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This text provides an overview of sensation and perception, including topics such as transduction, sensory adaptation, the cocktail-party phenomenon, energy and chemical senses, the path of light through the eye, visual capture, feature detectors, color vision theories, the ear, and transduction in the ear.
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Sensation and Perception Sensation: your window to the world Perception: interpreting what comes in your window.
Transduction • Transforming signals into neural impulses. • Information goes from the senses to the thalamus , then to the various areas in the brain.
Sensory Adaptation • Decreased responsiveness to stimuli due to constant stimulation. Do you feel your underwear all day?
Cocktail-party phenomenon • The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. • Form of selective attention.
Energy v. Chemical senses Energy Senses Chemical Senses
Phase One: Gathering Light • The height of a wave gives us it’s intensity (brightness). • The length of the wave gives us it’s hue(color). • ROY G BIV • The longer the wave the more red. • The shorter the wavelength the more violet.
Vision • Our most dominating sense. • Visual Capture:refers to our tendency to allow visual images to dominate our perception. For example, when we watch a movie in a theater, we tend to think that the voices we hear come from the moving images on the screen, rather than from the speakers that could be located all around the theater.
Path of light through the eye • Cornea When light first enters the eye, it passes through the cornea, which is a protective clear covering over the pupil and the iris. The light bends as it passes through and begins to make an image. • Pupil The light then passes through the pupil, a dark HOLE in the center of the iris (IRIS IS A MUSCLE), which is the colored portion of the eye. The pupil regulates light entry into the inner eye and brings objects into focus. • Lens The light continues to travel through to the lens of the eye. The lens is a clear, flexible structure that focuses the image onto the retina. It is flexible so that it can focus images that are close up or far away….misshapen lens = you need glasses • Retina The light and images are then focused on the retina, which is a layer of light-sensitive cells at the back of the eye. It is made up of two kinds of photoreceptor cells: cones/color and rods. The cones respond to bright light and color and also transmit sharp images. The concentration of cones is low on the sides of the retina and increases as the cones approach the center of the retina. The rods are more sensitive to light and are more numerous than cones. • 0ptic Nerve The image is then sent to the optic nerve at the back of the eye. The optic nerve receives the signals from the retina, then sends them to the brain.
Transduction Continued Order is: • Rods/Cones to • Bipolar to • Ganglion to • Optic Nerve. Sends info to thalamus- Then sent to cerebral cortex • Where the optic nerves cross is called the optic chiasm.
Phase Four: In the Brain • Goes to the Visual Cortex located in the Occipital Lobe of the Cerebral Cortex. • Feature Detectors -process by which specialized nerve cells in the brain respond to specific features of a visual stimulus, such as lines, edges, angle, or movement . • Parallel Processing - ability of the brain to simultaneously process incoming stimuli of differing quality We have specific cells that see the lines, motion, curves and other features of this turkey. These cells are called feature detectors.
Color Vision Two Major Theories
Trichromatic Theory Three types of cones: • Red Blue Green • These three types of cones can make millions of combinations of colors. • Does not explain afterimages or color blindness well. • The trichromatic color theory began in the 18th century, when Thomas Young proposed that color vision was a result of three differentphotoreceptor cells. • Hermann von Helmholtz later expanded on Young's ideas using color-matching experiments which showed that people with normal vision needed three wavelengths to create the normal range of colors.
Opponent-Process theory The sensory receptors come in pairs. • Red/Green • Yellow/Blue • Black/White • If one color is stimulated, the other is inhibited. Since one color produces an excitatory effect and the other produces an inhibitory effect, the opponent colors are never perceived at the same time (the visual system cannot be simultaneously excited and inhibited).
While the trichromatic theory defines the way the retina of the eye allows the visual system to detect color with three types of cones, the opponent process theory accounts for mechanisms that receive and process information from cones
Hearing Our auditory sense
We hear sound WAVES • The height of the wave gives us the amplitude of the sound. • The frequency of the wave gives us the pitch if the sound.
Transduction in the ear Sound waves hit the eardrum then anvil then hammer then stirrup then oval window. • Everything is just vibrating. 2Then the cochlea vibrates. • The cochlea is lined with mucus called basilar membrane. In basilar membrane there are hair cells. • When hair cells vibrate they turn vibrations into neural impulses • Sent then to thalamus up auditory nerve. It is all about the vibrations!!!
Path of sound • Sound waves enter through the outer ear/pinna • Sound waves move through the ear canal • Next sound waves strike the eardrum, causing it to vibrate • Vibrations enter the middle ear • Hammer picks up the vibrations, vibrations are passed to the anvil, to the stirrup • Vibrations are now in the inner ear • V vibrations are channeled to the cochlea, lined with cilia • Then nerve cells detect vibrations and convert them to electrical impulses • These electrical impulses are transmitted to the brain • The brain, through the thalamus, and temporal/auditory association cortex interprets electrical impulses as sound.
Place Theory • Different hairs vibrate in the cochlea when they different pitches. • So some hairs vibrate when they hear high and other vibrate when they hear low pitches.
Frequency Theory • All the hairs vibrate but at different speeds.
Deafness Conduction Deafness Nerve (sensorineural) Deafness The hair cells in the cochlea get damaged. Loud noises can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible. • Something goes wrong with the sound and the vibration on the way to the cochlea. • You can replace the bones or get a hearing aid to help.
Touch • Receptors located in our skin. • Gate Control Theory of Pain
Taste • We have bumps on our tongue called papillae. • Taste buds are located on the papillae (they are actually all over the mouth). • Sweet, salty, sour and bitter.
Vestibular Sense • Tells us where our body is oriented in space. • Our sense of balance. • Located in our semicircular canals in our ears.
Kinesthetic Sense • Tells us where our body parts are. • Receptors located in our muscles and joints. Without the kinesthetic sense you would not know you are sitting in a chair which is on the ground.
