CCC- Week 2- Object recognition Flashcards
What is perception?
Perception refers to our ability to extract meaning from sensory input.
It includes the 5 aristotelian senses audition, taste, touch and olfaction (smell), but research is dominated by vision.
How many senses are there estimated to be?
9-22
What is proprioception?
Is the sense that lets us perceive the location, movement, and action of parts of the body.
It encompasses a complex of sensations, including perception of joint position and movement, muscle force, and effort.
What are the different types of receptors & where are they?
Chemical receptors- drive out taste & smell
Photoreceptors- found in eyes
Mechanoreceptors- Cover lots of things such as touch, like proprioception- muscles etc.
Thermoreceptors- Temperature
What are all of our senses reliant on?
One of the 4 receptors.
What does vision account for in our cortex?
Over 50% of all the neurons- so lots of research is focused on vision (especially as it is our dominant sense)
What sort of process is perception?
A constructive process- not a passive one.
When you look outside, you are not just passively receiving the information & interpreting it- you are actually doing so much more - essentially hallucinating- controlled hallucinations. A lot of what you think you have seen is completely illusive.
What is an example of us experiencing an illusion?
All aware we have a blind spot (the point of entry of the optic nerve on the retina insensitive to light- an area where view is obstructed)- it is about the size of an orange at arms length.
When you have both eyes open, your blindspots are each in different places so you don’t see your blindspot. However when you close one eye, you still can’t see a hole in your vision. Your brain fills in that gap- yet you have no sense of their being a gap in your vision (you think all the right details/ color is all there)However it isn’t there - we have a hole in our vision that we cant perceive- yet we perceive it as complete. That is an example of how it is an illusion- we think we see more than we actually do.
A lot of our thinking about perception & our ability is contributed to the eye- yet in reality- the eye is very lousy - what’s impressive is the processing in V1- our visual system- that incorporates what’s coming in ( the visual stimuli) & all of your history & experience & biases- which are suitable for our particular history/ evolutionary history- so theres lots more going on than whats just happening in the eye.
What is a blind spot?
The point of entry of the optic nerve on the retina insensitive to light- an area where view is obstructed.
The visual system model
Whats in it?
Brain receives sensory input allowing us to perceive an object.
Cognitive system constructs perception.
How many neurons in our cortex does vision account for?
50%
Processing streams- ventral/ dorsal
What is the dorsal pathway used for?
Spatial integration & location information.
What is the ventral pathway used for?
Used for identifying objects (it goes down the temporal cortex)
What are the two visual pathways?
Dorsal pathway
Ventral pathway
What is the different between the ventral and dorsal pathways?
Ventral- processes visual information- for perception.
Dorsal- processes visual information for the purpose of executing movements.
Why is our general belief about how the eye works in the model unrealistic?
We have different visual fields- in each eye- there is a left and right visual field.
The information goes to the two halves and gets processes separately.
Half the information goes to one hemisphere- half goes to the other hemisphere.
In order to see & recognize objects- you have lots of inter hemispheric communication- but we are not aware of this.
What happens with individuals who suffer from epilepsy?
Many have a corpus colostomy- surgery to treat epileptic seizures.
Involves cutting the corpus callosum- which stops the brain from sending seizure signals from one half of the brain to the other.
After the surgery- the seizures tend to be less severe- as they will only affect half of the brain.
What happens to the image on the retina?
Its inverted!
Where does language tend to be specialized?
On the left!
The visual system- A misleading impression of simplicity
What study was conducted & on what animals?
What did the study support?
Tootel et al 1982
Study tested on monkeys.
Monkeys- unconscious with eyes propped open.
Were presented with stimulus (25-30 mins) & injected with a radioactive isotope in glucose- so where brain was most active- the isotope got concentrated.
Supported the notion that a near perfect representation of the external world is “projected” onto our primary visual cortex.
Object recognition- what is the model called?
Three stage model
What is in the Three Stage Model?
Image
Stage 1- Local Features- Edge detection/ contrast
Stage 2- Shape representation- Gestalt principles/ feature
integration
Stage 3- Object representation- Stored representations/
knowledge
Three stage model
What happens at stage 1?
Local features- edge detection/ contrast
You’re extracting the local features- simple features- just like lines & edges & contrasts.
Three stage model
What happens at stage 2?
Shape representation- Gestalt principles/ feature integration
The basic features are being combined using things like gestalt principles & feature integration to perform larger but still primitive blocks and regions. You have slightly bigger blocks and regions performed from the really basic ones.
