Chap 4: Sensation & Perception Flashcards
Describe how a sensation occurs and what happens during a sensation.
It occurs when special receptors in the sense organs (eyes, ears, nose, skin and taste buds) are activated.
It allows stimuli outside to become neural signals in the brain.
What is the name of the process of converting outside stimuli into neural activity?
Transduction.
What are sensory receptors and what are they stimulated by? Provide some examples.
Specialised forms of neutrons which are stimulated by different kinds of energy.
For example, receptors in the eyes are stimulated by light, receptors in the ears are activated by vibrations.
What is the condition synesthesia?
A condition in which signals from the sensory organs are processed differently, resulting in the sense information being interpreted as more than one sensation.
What is a just noticeable difference threshold in sensations?
It is the smallest difference between two stimuli that is detectable 50 percent of the time.
Whatever the difference between stimuli might be, it is always a constant.
What is an absolute threshold in sensations?
An absolute threshold is the lowest level of stimulation that a person can consciously detect 50 percent of the time the stimulation is present.
What is Weber’s law in relation to sensations?
Under Weber’s law, the size of the JND is proportional to the initial (or reference) intensity of the stimulus. The more intense the stimulus, the higher the JND.
What is habituation in regards to sensations?
Habituation is when some of the lower centres of the brain filter sensory stimulation (not sending signals from the sense receptors to the cortex) and “ignore” or prevent conscious attention to constant, unchanging information.
What is sensory adaptation?
Sensory adaptation is when the tendency of sensory receptor cells becomes less responsive to a stimulus that is unchanging.
What is light and what are the 3 aspects to the perception of light?
Light contain tiny packets of waves called photons which have specific wavelengths associated with them.
The 3 aspects to the perception of light is brightness, colour and saturation.
How is brightness determined in sight perception?
It is determined by the amplitude of the wave, the higher the wave, the brighter the light appears to be.
How is colour determined in sight perception, what is the difference between the colours blue or red?
Colour is largely determined by the length of the wave.
Shorter wavelengths are found at the blue end of the visible spectrum (the portion of the whole spectrum of light visible to the human eye), whereas longer wavelengths are found at the red end of the visible spectrum.
How is saturation determined in sight perception?
Saturation refers to the purity of the colour people perceive.
For example, a highly saturated red would contain only red wavelengths, whereas a less-saturated red might contain a mixture of wavelengths.
Where does transduction of sight happen?
The retina of the eye.
What are the three layers of the retina?
Photoreceptors (rod and cones, back layer)
Bipolar cells (middle layer, type of interneuron)
Ganglion cells
What is the cornea and what is its function?
The surface of the eye is covered in a clear membrane called the cornea, it protects the eye but also focuses most of the light coming into the eye.
In general, how does light travel into the eye to make sure an object appears clearly?
Light enters the eye directly from a source or indirectly by reflecting off an object.
Light must travel through the structures of the eye and end up on the retina as a single point.
What is the aqueous humour and what is its function?
A clear, watery fluid, and is the next visual layer after the cornea.
This fluid is continually replenished and supplies nourishment to the eye.
What is the iris and what is its function?
A colored area on the eye containing muscles that control the pupil.
It can change the size of the pupil, letting more or less light into the eye.
What are lens in the eye, where are they located and what are their function?
The lens is a clear structure suspended by muscles located behind the iris.
It finishes the focusing process by the cornea by visual accommodation, where the lens changes its thickness as the eye focuses on objects that are far or close.
What is the vitreous humour, where is it located and what is its function?
A clear, jelly-like fluid which nourishes the eye and gives it shape. It is located past the lens.
What is the visual pathway for light for the eye?
Cornea > Aqueous humour > Iris > Pupil > Lens > Vitreous humour > Retina
What are the 3 most common eye diseases?
Presbyopia (Hardening of lens due to age)
Myopia/nearsightedness (Focal point falls short of the retina due to the eyeball too long)
Hyperopia/farsightedness (Focal point falls beyond the retina due to eyeball being too short)
How does the transduction of light occur in the retina?
The rods and cones of the retina receive the photons of light, and turn them into neural signals for the brain.
The bipolar cells in the middle layer then collects the neural signals from the rod and cone cells and integrates the information.
It then passes the information to the ganglion cells, which axons form the optic nerve.
What are the functions of cones in the retina and where are they located?
Cones are visual sensory receptors also found at the back of the retina, it is responsible for colour vision and sharpness of vision.
The cones are more concentrated at the centre of the retina, the area called the fovea.
What are the functions rods in the retina and where are they located?
Rods are visual sensory receptors found at the back of the retina, it is responsible for non-colour sensitivity to low levels of light.
Rods are located all over the retina except the fovea. They are more focused on periphery and peripheral vision.
What is the visual pathway of neural information about light from the eyes to the brain?
Retina → optic nerve → optic chiasm → optic tract → lateral geniculate nucleus (LGN) of thalamus → primary visual cortex
How does light from the right visual field travel from the eye to the brain?
Light from the right visual field falls on the left side of each eye’s retina, then to the left visual cortex.
How does light from the left visual field travel from the retina to the brain?
Light from the left visual field falls on the right side of each retina, then to the right visual cortex.
As light from an object travels through the cornea and lens, what is the resulting image projecting on the retina?
The image is projected upside down and reversed left to right.
What are the two theories about how people see and perceive colours?
Trichromatic theory and opponent-process theory.
Explain the trichromatic theory of colour sensation and perception.
The trichromatic theory proposed that there are three types of cones: red, blue and green. One for each of the three primary colours of light.
Different shades of colour correspond to different amounts of light received by the three types of cones, the cones then fire their message to the brain’s vision centres.
