Upgrade to remove ads
S & P - MBB1
Terms in this set (60)
which of the following best describes the platonic view of the world
Could never actually see reality -
we can never see truth or the real world, we are confided by our senses
· 'The prison-house is the world of sight'/shadows on a cave wall
· There is a 'real world' but our mortal senses are only capable of sampling a small subsection of that world
The Cave Analogy: Everyone is trapped in a prison with a fire behind them where puppeteers reflect visions onto the wall in front of the prisoners and this is all they see. Philosophers are those who have left the cave and discovered reality
what view is illustrated by friedrich nietzsche
there is no real world - only the world in our heads
that each individual creates the world we perceive from our input, constructing our own reality
the world we visually sense is dependent on
our retina is the only contact we have to the external world
-retina works out colour, brightness , then it adds in form, structure, motion and depth
- retina info + light source
excitation refers to
our cones spectral sensitivity at a retinal level
- cones superficially fire to a specific wave length of light
- simply firing of neurones
(An act of irritation or stimulation or of responding to a stimulus, the addition of energy, as the excitation of a molecule by absorption of photons)
sensation refers to
an impression made upon the central nervous system, through the medium of a sensory or afferent nerve
- a feeling, or state, produced by external stimulus or change in internal state of the body
L, M ,S denote when applied to cones
Long, medium and short wave lengths
a system for measuring behaviour
- behavioural response to a given input stimulus
- must now the input
must restrict the output - binary yes/no response
the crux of the argument between hering and helmholtz
- Hering instead believed that the visual system worked based on a system of colour opponency
-In this model, colors are perceived through receptors sensitive to three couples of opponent colors: red-green, yellow-blue and white-black
-Hering disagreed with the leading theory developed primarily by Young, Maxwell and Helmholtz. Young proposed that color vision is based on three primary colours: red, green, and blue. Maxwell demonstrated that any color can be matched by a mixture of 3 primary colors. This was interpreted by Helmholtz as proof that humans perceive colors through 3 types of receptors, while white and black would reflect the amount of light.
the spectral sensitivity of the three cone types must overlap because
you need more then one reference point in order to determine colours and shades
a colour space is
colours are created by the primary colours - they then define a colour space. we can specify the amount of each colour using the X,Y,Z axes,
- colour space is a method by which a particular light and colour may be represented such that its a definition is unique and replicable
your sensation of a particular colour depends on
i) you individual arrangement of cones in the retina V4
ii) emotional memory
iii) psychological association
the statement the brain turns the image the right way up is incorrect because
When the image is focused on the retina, it is inverted relative to the source, both vertically and horizontally.
However, the first thing that happens to that image is that it is immediately shattered into a collection of responses to the absorption of photons over space and time (ref to first commentary)
what is red
ii) perception varies
iii) physiological experience
What reason may you have to expect the photoreceptors to be physically anchored on the retina despite the observation that this means that there is neuron matter between the light source and the photoreceptor
· The presence of a blind spot in the retina due to converging neural material in front of the retina
An inverted retina also allows photoreceptors to receive blood and nutrients from the retinal pigment epithelium which absorbs most of the light not captured by the retina. This inverted retina design also prevents light from being reflected off the back of the eye onto the retina which would degrade the visual image.
opponecy confers which of the following properties upon that stage of the system
which statement best describes a receptive field
specific function, abstract concept rather than a physical thing, receptive fields are sensitive to different stimuli,
a sheet of photoreceptors
what is the likely format of the first specially structured receptive fields in the visual system
Center-surround organization (2D donut shaped) receptive field with ON-receptors (excitatory) in the middle and OFF-receptors (inhibitory) in the periphery. Increasing events in the centre of the receptive field increases the output and vice versa
the receptive field arrangement in the above question "what is the likely format of the first specially structured receptive fields in the visual system " confers what properties to the system
why, when considering the processing of the neural signal, is the actual physical location of any visual neurone other then the photoreceptors, arbitrary ?
