A Distinct Sort of Auditory & Verbal Dysfunction
by Adel Olvera
There are different types of auditory and verbal
disorders. The auditory and verbal disorders that I will
be addressing are not be confused with speech disorders,
such as stuttering, or auditory dysfunctions, such as
deafness. I would like to emphasize disorders that deal
with recognition of spoken words and understanding of
their meaning, such as pure word deafness, word-meaning
deafness, and dysphasia. Before I discuss each disorder,
I would like to address Ellis and Young (1988) model for
recognition, comprehension, and repetition of spoken
words. They purpose that:
"The first stage of auditory word recognition
performed by an early auditory analysis system
attempts to identify phonemes in the speech
wave. The results of this analysis are
transmitted to the auditory input lexicon where
a match is sought against the stored
characteristics of known words."
If there is a match, it then proceeds to the
semantic system that activates the representation of the
meaning of the heard word. The information continues
its route to the speech output lexicon, which is a
storage for memory of the pronunciation of words. The
connection between the auditory input lexicon and the
semantic system is bi-directional. It allows "the
semantic system to exert an influence upon the level of
activity in the word-units which, in turn, provides a
mechanism whereby the semantic context in which a words
occurs can affect its ease of identification." (Ellis,
et. al., 1988) From the speech output lexicon it would
then go directly to the phoneme level (speech).
There are two other routes in this model, which are
also known as bypass routes. One in which a heard word
can go through the auditory analysis system directly to
the phoneme level. This route allows the passage of
nonwords. If "klijip" is identified as a non-word in the
auditory analysis system it can then be repeated at the
phoneme level. Second, if "toy" was identified as a
known word, then it's next step would be to go to the
auditory input lexicon. If no characteristics match in
the auditory input lexicon it would bypass the semantic
system, moving towards the speech output lexicon, where
there would be storage for its pronunciation. (Ellis, et.
al., 1988)
Howard and Franklin (1988) looked at Morton's view
of evidence for separate auditory input and phonological
output lexicons. At first Morton believed that there was
only one lexicon serving both recognition and production
of phonological and orthographic word forms. He later
revised his model after looking at other studies. His
revision separates the single lexicon into four separate
lexicons. The four separate lexicons are:
1. Auditory input lexicon: "used to recognize
familiar spoken words."
2. Orthographic input lexicon: "recognition
device for written words."
3. Phonological output lexicon: "the source
of a specification of the word's spoken form."
4. Graphemic output lexicon: "specifies its
written form." (Howard, et. al., 1988)
All 4 lexicons revolve around the cognitive system. The
cognitive system deals with specifying "word meanings as
well as knowledge about the concepts evolved." They then
added six systems (i.e.: "sub-word level auditory-to-
phonological conversion") "that allow conversions between
different input and output codes; because these processes
do not rely on word-specific whole word information they
are able to account for the normal person's ability to
perform processing tasks with nonwords." (Howard, et.
al., 1988)
Pure word deafness "involves impaired speech
perception in the context of good speech production,
reading, and writing and, importantly, intact perception
of non-verbal environmental sounds (Ellis, et. al.,
1988)." Patients with pure word deafness have difficulty
understanding what is said to them, yet what they can do
varies. Many of them can write well, with no major
grammatical or spelling errors. They can "read well with
understanding" and can distinguish "voices of different
people familiar" to them. A patient, reported by
Hemphill and Stengel in 1940, complained, "I can hear you
dead plain, but I cannot get what you say. The noises
are not quite natural. I can hear but not understand."
(Ellis, et. al, 1988)
Lesions in the temporal lobe of the left hemisphere
can cause pure word deafness, which is "half of the brain
which controls many language functions in the majority of
right-handed people. The left and right hemispheres
receive their most important auditory inputs from the
right and left ears respectively. (Ellis, et. al., 1988)"
Ellis's and Young's (1988) example of a right hemisphere
lesion is paragnosia, "in which patients are impaired at
recognizing individual voices while still being able to
recognize the words they are saying."
Ellis and Young (1988) fail to explain pure word
deafness according to their model of recognition and
understanding of spoken words. I assume that a patient
with pure word deafness hears the sounds of the word,
attempts to identify it's phoneme in the auditory
analysis system, finds no match in the auditory input
lexicon and bypasses the semantic system, causing him/her
to repeat it incorrectly. Since they are able to
pronounce what they read accurately their speech output
lexicon must be intact.
"Patients with pure word deafness cannot repeat
spoken words any better than they can understand them.
