After visual information is processed by V1, where does it go? What type of visual information is processed here?
The extrastriate cortex, which contains multiple sub-areas (indicated by V and then a # larger than 1)
This is considered Mid-level Vision, or the “in-between” of more complex things
As we go from low-level vision (V1 and prior) to mid and high levels, what changes about the cells?
The types of info that cells are sensitive to becomes more complex
The size of space receptive fields cover generally increases as well
What are the two general pathways for visual information after V1 and the extrastriate cortex? What are they each concerned with?
Dorsal (“where”): only concerned with detecting presence
Ventral (“what”): only concerned with detecting identity
After V1, where does the “what” pathway go? How does this area process information differently than V1?
V2 - still works with contrast between light and dark, but has a better understanding of what this means
- Categorizes boundary ownership (can tell when edges are part of stand-alone things or a continuous object)
- Can tell foreground vs background
- Understands transparency
After V2, where does the “what” pathway go? What does this region of the brain do and what level of vision does it process?
Inferotemporal Cortex - the region of the brain that knows what objects are
- deals with high-level (complex) vision
What would a lesion in the inferotemporal cortex lead to?
Agnosia: a deficit in the ability to identify objects even when one is able to see them
- have intact acuity, but impairments in grouping principles
How do receptive fields in the inferotemporal cortex work? (What do they respond to?)
Respond less to specific parts of space and more to particular types of stimuli, with different subregions for specific objects
What are a few of the different subregions in the inferotemporal cortex?
Fusiform Face Area: selective to faces
Parahippocampal Place Area: selective to scenes
Word Form Area: selective to the physical properties of words
What are grandmother cells? Why is there skepticism about their existence?
Hypothetical cells in the inferotemporal cortex that code a VERY specific stimulus, such as the face of a specific person
- we cannot sample all possible faces
- cells recode over time (don’t hold the same information forever)
There are two different theories for how information is processed in the visual system, what are they?
Feed-Forward Process: a unidirectional form of exchange in which higher levels do not send feedback to lower ones
Reverse Hierarchy Theory: allows for feed-forward processing (for initial information) as well as top-down control (in order to alter processing and attend to particular details)
What is a heuristic and why are they necessary for object recognition?
A shortcut that our brain uses to make processing faster
- our visual system makes assumptions about the state of the world (emergent processing) in order to make us more efficient
- they’re not always 100% accurate, but work most of the time
- aren’t a conscious decision that can be “turned off”
Illusory Contours
Perceive a contrast even though the actual visual information doesn’t change between the two parts
What is Gestalt Processing and what are the different assumptions that are part of it?
The whole is greater than the sum of its parts, as in, our perception cannot be defined by the actual pieces of the visual world
Examples: closure, proximity, similarity, continuation, parallelism, symmetry, connectedness, and common region
Closure
Assumption that objects are complete despite being obscured or occluded by other information
- nothing about the actual visual stimulus tells us that the figures close
Proximity
Information that is relatively close together is grouped together
Similarity
Assumption that information of the same kind (shape, color, etc.) must group together
Continuation
Assumption that lines, edges, and contours keep going in their general direction even when encountering other objects
Parallelism and Symmetry
Parallel = moving in identical orientations
Symmetry = mirrored images of each other
Neither of these things typically occur unless they are part of the same object
Connectedness and Common Region
Connectedness = it’s rare that objects be connected if they’re not part of the same system
Common Region = things enclosed in a shared space get grouped together
What part of the “what” pathway sits between V2 and the inferotemporal cortex? What information does it process and understand?
V4: deals with more complex shapes, but not necessarily full objects
- may be particularly interested in curves and angles
- has “shape selectivity”, where cells respond more to certain patterns compared to others
- understands boundaries and occlusion (angles intrinsic to an object vs caused by occlusion)
What does V4 assist with (theoretically)?
Might be the start of our visual system’s ability to detect object parts
How does camouflage trick our visual assumptions?
Capitalizes on visual heuristics to disrupt Texture Segmentation - the visual system’s process of carving an image into regions based on texture properties
What is Dazzle Camouflage?
Sort of like reverse camo, where you can definitely detect them, but it’s hard to identify edges, direction, and distance
Ex: zebras
What is the purpose of camouflage?
Doesn’t have to be complicated or perfectly hide something, it’s meant to slow down object recognition to aid with survival
