Basic Principles

Sensation & Perception

sensation is the process of being aware of incoming stimuli.

• It processes information from the bottom up.• Your vision, hearing, and other senses make you aware of the raw

sensory information.

perception the process of organizing and interpreting incoming sensory information.• Your memories, emotions, and experiences all affect how you

perceive, or interpret, the world around you through top-down processing

• Top-down processing: Information processing that draws on expectations and experiences to interpret incoming sensory information.

List all the sensations that you would experience while sitting in a Roller Coaster…

Read these sentences carefully and you will note some odd things about them.  

Thresholds

• A threshold is an edge, a boundary.• Absolute Threshold• Subliminal Message: messages played at a frequency

you cannot consciously perceive, into the sound of ocean surf. It is true that you can be influenced by a stimulus you are unaware of. In one experiment, participants were shown a brief image of an emotionally positive scene (like kittens) or an emotionally troubling scene (like a dead body) so quickly that the scene registered only as a flash of light.

Thresholds

• Absolute Threshold: The minimum amount of stimulation needed to detect a particular stimulus.If you stand in a quiet room away from a clock what the minimum proximity you need to hear the tick tock.

• Difference Threshold: represents an edge, too—this time, the minimum difference to detect that two stimuli are not the same. If I start increasing the volume on the dial..at what point can you detect that its louder than before.

Signal Detection Theory

• Signal Detection Theory: predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise).

• The dimmest start we can see in the night sky.

Signal detection formulas consider three kinds of variables:• Stimulus variables—How bright is the blip on the radar

screen?• Environmental variables—How much distracting noise is

there in the room with the radar equipment?• Organismic variables—Is the operator properly trained

and motivated?

Signal Detection Theory

• Imagine that a radiologist is examining a CT scan, looking for evidence of a tumor.

• In 2 instances the doctor correctly diagnosed, where as in 2 other instances there was a misdiagnoses.

• Law enforcement officers X-raying the contents of luggage, or Air traffic monitors are other examples of Signal detection.

Tumor Present Tumor Absent

Doctor -YES HIT False Alarm

Doctor - NO MISS Correct Rejection

Sensory Adaptation

• Sensory Adaptation means we filter out the non-changing aspects of our environments.

When stimulation is constant and unchanging, you eventually fail to respond because you usually don’t need to.

Selective Attention

Selective Attention

• The noise from TV while you are having a phone conversation.

• Studying for an exam, and getting distracted or NOT.• At this moment what are you paying attention to and

what are the things you are not paying attention to:• Your clothes: how soft or coarse is there texture.• Your shoes: the grip on your foot.• Any previously written information on White board. • The air temperature.

The Nature of Light

The Nature of Light

The shorter wavelength = blue, purple- Higher wavelength = Red, orange. Taller peaks = brighter colors. Shorter peaks = dull colors.

Vision

Parts of the EYE

Pathway of Light-• Cornea: the clear curved bulge in front of the eye. It is rich

with nerve endings. • Iris: The ring of muscle tissue that forms the colored part of

the eye. Regulates pupil.• Pupil: black circular opening in the middle of Iris.• Lens: A transparent structure behind the pupil. Focuses the

light. • Retina: Light sensitive surface at the back of the eye. • Fovea: spot with concentration of cones. • Optic Nerve: The bundle of axon going to the brain.• Blind Spot: the exit point of nerves, absent of rods n cones

RETINA• It is made up of 3 layers of specialized cells. Deepest

layer of retina contains receptor cells. • Receptor cells: change the light energy into nerve

impulses. 1. Rods: detect black, white, and shade of grey. 2. Cones: detect color and sharp details, and require more light than rods.

• Bipolar cells: activated by rods and cones. • Ganglion cells: neural cells with axons forming the

optic nerve.

Retina

The numbers of rods and cones in retina of human eyes.

Healthy Retina

Retina with Diabetic

Retinopathy

Retinopathy in Human Retina

Near and Far sightedness

• Near sightedness: Light rays converging in front of the retina. Is vision clear for near objects or far?

• Far sightedness: When light rays converge behind the retina. Are the objects that are near blurred, or those that are far?

Two Theories of Color Vision

1. The Trichromatic Theory of Color: All colors that we perceive are a combination of three colors- Red, Green, and Blue.

2. Opponent-Process Theory: Color is processed by cones organized in opponent pairs, red-green, yellow-blue, and black and white. Light that stimulates one half of the pair inhibits the other half.

Photo-energy Transmission as Action Potential

VISUAL PATHWAY

Optic Chiasm

• Dr. Erskine & Ruhrberg, discovered that VEGF164, a molecule usually known for triggering the growth of blood vessels, is actually leading the nerve cells across the chiasm and causing neural cells to cross over to opposite sides of the brain during visual development. They saw that in mice who lacked VEGF 164, there was no crossing of ganglion cells at the optic chiasm.  Who knew that something we thought only would affect the development of blood vessels in the brain would also be responsible for neuron placement and organization!

Hearing

The Nature of Sound:- Frequency- The pitch of the sound. A sound’s highness or

lowness, which depends on the frequency of the sound wave.

- Intensity- Loudness.

How can you connect pitch and loudness to wavelength and amplitude?

Structure of the Auditory System

• Sound wave travel through air, tissue, bone, and fluid before they reach the receptor cells- the hair cells located in Cochlea.

Ossicles: a tiny mechanism consisting of three small bones that transfer sound waves from the eardrum to the cochlea.

Hammer

Anvil

Stirrup

Cochlea is the Latin term for “snail.” It is a fluid-filled, snail-shaped bony tube in the inner ear where sound waves are changed to neural impulses.

oval window: The point on the surface of the cochlea that receives sound vibrations from the ossicles.

Hair Cells: tiny projections in the cochlea that are the receptor cells for hearing. When vibration causes the tips of these hair cells to move even the width of an atom, the vibrations cause the hair cells to generate neural impulses that your brain can process

Hair Cells

Sound Localization

• Two important cues to locate sound sources:

• 1. determine which ear hears the sound first

• 2. determine which ear hears the louder, more intense sound.

• Inner hair cells synapse on bipolar cells forming the auditory nerve

• Input from the left ear crosses to the right inferior colliculus

Medial geniculate nucleus of the thalamus

Primary auditory cortex of the temporal lobe

AUDITORY PATHWAY

• TASTE: a chemical sense. • Receptors are located on our

tongue that detect 5 tastes, salty, sweet, sour, bitter and scientist recently added savory (meaty taste).

• We don’t all have the same sensitivity for taste

SMELL: a chemical sense. Receptors are called Olfactory cells.

Taste and smell interact to produce flavor.

• TOUCH: Our skin is embedded with different kinds of receptors for different stimulations.