February 2, 2006

• Sensation vs. Perception
• Sensation is the activity of a sense organ (the response of a sense organ).
• Perception is the higher state- the interpretation of the sensor response- the rods and cones that are firing off.
• The Visual System:
• Starts with the eyes. There is an entire system there that is dedicated to processing light. Light is a narrow band in a spectrum of energy- electromagnetic radiation or energy. Our visual systems are tuned into the energy from the environment. We will never know what the world looks like in all forms of energy. A spectrum starts with a tiny way of energy.
• Different kinds of light rays:
• 1. Gamma rays: if you’re in a room with a lot of these rays you will eventually die. They can penetrate into your skin, into various parts of your body and may also cause cancer.
• 2. X rays: Can penetrate through your skin but the bones block the radiation. These have longer waves.
• 3. Ultraviolet radiation: you won’t know you’re in an environment with these rays but you’ll eventually know because you will have a sun burn. Your skin picks these rays up but these waves are not visible. Bees can pick up ultraviolet radiation to see where to fly and where the food is. They are tuned into a different kind of energy.
• 4. Infrared radiation: you are aware of it but you’re eyes aren’t able to see it. You are aware of it as heat.
• In between Ultraviolet radiation and infrared radiation there is a tiny span of every called the waves of visual light. It runs from about 400 nanometers to 700 nanometers. (A nanometer is a billionth of a meter.
• Radios, televisions, and electricity have long wavelengths.
• Energy carries all kinds of information.

