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Neural Control of Phonation:
Peripheral Nervous System
3/2/00
Peripheral Nervous Sysytem
• Part of nervous system outside the bony
confines of the skull & vertebral column
– 12 pair of cranial nerves & ganglia (Roman
numerals I-XII)
– Dorsal and ventral roots of the spinal nerves
– 31 pairs of spinal nerves & their dorsal root
ganglia
Peripheral Nervous System
Cranial Nerves
• Peripheral nerves of the head
• Nuclei (center) in the brain stem
• Foramina in the base of the skull
Cranial Nerves vs. Spinal Nerves
• Same origin- Brainstem
• Differ because:
– Not all cranial nerves are mixed like spinal
– No dorsal or ventral roots or rami
– Not every nerve has a ganglion
Functional Anatomy of the PNS
• Efferent (or motor) neurons- Carry
impulses away from CNS
• Afferent (or sensory) neurons- Carry
impulses toward the CNS
• Mixed neurons- Nerve containing both
efferent and afferent fibers
• **Some cranial nerves are exclusively
sensory or motor in function.
Phonation: The Vagus Nerve (CN X)
• Extensive distribution through the neck & thorax
extending down to abdomen
• Controls all intrinsic laryngeal muscles
• Branches:
– Pharyngeal - supply muscles & mucous membranes of the
pharynx & soft palate
– Superior laryngeal• External (motor): CT & inferior constrictor
• Internal (sensory): mucous membrane of tongue base & supraglottal
portion
– Recurrent laryngeal- supplies all intrinsic laryngeal muscles
except CT
Distribution of the vagus (X) nerve
Nucleus ambiguus
chief part
Pharyngeal
nerve
Nucleus
ambiguus
vagal
Vagus
(X) nerve
accessory
Jugular foramen
Vagus (X) nerve
Superior laryngeal
Pharyngeal
nerve
nervelaryngeal
Superior
nerve
Jugular foramen
Recurrent laryngeal nerve
Cricothyroid
muscle
Innervation of Intrinsic Laryngeal
Muscles
Aryepiglottic muscle
Superior laryngeal
nerve
Arytenoid muscle
Lateral cricoarytenoid
muscle
Posterior
cricoarytenoid
muscle
Recurrent laryngeal
nerve
Thyroarytenoi
d
muscle
Recurrent Laryngeal
• Courses along the laryngeal branch of
the inferior thyroid artery.
• It passes under the caudal border of the
inferior constrictor muscle.
• Divides into a motor & sensory branch
prior to entry into larynx.
• Innervates the int. muscles that control
abduction/adduction of the vocal folds
Superior Laryngeal
• Innervate the nerves capable of
changing pitch of the voice.
• Controls length-tension relation of
the vocal folds.
Posterior Cricoarytenoid
• Rocks arytenoid
cartilage posteriorly
& laterally.
• Sole abductor of the
vocal folds.
• Recurrent laryngeal
nerve innervates
posterior surface.
• 1957- innervation
ratio of 116 muscle
fibers per motor
neuron in this
muscle.
Arytenoid
cartilage
Post.
cricoarytenoid
muscle
Cricoid Cartilage
Lateral Cricoarytenoid
Arytenoid cartilage
Lateral
cricoarytenoid
muscle
Cricoid cartilage
• Capable of rocking
arytenoid cartilage
forward.
• Adduct the vocal folds.
• Hirano-1981, muscle
activity during pitch
change.
• Innervation from inferior
branch of the recurrent
laryngeal nerve of vagus
nerve.
• Evidence of innervation by
the caudal portion of the
internal branch of the
superior laryngeal nerve.
Cricothyroid
• Draws thyroid and
cricoid cartilage's
together.
• increases longitudinal
tension & reduces
thickness.
• Raises pitch.
• Innervation: Pharyngeal
nerve & external
superior laryngeal of the
vagus.
Thyroid cartilage
Cricothyroid muscle
Cricoid cartilage
Thyroarytenoid
• Complex muscle forming
the bulk of the vocal
folds.
• fibers coursing
longitudinally are the
vocalis muscle.
• Motor innervation
supplied by a portion of
the inferior branch of the
recurrent laryngeal
nerve.
• This nerve is derived
from the internal branch
of the superior laryngeal
nerve.
Thyroid
cartilage
Thyroarytenoid
muscle
Interarytenoids
Interarytenoid
muscles
Cricoid
cartilage
Arytenoid
cartilage
• Transverse & oblique
interarytenoids adduct the
vocal folds.
• Share motor innervation
from inferior branch of the
recurrent laryngeal nerve of
the vagus nerve.
• Portion of the innervation
may be derived from caudal
offset of internal branch of
superior laryngeal nerve.
• Transverse interarytenoids
might receive visceral motor
fibers from internal branch
of superior laryngeal nerve.
Vagus lesions: What can go wrong?
