Goals

• Explain the difference between sensation and perception and describe how psychologists measure sensory and difference thresholds.
• Summarize how the eye and visual cortex work together to sense and perceive the visual stimuli in our environment.
• Describe the process of transduction in hearing.
• Describe the process of taste.
• Outline the gate control theory of pain. Explain why pain matters and how it may be controlled.
  • Large fibers which don't carry pain signals can override the small fibers which carry pain signals.

Psychophysics

Psychophysics is the branch of psychology that studies the effects of physical stimuli on sensory perceptions and mental states.

Weber's Law

Noticeable difference in stimulus is relative/proportional to the initial intensity of the stimulus. A 1kg difference in weight is easier to notice after having held a 10kg weight then a 100kg weight.

Sensation and Perception

This is the field of psychophysics.

Sensation

Stimulation of the sense organs.

Transduction

Conversion of stimuli to electrical signals for the brain.

Perception

Organization and interpretation of sensations by the brain.

Image Processing

Rods and Cones

Think of a flashlight. Cones are in the inner part of the retina and sense color and detail. Rods are part of the outside of the retina and sense movement.

Rods/cones -> Optic Chiasm -> Thalamus -> Occipital Lobe

Optic Chiasm

The space where part of the optic nerves switch sides so the left side of the visual field goes to the right half of the brain and vice versa.

Thalamus

Routes sensory signals to the correct area of the occipital lobe.

Occipital Lobe

Interprets visual signals. High frequency wavelengths are different colors. High amplitude wavelengths are brighter.

Hearing

Pinna - Outer ear -> Eardrum -> Oval Window -> Fluid Cochlea -> Hair Cochlea -> Auditory Nerve -> Thalamus -> Auditory Cortex (in Temporal Lobe).

Pinna

The outer part of the ear. Funnels in sounds waves.

Eardrum

Relays sound waves into the middle part of the ear.

Ossicles

Three tiny bones that relay sound vibrations to the cochlea.

• Hammer
• Anvil
• Stirrup

Oval Window

The membrane covering the opening of the cochlea.

Cochlea

A snail-shaped, liquid filled tube in the inner ear.

Fluid Cochlea

Vibrations from the oval window move the fluid inside the cochlea.

Hair Cochlea - Cilia

Movement from the fluid in the cochlea bend the cilia--hair cells-- of the inner ear. The cilia trigger nerve impulses in the attached neurons.

Auditory Nerve

Receives nerve signals from the cilia.

Thalamus

Relays auditory nerve signals to the auditory cortex.

Auditory Cortex

Resides in the temporal lobe. Interprets sound signals.

Frequency Theory of Hearing

Whatever the pitch of a sound wave, nerve impulses of a corresponding frequency will be sent to the auditory nerve.

Place Theory of Hearing

Different areas of the cochlea respond to different frequencies.

Taste

Fungiform Papillae

Small, numerous, bumps on the tongue and the throat. They contain your taste buds and temperature sensing cells. The taste receptor and temp sensing cells connect to your afferent nerve. Signals are then relayed from the thalamus to the appropriate part of the brain. Taste buds can sense savory, sweet, salty, sour, spicy... depending on the chemicals in the food.

Smell

Doesn't go through the thalamus due to evolutionary needs--smell danger.

Pain

Nociceptors, which are specialized nerve endings throughout the body, detect harmful stimuli, such as harmful temperatures, excess inflammation, and mechanical damage.

Why pain matters

Pain helps protect the body from harm, and encourages rest by making sure the body remains aware of the injury so activity isn't restarted too soon.

Treatment

Non-painful sensations can override and reduce painful sensations. Small fibers carry pain to the brain.

Gate Control Theory

Large fibers can open/shut the flow of pain to the brain.

Since large fibers don't carry pain signals, when they are active (from touch/ other sensations), they take precedence over the small fiber pain signals and reduce the intensity of the pain. Acupressure for example.

CBT-CP

Cognitive behavior therapy for chronic pain. Involves re-focusing your mind away from the pain in order to lessen it's intensity.