February 7, 2006
 

• Psychophysics: refers to the whole discipline of looking through the physical relationship or stimulus and the processing of the physical stimulus.
• The most prominent issue is the issue of thresholds: the whole idea of when you change the physical stimulus in some way and if the perceptual system really registers the change.
• There are 2 important thresholds:
• 1. Absolute threshold:  the minimum amount of stimulus energy that’s necessary for detection. Our visual signals can’t pick up all of them, but there is actual energy there.
• 2. Difference threshold: the minimum amount of changer that you have to make in the physical signal for the person to be aware that it has changed.
• It’s always above the absolute threshold. How much you have to increase the brightness of light or make the lights dimmer for someone to see that it has changed.
• It gets a little complicated because the difference threshold is not a constant amount. The amount by which you have to change the signal for the person to know the signal changed varies, depending on the strength of the signal that you start with.
• It is also called Just Noticeable Difference.
• If you start off softer or lighter, you don’t have to changed it much to see a difference. If you start off harder or heavier, you will have to change it a lot to notice a difference.
• The Human Eye:
• The organ that processes the incoming light is the eye. The visual system starts with the eye.
• If you take something sharp on the side of the eye, you would find that the eye is made of 3 concentric layers. The 1st layer is the outermost layer, called the fibrous layer. It is a tough layer of tightly interwoven fibers. It is the layer that is in the most contact with the outer world. It endures punishment form the outer world and provides protection for the inner eye.
• If you follow the outermost layer to the front, you would see something bulged out. This is the cornea. If it bulges it becomes transparent. When it becomes transparent, it allows you to see. It will refract or bend the light by virtue of its convex shape. It converges light into a point.
• As soon as you get through the outer layer, it will bleed, which shows that you poked through a 2nd layer, the vascular layer. It is richly filled with veins and capillaries. It is the layer that is there for nutrition and maintenance. If you follow the vascular layer through the front, interesting things will happen. You can’t use blood to go through because it will inhibit vision.
• When the cornea bulges out, it creates an opening called the anterior chamber. It forms cilliary bodies. Above and below it surrounds the chamber. Cilliary bodies create a substance called aqueous humor. It is a clear substance that is pumped from the cilliary bodies to the front chamber. It is clear, which allows light to pass through without blood blocking it.
• The vascular layer is using the same things as the back of the eye and the front of the eye. Aqueous humor doesn’t do as well as blood does.
• Aqueous humor doesn’t circulate as well as blood. It is less than optimal at the front. Pressure starts to build in the front of the eye. It will start to give at its weakest point, which is the optic nerve. It will crunch in at the optic nerve, which causes glaucoma.
• Retina: the innermost layer. It is the area for seeing and it processes the light signal.
• Detached retina: the retinal layer starts to be detached from the vascular layer.
• Front to back- following the beam of light. As light energy strikes the cornea, the cornea will refract the light. The cornea, in combination with the lens, forms the optics of the eye. They are the optical structures of the eyes and the structures responsible for refracting light.
• The cornea and the lens are supposed to give you a pinpoint of light towards your eye. This allows you to have clear vision.
• If the system works correctly, it is referred to emmetropic. This is when people can see clearly, without the help of contacts or eye glasses.
• When it doesn’t work right, it could be because of the optics of the eyes bend lights too much. It is usually the cornea that’s responsible for this. People with big eyes tend to have a big cornea that is bending the light too much.
• Myopia: near sightedness. As you bring something in too close, the light waves have to be bended more and more. It has to be bended as much as the cornea wants to bend it. The light wavers are divergent. To fix this problem, a concave lens could be put in front of the cornea. It will counteract the effects. This will cause the light waves to diverge even more.
• Hyperopia: far sightedness. Their cornea has no bulge. The light energy isn’t bended enough. The light is converged way behind where it’s supposed to be.
• The Lens:
• The lens is a flexible, convex structure.  It responds to the distance that you’re trying to focus on. The lens is accommodating. Cilliary muscles push in and the lens bulges out. It bends to the light to keep it in focus.
• Presbyopia (“old eye”): becoming more far sighted as you get older and may cause you to need reading glasses. It is possible to be near sighted and as you get older, you can also be far sighted at the same time.
• Iris: muscle that controls the opening, which is called the pupil. In a bright environment, the iris constricts, causing the pupil to become smaller. In a dark environment, the iris will dilate, making the pupil bigger.
• Vitreous chamber: filled with a fluid called vitreous humor. Vitreous is supposed to circulate around and filter the debris out. When you close your eyes, you may see an amoeba floating around. That is just debris in the vitreous humor.
• Retina: back of the eye. This is where the business of processing the incoming light begins. It makes sense out of the incoming light energy.
• Landmarks on the retina:
• Optic disk: (blind spot): an actual spot on the retina where there are no photoreceptors. It can’t process the light. All of the axons from the retina are forming a cable.
• Fovea: point of the highest visual acuity on the retina. This is where you see the best. It is your best vision and pattern recognition. When you’re looking directly at something, the best part on the retina, the fovea, focuses on it. The fovea is the center of the retina. It expands out to the peripheral of the retina. As you move further and further away, the vision degrades or declines.
• Cells that are present in the retina:
• There are 2 types of photoreceptive cells: These are the rods and cones.
• The difference in shape corresponds to different functions. They are mirror images of each other, they complement each other. What you see in one, you won’t see in the other.
• Rods and Cones differ in a number of ways:
• 1. They different in number. There are more rods than cones. There is about 120 million rods and there are about 7 million cones.
• 2. They different in geographic location. Cones are almost exclusively in the fovea region. The depressed area in the fovea in the cones. They are tightly packed in. Cones disappear in the peripheral region and rods appear. The rods are almost exclusively in the peripheral region.
• 3. They differ in their sensitivity to light. Rods are a lot more sensitive to light than cones. It takes more light to get the cones to function.
• 4. Cones see in color but the rods don’t. The rods are color blind, everything becomes shade of gray.