The combination of cones and the rate at which they are firing determines the colour that will be seen.
Order these colours based on their wavelength (shortest to longest) with regards to the trichromatic theory of colour perception: green, cyan, yellow, red, violet, blue, orange
- Violet (Shortest)
- Blue
- Cyan
- Green
- Yellow
- Orange
- Red (Longest)
Explain the opponent-process theory of colour sensation and perception.
The opponent-process theory proposed that visual neurons (or groups of neurons) are stimulated by light of one colour and inhibited by light of another colour.
In opponent-process theory, there are four primary colours: red, green, blue, and yellow. The colours are arranged in pairs, with each member of the pair as opponents. Red is paired with green, and blue is paired with yellow.
If one member of a pair is strongly stimulated, the other member is inhibited and cannot be working.
What are afterimages?
When an image occurs when a visual sensation persists for a brief time even after the original stimulus is removed.
Which theory best explains the phenomenon of afterimages?
Opponent-process theory.
What is colour-deficient vision and how does it occur?
It is colour blindness and is caused by defective cones in the retina of the eye.
What are the different types of colour deficient-vision?
Achromatopsia or monochromatic vision (black-white vision) and dichromatic vision.
What are the different types of dichromatic vision for colour deficient-vision?
Protanopia and protanomaly (Red colour blindness & red-weak vision)
Deuteranopia or deuteranomaly (Green colour blindness & green-weak vision)
Tritanopia or tritanomaly (Blue colour blindness & blue-weak vision)
What is monochromatic vision?
A condition in which two or three cones do not work properly as the result of genetic mutations.
What is dichromatic vision?
Condition in which one cone does not work properly, with resulting colors being determined by combination of
only two cones.
What are soundwaves and what are the properties of the waves?
Sound waves are vibrations of molecules of air that surround us.
Sound waves have the same properties of light waves: wavelength, amplitude, and purity.
What is wavelength, amplitude and purity of soundwaves interpreted as?
Frequency or pitch, volume and timbre respectively.
What are the three main categories of the ear?
Outer ear, middle ear and inner ear.
What does the outer ear consist of?
Pinna and the auditory canal.
What is the pinna of the ear and what is its function?
Visible external part of the ear and the entrance to the auditory canal.
It funnels & concentrates sound waves from the outside into the structure of the ear.
What is the auditory canal of the ear?
A short tunnel that runs down to the tympanic membrane, or eardrum.
What does the middle ear consist of?
The tympanic membrane (eardrum) and the middle ear bones (hammer, anvil & stirrup).
What is the tympanic membrane (eardum) and what is its function?
Thin membrane that separates the outer ear from the middle ear, when hit with sound waves, causes the middle ear bones (hammer, anvil and stirrup) to vibrate.
What does the inner ear consist of?
Oval window, cochlea (snail), basilar membrane and Organ of Corti.
What are the functions of the middle ear bones?
It amplifies the vibrations from the ear drum, the stirrup causes the oval window in the inner ear to vibrate.
What is the oval window of the inner ear?
A connective tissue membrane-covered opening from the middle ear to the cochlea of the inner ear.
What is the cochlea of the inner ear?
A snail-shaped structure of the inner ear filled with fluid.
When the oval window vibrates, the fluid (which surrounds the basilar membrane) also vibrates.
What is the basilar membrane of the inner ear?
It is the resting place of the organ of Corti, it vibrates the organ of Corti when the membrane is vibrating.
What is the organ of Corti and what is its function?
The organ of Corti contains hair cells or receptor cells for sense of hearing.
When vibrating, it causes the hair cells to bend against another membrane, which causes a neural message to be sent through the auditory nerve, into the brain, through the thalamus, and into the auditory cortex to interpret the sounds.
How does the transduction of sound occur?
Transduction of sound occurs when the basilar membrane converts vibrations into neural impulses.
The hair cells or receptor cells on the organ of Corti sway due to the vibrations, which stimulates the sensory nerve endings and generates electrical impulses.
What is the neural signal pathway for sound?
Cochlea > Auditory Nerve > Thalamus > Auditory Cortex
What are the three primary theories of how the brain processes information about pitch in sound?
Place theory, frequency theory and volley principle.
Describe the place theory for pitch in sound.
States that different pitches are experienced by stimulation of hair cells in different locations on the organ of Corti.
For example, in hearing a high-pitched sound, all of the hair cells near the oval window are stimulated.
In a low-pitched sound, hair cells further away on the organ of Corti are stimulated.
Describe the frequency theory for pitch in sound.
States that pitch is related to the speed of vibrations in the basilar membrane.
The faster the membrane vibrates, the higher the pitch.
(note: does not account for frequencies above 1000 Hz)
Describe the volley principle theory for pitch in sound.
States that frequencies from about 400 Hz to 4,000 Hz cause the hair cells to fire in a volley pattern, or taking turns to fire.
For example, if a person hears a tone of about 3,000 Hz, it means that three groups have taken turns sending the message to the brain - first group for first 1,000 Hz, second group for the next 1,000 Hz, etc.
What are taste buds or taste receptor cells and what are their functions?
Special kinds of neurons, also called gustatory cells, found in the mouth that are responsible for the sense of taste, or gustation.
They transmit signals to the brain when stimulated by food molecules.
Where are taste buds located?
Most taste buds are located on the tongue, but there are a few on the roof of the mouth, cheeks, under the tongue, and in the throat.
What are the small bumps on the tongue called and what do they contain?
Papillae, they contain numerous taste buds.
What are the 5 primary tastes and 1 proposed taste which gustatory cells are able to detect?
Sweet, sour, bitter, salty & umami (savoury flavour in protein rich foods)
Oleogustus is the proposed taste which is the taste of fatty acids.