· The actual physical location of the visual neuron does not matter because all receptive fields in the visual system have some relationship to the same x,y, z space that constitutes the axes of the visual input, but they sit in various places within visual pathway - mostly at the back of the head
Photoreceptors are our only link to the visual world. Once the photoreceptors have encoded the relevant information, it doesn't make any difference where that information is processed
why, however, is the relative location of any sensory neurone potentially important ?
This is because any other imagery that we perceive is first and foremost detected by the photoreceptors/neuron. WIthout this initial point of contact, everything else does not exist since all direct contact with the image is lost; the relative location of any sensory neuron is important because lines next to each other in the 'real world' have to be represented next to each other in the mind, otherwise they would just be random lines and we wouldn't be able to work out the outlines and shapes of what we see
what is it meant by the term retinotopic mapping
-two neurone that receive input from adjacent group of photoreceptors will be adjacent in cortex - xy map of retina early in visual system is maintained throughout ?
-V1 has columns that contain every neurone you will need for that bit of the world and one specialises in colour
The term "phase-coherence" refers to the hypothesis that.....
an edge or border is singled consistently across all scales of analysis
The idea of modularity in visual processing refers to......
Visual modularity is an organizational concept concerning how vision works. The way in which the primate visual system operates is currently under intense scientific scrutiny. One dominant thesis is that different properties of the visual world (color, motion, form and so forth) require different computational solutions which are implemented in anatomically/functionally distinct regions that operate independently - that is, in a modular fashion.
What reason may you have for questioning the assumption that the LGN is just a relay station for signals traveling from the retina to the cortex?
The LGN sends and receives from the cortex, lessoning it creates difficulty in one not both areas to understand it has more then one function
Taken as a population, primary visual cortex (V1) neurones have what critical property
V1 represents everything that one is able to see - as all visual input to the cortex enters at this point
- They're sensitive to various aspects of stimuli and put together all the info that's processed in other areas of visual cortex to create the picture we see (depth, colour etc) and doesn't specialise in one particular area
What is an example of an artificial receptive field?
myke, iphone, keypad
what is the binding problem
If we have all these multiple maps of the visual world, how and where (in the brain) do we put them back together for form the coherent single representation that matches our experience.
What is the potential problem with the binding problem?
Firstly, if we never completely segregate the image into these separate representations but always keep them linked, is there ever a problem to be solved? - just because we have a coherent, unitary representation of the world that we identify as our visual sensation, does that mean we should expect the underlying brain function to mirror that experience and provide a single unitary neural representation? → My answer to that question would be that there is no good theoretical reason why we should expect to the brain to appear as if its behaving that was just because that is the experience that it confers on to the organism. Our experience of the world is just the product of whatever is going on in our head.
An example of context dependancy in vision is ...
Straight matchsticks arranged into a curve gives the whole impression of a curve even though individual matchsticks are straight.
Context-dependency is: the fact that the perceived visual attributes of a target stimulus depend on the context within which the target is placed.
An attentionally-controlled motion system may....
allow isolation of a particular aspect of motion
- a good example is turning our heads, under normal circumstances, doesn't make us dizzy but we are able to distinguish objects in our field of vision
The visual system appears to dissociate motion-signals elicited by eye-movements or from retinal motion by.....
Inflow (relies on feedback from eye movement to account for the effect of the retinal motion) and outflow (uses same signal that commands the eye movement and is therefore quicker and possibly more accurate) hypothesis
The spatial structure of natural textures is consistent with the properties of the system because......
· It has tiny receptive fields sensitive to tiny fragments of texture and uses the same component input but interaction between them is different;
· One indicates texture/random surface, other indicates smooth lines on the surface.
The difference with the texture receptor fields is that it doesn't have coherence and there isn't the smooth continuous line in the larger receptive field that is sensitive to lines (ink in the case of the tattoo)
adaption refers to reduced sensitivity to stimulation as a result of repeated exposure
What is meant by the term "parallel processing"...