• Paralysis of soft palate (nasality)
• Swallowing problems
• Deviation of the uvula
• Voice problems (aphonia, breathiness,
unilateral muscle paresis)
References:
• Colton, R.H. & Casper, J.K.,(1990), Understanding
Voice Problems: A physiological perspective for
diagnosis and treatment,, Williams & Wilkins.
• Bhatnager, S.C. & Andy, O.J., (1995), Neuroscience for
the study of communicative disorders, Williams &
Wilkins.
• Kuehn, D.P., Lemme, M.L. & Baumgartner, J.M.,
(1989), Neural basis of speech, hearing, and language,
College- Hill Press.
• Lieberman, M., (1991), Neuroanatomy made easy and
understandable, Aspen Publishers.
• Netsell, R., (1985), Speech and language evaluation in
neurology-adult disorders, Grune & Stratton.
• Poritsky, R., (1992), Neuroanatomy: a functional atlas
of parts & pathways, Mosby-Year Book.
Physiological Phonetics
Speech Physiology
• Speech physiology addresses the
concrete physical processes by
which speech is formed.
– Speech is movement?
– Study speech movements?
Questions?
• 1. What is the unit of speech?
• Must be able to record & analyze
• Movement patterns of: respiratory, laryngeal & supralaryngeal
subsystems
– Their organization may illustrate the units of control
• 2. How are the various components of speech
production coordinated to produce fluent
speech?
– Investigation how muscles or movements are
coordinated in the typical speaker
– How a child learns this coordination
Questions?
• 3. Given that speech is produced by
means of aerodynamic forces, how are
aerodynamic variables such as volume,
pressure & flow used to study speech
production?
• To answer questions, a number of
methods have been developed to study
speech physiology.
Methods of Speech Physiology
Levels of observation in the study of speech
Level of Observation
Techniques
Neural
Brain imaging methods:
electroencephalography (EEG),
evoked potentials, positron
emission tomography (PET),
magnetic resonance imaging
(MRI).
Motor
Electromyography (EMG)
Structural Movement
Strain gauges, panendoscopy,
photoelectric &optical methods,
X-ray (videofluoroscopy,
ultrasonography, palatography
Aerodynamic events
Airflow, air pressure,
air volume
Neural Impulses
• Neural impulses are transmitted to
muscles
– Neural instructions to the musculature= motor
commands
– Pathway for phonation:
• Transmitted along the corticobulbar pathway of the
pyramidal motor system
• Neural instructions from cortical-sub cortical neural
circuits are issued to the motor nuclei of the cranial
nerves
Neural Impulses
• It is difficult to record the actual neural
signals prepared in the brain and sent to
muscles of speech
• Brain imaging permits us to look at brain
activity during speech production &
perception
– PET, EEG, FMRI
Motor Commands
• Motor commands result in sequences of
muscle contractions in the respiratory,
laryngeal and upper airway systems of
speech production
– Contraction of muscle= cumulation of the
contraction of many motor units
– Muscle contraction result in forces that create
structural movement
• Displacement of diaphragm
Motor Commands
• Studied using electromyography
(EMG):
– Records electrical activity
– Electrode placed in muscle
• Microelectrodes
• Needle electrodes
Structural Movements
• Several types:
– Jaw or lip (visible)
– Vocal fold or tongue (not visible)
• Kinesiology:
– Study of movement
• Determination of timing patterns between speech
movements
– How are magnitude & speed regulated
• Stop-to-vowel sequence= 50 ms
– Constancy of transition duration is maintained across
articulatory movements
Structural Movements
•Specific Techniques:
–Strain Gauges•Thin strips of piezoelectric material bonded to a support plate
•Produce differential electrical signals when plate is deformed by external
forces
•Used to study lip & jaw movement
Structural Movements
• Oral Panendoscope– Permits visualization of internal structures
by means of an optical viewing system
such as fiberoptics
• Visualize pattern of velopharyngeal closure
• No radiation
• View interior of oral & pharyngeal cavities
Structural Movements
• Photoelectric or Optical Tracking– Used to study speech movements
– A light emitting diode attaches to
structure to be studied
– A receiver is used to record the motion of
the light
– Especially good for lip & jaw movement
Structural Movements
Soft Palate
Maxilla
Lips
Vertebrae
Tongue
Mandible
Hyoid Bone
•X-Ray (Fluoroscopy)–Employ ionizing radiation to obtain images of internal structures
–Lateral image of the vocal tract (still X-rays)
–Videofluoroscopy- Motion picture or video record of speech
Structural Movements
• Palatography or Electropalatography
(EPG)– Record articulatory contacts
– Uses a pseudopalate that is embedded
with tiny electrodes
– When the speaker touches the tongue to
the pseudopalate, the electrodes record the
region of contact
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EPG Patterns for Selected English Consonants
Reading
• Text–Kent, R.: Chapter 8
• Pgs. 303-313