week 6: pattern recognition Flashcards
what is agnosia
impairment of object recognition ability
how does agnosia work
people can recognise its an object but cant verablise it
what are intact for agnosia
processes such as colour, shape and motion perception are intact
what did agnosia help us understand
recognising a whole object is more than just recognising its parts
what are the 2 cortical pathways for vision
ventral pathway
dorsal pathway
ventral pathway route
occipital to temporal
what does the ventral pathway do
processes info about object appearance and identity
what is the ventral pathway important for
object perception
what is the dorsal pathway
occipital to parietal
what does the dorsal pathway do
processes spatial info about objects
what is the dorsal pathway important for
guiding action
what is optic ataxia
intact object recognition
what do people with optic ataxia do
inability to use visual info to guide action
what part of the brain is optic ataxia associated with
associated with lesions in the dorsal pathway (typically in the parietal cortex)
what does face perception require
holistic processing
what are the gestalt principles
similarity
closure
good continuation
proximity
what is template-matching and feature analysis
we tend to recognise different stimuli as the same object irrespective of superficial variations
what is feature analysis
a visual pattern is perceived as a combination of elemental features
type of model looking at feature analysis
selfridges pandemonium model
how do we recognise 3d objects
the same way we do for 2d, an object is first segmented into a set of basic sub-objects and then recognised as a pattern composed eg. broken up into smaller shapes
what are the subobjects of an object called
geons
what happens if the 3D object is midsegment deletion
takes alot longer to recognise the object
in centre surround receptive fields, what happens if the illumination is the centre
its inhibitory
what happens if the illumination is of the surround for receptive fields
its excitatory
what is the grandma cell hypothesis
a hypothetical neuron which encodes and responds to a highly specific but complex stimulus
weaknesses of the grandmother cell hypothesis
the final percept of an object is coded by a single neuron. However, each neuron’s firing is not so reliable. If that neuron is lost, our perception of the corresponding object would be lost
what are some other weaknesses of the grandmother cell hypothesis
perception of novel objects cannot be explained well
flexibility of object recognition cannot be explained well
what is ensemble coding
object recognition results from the firing of an ensemble of cells
eg. grandma is broken up into parts (hair, nose, glasses, dress)
what is really important to recognition
the context
what is phonemic restoration effect
a perceptual phenomenon where under certain conditions, sounds actually missing from a speech signal can be restored by the brain and may appear to be heard
when does phonemic restoration effect happen
occurs when missing phonemes in an auditory signal are replaced with a noise that would have the physical properties to mask those phonemes