February 9, 2006

• The retina is made up of other things besides rods and cones; there is other cells there.
• The cones have a fatter shape. Rods have a longer shape.
• Color vision:
• The rods are all of the same type. If rods were tested for spectral sensitivity, all of them would come out the same.
• Spectral sensitivity:
• Visible lights in 400 nm to 700 nm.
• Photoreceptors don’t respond the same way to wavelengths. They vary in their response. When rods are tested by shooting different wavelengths at them, their favorite wavelength is 505 nm. They are the most sensitive to this wavelength. All of the rods respond this way.
• Cones aren’t all the same. When different wavelengths are shots at them, they form different sub groups. They are subdivided into different groups or families. Their spectral sensitivity is different.
• Some cone’s favorite wavelength is 530 nm. Others get excited at 560 nm and others get excited at 435 nm.
• There are 3 different families:
• 435- small cones
• 530- middle cones
• 560-long cones
• When it comes to wavelength all rods are all the same, whereas, the cones have 3 different ones.
• Trichromatic theory of color vision- the 3 color theory: 3 different patterns mixing together, giving 3 different colors.
• The way they provide color vision: they all give different responses that are unique for the different wavelengths. The patterns show different colors.
• 435 nm would be modest, 530 nm would be big, and 560 nm would be modest.
• The brain takes the pattern and gives it a color according to their response.
• You can’t do this with rods because they are all in the same family
• The trichromatic theory explains some aspects of color vision, but doesn’t explain one particular phenomena. This leads to another theory of color vision which is after images. If you stare at something red for a long time, you will see green. Blue is paired with yellow. Dark is compared with light. Each color is complemented by another. After images suggest certain pairing exists in the visual system.
• The complementary theory is called the opponent processing theory. It appears that both things are going on in the visual system.
• As we go further along in the visual system, you will find certain cells in the thalamus and occipital lobe that are participating in this process.
• One of the most common ways you have color deficiency- one of the families is knocked out of the visual system. You are only able to see shades of gray. The medium or long one is usually the one that is knocked out. This will enable you to see some color but not all.
• Males are more color blind than females. This is due to the X chromosome. Females have a back up x chromosome and males don’t. The back up can also be different from each other and some females may have 4 families.
• Perceiving depth and distance: another important function the visual system has is to give the organism something about depth and distance. This helps to navigate the space in a room, etch.
• It provides the information to do this from a number of different sources or cues that the visual system is tuned into.
• We divide the cues according to different categories:
• Ocular motor cues: the cues that have something to do with the muscles of the eye.. They use the tension in the ciliary muscles to determine how far away something must be. This is called accommodation. It only works within a restricted range, about 10 feet or so. After about 10 feet, they are relaxed state and don’t change as much.
• Convergence: extra ocular muscles- muscles that are on the outside of the eye that control eye movements.
• As something gets closer, these muscles have to jerk the eye inward more.
• This works about 20 feet, after this, they are in a relaxed state and don’t change as much.
• Monocular cues: (pictorial cues) - artists discovered this first. Artists conveyed on a canvas, something that gave the impression of depth or distance. You only have to have one eye for this to work.
• Linear perspective: a type of monocular cue- a kind or parallelism that converges together as it gets further and further away.
• Texture gradient: the pattering you have on a flooring or ceiling surface. When you’re close, the texture is perceivable. As you go further away, the detail gets lost. (It becomes one homogenous mass.)
• Relative size: using the known or familiar size of something for how far way it must be. When we see a large or small image, we scale on our retina, distance to see size.
• Occlusion: when one thing blocks visual access from another, we assume that the one who is blocking is closer.
• Aerial perspective: particulate matter in the air. It ends to obscure further objects more than it does closer objects.
• All of the cues are those that are present in the natural world and all require just one eye.
• Binocular cues: you have to have 2 eyes to be able to process this type of cue. The most important and powerful of this cue is retinal disparity; because humans have 2 eyes that are displaced on the eye in different places, they each have a different angle or perspective on the same thing. This cue is powerful as long as there is 2 eyes to see it.
• As the object gets closer, disparity increases.
• When people have problems with their eye, it is due to binocular cues.
• Hearing and the auditory system:
• The physical signal for hearing is sound pressure waves in the atmosphere. To create these sounds pressure waves, you have to have some kind of vibrating body, such as vocal cords when talking. Vibrations set up a travel pressure wave where air molecules are alternatively compresses or spread out. Any time you vibrate, these waves are created.
• The wave itself: to represent a sound wave to show where molecules are compressed by the peak and where they are expanded by the trough at the bottom of the wave.
• Distance between peaks:
• Wavelength- length of the wave.
• Frequency- the common term for sounds waves.
• Pitch- the difference in compression
• Amplitude: height of the sound waves- determines loudness.
• All pressure waves crate frequency and amplitude;
• The organ that processes the signal is the ear, which is the start of the auditory system.
• It can be subdivided into 3 different parts:
• 1. Outer ear: cartilage from the pinna to the ear drum.
• 2. Middle ear: the 3 little bones in the center.
• 3. inner ear: the whole big structure. The bottom part, the cochlea, is used for hearing.
• The rest of the inner ear has other functions.
• The pinna’s function is to help funnel pressure waves inwards. It only funnels things in the front. It divides the auditory worlds from the front to the back. You are only able to hear things coming from the front of the pinna, not the back.
• The sounds waves then go to the eardrum that vibrates from the incoming sound wave. It then transmits the vibrating to the middle ear to the 3 bones that vibrate in response.
• The 3 bones are the malus, incas, and stapes. (Hammer, anvil, and stirrups). They are collectively called the ossicles.
• All of these vibrate because we have to amplify the sounds wave. That is why we have these bones. It has to be pushed into the cochlea, which is a fluid filled chamber. It is hard to move sound waves through fluid. Inside the cochlea is hair which bends the sounds. This is where responding to the incoming signal begins.