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Flashcards in Sensetion And Perception Deck (73):

Where does sensation come from?

Our environment


For environmental stimuli to be passed onto the brain they have to be converted into what?

A form that the brain could understand (neural impulses), know as transduction


What does lateral geniculate convert light rays to?

Converts light rays to electrical energy by ganglion cells and these signals travel along the optic nerve through lateral geniculate nuclei


We can only see in 2D but out perception of the world is...

In 3D


Why is the image we create in the retina of the eye upside-down and back-to-front?

So we do not directly translate the exact image of the object


Sight is what?



The visual information we receive in our eyes doesn't come directly from the stimulus, but from where?

From the light (electromagnetic radiation formed from oscillated waves of electrical and magnetic energy) reflected directly off it


How much of the electromagnetic spectrum is visible to us?

We only see a very small part


Light travels in waves that can be defined by what?

Their amplitude and wave length


What is the amplitude of light waves?

Height of wave which is perceived as brightness


What is wave length perceived as in relation to light wave?

It is perceived as colour


A small retinal image can be generated from what?

An object which is up close or far away


The eye has many important structures for focusing light on the relevant structures, what are they?



What is the cornea?

Front part of the eye where light enters


What is the lens?

Where the light is focused and can change its shape to do so


What is the retina?

The film that you would find on the back of the eye made up of fovea and optic disc and multiple cells


What is the fovea?

A dip in the retina that has a high concentration of specialised neurons that respond to light energy called cones so that sharp and detailed objects are processed and is the black part which is visible in the eye


What is the optic disc?

Where nerves leave the eye and go onto from the optic nerve which is the first part of the pathway to the brain and is the white part which is visible in they eye and you can often see the blood cells radiating out


What are specialised cells used for capturing light known as?



What are photoreceptors connected to?

Bipolar cells which are connected to ganglion cells which go into form the optic nerve


There are two types of photoreceptors, what are they?

-a rod
-a cone

They are named for their shape


What are rods

Primarily black and white detectors and do not give any indication about colour or details but instead used in low light and are concentrated in the peripheral areas of the retina and there are around 120 million rods in the human retina


Cones give rise to what?

Colour sensation and detailed high quality visual equity that are connected at the fovea and there are around 6 million cones in the human retina


There are 3 different types of cones so that maximum amount of wavelengths is absorbed, what are they?

-short responds to blue wavelengths
-medium responds to green wavelengths
-long responds to red wave lengths


The three types of cone cells are compared and this gives rise to what?

Colour vision


The destination for almost all visual information is v1 and v2, where is this?

In the visual cortex which sorts and segregates visual information before being passed onto different regions of the Brain for further processing


What are the three main categories of segregation?



Area v3 specialised in what?

The form of an object with additional information about the motion


What does v3 contain?

Specialised cells which respond to the motion of particular edges which would correspond to a stationary object that is in one place is tilting or rotating


What does area v4 specialise in?

Colour information (colour which is perceived not the stimulus properties of the object like wavelengths of light) with some information about the form of an object


Area v5 also captures motion but unlike in v3 the cells in v5 will respond to?

The overall motion of an object (speed and direction) with no identity of what the object is


What does the inferno-temporal cortex identify?

Objects and information about shape, colour and form are all integrated


What do visual illusions tell us?

Things about the visual system


Much of perception is problem solving and that the visual system comes up with?

A hypothesis about what is being seen which is top down aspect and the hypothesis is tested using information that comes information rant comes from the stimulus


What is top down aspect?

Knowledge driven


What is the stimulus?

Data driven/ bottom up part of perception


When the data from the top down and bottom up meet what do we get?

We get perception and sight but if we do not have generated the correct hypothesis than another hypothesis is generated and would be tested against the information


This does not reach our consciousness and it is so rapid that we see it as?



Sometimes we see things which aren't there and sometimes we fail to see things which should be perfectly visible and this tends to happen when?

The stimulus is not obvious and we become aware of this process- this tells us that there is interpretation and construction of the visual image


What is challenge blindness?

The failure to notice an obvious change


What is intentional blindness?

The failure to notice the existence of an unexpected item


How does challenge blindness and intentional blindness result?

Results as out visual system is resource limited so we have to focus on the salient parts of the visual scene and we do not have the capacity to process everything and send resources to where they are most necessary


How can we see visual illusions?

Due to contrast (the difference in brightness and colour that differentiates a colour from its background and from other objects in the visual scene) contrast effects can create visual illusions


What is the match bands?

An illusion which shows bands which all have the same brightness but what we perceive that they are brighter on the left so our perceptions does not correspond to the physical properties


In a Hermann Grid we perceive?

That there are spots on the grid but in reality they are not there and they occur because of contrast and our perceptual system is filling in the gaps between because it believes there should be more contrast there


The visual system tries to simplify things as

It emphasises differences


In colour sensation what is hue?

Technical term to describe colour


In colour sensation what is brightness?

How dark or light an object is


In colour sensation what is saturation?

How vivid the colour is


There are two main historical theories about colour perception- what are they?

1. Young- Helmholtz theory
2. Opponent- Process theory


What is the young-Helmoltz theory?

Trichromatic theory of colour vision- three separate pathways for processing colour I.e one for blue, red and green and each pathway would extend to the brain but the theory does not explain how we like colours like yellow or colour mixing


What is the opponent-process theory?

Colours are processed in pairs and their is an antagonistic relationship so if the red part was excited then the green part would be inhibited


Both theories (young and opponent)

Feed into modern understanding of colour perception


The opponent-process theory is accurate to what we know as?

The information that we receive from the photoreceptors is recoded into pairings


There are three types of pairings- what are they?



Colour contrast allows us to?

See these theories in action


Colours induce their antagonists in?

Neighbouring areas


Negative colour imaging provides evidence that?

Colours are presented in pairs


Perception of shapes depends on?

Feature detection


In perception of shapes in area v1 there are specialised cells which are?

Feature detectors and are tuned to respond to specific feature of an object I.e one cell which responds to a horizontal line that is located in the upper right corner of the visual field


Visual receptors tend to respond best to?

A line or an edge and other cells assemble the visual output and are passed onto other cells


A specifi feature a cell responds to is known as?

The cells receptive field and its optimal output is what defines its receptive field and different cells have different receptive fields


Torton Wiesel and David H. Hubel were pioneers in examining?

The roles of single cells in the visual cortex


The cat experiment showed?

That the more of a firing response when the cell was presented with a certain stimuli but there was not the same response when there was a less preferred stimulus


The recognition of form begins with?

The detection of simple features and the importance of theses tasks is highlighted by visual search tasks


What are visual search tasks?

Where we have to determine whether a particular target is present or not and when the target differs from the distractors in one aspect it is easy to detect but it differs in a number of ways, it is difficult to tell whether the target is present or not


The detection of features is one aspect of the perception of objects and forms part of the bottom up processing but ?

There are constraints posed by our expectations and experiences that feed into our perception of objects


Most stimuli

Is not ambiguous and we can see the process going on when there is ambiguity and we have to segregate what is the object of importance and what is the background known as figure ground segregation


The perceived has to

Organise visual information


What does the visual system pathway include?

-optic nerve
-lateral geniculate nuclei
-visual cortex


Our visual experience is...

Constructed and interpreting the information we receive - it is in the part of the brain where sensation happens


Our sense organs are responsible for?

Sensation by capturing environment stimuli


Our eyes are designed to?

Captors light energy which passes the information onto the cortex of the brain where the information is organised interpreted and is given meaning