lecture week 3 Flashcards
what is sensation
the process by which sensory receptors transduce physical stimulation in the environment into neural impulses. it is how we take information and process it into our brain
what is perception
the process by which sensory input is interpreted to form a meaningful subjective thought. how your brain interprets what it is given
what is the basic physiology of visual perception
the light enters through the cornea, which hits the iris and travels through the lens. hitting the back of the eye on the retina which is lined by photoreceptors (rods and cons which perceive colour and shadows).
what is the fovea
part of the retina that has the most photoreceptors because it carries the most cons
what is the optic nerve
there are no photoreceptors at this part of the optic nerve which represents a blind spot
what is contralateral organization
stimuli on the left side are projected to the right side of the brain and vice versa, the information on the right side of the center line is processed by information on the left hemisphere.
what happens to any information that crosses the nasal side
it will cross both hemispheres
what is psychophysics
the scientific study of how our subjective percept is related to the physical properties of enviornmental stimuli
what is fechners law
when you are listening to something at low intensity, how much do you need to turn it up to detect a difference
what is the solution to fechners law
if you increase it by a little bit, you will notice, but if you start with high intensity, it will take more for you to notice
what is the brain sensitive too
contrast, the difference in luminance between adjacent elements of a scene
what is orientation
refers to direction information contained within an image
what is spatial frequency
amount of detail in an image, higher spatial frequency is more defined
what is contrast sensitivity function
we do not perceive all spatial frequencies equally well
what happens if you have low spatial frequency
you need to add more contrast
how does high spatial frequency develop
once the eye develops, the optic nerves get better, and they can see better
what is depth perception
you can see depth more clearly because you have both eyes
what is binocular disparity
each eye receives different information about stimuli; one is represented near the fovea for the left eye but in the periphery for the right eye and reverse for the other eye.
how does the brain relaize the different deoth perception
because information one eye is different the the information on another
what is special about colour vision
different colours have different wavelengths
what is colour vision
the perceived colour of an object depends on which light components are absorbed by the material of that object
what do material properties do
absorb these colours except for the one that the person perceives. they reflect different wavelengths of light that are reflected back by the retina
what can be sensitive to different wavelengths of light
the cones in the retina since most of the colour perception comes from the fovea
what is the processing hierchary
basic visual features are processed hierarchically, with more complex features being extracted at higher levels of analysis
what is in the occipital cortex
V1-V4 which all connect to the MT which processes motion
what happens in the parietal cortex
deals with visual attention and plans movement
what does the inferotemporal cortex do
object recognition
how does bottom-up data driven work
starts with simple visual features, down to object recognition to knowledge. it is more about the sensation
how does top down processing work
it starts with knowledge, based on what we can see from the simple visual features, and then it goes up to object recognition. it is more about the perceotion, because the intermideate knowledge forms what we perceieve
what happens when bottom up and top-down meet
it is what you typically perceive
what is colour constancy
differences in background illumination can trick the brain
what is our interpretation based heavily on
the sensory input is shaped by our prior knowledge
what is normally perceived in general
what our brain predicts and what is out there with constraints to options due to our enviornment
what does the human mind do
ready every letter as a whole rather than itself
what are gestalts cues used for
to chunk the visual world into discrete units
what is denotivity
features that are familiar and meaningful tend to be perceived as foreground
what happens after processing in early visual areas (V1)
information is processed hierarchically in two different pathways
what are the two different pathways
- the ventral stream (what pathway)
- the dorsal stream (where pathway)
what is the ventral stream
the pathway that extracts shapes and texture information to identify objects. it allows you to consciously recognize things designed to tell you whats out there
what is the dorsal stream
the where pathway that possesses relevant spatial information for the purpose of guiding actions.
what does a patient with visual agnosia expereince
they can not identify visual objects, but they can use information to guide their behaviour. this patient has damage somewhere in the ventral stream
what does a patient with optic ataxia expereince
they can identify visual objects but can not use the visual information to guide behaviour; this patient has damage somewhere in the dorsal stream
what does double dissociation mean
both the dorsal and ventral pathways are independent so damage to one should not affect the other one negatively
what happens in the ventral stream specifically
it is sensitive to large regions of space, as cells in the inferior temporal cortex respond to complete visual information but are sensitive to variations in size. this allows us to recognize familiar objects. these cells have large receptive fields and respond to preferred stimuli presented
what happens to the memory of visual agnosia patients
they do not lose the memory; they just struggle with linking information to the object in that form
what are the two kinds of agnosia
- associative agnosia: can replicate but can not recognize
- apperceptive agnosia: can recognize but can not replicate
what are some cells very responsive too in the ventral stream
faces
what is thatchers illusion
when the face is upside down, and we have trouble identifying changes
why is it different when you idenfity faces rather than objects
faces have a stronger deficient to seeing upside down faces compared to other objects
what happens in the dorsal stream specifically
thought to transform visual information for the purpose of action, it can guide our behaviour without us knowing
what is vulnerable to trickery
the ventral stream. the dorsal stream does not let the brain fall into the trickery
what happens to damage to the right visual cortex
no vision on the left side of the space, but they can act appropriately with this vision on the left side because the dorsal stream gets information from others due to the visual information being processed in subcortical regions of the thalamus
can visual information still guide action while blind
yes, because they can act as if they still perceive something due to the information coming from the thalamus.
what kind of quality is sound
perceptional
what do auditory systems have multiple of
frequency channels, cells that respond preferentially to certain frequencies much like visual cells that respond to spatial frequency
what does our sensory system never do
work in isolation, they must be integrated
what did McGurk effect find out
visual information can bias what is heard and what is heard can be bias to what is seen
is perceptual infromation from different sensory modalities processed at the same speed?
the visual stimuli must be presented slightly before the auditory stimulus for them to be perceived as simultaneous since visual processing is slower than auditory processing
