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

Pharyngeal nerveSuperior laryngeal

nerve

chief part

vagal accessory

Nucleusambiguus

Jugular foramen

Vagus (X) nerve

Pharyngeal nerve

Recurrent laryngeal nerve

Superior laryngealnerve

Vagus (X) nerve

Jugular foramen

Nucleus ambiguus

Cricothyroid muscle

Innervation of Intrinsic Laryngeal Muscles

Aryepiglottic muscle

Superior laryngeal nerve

Arytenoid muscleLateral cricoarytenoid

muscle

Posterior cricoarytenoid muscle

Recurrent laryngeal nerve

Thyroarytenoidmuscle

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.

Arytenoidcartilage

Cricoid Cartilage

Post.cricoarytenoidmuscle

Lateral Cricoarytenoid• 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.

Lateral cricoarytenoid muscle

Arytenoid cartilage

Cricoid cartilage

Cricothyroid• Draws thyroid and

cricoid cartilage's together.

• increases longitudinal tension & reduces thickness.

• Raises pitch.• Innervation: Pharyngeal

nerve & external superior laryngeal of the vagus.

Cricothyroid muscle

Thyroid cartilage

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. Thyroarytenoid

muscle

Thyroid cartilage

Interarytenoids

• 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.

Interarytenoidmuscles

Cricoidcartilage

Arytenoidcartilage

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– How coordination can be disturbed in individuals with speech &

voice disorders

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, positronemission 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

– Motor neuron pool= available motor resources or the reserve of motor neurons controlling individual muscles

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

• Movement of vocal folds

• Lowering the jaw

Motor Commands

• Studied using electromyography (EMG):

– Records electrical activity

– Electrode placed in muscle

• Microelectrodes

• Needle electrodes

• Surface 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– How is this constancy accomplished?

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

•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

Maxilla

Lips

Mandible

Soft Palate

Tongue

Hyoid Bone

Vertebrae

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

EPG Patterns for Selected English Consonants

s n

l

j r w

Reading

• Text-–Kent, R.: Chapter 8

•Pgs. 303-313