Chapter 3

Transduction- word of the day for this chapter

Defining Sensation- where our senses pick up stimuli

Motivations of behavior are many like

  • religion

  • fear

  • etc

Overview

  • The Process of Sensation

  • Vision

  • Hearing and Balance

  • Smell, Taste, and Touch

  • Influences on perception

  • Principles of Perception

The Process of Sensation

  • Sensation

    • process whereby senses pick up visual, auditory, and other sensory stimuli from the environment

    • Information (in the form of neural impulses) is then transmitted to brain to be processed (or perceived)

      • how the body receives stimuli

  • Perception

    • process whereby the brain actively organizes and interprets sensory information

    • provides the “finished” product

    • How we understand our world

      • what is your brain going to do with the information

  • Sensory Receptors

    • highly specialized cells in the sensory, organs, skin, muscles, tendons etc..

    • detect and respond to one type of sensory stimuli

    • transduce (convert) stimuli into neural impulses (brain communication)

    • provide the link between the physical, sensory world and the brain

  • Transduction

    • process by which sensory receptors “convert” sensory stimulation into neural impulses

Sensory Adaptation

  • Process whereby sensory receptors grow accustomed to constant, unchanging levels of stimuli (auditory, olfactory especially) over time

  • Not likely to occur in the presence of sa very strong stimulus

    • getting used to very dark spaces or loud levels of sound

The Process of VIsion

  • Our eyes respond only to visible light waves

    • Light waves form a small subgroup of electromagnetic waves called the visible spectrum

  • Electromagnetic waves are measured in wavelengths

    • the distance from the peak of a light wave to the peak of the next wave

    • Light occurs in waves

  • Light first enters the eye through the cornea

    • bends light rays inward

    • directs the light rays through the pupil

  • The iris contracts and dilates the pupil to regulate the amount of the light entering the eye

  • The lens focuses on the viewed objects, directs images to the retina

    • Accommodation: flattening and bulging action of lens. Presbyopia: age-related loss of flexibility in the lens

  • Retina: tissue lining the back of the eye (inside the eye) contains specialized neurons that transduce light stimulation into neural impulses

    • full of specialized receptor cells

    • where transduction occurs

    • its inside the back of the eye

  • The image projected onto the retina is upside down and reversed from left to right

  • Rods and Cones arrears light-sensitive receptor cells located at the back of the eye in the retina

  • There are 120 million rods and 6 million cones in each retina

What kind of receptor cells exist on the retina

  • Rods

  • Cones

  • Horizontal cells

  • Ganglion cells

  • Bipolar Cell

Transduction occurs when light stimulates the receptor cells, which in turn trigger the neural impulse.

  • Rhodopsin in the rods enables adaptation to light

    • 2 components

      • opsin and retinal

    • light adaptation: opsin and retinal break apart

    • dark adaptation: opsin and retinal bond, forming rhodopsin

    • getting together and breaking apart to regulate

  • Macula: functional center of the retina, gives us the ability to see 20/20 vision. About 5 mm in diameter. Can be damaged by diabetes or degeneration.

  • Fovea: Large concentration of cones only; produces our clear sharp vision. The fovea is the pit inside the macula

    • allows you to focus sharply on something and have your perepheriral vision

  • Light passes through 4 layers of tissue in the retina after reaching the rods and cones

  • Each layer contains specialized neurons

  • Axon-like extensions of of ganglion cells are bundled together in a pencil-sized cable (optic nerve) exiting the retina

    • blind spot

      • no rods or cones present

      • located where the ganglion cable exits the retina

  • Optic nerve - formed by Bundled ganglion cells

  • Optic Chiasm

    • point where some optic nerve fibers cross to opposite side of brain

    • crossing over allows the image to be projected to both hemispheres of the brain

  • Nerve fibers extend from the optic chasm to the thalamus, transmit neuronal impulses to the primary visual cortex, where they are processed and perceived

  • The primary visual cortex is located in the occipital lobes in the back of your head

