Behavioral Neuroscience Chapter 7

Taste

- Both taste and smell are stimulated by chemical stimulation/transduction

-Food dissolves in saliva and stimulates taste receptors

Taste Qualities

Basic stimuli is the number of molecules in solution of spit "molar concentration"

Flavor

Dependent on both taste and smell

Six Basic Tastes

Sweet, bitter, saltiness, sour, Umami, Fatty acids

Sweet

Organic molecules with proper H-O-C balance "sugar"

Bitter

Organic molecules with proper H-O-C balance with nitrogen tacked onto it, some are our sot dangerous poisons.

Saltiness

Need Na to keep the sodium- potassium pump and action potential working.

Sour

Organic molecules with excess hydrogen, test for ripeness

Umami "savory"

"MSG" Glutamate ion binds to the glutamate receptor (flavor enhancer)

Fatty acids

Used for insulation and building the myelin sheath

taste buds

- all over the mouth, tongue, roof of mouth, and throat.

-each contains 20-50 receptor cells which live for 10 days

Three types of tasters

average, hard of tasting, super tasters

Taste Receptors

- Fungiform papillae

-Foliate Papillae

-Circumvalate Papillae

-Filliform papillae

Fungiform Papillae

Mushroom shaped, tip of the tongue and front sides

Foliate Papillae

Fold like shape, Primarily found on sides of the tongue

Circumvalate papillae

Hill like shaped, look like bumps, middle and back of the tongue

filliform papillae

File shaped, few in humans

- all over, but mainly front half and middle

Gustatory Pathway

1. Receptor cell s

2. Glossopharyngeal, facial, and vagus nerves

3.Nucleus of the solitary tract in the medulla

4. Thalamus

5. Primary gustatory cortex

6. Secondary gustatory cortex

7. Amygdala, hypothalamus

Factors affecting Taste intensity

- number of taste buds: more taste buds

-Temperature: our body temperature

-Tongue position: front of the tongue

-Olfaction: smell is strongly connected to taste

-Age: increased age = decreased taste buds (decay)

-Cross adaptation: potentiation

Deficits in Taste

Dysgeusia and Ageusia

Dysgeusia

Perception of a taste that is not present

-drugs use can cause this

-nerve damage

Ageusia

Lose the ability to taste substances : specific quality (bitter)

-total ageusia, total loss of tasting anything

-Partial ageusia, very insensitive to taste (can't taste very well)

Olfaction-"smell"

We can detect thousands of odors, but it is difficult to describe them.

- More so than others this sense is linked to the emotional areas of the brain

-Works both dismally and proximally (close and far)

- Compared to other senses we don't know much about this.

Olfactory epithelium (smell skin)

- Produces mucous

-Olfactory rods stick out of it. At the ends of these rods are projection cilia.

-Axons of olfactory nerves come together to form the olfactory nerve. (Must pass through a small opening in sinus cavity)

Factors affecting olfaction

-Flavor

-Number of molecules

-Volatility

-Solubility

-Age

number of molecules

concentration gradient

Volatility

How easily a substance sheds off molecules into the air (evaporate).

Solubility

Ability to dissolve in liquid

Age

We lose our sense of smell when we age

-Asomia: the loss of smell

Pheromones

Chemical detection of smell for communication

- unconscious detection of smell (cranial nerve zero)

-Most of the research done is with insects

Mammal Pheromones

Alpha-androstenal- sexual activity

Human research done on pheromones

-Babies can identify who their mother is and vice versa

-Dormitory Phenomena: females menstruating who live in the same area will often times find their cycles syncing up (if they are not on medication such as birth control).

Audition: three perceptual dimensions of sound

1. Pitch

2. Loudness

3.Timbre

Pitch

- The frequency of vibration (measures in hertz)

-The greater the Hz, the higher the pitch

-Subwoofer is <10 Hz, (rather than hear this you instead feel it)

Loudness

The intensity of a sound

Timbre

- Complexity of sound frequencies, mixtures of frequencies

-In Addition to the note you were aiming for, what else is out there.

Amplitude (pressure one sound waves)

Measured in decibels (db)

Outer Ear: Pinna

- Gather sound waves in and channel to external auditory canal

-Helps with sound localization alters the shape of sound waves

-Can live without this but would lose a few decibels of hearing

External Auditory Canal

Contains hair and wax glands to prevent dirt from entering deep into the ear

-Acute otitis external (Swimmers ear): Water can get stuck and form the breeding grounds for bacteria

Tympanic Membrane "eardrum"

-Vibrates in and out in correspondence to sound waves hitting it.

