Articulation and Phonology Disorders 31Two types of neurological impairments can affect articulation: apraxia of speech and the
dysarthrias. Although both types often occur in aphasia, they are motor, not language, com-
munication disorders. In motor speech disorders, articulation, one of the five basic motor speech
pro cesses, can be impaired by the neurological damage.
Apraxia of speech primarily affects articulation and is a disorder of speech programming. The
articulatory plan, consisting of all of the articulatory movements necessary to produce an utter-
ance, is disrupted. Although it can affect voluntary movements of the lips and velum, the tongue is
primarily affected. The articulatory plan may be formulated in several areas of the brain, including
the anterior insula and lateral premotor cortex (Wise, Greene, Büchel, & Scott, 1999). In apraxia of
speech, this plan may be disrupted at the conceptual level, where the speaker is unable to discern
the idea or concept driving the speech act. The speaker is impaired or unable to articulate due to
ideational apraxia. Apraxia of speech may also impair articulation at the planning level, where the
tongue’s timing, speed, and strength are determined. Fi nally, apraxia of speech may disrupt the
activation of the neural commands to the muscles of the tongue.
The dysarthrias are neurogenic communication disorders arising from muscular paralysis
and/or an imbalance/deficiency of neurotransmitters. When the dysarthrias affect the articulatory
valve, the type of paralysis determines the effects on articulation. Lower motor neuron involve-
ment results in f laccid paralysis, in which the articulatory muscles have reduced tone. Unilateral
and bilateral upper motor neuron damage causes spastic articulatory muscles, with excessive tone
and limited excursions. Damage to the cerebellar system causes the articulatory muscles to be
jerky, ill coordinated, and inefficient in producing voluntary speech movements. The articulatory
errors in ataxic dysarthria are usually inconsistent. Disorders of the extrapyramidal motor system
affect articulation in two ways. First, hypokinesis causes rigidity, reduced range of articulatory
movement, diminished stress, and imprecise articulation. Second, hyperkinesis results in involun-
tary articulatory movements such as muscular tics and jerks. These movements result in interjec-
tions of grunts and other unwanted sounds during speech.
One way of determining whether a child has a communication disorder is to compare the
child’s chronological age with his or her mental age. (The other way is to look at the child’s func-
tional communication abilities in everyday interactions.) Chronological age is the number of years
and months the child has been alive. Mental age, also expressed in years and months, is a mea sure
of the child’s intelligence, or some other category of cognitive functioning and maturation, relative
to established age norms. When a child’s chronological age is significantly greater than his or her
mental age on some pa ram e ter of language competence or per for mance, the child is considered
to have language delay. Children who have phonological delay have not acquired the phonological
systems of their peers.
Children whose test scores indicate they have intellectual disability often have delayed phono-
logical development. For example, an individual with a tested mental age of 2 years, regardless of
chronological age, is likely to have the phoneme acquisition and phonological pro cess of a toddler.
There are exceptions because of the variability of acquisition rates (see earlier) and because some
children have unusually sophisticated fine motor development. However, as a rule, a child’s mental
age is indicative of his or her phonology acquisition potential.
There are etiological forms of stuttering, voice disorders, and deafness resulting from psy-
chological and emotional factors. They are well- established clinical entities and are usually based
on hysteria and conversion reactions. In these psychological phenomena, the physical disorder
originates in a psychological conf lict or repressed need. Often the physical disorder characterizes