  • Feature Detectors

    • specialized neurons of the primary visual cortex

    • respond only to specific visual patterns (

      • like angles

      • curves

      • color

      • ect

    • coded at birth to make their unique responses

  • Perception of Color

    • results from reflection of particular wave lengths of the visual spectrum

    • three dimensions of light produce color distinctions

Characteristics of light

  • Hue

    • the specific color perceived

  • Saturation

    • the purity of a color

  • Brightness

    • the intensity of the light energy perceived as a color

Color Vision Theories

  • Trichromatic Theory

    • there are 3 types of cones in the retina

    • each is sensitive to and responds to 1 of 3 colors

      • red, blue, or green (RBG)

  • Opponent-Process Theory

    • Cells respond by increasing or decreasing their rate of firing when different colors are present

      • red/green cells: increase rate with red, decrease with green

      • yellow/blue cells: increase with yellow, decrease with blue

      • white/black cells: increase rate with white, decrease with black

    • Afterimage

      • visual sensation that remains after the stimulus is withdrawn

      • The brain will give the sensation of the opposite color

  • Each theory explains a different phase of color processing

    • Trichromatic theory best explains cone processing of color

    • opponent-process theory: cones pass on information about wavelengths to ganglion cells

  • they’re both correct

The process color vision continues in the visual cortex found in the back of the brain

Colorblindness

  • Inability to distinguish certain colors from one another

  • 8% of makes and 1% of females experience difficulty distinguishing colors.

  • Genetic cause due to X-Y chromosome

  • Distinguishing red from green is the most common form of color blindness

Sound

  • Sound waves require a medium, such as air or water, through which to move

  • Frequency

    • number of cycles per second completed by sound wave

    • determined the pitch of a sound

    • measured in hertz (Hz)

    • Range for humans 20-20,000Hz

  • Amplitude

    • loudness of sound

    • measured in decibels

  • Timbre

    • quality of a sound that distinguishes it from other sounds of the same pitch and loudness

  • Pitch

    • The quality of a sound governed by the rate of vibrations producing it

    • how high or low the sound is

  • Amplitude is measured in decibles

  • Each increase of 10 decibles makes a sound 10 times louder

  • Exposure to 130 decibels or higher creates a risk for hearing damage

  • Audition the sensation and process of hearing

  • Outer Ear

    • pinnae and auditory canal

  • Middle Ear

    • ossicles

      • hammer, anvil, and stirrup

  • Inner Ear

    • cochin and semicircular canals

  • Sound waves enter the pinna, the visible part of the outer ear.

  • Waves travel the auditory canal, which causes the eardrum to vibrate

  • Ossicles in the middle ear amplify sound waves

  • Amplified waves cause vibration of the oval window

  • The oval window initiates activity, stimulating the cochlea. Fluid in the cochlea sets in motion.

  • Hair cells attached to the basilar membrane inside the cochlea are stimulated

  • These specialized receptor hair cells, now activated, transcode (translate) or convert vibrations into neural impulses

  • Neural impulses travel through the auditory nerve to the brain

Hearing theories

  • Place theory

    • Specialized receptor cells located along the basilar membrane vibrate in response to differently pitched sounds

    • this theory explains how we hear sounds with frequencies higher than 150 Hz

  • Frequency theory

    • Hair receptors vibrate the same number of times per second as the frequency of the sound waves that stimulate them

    • A tone of 500 Hs would stimulate the hair cells to vibrate 500 times per second and even up to 1000Hz

    • This theory explains how lower frequency sounds are heard

The source of sound is determined bu the difference in intensity and timing of the sound waves reaching your ear and the position of your head

Kinesthetic Sense

  • Provides info about:

    • the position of body parts in relation to each other

    • movement of the entire body to its parts

  • Information detected bye receptors in nouns, ligaments, and muscles

  • Other senses provide additional information about body position and movement (primarily vision)

Vestibular Sense

  • Detects movement, information about body’s orientations in space

  • Located in semicircular canals and vestibular sacs of the inner ear

Motion activates sensors

  • semicircular canals sense rotation of head

    • canals filled with fluid

    • moving fluid moves hair cells

    • stimulating specialized receptors located at the base of the base of the hair cells, creating the neural impulse (transduction)

