sens3

objects appear smaller when the head is tilted up than when held parallel to the ground

Earth's terrain causes moon to appear further away and thus bigger at the horizon

two lights blinking on and off will, at the proper frequency, appear to be one light that is moving

if a stationary small light in complete darkness is fixated, it will eventually appear to be moving erratically

after adapting to motion in a particular direction, the visual world appears to be moving in the opposite direction

disorder in which lines of one orientation are in focus while lines of other orientations are not

inability to bring objects into focus during old age

nearest point that someone can bring into focus

the furthest point that someone can bring into focus

someone who does not have a lens

a period of neural plasticity when certain environmental stimuli must be present for normal brain development to occur

pressure changes in a medium that can be detected by auditory organs

the set of all points that could produce a particular time and intensity difference between the two ears

• Retinal size of a stimulus
• Perceived distance to the stimulus

the perceived distance to the horizon

• Phi Effect: cells some distance apart on the retina can be wired to excite another cell, indicating motion in a particular direction, when they are stimulated with a particular delay between them. The Phi Effect simulates this pattern of stimulation.
• Autokinetic Effect: To compensate for muscular fatigue, the eyes require abnormally strong signals from the brain. These abnormal signals are the same as would be required to track a moving object so the brain assumes the light is moving.

damage to MT in both hemispheres

Ophthalmologist

Optometrist

Optician

Orthopist

• Astigmatism: lack of spherical cornea
• Presbyopia: hardening of the lens and weakening of the ciliary muscles

• Myopia: Negative (concave) lens |(
• Hypermetropia: Positive (convex) lens |)

the ability to detect high spatial frequency information (small things)

• Numerator: the distance, in feet, at which the test was conducted
• Denominator: the distance, in feet, at which the critical feature of the test symbol covers one minute of visual angle

• PRK: Epithelial layer of cornea is removed and laser reshapes the cornea.
• LASIK: 25% of cornea is cut into a flap and folded back. A laser reshapes cornea and then the flap is replaced, preserving the epithelial tissue.
• Intacts: Pieces of plastic are placed in cornea to change its shape.

• Cause:
• 1. Congenital and inherited at birth
• 2. Aquired by injury or disease
• 3. Old age
• Treatment: Artificial lens implants, or removing lens and using spectacles to correct vision

• Cause: inherited disorder where photoreceptors slowly degenerate, starting with rods in the periphery
• Treatment: none presently, maybe artificial retinas or stem cells

• Cause: photoreceptors become detatched from the pigment epitheliam
• Treatment: cryotherapy - eye is purposefully injured to create scar tissue that locks retina into place

• Cause: Blood vessels serving retina start to leak. New blood vessels sprout across the retina and can cloud the vitreous humor with blood.
• Treatment: Laser photocoagulation - laser ios used to seal the leaks in the blood vessels

• Cause: Aqueous humor is not properly drained, resulting in increased intraocular pressure. This pressure compresses the blood vessels serving the optic nerve and the optic nerve fibers die.
• Treatment: drugs that decrease production of aqueous humor or remove blockage. surgery can also remove blockage

• Eye: completely normal
• LGN: Fewer cells devoted to the closed eye, but cells responded normally
• V1: abnormally preferred the open eye

• 1. For binocular cells, neural plasticity may allow accomadation due to changing distance between the eyes.
• 2. As a survival mechanim, it may be wise to kill (or repurpose) unused cells.

• Disadvantage: very poor acuity
• Advantages:
• 1. Allow equal visibility across the entire visual field.
• 2. Always in focus.
• 3. Higher Flicker Fusion Frequency

• Humans: 10-24 Hz
• Insects: 300 Hz

• 1. Bird photoreceptors are more densely packed than human photoreceptors.
• 2. Birds have much higher ratio of ganglion cells to photoreceptors.

• 1. Having very sensitive eyes
• 2. Having organs sensitive to heat rather than light
• 3. By using sonar

30,000-70,000 Hz

suppress the vibration of the eardrum just prior to sending a signal

• Form Vision
• Stereopsis

Blur by the optic media, lateral inhibition in retina, and processing strategies all affect this illusion.

Large number of small Poggendorf Illusions.

Linear Perspective and Texture Gradients make the top bar appear further away and thus bigger than bottom bar.

Retinal image is consistent with both a trapezoidal window rotating or a rectangular window that switches direction every 180. Because we are use to seeing rectangular windows, our visual system prefers that interpretation.

If frame rate of a movie is out of synch with the rotation of the wheel, the image of the wheel on the retina can be more consistent with the wheel spinning backwards.

• Frequency: Hertz (Hz)
• Amplitude: Decibels (dB)

• dB=20 log (P/Po)
• dB: Decibels
• P: Pressure of soundwave being measured
• Po: Reference pressure

• Frequency: Pitch
• Amplitude: Loudness

20 Hz - 20,000 Hz

• Pinna
• Meatus
• Tympanic Membrane

• Pinna: Appears to help amplify and localize high frequency sounds
• Tympanic Membrane: Vibrates in response to pressure changes in the atmosphere

• 1. Amplify tympanic vibrations
• 2. Protect the ear from loud sounds

• Oval Window: transmit vibrations to the fluid in the cochlea
• Basilar Membrane: vibrates differentially, depending on the frequency of the sound
• Hair Cells: hen the region of the Basilar membrane below a particular hair cell is bent, the hair cells attached to that region release neurotransmitters that stimulates particular neurons in the auditory nerve.

• 1. Inability to distinguish different tunes
• 2. Inability to distinguish changes in the duration of tones
• 3. Inability to localize sounds
• 4. Inability to determine which ear is being stimulated

Different places on the basilar membrane vibrate in response to different frequencies. The hair cells being stimulated by the region with the greatest amount of vibration indicate the frequency that is present.

• 1. A strong relationship exists between the frequency of the stimulus and the place of greatest basilar membrane vibration.
• 2. Selective deafness experiments show damage restricted to the hair cells at a particular basilar membrane location.

The basilar membrane vibrates at the same frequency as the stimulus. Every time the basilar membrane vibrates, it causes an action potential in the Auditory Nerve. Thus, the rate at which the auditory nerve fires codes the frequency of the stimulus.

• 1-15 Hz: One tone widway in frequency between the two tones is perceived that ossilates in loudness at the same frequency as the difference between the two tones. (beats)
• More than 15 Hz: A single tone midway in frequency between the two tones is perceived but it sounds "rough"
• Critical Bandwidth: Two separate tones are perceived

• Intensity
• Doppler Shift

• Interaural Time Difference
• Interaural Intensity Difference

When localizing high frequency sounds

Moving our head