Hearing!

• Audition the sense or act of hearing.

• We hear a best of sounds with frequencies in a range corresponding to that of the human voice.

• Frequency the number of complete wavelengths that pass a point in a given time (i.e. per second).

• Pitch a tone’s experienced highness or lowness; depends on frequency.

Sound Waves

• Sound waves are essentially changes in air pressure that our ears are able to detect.

• This is why you can feel vibrations in very loud or low pitched sounds.

• Amplitude refers to their loudness.• The ears turn the vibrating air into nerve impulses,

which are decoded into sounds.• Long waves = low frequencies = low pitch.• Short waves = high frequencies = high pitch.• Sound is measured in decibels.

How does the ear hear?• Conversion of sound waves into neural activity.• First the outer ear channel sound waves through the auditory canal to the ear

drum, which is a tight membrane that vibrates with waves.• The middle ear (the chamber between the eardrum and cochlea containing

three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window.) then transmits the eardrum’s vibrations through a piston made of 3 tiny bones (hammer, anvil and stirrup).

• This signal is sent to the cochlea a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses, which is found in the inner ear the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.

• These vibrations cause the cochlea’s inner tube to vibrate, jostling the fluid in the tube.

• This then causes small hairs to bend, which then sends the auditory signals to the temporal lobes of the brain.

The structure of the ear

The ear is divided into the outer, middle and inner ear.

The sound waves travel down the auditory canal to the eardrum.

Eardrum = tight membrane that vibrates when struck by sound waves.

The structure of the ear

Eardrum

The structure of the ear

Bones of the middle ear = the hammer, anvil, stirrup which vibrate with the eardrum.

The structure of the ear

Hammer

The structure of the ear

Anvil

The structure of the ear

Stirrup

The structure of the ear

Oval window = where the stirrup connects to the cochlea.

The structure of the ear

Cochlea = a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger

nerve impulses.

The structure of the ear

Oval Window

The structure of the ear

Cochlea

The structure of the ear

Fluid in the cochlea

The structure of the ear

Hair cells in the cochlea

The structure of the ear

Auditory nerve = nerve which sends the auditory message to the brain via the thalamus.

The structure of the ear

Nerve fibers

The structure of the ear

Auditory nerve

Neural impulse to the brain

Perceiving Loudness

• It’s the number of activated hair cells that creates the perception of a sound being louder.

• If the sensitivity of hair cells decreases, hearing loss may ensure.

• However, because it has to do with the number of hair cells activates, people with hearing difficulties perceive a sound to be loud, just like someone with normal hearing.

Perceiving Pitch • Both are theories on how we hear… either is seen as correct depending on

how you look at it. • Place Theory in hearing, the theory that links the pitch we hear with the

place where the cochlea’ s membrane is stimulated.• Best explains how we hear high pitched sounds • High frequencies produced large vibrations near the beginning of the

cochlea’s membrane, low frequencies near the end.• Like fluffing a bed sheet. • Frequency Theory in hearing, the theory that the rate of nerve impulses

traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.

• Best explains how we hear low pitched sounds • Brain reads pitch by monitoring the frequency of neural impulses travelling

up the auditory nerve.

Locating Sounds

• Placement of our ears allows us to have stereophonic (‘three-dimensional’) hearing.

• Looks at intensity and the speed of the sound.

• Think of if you heard a car honking on your right side – your right ear receives a more intense sound and receives the sound slightly sooner than your left ear.

• When our ears are struck with a sound that is equidistant between both ears, we don’t hear as well. This is because the sounds hit both ears simultaneously.

Hearing Loss and Deaf CultureConduction Hearing Loss hearing loss

caused by damage to the mechanical system that conducts sound waves to the cochlea.

• Problems with the eardrum or three bones of the middle ear.

• Sensorineural Hearing Loss hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness.

• Cochlea Implant a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.

• Signing becomes a part of deaf culture for communication.

• Debate on whether cochlea implants should be used: Hearing parents say yes, deaf parents say no.

