Transduction Transformation of stimulus energies to electrochemical energy of neural impulses Sensory receptors are responsible for transduction Rods and cones in the eye Tastebuds in the mouth Hair cells in the ear Olfactory receptors in the nose Receptors in the skin

How we see color. Color (hue) does not exist outside the brain! Color is a sensation that the brain creates based on the transduction of the wavelength in the retina of the eye. Transduction- conversion of one form of energy to another In the visual system the retina transduces light waves into neural impulses.

Vision- Physical Properties of Waves Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Great amplitude (bright colors, loud sounds) Small amplitude (dull colors, soft sounds) (a) Waves vary in wavelength, the distance between successive peaks. Frequency, the number of complete wavelengths that can pass a point in a given time, depends on the wavelength. The shorter the wavelength, the higher the frequency. (b) Waves also vary in amplitude, the height from peak to trough. Wave amplitude determines the intensity of colors and sounds.

The Eye Preview Question 5: How does the eye transform light energy into neural messages?

Parts of the eye Cornea: Transparent tissue where light enters the eye. Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light. Lens: Focuses the light rays on the retina. Retina: Contains sensory receptors that process visual information and sends it to the brain. Pupil- adjustable opening in the center of the eye

Retina Retina: The light-sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual information.

Vision Structures of the Eye Retina neural tissue lining back surface of the eye Fovea part of the macula; contains cones only; where visual acuity is greatest

Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. Fovea: Central point in the retina around which the eye’s cones cluster. http://www.bergen.org

Vision Theories of Color Vision Trichromatic Theory (Young-Helmholtz) http://www.youtube.com/watch?v=W-yLfm5HsHc 4 minutes Vision Theories of Color Vision Trichromatic Theory (Young-Helmholtz) have 3 different color photoreceptors (blue, green, red) sensitive to certain wavelengths of light all other colors are seen through firing of combination of cones Proposed by Hermann von Helmholtz & Thomas Young Color-blindness results from lack of chemicals being produced by one or more types of cones Monochromats or dichromats Red-green colorblindness most common

Stare at the center of the flag for a minute and then shift your eyes to the white space beside it. What do you see? (After tiring your neural response to black, green, and yellow, you should see their opponent colors.) What you are seeing is the AFTERIMAGE which is the color compliment of the original colors. Opponent Process Theory – all of the colors in the image have been replaced by their complementary colors in the afterimage . The photoreceptors (rods and cones) in the eye become "fatigued", and do not work as well as the those photoreceptors that were not affected

After staring at the four vertical dots in the middle of the image for one minute look to the white space to the right of the image? You probably are now perceiving the afterimage.

Google Youtube and type in>>>>> Test Yourself: Stroop Effect Take the test and record how you did. Search the web and explain what causes the Stroop Effect