bio psych chpt 10

evolution of music and language

music likely evolved from the biological continuity between modern humans and their hominin and primate ancestors

• output of highly structures neural system for complex signaling; increasing fine-tuned neural and anatomic mechanisms underlying auditory perception

• protolanguage for strengthening social cohesion

evidence of innate and inherited predisposition toward music

• responses of very young infants to music

• caregivers use music and speech to communicate

sound waves

undulating displacement of molecules caused by changing pressure

air molecule density is plotted against time at a single point relative to the tuning fork’s right prong

physicists call the resulting cyclical waves sine waves

frequency

amplitude

sound wave frequency

frequency -number of cycles that a wave completes in a given amount of time, measured in hertz

hertz -measure of sound wave frequency; 1 Hz → cycle per second

corresponds to our perception of pitch -low pitch, low frequency: fewer cycles per second; high pitch, high frequency: many cycles/second

differences in frequency, differences in pitch

amplitude

intensity, or loudness, of a sound, usually measured in decibels (dB)

magnitude of change in air molecule density

corresponds to our perception of loudness

• soft sound, low amplitude

• loud sound, high ampltiude

sound wave complexity

pure tones

• sounds with a single frequency

complex tones

• sounds with a mixture of frequencies

corresponds to our perception of timbre, or uniqueness

breaking down a complex tone

fundamental frequency

• rate at which the complex waveform pattern repeats

overtones

• set of higher- frequency sound waves that vibrate at whole-number (integer) multiples of the fundamental

perception of sound

pebble hitting water (makes waves) like tree falling to ground

• air pressure waves that derive from the place where tree strikes ground

  • frequency of waves determines pitch of sound heard by brain

  • amplitude determines how loud

physical properties of sound wave converted electrochemical neural activity

left temporal lobe vs right temporal lobe

speech for meaning - musical sounds for meaning

language

hear variations of sound as if they were identical even though the sound varies considerably from one context to another

• unique to perception of speech sounds

• auditory system has mechanism for categorizing sounds as the same despite minor differences in pronunciation

  • learning languages later in life more difficult

properties of music

loudness, amplitude, sound wave: subjective

• what is very loud can differ for others

pitch

• position of each tone on a musical scale; frequency of the sound wave

• defined as fundamental frequency, regardless of timbre

quality

• timbre of a sound, regardless of pitch

functional anatomy of auditory system

ear collects sound waves from surrounding air

• mechanical energy → electrochemical neural energy

• routed through brainstem to auditory cortex

auditory system structured to decode frequency, amplitude, complexity

• some mechanisms must locate sound waves in space

neural systems for sound production and analysis must be closely related

pinna

funnel-like external structure designed to catch sound waves in the surrounding environment and deflect them into ear canal

external ear canal

amplifies sound waves somewhat and directs them to eardrum, vibrates by the frequency of the sound wave

middle ear

air-filled chamber that comprises the ossicles

ossicles

bones in middle ear

• hammer

• anvil

• stirrup

connects eardrum to oval window of cochlea, located in inner ear

inner ear

cochlea

basilar membrane

hair cells

tectorial membrane

cochlea

fluid-filled inner ear structure that contains the auditory receptor cells

organ of corti: receptor cells and the cells that support them

basilar membrane

receptor surface in the cochlea that transduces sound waves to neural activity

hair cells

sensory neurons in the cochlea tipped by the cilia

tectorial membrane

membrane overlying hair cells

auditory receptors

transduction of sound waves to neural actvivity takes place in the hair cells

• 3500 inner hair cells (auditory receptors)

• 12,000 outer hair cells (alter stiffness of tectorial membrane)

movement of basilar membrane stimulates hair cells via bending and shearing action

movement of cilia on hair cells changes membrane potnetial and alters neurotransmitter release

animals with intact outer hair cells but No inner hair cells are deaf

outer hair cells function by sharpening cochlea’s resolving power, contracting or relaxing, changing tectorial membrane stiffness

movement of cilia toward tallest cilia depolarizes cell, calcium influx and release of neurotransmitters, stimulates cells that form auditory nerve

