WEEK 6 - Sensory Systems and Perception Flashcards
how do we know about our environment?
live in it but we dont perceive it directly,
we continuously interact with it to understand it
as soon as there is a distruption sensory input (vision/hearing) we get lost
what is our conscious experience of the environment?
a construction of our minds - the way we see our reality is based on our construction
In relation to cameras, what is the human eye?
a digital camera
In stead of CCD sensors (in cameras) what do we have
photoreceptors
how are eyes like cameras?
lens at one end, receptor layer on the other
what does the retina do?
like a camera, they pick up points of light
how do we get from seeing points of light to seeing objects / lines / shapes?
we have a system for enhancing edges - discontinuities in adjacent parts of the image (like modern cameras)
how does the retina work?
through cells such as the ganglion cell
ganglion cells
are in the retina and have a receptive field
how can some ganglion cells be excited?
by light inside the receptive field and
how can ganglion cells become inhibited
by light outside the receptive fireld
what happens in other center-surrounding receptive fields?
illumination of the center is inhibitory while illumination of the surrounding is excitory
what does the retinal ganglion cell act as?
edge detectors - where they integrate patterns of lightness over an area and indicate whether that pattern of lightness within an area is different to that in an adjascent area (an edge)
Where is the Fovea
exact center of the visual field where light rays enter the eye sight along the axis of the eye.
what is the fovea?
the area with the greatest concentration of photoreceptors
what are the two types of photo receptors in the fovea
cone cells and rod cells
what are cone cells responsible for?
colour vision
what is the level of acuity that cone cells process
high acuity as they can see very fine detail with cones as they are densely packed in the fovea,
what kind of light does the cone cells work primarily in?
bright light or daylight ‘photopic’ vision
what are the rod cells responsible for?
black and white vision
what is the level of acuity that rod cells process
low acuity - mostly widely spread throughout the retina, more peripheral visual field)
what kind of lights do rod cells work best in?
night time ‘scotropic’ vision
what is depth perception
two eyes, two differeny images
what side of the brain does the right visual field project to?
left
what side of the brain does the left visual field project to?
right
where do the nerve cells cross over when projecting images to the brain?
optic chaism
where is the optic chaism located
midbrain
what is the process of visual information?
travels to laterial geniculate nucleus of thalamus (LGN) then back to occipital cortex and the back of the brain
what is another word for the occipital lobe?
primary visual cortex (V1)
what are simple cells in the V1?
respond to an edge at a particular orientation in a specific part of the visual field
complex cells in the V1
respond to an edge at a particular orientation by falling anywhere within a wider field. May also respond to direction of motion
hypercmplex cells in the V1
redpond to a line which ends within the receptve field (end-stopping)
what are the higher levels of the ascending visual system?
temporal lobe, colour and orentation combinations AND higher still feature detectors
what is the temporal lobes function in relation to vision
detectors for combination of line/edges (squares or cone shapes)
agnosia
the inability to recognise objects
prospagnosia
inability to recognise faces
what happens when there is damage to the parietal lobe?
causes problems of spatial awareness eg visual neglect
what is visual neglect?
visual unawareness of half their visual field. therefore lost information form half of both eyes
where does information from all levels of the visual system get distributed?
in the multi parallel visal maps
retinotopic
mimics the layout of visual field
what happens when you move your eyes?
other connections exist with higher cortical levels, including frontal association cortex that tell you where your eyes are pointing to make an internal map of where things are located
blindsight
unconscious, but not conscious, awareness of a visual stimulus. this must be observed in sme cases of visual neglect
what are the things one would give to a robot?
− A system for detecting light
− System for focussing on the important stuff – fovea, rods and cones
− System for detecting edges (‘stuff’) – ganglion cells and simple cells
− Higher system for identifying objects from the edges and patterns – temporal lobe
− Higher system for identifying where the objects are – parietal lobe system