Touch

• Vital in motherhood and upbringing. • Types of Touch:

– Pressure– Warmth – Cold– Pain

• Some spots will be more sensitive to pain, pressure, warmth, cold, etc.

• Self induced touch is less activating than non-self induced touch.

Top Down Influence in Touch – Rubber hand illusion

• Kinesthesis the system for sensing the position and movement of individual body parts.

• Ex – Case where a viral infection caused the nerves that enabled his sense of light touch and body position/movement. Person felt disembodied, as though their body was dead.

• Vestibular Sense the sense of body movement and position, including the sense of balance.

• Looks at your head in relation of position to the rest of your body.

• Inside your head there are semicircular canals (look like pretzels) and vestibular sacs, that contain fluid that moves as you move your head. These allow you to maintain your balance.

• Twirl around really fast, then come to a halt. What do you notice?

Pain • Pain is the way your body tells you something is wrong. • https://www.youtube.com/watch?v=n6iOUW523BE• However, think of people who live with chronic pain. It’s like an alarm that

won’t shut off.• Pain is detected by nociceptors, which are sensory receptors that detect

harmful temperatures, pressures or chemicals. • Gate-Control Theory of Pain the theory that the spinal cord contains a

neurological “gate” that blocks pain signals or allows them to pass on to the brain. The “gate” is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain.

• This explains why if you stub your toe, then rub it, the pain is not as intense. You stimulate the area, stimulating ‘gate-closing’ fibers.

• Phantom Limb Syndrome… Phantom hearing, seeing, taste and smells

The pain circuit

Psychological Influences of Pain : Understanding Pain

• Psychological Influences of Pain:– Rubber hand illusion again, but bend the finger,

less on real hand, more on rubber hand, people perceive as their own hand, feel the pain more severely.

– Pain memories – We tend to remember the most severe moments of pain, or the peak, as well as the pain at the very end, not necessarily how long we were in pain. Think childbirth.

• Social Cultural Influences – Playing a sport through injury.

Biopsychosocial approach to pain

Pain Control• Physical Methods – drugs, surgery,

acupuncture, electrical stimulation, massage, exercise.

• Psychological Methods – hypnosis, relaxation training, thought distraction, placebo effect.

• Should be used together to effectively control pain. However, the physical is more commonly prescribed by doctors.

Taste... Yum!

• Basic Tastes – sweet, salty, sour, bitter and umami (taste of savory meat).

• We equate different tastes to different basic functions of survival.

• Ex. Protein rich = good! Very bitter = bad! Maybe poison?

• We taste with our taste buds and it is a considered a chemical sense. We sense

different molecules as different tastes that are sent as signals to the temporal lobe of your brain.• Taste buds renew every 2 weeks.• As you grow older, the number of taste buds

decreases, along with their sensitivity.• Smoking and alcohol consumption also

deteriorate them.• Taste placebo effect – bad taste trick, cheap

wine trick.

Taste and Sensory Interaction

• Sensory Interaction the principle that one sense may influence another, as when the smell of food influences its taste.

• McGurk Effect.• Interaction of other senses – Ex. Seeing

the mouth movements of ‘Ga’, while hearing ‘Ba’, we will perceive the sound as ‘Da’.

• Synesthesia – joined senses. • https://www.youtube.com/watch?

v=qiN5kSRxcqM

What’s that… smell?

• 20,000 daily inhales and exhales of air a day, always with a smell attached.

• Olfaction, or smell is a chemical sense, like taste.

• Smell with our 5 million receptor cells at the top of each nasal cavity.

• These send the signals to the brain, via the olfactory nerve, by passing the thalamus entirely, to the olfactory bulb, located behind the eyes.

• Also associated with emotion, which explains why smells can trigger emotional memories.

• Ex – Wintergreen in NA as compared with UK.• Smell is also used in animals for detection –

mother and child. • Women tend to have better senses of smell

than men. • Humans tend to have a hard time describing

smells. They don’t connect well with language.

Smell (olfaction)

Smell and age