    • neural impulses conveyed to the brain (motor cortex) for processing

  • Olfaction: sense of smell

    • aids in survival

    • influences emotional states

    • serves as a memory cue

Most substances in the environment release odor molecules which make their way into our nose

Olfactory Epithelium

  • one-inch square patches of tissue

  • one at the top of each nasal cavity

  • contain olfactory neurons which connect directly to the olfactory bulbs. Smell sensations then travel to the amygdala for emotional interpretation and to the orbitofrontal cortex for cognitive interpretation

Orbitofrontal Cortex

  • receives messages from olfactory bulbs via the thalamus

  • 10 million olfactory neurons

  • Each neuron contains only 1 of 1000 different types of odor receptors

  • we’re able to detect 10,000 different odors

Taste sensations

  • Gustation : sense of taste

  • Five primary taste sensations have been identified

    • sweet

    • sour

    • salty

    • bitter

    • Umami - produced by amino acids and glutamate, resulting in a meaty, soy-like taste

  • Papillae

    • small bumps on the tongue

  • Taste buds lie alongside some of the papillae

    • each taste bud is composed of 60 to 100 receptor cells

    • All 5 taste sensations can be detected on all locations of the tongue

Transmission of Touch Sensation

  • Tactile information is conveyed to the brain: the skin is pressure and temperature sensitive

    • One or more of several types of receptors are stimulated

    • Touch messages are sent through nerve connections to the spinal cord

    • The message is relayed next to the somatosensory cortex of cerebrum

Pain: The Gate Control Theory

  • An area in the spinal cord acts as a gate and blocks or transmits pain messages to the brain

  • Pain messages are carries by small, slow-conducting nerve fibers, reach gate and open it

  • Large, fast-conducting nerve fibers carry other sensory messages

  • Messages from fast-conducting fibers

    • “tie up” gate

    • prevent pain message form transmission to the brain

  • Rub or apply gentle pressure to injury

    • Large, fast-conducting nerve fibers are stimulated

    • Pain message is blocked

Functions of pain

  • Pain can be a valuable warning and a protective mechanism

    • Pain motivates people to tend to an injury, to restrict activity, and to seek medical help

    • Certain medical, physiological, and pharmacological conditions can distort our perception of pain

Pain: Perception and Cross-cultural Variations

  • Distraction can be effective with short-term pain, but not long-term pain

  • Cross-cultural variations in chronic pain may be linked to differences in people’s emotional states

Endorphins

  • Endorphins are natural painkillers produced by the body

    • block pain and produce a feeling of we’ll being

    • Some individuals release endorphins when they think they are receiving pain medication (placebo effect)

    • The body produces 20 different types of endorphins and are found in the pituitary gland and other places

Perception

  • Process of assigning meaning and intensity to environmental stimuli that has been received and processed by sensory organs into neural impulses

  • Influences by 3 factors

    • attention and focus

    • Prior knowledge/experience, preference

    • Cross-modal perception, ie., 2 or more senses working in unison

  • When attention is focuses on some sensations, and others are missed altogether or misperceived

    • inattention blindness

      • fail to notice changes in objects not receiving direct attention

    • cocktail party phenomenon

      • Auditory attention focuses on information that is personally meaningful

Principles of Perceptual

  • Sensory elements experience brought together as a whole

  • Gestalt: a German word that refers to the whole form, pattern, or configuration that a person perceives

  • Sensory experience is organized according to basic principles of perceptual organization

  • Perceptual Constancy

    • Objects maintain their physical properties, such as size, shape and brightness, despite differences in distance, viewing angles, and lighting

  • Depth perception

    • Our ability to perceive the visual world in 3 dimensions and to judge distances fairly accurately

  • Our eyes are able to create dimensionality from a one-dimensional image on the retina due to depth cues.

    • monocular

      • types include: interposition, linear perspective, relative size, texture gradient, atmospheric perspective, shadow or shading, and motion parallax.

    • binocular

      • types include: convergence and binocular (retinal) disparity

  • Brian perceives real motion by comparing the movement of images (light) across the retina to visual reference points

    • assumes points to be stable