The ability of the brain to do many processes simultaneously e.g. a objects depth, colour, form, motion
Eg, a black car is only recognised as a black car when there is a combination of various inputs from different parts of the visual system
The terms M and P in the context of the visual system refer to....
motion and perception or M (magnocellular) and P (parvocellular)
Retinal ganglion cells actually come in 2 sorts: M (magnocellular, or parasol) and P (parvocellular, or midget).
· P cells also exhibit color-opponent responses: their firing is also dependent on the wavelength of light in their receptive field. M cells do not exhibit color-opponency.
· M cells make transient responses: they fire action potentials when a stimulus is introduced, but quickly fade if the stimulus does not change. P cells, meanwhile, give sustained responses to stimuli in their receptive field.
the perception that our sensory organs create of the outside world i.e. what we see is translated into information for the brain to process
- the perception our sensory organs create of the world (the difference that makes a difference) - difference between 2 forms or organisation or certainty
A vector is...
a quantity having direction as well as magnitude esp. determining the position of one point in space relative to another
The theoretical hierarchy established by David Marr is......
Developed a framework of how vision worked: first involving edges, second texture and depth, third (3 stage sketch)
"Retino-cortical expansion" refers to.....
Having more cortical neurons dedicated to deducing what is going on in the cortical field.
- There are more cortical neurons dedicated to figuring out what is happening in the visual field
The two most likely kinds of motion detector in the human visual system are called....
1. Correspondence type detector
2. spatiotemporal gradient.
The three critical dimensions of vision are...
X (computationable , Y (algorithmic) , T (implementational)
The term "Biological motion" describes.....
brains are primed to notice biological movement compared to mechanical movement (eg. seeing lions/ people) we interpret random dots to be people as brains are wired that way
Interaction between V1 orientation-selective receptive fields follows what ʻlawsʼ?
Full and partial activation (on off system surround)
One critical similarity between the visual and auditory systems is
Both have ability to perceive speed and direction, both have specific brain regions,
One critical difference between visual and auditory systems is...
One responds to photons
The visual system is sensitive to...
The auditory system is sensitive to...
What aspect of the relationship between the stimulus and the cortical representation is different between vision and audition?
One organised by functional modules and ones organised by frequency
What is meant by "tonotopic mapping"?
· Tonotopy is the spatial arrangement of where sounds of different frequency are processed in the brain
· Tones close to each other in terms of frequency are represented in topologically neighbouring regions
Tonotopic maps are a particular case of topographic organisation, similar to retinotopy in the visual system
What is one way in which the auditory system may deal with the problem of dealing with a unidimensional input (i.e. variation only time only)?
We become habituated to it and resultedly respond less (we only pay attention again once it changes) eg. fan
"Place theory" in hearing refers to...
Where sound's coming from
- The frequency to space mapping on the basilar membrane provides the initial means of frequency coding
"Frequency theory" in hearing refers to...
Frequency (pitch) of sound
- The physical location of stimulation on the basilar membrane signals the frequency of stimulation but in the form of a travelling wave - membrane properties altered physically by outer hair cells.
A form of parallel processing in the auditory system is implemented in the cochlear nucleus by...
Amount of neurons in different areas of cochlear (can process different sounds at different times)
What critical neural interaction is affected by, among other things, hallucinogenic drugs?
Increased cortical activity, and mess up LGN (make it send a lot of signals to visual cortex which is why you see extra things) the neural interaction is increased from LGN
What is the problem for a system that needs to have a high sensitivity to both time and frequency in its input?
Needs a lot of processing power to be sensitive to a time and frequency (uses a lot of energy)
Your experience of reality is.....
One fish, two fish,.......
red fish, blue fish
where are the doors to perception
the mind, beyond the self
YOU MIGHT ALSO LIKE...
Sensation and Perception
Sensation and Perception