Music and the Brain

Auditory Reactions and Processing

Sound Waves to Brain

• Tiny hairs inside the ear move in response to sound waves.
• The sound eventually reaches the auditory cortex, located in the superior temporal gyrus of the temporal lobe.
• The brain transforms acoustic energy patterns into elements of music.

Basic Elements of Music

• Melody: The overall tune.
• Tone/Chords: Specific sounds.
• Rhythm: The timing or speed of music.
• Pitch: Frequency of sound, distinguishing low versus high. (e.g., $low$ and $high$).

Evolution of Auditory Pathways

• Auditory pathways are evolutionarily old, inherited from animals.
• Developed for:
  • Source Identification: Determining the origin of a sound for survival (e.g., predator or prey).
  • Communication:
    • Mate selection.
    • Territoriality: Announcing territory through sounds (e.g., bird songs).
  • Auditory Object Segregation:
    • Detecting objects in their environment by bouncing sounds (e.g., frogs and crickets).
    • Sounds made by frogs or crickets bounce off of intruding objects and back to the frog or the cricket so they can hear if it bounces off.

Auditory Cortex

• Two auditory cortices (left and right hemispheres).
• Used for musical sounds and language.
• Heschel's Gyrus:
  • Primary auditory cortex.
  • Organized by frequency (low-pitched sounds in the front, high-pitched sounds in the rear).
  • Evolved primarily for language but is also used for musical interpretation.
  • People with perfect pitch have highly specialized sound interpretation in this area.

Auditory Pathway

• Sounds do not first go to the auditory cortex in the cortex. They first synapse on these nuclei.
• Sounds synapse on several nuclei before reaching the primary auditory cortex:
  • Cochlear Nuclei (in the brain stem).
  • Superior Olive (in the brain stem).
    • The right side of the cochlear nucleus feeds into the left superior olivary nucleus, and vice versa.
  • Inferior Colliculus (in the midbrain).
  • Medial Geniculate Nucleus (in the thalamus).
• These areas show that the auditory system is very old (evolved before the cortex).
• The fact that we inherited such a system shows that the sounds we hear are not trivial.

Music and Brain Damage: Amusia

• Studying patients with localized brain damage helps understand brain regions responsible for musical components.
• Amusia: Difficulties in processing music or musical elements.
  • Tone Deafness: Inability to distinguish tones due to left temporal lobe injury.
  • Melody Deafness: Inability to recognize melodies due to right temporal lobe injury.
    • Indicates functional specialization for elements of music in the brain.
• Aphasia: Language difficulties, but melody recognition can still be intact, showing a separation between language and music processing.

Hemispheric Specialization

• The right hemisphere specializes in:
  • Segregation.
  • Localization.
  • Timbre (recognizing instruments).
• The left hemisphere specializes in:
  • Timing.
  • Rhythm.
  • Melody naming.
  • Distinguishing among tones and naming them.
• Rhythm is linked to language processing in the left hemisphere.

Composers and Brain Damage

• Limited data on composers with unilateral hemispheric damage.
• Approximately seven established composers with localized left hemisphere damage. Strokes are more frequent in the left hemisphere due to heart conditions.
• Case of Mauricio Ravel:
  • Suffered from a slow, progressive neurodegenerative disease affecting both hemispheres.
  • Composed "Bolero" after disease onset - indicating multiple brain areas are involved in composing
    • Bolero is a slow song that takes forever

Brain Areas involved in composing

• Mental translation of musical concepts into writing musical notations: Left frontal lobe and posterior inferior parietal regions.
• Planning ahead of the progression of sound: Frontal lobes.
• Timing: Left temporal lobe.
• Composing is a rare ability.

Factors Influencing Musical Composition

• Status of Arms:
  • Composers wrote pieces based on the status of arms (for instance, crossing of hands in piano playing).
• Health Status of Hands:
  • Alexander Scriabin: Chronic pain in his right hand led to left-hand focused compositions.
• Physical Characteristics:
  • Niccolo Paganini: Exceptionally long, flexible fingers allowed unique violin compositions.
• Health Status of Hearing:
  • Beethoven: Composed extensively despite becoming completely deaf at age 44, including his famous ninth symphony.
  • Smetana: Deafness from Syphilis but still continued to compose.

Singing and the Brain

• Ability to sing can be preserved even with language difficulties.
• Anterior Temporal Lobectomy: Procedure to alleviate severe intractable epilepsy.
• Hemispherectomy (removal of an entire hemisphere):

Hemispheric Anesthetization (Sodium Amytal Procedure)

• Procedure involves injecting a drug into one of the carotid arteries to anesthetize one hemisphere.
• Findings:
  • Right hemisphere awake: Singing is good but not perfect.
  • Left hemisphere awake: Singing is monotone and incorrect pitch, but rhythm is unaffected.
  • Conclusion: Both hemispheres are needed for perfect singing.

Hemispherectomy

• Removal of an entire hemisphere (usually due to cancer).
• Example: A girl who had her left hemisphere removed at age nine lost speech but could still sing songs learned before surgery with lyrics.
• Could not learn new songs, indicating that both hemispheres are needed for learning new songs.