Object Processing 1+2 Flashcards
Two visual streams
30+ visual areas are arranged along two pathways, the dorsal stream, from V1 to ______ ______ lobe, and the ventral stream, from V1 to ______ ______ cortex. These pathways are divided according to the ____ of information they encode, and according to the functional _______ related to vision.
The ______ stream is the ______ (spatial location) and ______ pathway (uses vision to guide ____ and has strong interactions with motor system). The _____ stream is the ______ pathway (computes shape and identity of objects) and is also involved in conscious ________ and ______.
posterior parietal lobe
inferior temporal cortex
type
functional
dorsal where how action ventral what perception awareness
Beyond the posterior parietal lobe, the dorsal stream has 3 projections
- projects to _____, and involved in spatial ______ memory (“where”)
- projects to ______ cortex involved in action (“how”)
- projects to _____ _____ lobe (hippo) and involved in spatial ______ (“where” on an environmental scale)
PFC
working
premotor
medial temporal navigation
The Ventral Stream - stimulus complexity and receptive fields
In early visual areas such as V1 and V2, the neurons respond to _______ stimuli, such as edges, ______, etc. The receptive fields they respond to are quite _____, and it is strongly ________ organised
simple
orientation, point of light
small
retinotopically
The Ventral Stream - stimulus complexity and receptive fields
Intermediate areas of the visual cortex (eg V4 and TEO contain neurons that respond to _____ complex features such as _______ of edges to form shapes and ______, etc. The receptive fields they respond to are _____ and _____ restricted than earlier in the visual cortex. But they are still restricted to a certain _______.
moderately conjunction textures larger less quadrant
The Ventral Stream - stimulus complexity and receptive fields
High-level areas in the visual cortex (eg ______ ______ cortex or IT) have neurons which have very ______ receptive fields, and almost no _______ organisation (lots more ______ as to where in the visual field the stimulus is). These neurons respond to ______ objects, such as _____ (FFA), or _____ (PPA) or body parts (_____). They are involved in the _____ between perception and ______ (aka they analyse an object an recognise it as familiar)
inferior temporal large retinotopic tolerance specific faces places EBA interface memory
The Ventral Stream - stimulus complexity and receptive fields
The studies in monkeys about the hierarchical organisation from _____ to ______ objects have also been replicated in humans. The early visual areas are more __________ organised and _____ responsive to textures and scrambled objects. Then as we move along the ventral stream there is a ______ progression to whole objects. This is a progression along the ______ to _____ axis.
An anterior area identified as specifically recognising objects is called the ______ ______ complex (LOC).
parts whole retinotopically more gradual posterior anterior
lateral occipital
The Ventral Stream - recognition and awareness
What our brain perceives and what we are consciously aware of are two different things. A technique to tap into this is called _______ ______ displays, where the visual input is ______, but our _____ flips from one to the other, so you “see” _______ pictures rather than the overlapping one. Participants press a ______ whenever they see a flip.
binocular rivalry constant percept alternating button
The Ventral Stream - recognition and awareness
In the visual cortex, a perception _______ is seen in recognition and awareness. In monkeys, only 20% of ______ neurons show correlation between activity and the _______ experience. This increases to 40% of ____ neurons and 90% of ____ neurons.
In humans, studies have been done where you “_____” the noise out of an image. In these studies, ____, ____, and ____ do NOT show much difference between activity and perception. However, there is a difference seen in higher-level areas such as the _____ (particularly a part of this called the ____) where recognition correlates with conscious awareness.
hierarchy V1/V2 perceptual V4 IT
titrate V1 V2 V4 LOC vOT
The High-End Ventral Stream
Different modules for different things. Name the 3 discussed and what they are for.
- fusiform face area (FFA) - faces
- parahippocampal place area (PPA) - buildings and places
- extrastriate body area (EBA) - body parts
The High-End Ventral Stream
The accessible location of the PPA and FFA can be exploited during studies. Describe the study which confirms the specialised function of these modules and how they relate to conscious experience
- used binocular rivalry - alternated between red house and green face
- measuring the activity in the PPA and FFA demonstrated the rivalry (and opposing activity) of these two areas when the brain switched between the house and the face/.
- in the control condition, there was no rival stimulus - just flipping between the pictures. It showed the same activity
- further evidence that the activity in these areas correlated with conscious experience
Functional Specialisation
This is inferred from:
- _______ of the information processed - region responds _______ (not exclusively) to a particular category
- _______ clustering - neurons of similar functionality grouped together to minimise ______ constraints
- Damage to the area (lesions) ____ processing of a whole and specific ______ of objects
selectivity preferentially spatial wiring disrupts class
Functional Specialisation
Describe the domain-specificity hypothesis
- Anatomical modules of the brain are for different categories.
- The organisation principle is based on the information content
- Modules are innate (hard wired) and for adaptive reasons (b/c they are biologically important to us)
BUT what about VWFA (visual word form area)???
Functional Specialisation
An alternative to the domain-specificity hypothesis is that the organisation principle is based on the ______ requirements, rather than information content. This means that we have these areas to perform particular processes, such as _______ individual faces, which is generally a ________ class. This has been backed-up by evidence by bird experts who can differentiate birds, or “greeble experts”.
Also, these specialised areas (modules) are shaped by ______, and not innate. It has been shown that they get stronger across _______,
Finally, these brain areas could have become specialised by virtue of their _______ to other areas. Eg: PPA has strong connections to posterior parietal lobe - so not a “place” area but a “_____ layout” area. And VWFA has strong connection with language areas.
process
discriminating
homogenous
experience
innate
development
proximity
spatial layout
fMR is a technique used to probe object _______ areas to see whether a cluster of ______ are consistent ( _______) within a particular area. It has a higher resolution than _____.
It exploits the idea that the _____ response ______ when a stimulus is repeated - this is related to neural ______. Once the activity decreases with the persistent stimulus, the stimulus is changed. If there is a _____ of activity this means a ______ population of neurons is responding. If there is no recovery, it implies this population of neurons is ________.
representation
neurons
homogenous
fMRI
BOLD decreases adaptation recover new/different homogenous
The High-End Ventral Stream - Object representation in LOC
The LOC or human “object area” has been shown, with fMR, to be ______ to:
- size
- ______ in the visual field (aka NOT _______ organised),
- image ______ (greyscale, line drawing, photograph, motion, luminance, etc).
Also, when there is tactile input, no _______ is seen. However, there is some sensitivity to _______ and _______.
Hence, the LOC is a high-level _____ ______ representation area, which can receive input from multiple _______.
Invariant
position
format
recovery
viewpoint
illumination
–> makes sense as this can change the shape
object shape
modalities