-Mends itself if it gets torn or damaged, but mends with scar tissue so that it isn't as flexible.

-Very sensitive to touch

Middle Ear: Eustation Tube

-From middle are, to sinuses, to back of throat with a trap door

-Must equalize pressure between outer and middle ears

-Swallowing or yawning causes the trap door to open and release pressure

Acute Otitis Media- middle ear infection

Common in children, may have been born with genetically smaller or thinner eustation tubes

Ossicles

Three bones which transfers vibrations

-Malleus (hammer): connected to eardrum, pushes down on the incus

-incus (anvil): pivots on the stapes

-Stapes (stirrup): connected to the oval window of the cochlea (inner ear)

All three act like a lever system to amplify the force

Oval Window

Another membrane

- smaller than the tympanic membrane

Inner ear: Cochlea

Fluid-filled chamber

- spiral shaped like a seashell

-Contains receptor cell for sound detection: transfers sound from air to fluid

Organ of Corti

The actual receptive organ that contains:

-auditory receptor cell s

-basilar membrane

-hair cell cilia

Basilar membrane

Imbedded in this are thousands of auditory nerves

Auditory receptors

The hair cells in your ear

Hair cell cilia

Tiny hairs

Cochlear nerve

A branch of the auditory nerve

-bipolar cells (afferent) with cell bodies in the cochlear nerve ganglion; the axons make up the cochlear nerve

Auditory Pathway within the brain

1. Axons enter cochlear nucleus of the medulla

2.Superior Oliver's complex

3.Lateral Lemniscus

4.Inferior colliculi

5.Medial geniculate nucleus of the thalamus

5.Primary auditory cortex

6.Auditory association cortex

Auditory perception: perception of spatial location

-Phase difference's for low frequencies: difference of arrival times of sound waves at each ear

-intensity differences for high frequencies: difference in intensity of sound waves in each ear

-Analysis of timbre: determines if sound is in front or behind.

Sound processing in brain

Auditory cortex is responsible for pattern recognition

Hearing Problems

-Bilateral lesions of auditory cortex

-Lesions of left auditory cortex

-lesions of auditory association cortex

Bilateral lesions of auditor cortex

Problems with localization: trouble locating where a sound is coming from.

Lesions of left auditory cortex

Problems with discrimination of vocalizations: trouble knowing who is talking to you because you can't discriminate between voices.

Lesions of auditory association cortex

-auditory agnosia: inability to comprehend the making of sounds

-amusia: can't appreciate characteristics of music

Auditory fatigue

Overexposure to loud noises=some suppression of ability to hear for a given time

Age-related hearing loss

Damage to cilia from repeated use

Vestibular sense

Main parts are the vestibular sacs and semicircular canals of the inner ear

Vestibular sacs- utricles and saccules

-respond to the force of gravity

-information on head orientation

Semicircular canals

Respond to natural acceleration (rotation of the head)

-weak response to change in position and inner acceleration

ex- car sickness

vestibular nerve

Vestibular nerve axons project to the:

-vestibular nuclei in the medulla

-cerebellum, pons, and spinal cord

Somatosenses

Information for what is happening on the skin surface and inside the body.

cutaneous senses

Sense of touch

kinesthesia

position and movement

- receptors in joints, muscles, and tendons

Organic sense

-pleasurable and unpleasurable experiences

-receptors in internal organs

Types of stimuli

pressure, heating, cooling, pain, vibration

Receptors of the skin

-Ruffini corpuscles

-Pacinian corpuscles

-Meissner's corpuscles

-Merkel's disks

Ruffini corpuscles

Association with hair and detect low frequency vibrations, indentations

Pacinian corpuscles

Touch, high frequency vibrations

Meissner's corpuscles

low frequency vibrations

Merkel's disks

Skin indentations

Perception of stimulation

Touch- pressure and vibration caused by movement of skin

Temperature- have both warm and cold receptors in skin

Pain- pain receptors can detect

1. Intense pressure, heat and acids, and tissue damage

2. anterior cingulate cortex of the limbic cortex: emotional reaction to pain

3. Primary somatosensory cortex- pain perception

Somatosensory agnosia

Cannot Know the making of objects placed in hand despite normal somatosensory functioning

-can't identity by tactile exposure

-can't recognize shape, size, or other qualities by exposure only