The Neurobiology of vocal learning

Question 1

Basic neuroanatomy

Answer 1

• central nervous system
• peripheral nervous system
• navigating around the brain
• the forebrain: cerebral cortex, basal ganglia, limbic system, thalamus
• the midbrain - taciturn, tegmentum
• the hindbrain - cerebellum, pons, medulla

Question 2

Cranial nerves

Answer 2

• are peripheral nerves that arise directly front he brain rather than from the spinal cord
• 12 pairs of cranial nerves (left and right)

Question 3

Neurobiology of vocal control

Answer 3

• neural mechanisms for vocal control are very conservative amongst mammals
• many shared mechanisms:musculature of larynx and vocal tract, nerves innervating these structures, higher-order neural control systems

Question 4

Brainstem

Answer 4

• motor (cranial) nerves that innervate the face, tongue, larynx and respiratory muscles
• destruction leads to paralysis
• main function is breathing and eating
• damage leads to problems swallowing and breathing as well as speech problems

Question 5

Midbrain

Answer 5

• contains core region for vocal control, the peri-aqueductal grey (PAG)
• electrical stimulation of PAG induces automatic vocalisations
• PAG alone is not enough for cats and monkeys, no essential cortical connections required

Question 6

Medial cortical system

Answer 6

• older evolutionarily
• widely shared
• electrical stimulation induces vocalisations
• lesions lead to mutisms
• in humans, control speech and laughter

Question 7

Lateral cortical system

Answer 7

• evolutionarily newer system
• contains Broca’s area
• humans possess direct connections between frontal motor areas
• damage induces voice loss in humans but not other mammals

Question 8

The two cortical control regions

Answer 8

• distinct in humans
• double-dissosiation in song and emotional vocalisations
• Broca’s area lesion - often can still swear and sing
• suggested that the linguistic system has partially colonised the lateral circuitry involved in emotional expression

Question 9

Kuypers/ Jurgens hypothesis

Answer 9

• direct cortico-laryngeal connections underlie superior huma vocal control
• only human primates have direct connections to the laryngeal motor neurone that contralto he muscles of the larynx
• these neurones lie very close to the Broca’s area
• other mammals only have indirect connections between the larynx and the cortex
• Fitch suggests that human’s vocal control is due not so much to the vocal tract but to the larynx control

Question 10

Jarvis (2006)

Answer 10

COMPARATIVE APPROACH

• only vocal learners have brain regions in their cerebellums that control the acoustic output structure of their vocalisations
• non-learners only have regions in mid brain and medulla to control vocalisations
• anterior cingulate cortex in mammals control the motivations to vocalise innate sounds, but not acoustic structure of sounds

Question 11

Birds have seven comparable nuclei

Answer 11

1. four posterior (back) nuclei: HVC, RA, DM, nXllts

2. three anterior (front) nuclei: MAN, AreaX, DLM