Chapt 5 - Poem by imani halley
'• Sensation is the detection of physical energy from the environment which we
encode as neural signals.
• When we organize and interpret our sensations, it is known as perception
• The beginning level of sensory analysis is also known as bottom- up processing
• Top-down processing is the information processing guided by higher-level mental
processes, as when someone constructs perceptions drawing on our experience
• Bottom up processing is sensory analysis that begins at the entry level, with
information flowing from the sensory analysis that begins at the entry level with
information flowing from the sensory receptors to the brain
• Patient E.H. suffered from propopagnosia, which is the inability to recognize and
connect the outside the world. Complete sensation was present but perception was
incomplete. It is the lack of top-down processing
• Psychophysics is the study of relationships between the physical characteristics of
stimuli, such as their intensity, and our psychological experience of them.
• Absolute threshold is the minimum stimulation needed to detect a particular stimulus
50 percent of the time
• A hearing specialist would expose an individual to varying sounds in order to figure
out their absolute threshold
• Signal detection theory is the theory which predicts how and when we detect the
presence of a faint stimulus amidst background stimulation. Assuming that there is no
single absolute threshold and the detection depends partly on a person's experience,
expectations, motivation and level of fatigue.
• A person's heightened attention decreases after 30 minutes.
• More false alarms are detected in heightened responsiveness
• A stimulus is Subliminal if it is below your absolute threshold, you detect it less
than 50% of the time. For instance, a microscopic cell is subliminal to you because
you cannot see it with your naked eye.
• Subliminal advertisements (Drink Coke, eat popcorn etc.) , does have an affect on you
but do not persuade you.
• The final statement of subliminal messages could be that much of our information
processing occurs automatically, out of sight, off the radar screen of our conscious
• The Difference Threshold (just noticeable difference or jnd) is the lowest difference
you can detect between the two stimuli 50% of the time. For example, you
are just able to notice the difference between 1kg and 1.02kg half the time.
• Priming is an acuteness to stimuli because of exposure to a certain event or
experience. For example, an individual who has just purchased a new car may now
start to notice with more frequency other people driving her same make and model.
''This person has been primed to recognize more readily a car like hers because of the
experience she has driving and owning one.
• Weber's Law states that two stimuli must differ in percentages or ratios, not amount,
for a person to detect it (jnd) .
Sensory Ada p ta t ion
• Sensory Adaptation- lowered sensitivity due to constant exposure from
stimulus. For example, when you go into someone's house you notice an
odor...but this only lasts for a little while because sensory adaptation
allows you to focus your attention on changing environment.
• If a constant image was maintained on the eye's inner surface, the
person will first see the complete image, then their sensory receptors will
begin to fatigue and the image will start to vanish. The image will
reappear and then disappear. This experiment reveals that perceptions are
organized by the meanings that the mind imposes.
• This adaptation allows the person to focus on informative changes,
leaving out uninformative constant stimulations.
V isi on
• Transduction refers to Sensory energy being convert (transformed) into
• Light is composed of electromagnetic waves with Wavelengths (distance from
one peak to another peak on a wave) and Amplitudes (height of the wave)
• Wavelength determines hue and pitch determines the frequency in sound.
• Amplitude determines intensity and loudness in sound.
• External Light entering the eye first travels through the Cornea (protective layer)
• Pupil (an adjustable opening) is controlled by Iris (muscle around the pupil)
• Lens (an oval transparency) that changes shape to focus light by a process
• light is then focused onto the back of the eye called Retina (multi-neuron surface) .
• Johannes Kepler revealed that the retinas did receive upside- down images.
• Researchers later revealed that the retina does not read the image as a whole,
receptor cells convert light energy into neural impulses and these impulses then
are sent to the brain, it is then that the image is constructed and perceived.
• Acuity is how sharp and clear a vision is
• There are three basic types of Acuity: normal, nearsightedness (only see near
things clearly) , and farsightedness (only see far things clearly)
• The Retina has 2 types of receptor cells: Rods and Cones. Cells connecting
these detectors form the Optic Nerve that sends the impulses to brain.'
'Receptor cells are the specialized cells that respond to a particular type of energy.
• Rods are receptor cells in the retina responsible for night vision and perception of
• Everyone has a Blind Spot, a small region in the visual field where nothing could
be seen. This is because there are no receptor cells where the optic nerve leaves
the eye in the retina. Normally, we don't witness this effect because we have two
eyes that compensate for each other's blind spot, and the fact that our eyes are
• Fovea is the region in the retina where light is centrally focused. The fovea has
no rods, only cones.
• When light energy strikes the rods and cones, neural signals are generated. These
signals activate the bipolar cells. The bipolar cells then activate the ganglion cells.
They then form the optic nerve.
• Cones allow detail an color
• Cones allow one to perceive color. In the dark, the cone is ineffective. The rods
are not affected by the dim light and many rods will focus their energy into one
Visual Information Processing
• The retina is brain tissue that floats to the eye during early fetal development
• There are three levels in which visual information is received.
• First, the retina processes information before sending it via the thalamus to the
• The retina also analyzes the sensory information
• Information from the retina is received and transmitted ganglion cells.
• Pressure can trigger the retina
• Nobel prize winners Hubel and Wiesel discovered Feature Detectors in the brain
cortex that are sensitive to specific features in what we see, like shape,
color, depth, movement, and form.
