chap 5

Sensation

• When the sense organ receptor cells are stimulated and
  relay their information to higher brain centers for
  further processing.

Perception

• When we select and interpret sensory input so that it
  acquires meaning.

olfactory(smell)

• odourants (airborne chemicals)

Somatosensory (touch, heat, pain)

• pressure or damage to the skin

Gustatory (taste)

• chemicals (typically in food)

Auditory (hearing)

• sound waves

Visual (sight)

• light (photons)

sensory transduction

• converts environmental stimulus into neural activity

Sensory receptor cells

• specialized cells that convert a specific
  form of environmental stimuli into neural impulses

Sensory transduction

• he process of converting a specific form
  of environmental stimuli into a neural impulse that our brain can
  read

psychophysics

• The study of how physical stimuli are translated
  into psychological experiences.

Bottom-Up Processing

• A progression from individual elements to the whole.

Top-Down Processing

• A progression from the whole to the elements.

Stimulus

• Any “thing” we can detect in the environment.

Threshold (individual differences)

• The value of a sensory event at the point at which things are perceived as being different.

Absolute threshold

• the min about of stimuli needed for you to notice something, occurs 50% of the time

Just noticeable difference

• how much stimuli is needed to notice a difference in the environment

Signal Detection Theory

• An observer’s perception depends not only on the intensity of a stimulus but also on the observer’s motivation.

Subliminal Perception

• Perception below the threshold of conscious awareness.

Signal Adaptation

• Losing ‘conscious’ awareness of a sensory stimuli

5 taste receptors

• sweet, sour, salty, bitter, umami

Ageusia

• inability to taste, a rare disorder

Anosmia

• inability to detect odours

Hyposmia

• reduced ability to smell

Reflex epilepsy

• a seizure occurs only after exposure to a
  specific odour

Migraine headaches

• specific odours can trigger migraines

tactile or somatosensry system is a combination os skin sensese like

• pressure, touch, temp, vibration, and pain

Touch process

• 1) get a tactile stimulus that is then sent to the spinal cord (one for touch and one for pressure+vibration)

• 2) Then it gets sent to the thalamus  (relay sensory information)

• 3) Then sent to the somatosensory cortex which then processes the info

No pain (familial dysautonomia)

• rare genetic condition associated with an inability to detect pain or temperature and produce tears.

Phantom limb sensations

• tactile hallucinations of touch, pressure, vibration, and pain in the body part that no longer
  exists

Sound waves

• vibrations of the air in the frequency of hearing.

Frequency

• the number of cycles per second in a wave,

• Determines pitch of sound,

• Measured in units called Hertz (Hz), which represent cycles per second,

• We hear best in the range of 2000 − 20 000 Hz

Amplitude

• the magnitude (height of a wave), Determines loudness,

• Measured in units called decibels (dB)

how sound moves in the ear

• Tympanic membrane —--> ossicles (malleus, incus, stapes) —--.> oval window —--> choclea —--> basilic membrane (bends cillia over) —> cillia —-> signal impulse to auditory nerve

Deafness – loss of hearing (partial or complete)

• Can be genetic, caused by infection, physical trauma (headphone use), exposure to toxins, high doses of common medications such as Aspirin

Tinnitus

• ringing in the ear Due to abnormalities in the ear(maybe) One of every 200 people experiences tinnitus

Visual system

• light hits the retina → photoreceptors turn the light into electrical signals → they travel form the retina to the optic nerve to the brain → they are then turned into signals to images

• light enters the eye → iris adjusts the size of the pupil so more or less light can go in → light is transduced by the photoreceptors (rods and cones) in the retina at the very back of the eye → changes form the photoreceptors get passed down to other neurons in the retinal circuitry → photo projectors project to interneurons which communicate through ganglion cells in retina → ganglion cells send visual input from retina to brain via optic nerve

Amplitude

• perception of brightness.

Wavelength

• perception of colour.

Purity

• mix of wavelengths.

Perception of Saturation

• richness of colours.

Cornea

• transparent portion of the eye’s front surface, which refracts light and allows it to pass into the eyeball.

Pupil

• aperture in the eye formed by concentric bands of muscle.

Iris

• layered ring of tissue that gives the eye its characteristic colour.

Lens

• transparent eye structure that focuses the light rays falling on the retina.

What pathways

• helps identify an object

• Visual agnosia – damage to the “what” pathway; cannot visually recognize objects

• Prosopagnosia – a form of visual agnosia in which
  people cannot recognize faces

Where pathways

• locating objects in space

• Hemi-neglect – damage to the “where” pathway; people ignore one side of their visual field
  ▪ Example: eat food on only one side of plate
  ▪ People with damage to the right side of their “where” pathways neglect the left side of their visual field

figure ground

• the tendecy to precive one aspect as the figure and the other as the background. illusions (face or two faces, not two at the same time)

proximity

• objects that are physical close together are grouped together (3 groups of 6 hearts not 18 hearts)

continuity

• objects that continue a pattern are grouped together

closure

• the tendency to see a finished unit form an incomplete stimulus

similarity

• similar objects grouped together

Gestalt law

• how we perceive stimulus as whole forms or figures rather than individual lines and curves

retinal disparity

• the slightest difference in images processed by the retinas of each eye

convergence

• inward movment of the eyes to view objects close to oneself

binocular cues

• cues from both eyes

illusions

• A perception of a physical stimulus that differs from measurable reality and normal expectations about its appearance.

the muller-Lyer illusion

• one line appears longer but both are the same length

Ponzo Illusion

• the converging lines make the upper bar seem larger but both are identical length

Gestalts Law of Organization'

• the whole is greater than the sum of its parts

Law of Pragnanz

• when items or stimuli can be grouped together or seen as a whole, they will be

Strabismus

• lack of coordinated movement of both eyes; affects about 2%−4% of the population

Amblyopia

• a loss of visual abilities in a weaker eye; abnormal development of the brain’s visual cortex due to a failure to receive
  coordinated visual stimulation from both eyes by the age of six (an eye- patch is often the treatment)

About half a million people in Canada have visuals impairments. Each year, 50,000 Canadians lose their sight.

Braille

• a form of reading skill used by individuals suffering from
  visual impairments

Kinesthetic

• receptor cells in your muscles tell the brain when we are moving and where our body parts are in space

Vestibular

• located in the semicircular canals of our inner ears; the
  movement of fluid tells us if we are standing up or swaying from side to
  side