11.1 - Explain how the visual system can represent complex stimuli using multiple brain regions and parallel processing
Since there are too many complex details for one brain area to accurately process in V1, the brain breaks the information down to be processed in different areas
11.1 - Explain how the visual system can represent complex stimuli using multiple brain regions and parallel processing: How is the visual system organized?
In a hierarchical organization where each brain area processes a different aspect of vision (V1 is the foundation/first place of initial processing)
After V1’s processing, it is sent to different, neighboring regions (V2, V3, etc.)
11.1 - Explain how the visual system can represent complex stimuli using multiple brain regions and parallel processing: What is parallel processing?
The way the brain processes visual info: visual info is broken down and processed in areas specialized for specific aspects of vision, and recombined in higher-cognitive areas
11.2 - Explain which feature of visual stimuli is processed in the dorsal stream, and predict the effects of a brain area in this stream being damaged: What is the dorsal stream?
Collection of brain areas in the parietal lobe that process visual info
“where” pathway: processes where things are and how things move
11.2 - Explain which feature of visual stimuli is processed in the dorsal stream, and predict the effects of a brain area in this stream being damaged: What is the MT?
An area in the dorsal stream that processes complex movement (how things move through space)
11.2 - Explain which feature of visual stimuli is processed in the dorsal stream, and predict the effects of a brain area in this stream being damaged: What are the effects of a damaged MT?
akinetopsia (“motion blindness”): seeing the world like frames in a movie, cannot see things moving
- has a healthy retina and V1, but not MT
akinetopsia is a type of agnosia: can see, but not perceive/process something in their head
11.2 - Explain which feature of visual stimuli is processed in the dorsal stream, and predict the effects of a brain area in this stream being damaged: What is MST?
very similar to MT, specifically processes optic flow (what you see when moving forward)
11.2 - Explain which feature of visual stimuli is processed in the dorsal stream, and predict the effects of a brain area in this stream being damaged: What happens when the parietal lobe is damaged?
Since the parietal lobe is important to the dorsal pathway, someone won’t be able to process spatial information if damaged
11.2 - Explain which feature of visual stimuli is processed in the dorsal stream, and predict the effects of a brain area in this stream being damaged: What is hemispatial neglect?
a condition from one damaged parietal lobe, person is unable to process visual information from the opposite side of the damage (person is not aware of the deficit)
usually tested by asking patient to recreate a picture by drawing, if only half the object is there
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is the ventral stream?
Collection of brain areas in the temporal lobe that process visual info
“what” pathway: processes what something is and what features they have
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is the fusiform face area?
Fusiform face area (FFA): a region in the ventral stream that responds very well to faces
When recording FFA response in monkeys, strong responses occurred in monkey faces/human faces/drawings of faces, weak responses in faces with an error, and no response in non-faces
*very specialized to what we expect, so it will not activate in response to errors (upside down faces)
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: Do humans also have the FFA?
Yes + it might not only be a facial area, but a visual expert area > people who are experts in certain fields also show FFA activity for objects relevant to their skills
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is prosopagnosia?
“face blindness” resulting from FFA damage, can see faces but not recognize them/piece them together as a face/distinguish different faces that have similar features
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is object categorization, and how much do we respond to certain things?
How we recognize what something is, processed in the ventral temporal cortex
faces, limbs, places, words > objects
objects > scrambled things
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is the grandmother cell, and how is it inefficient?
Hypothesis to explain how we recognize specific objects Theorized that one single cell encodes for specific objects
We have too few neurons to represent everything we experience
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is the leading theory on how we recognize what things are, and how is it more efficient than the grandmother cell hypothesis?
Hierarchical coding hypothesis: we break down each object into foundational visual components (shape/color/size/etc.), and then use population coding to combine this info and represent it
*each unique object activates a unique combination of cells, allowing us to categorize a wide range of objects
this is more space-effective/dynamic than grandmother cell hypothesis
11.3: Explain which feature of visual stimuli is processed in the ventral stream, and predict the effects of a brain area in this stream being damaged: What is visual agnosia?
can’t visually recognize objects,. usually resulted from damaged temporal/occipital lobes, but also in dorsal path
Explain how concepts learned about the visual system can be applied to other sensory systems: How do the sensory systems process info?