• Perret identified nerve cells that specialize in responding to a specific gaze, head
Pa r a l l e l Pro c es s ing
• Our brain Processes lots of information simultaneously. For example,
looking at an orange, the brain processes the orange
color, the round shape, and the bumpy texture all at the same time.
• People who cannot consciously perceive can still remarkably locate
objects but are consciously unaware of how they knew. Such a
phenomenon is called Blind Sight
• Mrs.M was a woman who suffered stroke damage to both sides of her
brain. She became unable to perceive movement.
• David Milner revealed that an individual knows more than they are
• Young and von Helmholtz revealed that color can be created by combining
the light waves of blue, red and green colors. They inferred that the eye
must have three types of color receptors.
• Color processing is described in 2 stages:
o 1) Young-Helmholtz trichromatic (three-color) theory - Light is
detected by 3 types of cones each specifically sensitive to Red, Blue,
or Green. Combinations of them produce intermediate colors
(yellow, cyan, purple)
o 2) Opponent-Process theory - Color is then processed by their
opponent colors (red-green, blue-yellow, black-white) . Some cells
are excited by blue and inhibited by yellow, vice versa. Thus, you
cannot see a bluish-yellow.
Color c onst a ncy
o refers to the importance of surrounding background effects on perceived
color. Color constancy states that colors don't look different even in
different illumination (i sunlight or dark room) , even if the light and
o Hearing is highly adaptable
o Hearing Frequency (Pitch) is the number of waves travelling through a
point in one second, relates to how fast a wave travels.
o Audition, or hearing, requires sounds waves converted into
neural impulses, and this is done in the ear.
o Sound travels through the 3 sections of the ear to the brain:
o Outer ear: Auditory Canal
o Middle ear: Ear drum (tight membrane) . Concentrates the
vibrations of the eardrum on the cochlea's oval window
o Inner ear: contains the Cochlea (coiled, fluid-filled tube)
that contains the Basilar Membrane, which is lined with hair
cells that vibrates to excite nerve fibers. The fibers form the
Auditory Canal connecting to the brain.
o Loudness is determined by number of activated hair cells.
o Harder to hear sounds are amplified more than loud sounds
How do we perceive Pitch?
o Place theory says that we hear different pitches because
specific "places" in the cochlea are stimulated.
o Frequency theory says that we hear different pitches because the speed
of neural impulses traveling to the brain matches the speed of the sound
'waves ("frequency") . Does not explain how we hear low-pitched sounds, it
can explain our sensation of high pitched sounds.
o It does explain our sensation of low-pitched sounds
How do we locate sounds?
o We can tell which direction a sound is coming from because if it is closer
to our right ear, the right ear will receive the sound slightly faster than left
ear and the brain calculates this difference. If the sound is directly behind
or in front, where the distance between two ears is the same, then it is
difficult to differentiate.
o Sound waves strike one ear sooner and more intensely than the other.
o The ear uses parallel processing to analyze the differences in the sounds
received by the two ears, and then finds the source.
Hearing loss and Deaf Culture
o Conduction Deafness - loss of hearing due to damage of eardrum, and/or
the tiny bones in middle ear. (Could be fixed by hearing aid)
o Sensorneural hearing loss- damage to the cochlea's receptors. Destroys the
o Shark and bird hair cells are able to regenerate.
o Cochlear Implants are the only way to restore hearing for people with nerve
o These implants are wired to many sites on the auditory nerve, which allows them
to transmit electrical impulses to the brain
o Most effective when the child is very young
o Deaf people argue against the implants since they do not view deafness as a
disability, they also believe that the brain's plasticity allows a greater strength in
o Touch is composed of 4 senses: Warmth, Pain, Cold, and Pressure
o Only pressure has specific receptors
o Pressure and Cold = wet
o Cold and warm = hot
o Pressure and Pain = tickling itch
'o Phantom Limb Sensations occur when pain is felt in a nonexistent limb. Even
though the leg is not present, the receptor neurons previously connected to them
are still there. And they will fire, resulting in pain sensations.
o The Gate-Control Theory states that the spinal cord has "gates" that opens/closes
to transmit pain impulses.
o Small fibers open Gate = pain.
o Large fibers close Gate = no pain
o Pain is merely a physical and psychological interpretation. Distraction methods,
where attention is focused elsewhere, can ease the felt pain.
o Acupuncture (may affect gate-control) , electrical stimulation, exercise can
also relieve pain.
o The Biopschosocial perspective reveals that a person's experience of pain is
influenced by biological influences, past experiences and social cultural
o Taste is a Chemical Sense composed of 4 basic senses: Sweet, Sour, Salty, and
o. Taste receptors (taste buds) regenerate every 1 or 2 weeks, but age, smoking,
and alcohol will lower taste bud number and sensitivity.
o Sensory Interaction is when one sense affects another sense, thus interacting.
Smell and taste seem to interact.
o Taste buds on top and sides of the tongue and in the back and on the roof of the mouth contain taste
o The taster receptor cells send information to an area of the temporal lobe
o Smell or Olfaction is also a Chemical Sense that directly transmits
information from nose to the temporal lobe.
o The only sense that doesn't first relay impulses to the Thalamus.
Body Position and Movement
o Kinesthesis (using sensors in muscles, tendons, and joints)
o Vastibular sense (using fluids in semicircular canal, cochlea, and vestibular sacs
in inner ear)
o Both sense our position, movement, and balance.'
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