Anatomy of Occiptal Lobe
What area of the visual cortex is the first level of processing for incoming visual information?
primary visual cortex (V1)
Damage to __________ or _________ causes monocular blindness (loss of sight in one eye).
Retina or optic nerve
What are the 3 streams of vision discussed in lecture, and what are their functions?
Superior temporal sulcus (Visuospatial functions), Dorsal stream (Visual guidance of movements), and Ventral stream (object recognition)
Which of the five categories of vision is responsible for reflexive actions like ducking and catching?
Vision for Action
How many layers of cells is the overall human cortex?
What is the name of the structure at which the optic nerves cross?
the optic chiasm
_________ is typically due to a tumour of the pituitary gland putting pressure on the medial optic chiasm.
Bitemporal hemianopia
What functions aside from vision are associated with the STS?
Any of: language comprehension, theory of mind, biological motion, faces, or voices.
Vision for Action activates ________ visual areas in ________ stream.
parietal, dorsal
A right occipitotemporal lesion can cause a deficit in facial recognition known as _______________
Prosopagnosia
What divides the occipital lobes from the parietal lobes?
The parietal-occipital sulcus
Right nasal hemianopia is often due to a lesion in the __________ leading to loss of vision in one nasal field.
Lateral chiasm
I am having trouble processing an object that is changing its orientation over time. What visual stream might be functioning abnormally?
Ventral stream, Area V3
What are the two types of spatial locations in the visual space category and what do they mean?
Egocentric Space is location of an object relative to a person
Allocentric Space is location of an object relative to another.
_______ are metabolically more active structures in the occipital lobe, that stain deeply, and are sensitive to colour.
Blobs.
Name two examples of higher-order processing that happen in the extrastriate cortex.
recognition of shapes, motion, or colour
Occipital lobe lesions (as opposed to optic tract or thalamus lesions) can cause visual deficits that spare the ___________
BONUS: why might this occur?
Macula (Macular sparing)
BONUS: Macular part of V1 might receive double vascular supply from the medial and cerebral artery
Which stream does visual information travel to after area V2?
All of them! STS, Ventral, and Dorsal Streams
What is the difference between Visual Attention and Action for Vision?
Action for Vision is visual scanning, eye movements and selective attention
Visual Attention is paying attention to important characteristics of an image (trying not get overwhelmed).
Area V3 in the occipital lobe processes _________ in _________ visual areas.
dynamic form, temporal
A 42 year old man with no prior vision troubles sustained an injury to the back of the head and is now has difficulty distinguishing and perceiving colours. He now struggles with identifying certain hues and reports that some colours appear less vibrant. What area of the brain might have been damaged to cause these symptoms?
area V4
Patient B.K. suffered a right infarct in the occipital lobe and experienced blindsight (could perceive light once it moved to a visual quadrant).
1. Where might the damage be specifically?
2. What would a perimetry reveal for B.K? What type of disorder may be present?
3. The perimetry also reveals a blind spot. What is the technical term for this? Why might it go undetected in a healthy patient?
1. V1 (or near the calcarine sulcus)
2. Quadrantanopia (loss of vision in 1/4 of visual field)
3. Scotma. Often goes undetected due to nystagmus (constant tiny involuntary eye movements) and "spontaneous filling in" by visual system.
Case study: Patient T experienced a lesion to their left occipitotemporal lobe :(
1. What symptoms might this cause?
2.Why is this inability specific to the left occipitotemporal cortex?
3.What form of agnosia is this considered?
1. Alexia/ Dyslexia (inability to read)
2. Both hemispheres have the ability to read letters, but only the left can combine letters to form words.
3. Object agnosia OR associative agnosia.
Patient C presents with visual agnosia. Their eye movements are tracked using faces.
What kind of eye movements are expected of a normal individual vs. patient C?
Which category of vision would be affected in patient C?
A normal person would focus on the facial features and direct more attention to the left side of the image.
Pt. C (w/ visual agnosia - loss of knowledge) would have random eye movements.
Action for Vision affected.
Interblobs are sensitive to ____________
orientation