Ch 4 Flashcards
Sound
Changes in air pressure as a result of displacement of air molecules, creating vibrations in the air. Sound waves are sinusoidal (having the form of a sine).
Fundamental frequency (f0)
àMost powerful) The frequency at
which sound waves vibrate. Very energetic, meaning that they still have
power after the signal decomposes.
Harmonics
Component of a frequency wave. The fundamental frequency × an integer (1
The human ear is sensitive for frequencies ranging between
20 Hz and 20.000 Hz
The Peripheral Auditory System
a. External ear
b. Middle ear
c. Oval window
d. Internal ear
e. Cochlea
f. Basilar membrane
External ear
Collect and focus sound energy
Middle ear
Sound waves vibrate on the eardrum (= tympanic membrane), which moves the three tiny bones connected to it (malleus, incus, stapes), which amplifies sound energy.
Oval window
Where the stapes connects to the cochlea (in internal ear).
Internal ear
Consists of cochlea, basilar membrane, stereochillia, apex
Cochlea
Consists of three chambers filled with fluid
Basilar membrane
inside cochlea)àembedded hair cells (tips are called stereocilia) of which their movement causes an action potential.
Hair cells move depending on frequency
base) close to oval window= high frequency
apex) end of cochlea= low frequency.
Low frequencies travel far
auditory nerve
Signal from hair cells travel to brain
a. Cochlear nucleus
b. Superior olivary complex: Combines signals from both ears
c. Nucleus of lateral lemniscus
d. Inferior colliculus : signal integration.
- frequency recognition.
- pitch discrimination
e. Medial geniculate complex : Relay between inferior colliculus and auditory cortex (same as LGN in vision
f. Auditory cortices : Primary (A1) and secondary
(A2) auditory cortex
tonotopic organisation
Different parts of the cortex process different frequencies, with frequencies between 500 and 5000 Hz occupying the largest space because evolutionarily important sounds are within these frequencies.
Loudness
Has to do with air pressure and the amplitude of a wave. Interacts with frequency; perception of loudness doesn’t always depend on the physical properties, like brightness
Pitch
The frequency of a wave (Hz). Interacts with harmonics; brain creates the fundamental frequency, so the pitch we experience may be different from the true frequency.
pitch experienced in a harmonic series is the
pitch of the fundamental frequency
When you present all the
other stimuli (all missing
the fundamental
frequency), they are
experienced with the same
pitch. The pitch you
experience is that of the
largest common divisor
Timbre
How we can distinguish a piano from a violin that are playing at the same pitch and loudness
> 3kHz
Interaural time difference
For frequencies greater than 3 kHz. The head creates an acoustic shadow (an obstacle for high frequencies) and intensity differences. This means that a stimulus directed to the left ear will cause a stronger reaction from the left lateral superior olive (LSO) and inhibit activity in the right LSO
> 3kHz
For frequencies below 3 kHz. The speed of sound is slow and with the distance between the ears, the maximum difference can be 700 microsecs. The smallest difference we can detect is 10 microseconds, which coincides with how accurately we can determine the location of a sound source, about 1 degree on the horizontal field
Neurons in the medial superior olive (MSO) are coincidence detectors, meaning they detect sound inputs that occur at the same time. Axons projecting from the cochlear nucleus vary in length, creating delay lines. Action potentials are generated at different times from each ear, and thanks to the varying lengths, it is possible for the signal from the left and right ear to arrive in the MSO at the same time. The MSO responds most strongly to coincident arrivals
tactile perception
pressure, vibration, tension, and touch
specialized receptors
Tactile perception is initiated by a variety of
receptor types in the skin and subcutaneous
tissues. Each receptor is specialized to a
different category of mechanical force.
The quality of the perception (what, where)
depends on the receptors being stimulated and
where they project to in the brain
— root hair plexus (touch)
— ruffini endings (pressure)
— pacinian corpuscles (pressure
— meisser corpuscles (touch)
Some areas, such as
the fingertips, have a
high density of
receptors (with small
receptive fields; 1-2
mm).
Other areas, such as
the forearm, have less
receptors with larger
receptive fields
(several centimetres)
root hair plexus
touch
ruffini endings
respond to skin stretch
Meissen corpuscles
low frequency vibrations: small receptive fields
Pacinian corpuscles
high frequency vibrations
Path of signal cutaneous system
Dorsal root ganglion -> Spinal cord —> Thalamus —> Ventral posterior nuclear complex —> Primary somatosensory cortex (S1)
Nociceptive System
Free nerve endings that receive pain
Perceives pain and temperature. Pain is created in the brain; it is not a quality of an object
The Placebo Effect
When a placebo is administered instead of a painkiller, the same brain network is activated to alleviate pain.
the placebo response could be blocked by naloxone if it was induced by strong expectation cues
Opioid antagonists also block effect of placebos
Olfactory epithelium
A sheet of receptor neurons in the nasal cavity.
Each neuron contains just one receptor protein. Different types of odor molecules bind to specific receptors. The perception of scent is the combination of different odor molecules on different receptors.
The Olfactory System
Receptor neurons —> Olfactory nerve —> Olfactory bulb
Taste cells
determine the identity, concentration and
hedonic quality (pleasantness or unpleasantness) of a substance.
Receptors for bitterness, sweetness, saltiness, and sourness are unevenly distributed.