• nerve impulses increase

movement of cilia toward shortest cilia hyperpolarizzes cell, less neurotransmitter release

• activity in auditory neurons decreases

pathways to auditory cortex

inner hair cells synapse on bipolar cells that form auditory nerve (8th cranial nerve, hearing and balance)

• cochlear nerve axons enter brainstem at medulla and synapse in cochlear nucleus

cochlear nucleus projects to superior olive (nucleus in olivary complex) and trapezoid body

• projections from cochlear nucleus connect with cells on both sides of brain

cochlear nucleus and superior olive send projections to inferior colliculus in dorsal midbrain

inferior colliculus goes to medial geniculate nucleus (thalamus)

• ventral region of medial geniculate nucleus projects to primary auditory cortex, area A1

• dorsal region projects to auditory cortical regions adjacent to area A1

human auditory cortex

primary auditory cortex (A1) lies within Heschl’s gyrus, surrounded by secondary cortical areas

secondary cortex (planum temporale) lies behind Heschl’s gyrus

wernicke’s area

cortex of left planum forms speech zone

posterior speech area at the rear of left temporal lobe regulates language comprehension, also called posterior speech zone

heschl’s gyrus

cortex of larger right hemisphere has special role in analyzing music

lateralization

process whereby functions become localized primarily on one side of brain

• analysis of speech takes place in left hemisphere

• analysis of music takes place in right hemisphere

insula

located within lateral fissure; multifunctional cortical tissue containing regions related to language, perception of taste, neural strucutres underlying social congition

left handed people

70% - language in left hemisphere

remaining - speech either in right hemisphere or bilaterally

hearing pitch: tonotopic representation

reproduced in the cochlear nucleus

maintained throughout auditory pathways and into primary auditory cortex

similar tonotopic maps can be constructed for each level of auditory system

Broca’s area

anterior speech area in the left hemisphere that functions with the motor cortex to produce movements needed for speaking

positron emission tomography

imaging technique that detects changes in blood flow by measuring changes in uptake of compounds such as oxygen or glucose

Robert Zatorre and colegues

passively listening to noise bursts activates the primary audotry cortex

listening to words activates posterior speech area, wernicke’s area

making phonetic discrimination activates frontal region, Broca’s area

processing music

right hemisphere

left hemisphere plays some role, making music

• recognizing written music, playing instruments, and composing

Zattore and colleagues PET study

passively listening to noise bursts activates Heschl’s gyrus

perception of melody triggers major activation in the right-hemisphere auditory cortex lying in front of Heschl’s gyrus

making relative pitch judgements about two notes of each melody activates a right frontal lobe area

capacity for music is innate

birdsong

audition is as essential a sense to many animals as vision is to humans

• many nonhuman animals communicate with other members of their species by using sound

• birdsong functions

  • attracting mates, demarcating territories, and announcing locations

• whale songs

  • follow a distinct hierarchal structure

birdsong and language

song development in young birds is influenced not just by genes but also by early experience and learning

• gene-experience interactions are epigenetic mechanisms

  • brain areas that control signing in adult sparrows show altered gene expression in spring as the breeding and singing season begins

• diversity is apparent in sheer number of songs that some species possess

• song development is heavily influenced by experience during a critical period

both appear to be innate yet are shaped by experience

• if a young bird is not exposed to song until it is a juvenile and listens to recordings of birdsongs of various species, it shows general preference for its own species song

major structures bird song (neurobio)

higher vocal control center (HVC)

nucleus robustus archistriatalis (RA)

important characteristics of HVC and RA

asymmetry in some species

sexually dimorphic structures

size of birdsong-controlling nuclei related to singing skill

HVC and RA contain cells that produce birdsong and cells responsive to hearing song, especially the song of a bird’s species