Visual Perception Flashcards by Chloe Torkington

What is sensation?

Gathering stimulus from external environment via sensory organs

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Name the other names for these:
Eyes 👀 
Ears 👂 
Tongue 👅 
Nose 👃
Skin ✋️

Visual system - sensitive to light energy
Auditory system - sensitive to sound energy
Gustatory - sensitive to chemical energy
Olfactory - sensitive to chemical energy
Tactile - sensitive to thermal energy

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What is perception?

Organising and interpreting sensory info to give it meaning

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How do sensation and perception work?

Sense organs translate physical energy from environment into electrical impulses processed by the brain

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What would a person with no perceptual ability be unable to do?

Recognise faces, understand language or avoid threats

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What are sensory receptors?

Specialised cells that detect and transmit stimulus info to sensory nerves and brain

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Another word for Visual receptors?

What are they located?

Photo receptors

Retina

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What are rods for?
🌌🌃

What are cones for?
❤️💛💚💙💜🖤

Night vision

Colour vision

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What does the eye capture and where does it focus it?

What converts what?

Light and focuses it on visual receptors

Which convert light energy to neural impulses sent to the brain

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What can light be thought of?

🌊📷

Particles of energy (photons)

Waves of electromagnetic radiation

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What do humans see light between?

380-760 nanometers

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What is the shortest wavelength humans can see? What colour is it?

What is the longest wavelength humans can see? What colour is it?

400 nanometers, violet

700 nanometers, red

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What is sensitivity?

The ability to see when the light is dim

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What is acuity?

The ability to see details

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Where does light enter through?

The pupil

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What is the function of the lens?

Focuses light on the retina

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What is the function of the ciliary muscles?

Alter the shape of the lens as needed

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What is the process of accommodation?

Adjusting the lens to bring images into focus

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What is convergence?

Eyes turn slightly inward when objects are close

What is binocular disparity?

The difference between images on the two retinas

When are convergence and binocular disparity greater?

What does it provide the brain with?

When objects are close

With 3D image and distance information

What is the sequence vertical pathway?

What is the sequence of lateral communication?

Receptors>bipolar>retinal ganglion cells

Horizontal cells
Amacrine cells

What does the visual system use to fill in the blindspot?

What is the fovea?
What does the thinning of the ganglion cell layer reduce?

Information from cells around blindspot for completion to fill in blindspot

A high acuity area at the centre of the retina

Distortion due to cells between the pupil and retina

DUPLEXITY THEORY OF VISION
What are cones (photopic) involved with?

What are rods (scotopic) involved with?

High acuity and colour information in good lightning

High-sensitive, low acuity vision in dim lightning and lacks detail and colour information

What is there more of in rod system? What does it increase and decrease? What are only found at the fovea?

More convergence Increase sensitivity and decrease acuity Cones

Lateral inhibition

Reduction of activity in one neuron caused by activity in a neighbouring neuron

Retinotopic map

Arrangement of nerve cells that directly correspond to the layout of light-sensitive nerve tissue in the back of the eye

Rhodopsin What is it? What does this G-protein respond to? In the dark what remains partially open? Releasing what? In the light what happens? What do rods do? Inhibiting what?

The pigment found in rods Light rather than neurotransmitters Na+ channels (partial depolarisation) Glutamate release Na+ channels close Rods hyperpolarise Inhibiting glutamate release

Rods What is in rods? What are they sensitive to? Are they sensitive? What are they used for?

Rhodopsin pigment Blue-green light 500m Yes highly Night vision

Cones What are they sensitive to? What do they form the basis of? What is trichromatic vision? Where is it concrete?

Long wave light - red light Medium wave light- green light Short wave light- blue light Colour perception Young-Helmholtz theory of colour vision 3 receptors in retina sensitive to each colour (BGR) Fovea

The retinal-geniculate-striate pathways How many ganglion cells? What is the left hemiretina of each eye attached to? (Right visual field) What does the left LGN attach to? What do most LGN that project to primary visual cortex (V1, striate cortex) terminate in?

Approx 90% Connects to the right lateral geniculate nucleus (LGN) The right hemiretina of each eye (left visual field) Lower part of the cortical layer

Where is more cortex devoted to?

Areas of high acuity similar to the somatosensory cortex

How much of primary visual cortex is dedicated to input from the fovea?

About 25%

What happens at the optic chiasm? What is partial decussation? What does this allow? What fibres crossover? What fibres do not crossover?

50% of the fibres from each eye cross over to the opposite side of the brain Partial crossing over Corresponding retinal points in the two eyes to travel together Nasal retina cross over whilst temporal retina do not

After travelling down the optic tracts what happens to fibres? Where? What does the LGN maintain?

Synapse LGN Separation of fibres from the two eyes

What do axons from the cells in the LGN form? Where do these synapse? What is this also called?

Optic radiations In primary visual cortex V1

What do the six layers of the LGN receive synaptic input from? What are some? (M-Cells) And receive what? What are some? (P-cells) And receive what? What is each layer?

Contralateral or ipsilateral eye Magnocellular layers Receive synaptic input from M retinal ganglion cells Parvocellular layers Receive synaptic input from P retinal ganglion cells A retinotopic map

What do M-cells detect?

Movement, distance and speed of object moving towards us

What are P-cells?

Shape, colour, size, clarity, contrast and detail

What does the LGN do? What is an input to the LGN? Which does what? What is another input to the LGN? Which does what?

Called the Relay station Reticular activating system in the brain stem Controls state of alertness and acts as a volume control in LGN The primary visual cortex provides almost 50% of the input to LGN May be involved in shaping receptive fields of cortical neurones

Where is superior colliculus? What does it receive? What does it do? What does it receive? Which responds to what? What does it also receive? What is it's role?

Area in mid brain Receives 10-20% of fibres from the optic tract Mediates automatic reflexes e.g. Pupil size and eye movement Fibres from other type of retinal ganglion cells Responds to rapid changes and can signal position but not detail Auditory input Generates eye-movements to foveate a stimulus

What area responds to visual stimuli? What is the first part of this area called? What does V1 process? Another name for PVC?

Visual cortex Primary visual cortex Orientation Size Colour Motion V1, Area17 (Brodmann), striate cortex (striate= layers)

``` What does these deal with: V2 V4 V5/MT FFA EBA ```

``` 2-Illusionary contours 4-Colours (parvo pathway) 5-motion (magnopathway) Fusiform face area Extra striate body area ```

Who did the functional specialisation theory?

Zeki

What is chromatic adaption?

The decline in our sensitivity to a given colour over time