Perception Flashcards
SENSORY PROCESSING -
interpreting information our senses receive from the environment
Human’s brain have a limited capacity! true or false?
true
Even without a limited capacity it would not make sense to be constantly aware of irrelevant sensory information
Vision is interpretive –
brain interprets the visual input.
Vision is constructive –
brain constructs representations of the world around us.
Our sensory impressions are influenced by:
the contexts in which they take place
our emotional states
our past experiences
How do we construct the image we have in our mind?
Making eye movements
The retina:
Two types of photoreceptors:
cones (color sensitive, important for colored daylight vision; densely packed in fovea)
rods (important for night vision; vision in the dark is black & white)
Retinal ganglion cells-
group of retinal neurons with axons that give rise to the optic nerve
Our vision is ‘binocular’ for the middle field?
true
The visual information leaves both eyes via the optic nerve?
true
Information from each eye crosses over in optic chiasm and goes to the opposite hemisphere
true
Visual information goes through the Lateral Geniculate Nucleus (LGN)?
True
LGN directs visual information into the visual cortex in the brain
true
Vision is HIERARCHICAL
Brain starts by processing most simple properties and works its way up as processing continues
State the stages…
Dots – Lines – Edges – Objects – Movement..
Vision is MODULAR
Specific areas of the brain deal with specific information. E.g….?
colours, movement, position…
V1 =
PRIMARY VISUAL CORTEX (also Striate Cortex)
Left V1 contains a retinotopic map of the entire right visual field, while right V1 contains a map of the…
left visual field.
Loss of V1 =
cortical blindness
Damage to parts of V1 =
blindness in related part of visual field
Blindsightis the ability of people who are cortically blind due to…
lesions in their primary visual cortex (V1) to respond to visual stimuli that they do not consciously see.
Area V4 is especially important for…
color perception, and some neurons in V4 respond well to more complex features or combination of features.
V4 neurons are sensitive to…
curvature or to two lines that meet at a specific angle.
Damage to both V4s can lead to loss of…
colour vision
Inability to identify or discriminate colour
Damage to V4 in only one hemisphere can result in a loss of…
color perception to one side of visual space.
Area MT (V5) The middle-temporal -- MT -- area is important for...
motion perception. Almost all neurons in area MT are direction-selective, meaning that they respond selectively to a certain range of motion directions and not to others.
The fusiform face area (FFA)…
that responds more strongly to faces than to just about any other category of objects.
The lateral occipital complex (LOC)…
has a role in object recognition and responds strongly to a variety of shapes and objects.
The parahippocampal place area (PPA)is another strongly category-selective region that responds best to…
houses, landmarks, and indoor and outdoor scenes. This area responds more weakly to other types of stimuli such as faces, bodies, or inanimate objects.
Dorsal pathway leading from V1 to the parietal lobe that is important for…
representing ’where’ things are
Ventral pathway leading from V1 to the temporal lobe that is important for representing…
‘what‘ objects are. Ventral system includes visual association areas
Prosopagnosia is agnosia for…
faces
Sometimes called ‘face blindness’
Can be caused by brain damage to FFA or some people have milder version from birth…
Agnosia =
‘failure to know’
Impairment of visual perception due to brain damage, which is not attributable to sensory impairment or gross intellectual impairment
Visual Agnosia
Patients can no longer identify by sight even simple objects
Patients do not have problems with memory for the word
Patients do not have with language needed to say the word
Lissauer (1890) distinguished:
Apperceptive Visual Agnosia - Patients do not gather elements together to make a ‘whole’. Vision groups elements together (individual lines, colours etc…) to interpret shapes and objects – this ability is lost
Associative Visual Agnosia -Patients can ‘perceive’ the object – but can’t name it; they no longer associate it with the correct name.
Recognition by touch and verbal description good
Visual agnosia – famous case
Patient HJA (Humphreys and Riddoch, 1987)
This patient has elements of both ‘apperceptive’ and ‘associative’ agnosias Unable to integrate – in order to make sense of it Can copy (in 6 hours!) but not name
HJA – Object Decision Task
Study conclusion:
Visual perception has 2 important stages
Establishing overall GLOBAL form of stimulus
Process that BINDS all the features of a stimulus together
Sensory information that refer to the same aspect of the physical world are perceived by differerent senses
true or false
true
exlain Cross-modal correspondences
mappings between dimensions of a stimulus in different sensory modalities
these mappings induce compability effect between that dimensions of a stimulus
2 KEY features of cross-modal correspondences
Polarity (stimulus is experienced as „more than”, „less than” another stimulus)
Universality (all or most individuals share the same pattern of correspondences)
Cross-modal audio-visual correspondences alter:
Speed of information processing
Cross-modal associations can modulate audiovisual integration at perceptual level
Speed of information processing
explain Pitch VS shape/brightness (MARKS, 1987)
Upturned “V-shape” and upturned “U-shape” was presented with low or high pitched tone.
Visual stimuli varied either in brightness (dim vs bright) or angularity (low vs high)
Cross-modal correspondences can modulate PERCEPTION OF audiovisual Information
true or false
true
what our eyes see can influence what we hear
Proposed steps in creating cross-modal correspondences
- structural regularities of an environment are first to create cross-modal correspondences
- then they shape vocabulary used
- with time brain may develop mechanisms to process these cross-sensory mappings (effects of experience on brain’s function and structure)
How does the brain integrate auditory and visual information?
Multisensory (supramodal) neurons activation
Feedback projections from multisensory areas to sensory-specific areas provide a way for information from one sensory modality (e.g. vision) to inform another sensory modality (e.g., audition) (e.g. Bologini and Maravita, 2007).
Stimulation in one sensory modality can also activate brain regions that are specific for different modality via direct anatomical connections between sensory specific brain areas (e.g. Bologini et al., 2010)
Important brain areas for multisensory interactions
Subcortical
Superior colliculus
Neurons respond to multiple
sensory modalities (supramodal
neurons)
Cortical
Temporo-parietal junction
synesthesia key features
Syn (join) +aesthesia (feeling) Blending of senses Is involuntary Pairings are relatively stable over life-time Idiosyncratic
Two main types of mechanisms have been proposed for Synaesthesia:
Hyperconnectivity – there are extra connections in the brain
Disinhibition (at the neural level) – reduction in inhibition of brain areas, resulting in lower threshold for activation
