lobe
- humans: posterior right hemisphere
- monkey: configuration of face in correct way causes firing of cells in inferior temporal. specificity for kinds of configural info - upright but not for mixed.
- humans: configurational info leads to responses.
- inversion effect: ID better when upright than inverted.
thompson illusion
- right hemisphere damage effects
deals with face and configuration of face.
- right hemi damage = fusiform gyrus. when inverted pic- same performance as intact.
upright pic - poorer performance. - can’t ID face because areas of brain are lesioned.
N170 & face processing
- recorded in right temporal cortex. - face adaptation paradigm.
- respond if face is same as adapting. time locked paradigm.
- N170 = most negative when face is upright and same. when inverted or different = more positive.
more negative = need less brain area, neural procesing to interpret.
face processing - right hemisphere N170
- electrodes on left and right inferior temporal lobes.
- left hemisphere: encodes for both inverted and upright faces.
- right hemisphere - encodes v strongly to upright faces. preference*
shows right lateralization for face recognition.
role of experience in recognition
- radiologists
everyone had same ability in facial recogniton.
ID abnormal scan theyve seen before - better as spend more time in field.
- to ID normal scan theyve seen before- more experience get worse. all the normal scans begin to blend into each other - not detected.
role of experience in recognition - bird/car
bird man vs car man.
similar ID-ing faces. - in brains, found the FFA
cars - only car man had FFA light up.
brids - only bird man had ffa light up.
FFA = process configural info. not just faces.
role of experience in recogntiion
- greebles, 2 parts
- upright or inverted. after time, greeble performance matches face performance. - favour upright of both face and greeble.
- greeble expert vs novice. more FFA activation in expert than in novice.
prosopagnosia
face blindness
- category specific agnosia.
- related to damage in FFA.
- deficit in how features come together
covert face recognition task -saying name alongside picture
- normal: when name aligns with pic - quick. when face and name dont align - takes longer. even longer when not associated in any way.
- prosopagnosia, cant ID the face. but also seen that slower when names are incongruent.
= implicit memory: strong inference that prospagnosia can ID something about face because performance same as in normal. but, something about how processed in brain, or put together.
tactile recognition
- brain area involved?
lateral occipital. tactile visual info.
- area of convergence for recognition - using tactile and visual info.
- auditory not processed, but vision and tactile info are processed.