Patients with word meaning deafness in contrast can
repeat spoken words they still fail to understand (Ellis,
et. al., 1988)."
Word meaning deafness is considered an auditory word
recognition disorder. Patients with this disorder can
not understand spoken language spoken to them, but can
repeat what was said to them. In the case of the a young
woman in Scotland (Ellis, et. al., 1988), she was asked a
simple question and had no comprehension. She then
repeated it correctly but still had no comprehension of
what she said. She was then asked to write down what she
had heard. After reading her own dictation she
understood. Friedman and Kohn (Ellis, et. al., 1988)
established that a person must meet two conditions in
order to demonstrate word meaning deafness:
1. The word must have undergone adequate
acoustic analysis as evidence by correct
repetition.
2. The semantic representation of the word
must be intact as evidence by immediate
comprehension of the word when presented in
written form.
The problem must then lie between the auditory
input lexicon and the semantic system. Ellis states,
"word meaning deafness represents a complete or partial
disconnection of the auditory input lexicon from the
semantic system. If we were to try to explain word
meaning deafness according to Morton's model (Howard, et.
al., 1988) all four lexicons should function. The
dysfunction would lie between the auditory input lexicon
and the cognitive system. Though, there should be an
intact connection between the orthographic input lexicon
and the cognitive system, because the patients are able
to understand what was said only after writing the word
down.
Dysphasia evolves from a disorder called aphasia.
The difference between dysphasia and aphasia can be
unlimited, but it is difficult to distinguish between the
two. The definition by Darley, Aronson, and Brown (1975)
of an aphasic patient seems similar to that of a
dysphasic patient: "The aphasic patient is impaired in
comprehension, formulation, and expression of language.
His problem lies in the processing of the meaning bearing
units of language." This definition is so general that a
clearer definition is needed.
Emerick and Hatten (1979) better describe aphasia as
having:
"1. Disturbance in receiving and decoding
symbolic materials via auditory, visual, or
tactile channels. Although the individual can
still hear and see, he has difficulty
deciphering the learned associations of
messages.
2. Disturbance in central processes of meaning, word
selection, and message formulation.
3. Disturbance in expressing symbolic
materials by means of speech, writing or
gesture."
Emerick and Hatten (1979) then proceed to say that
not all aphasics are "totally impaired in the use of
language, and hence the term dysphasia may be more
appropriate." Though they insisted in referring to any
patient impaired in all three areas as aphasics. Ellis
and Young (1988) refer to this disorder as "deep
dysphasia". If a patient diagnosed with deep dysphasia
is asked to repeat the spoken word "truck", then he/she
should respond by saying, i.e.: "car". Ellis et. al. and
many others have proposed that this problem seems to
occur in the semantic system. "...Spoken words may only
be activating the approximate conceptual areas from which
the patient chooses a likely word." This would explain
why some patients are convinced he/she "repeated the
target word correctly" (Ellis, et. al., 1988).
Skinner and Shelton (1985) say that "aphasias are
usually caused by brain damage to the left cerebral
hemisphere where higher level language skills appear to
be localized in most humans," similar to that of pure
word deafness. Most of the patients studied by Lezak
(1976) had lesions in their dominant hemispheres. The
models discussed are still being contemplated; whether or
not the models coincide with the lesioned areas of
patients suffering with verbal and auditory disorders.
Schuell (1955) stated , "Impairment of any of the
cerebral systems essential to language processes is
usually reflected in more than one language modality;
conversely impairment of any modality often reflects
involvement of more than one process (Lezak, 1976)." The
reasons for why patients, with pure word deafness, word-
meaning deafness, and dysphasia, have difficulty with
recognizing spoken words and understanding their meanings
are still to be discovered in greater detail.
Reference Cited
Darley, F., Aronson, A., & Brown, J. (1975). Motor
Speech Disorders. London: W.B. Saunders Company.,
p.250-251.
Ellis, A. & Young, A. Human Cognitive Neuropsychology.
Hove: Lawrence Erlbaum Asso., Ltd., p. 144-160.
Emerick, L. & Hatten, J. (1979). Diagnosis and
Evaluation in Speech Pathology. New Jersey:
Prentice Hall, Inc., p. 265
Howard, D. & Franklin, S. (1988) Missing the Meaning.
Cambrige, Massachusetts: The MIT Press., p. 21,
117.
Lezak, M. (1976). Neuropsychological Assessment. New
York: Oxford University Press., p. 81, 26.
Skinner, P. & Shelton R. (Eds.). (1985). Speech,
Language, and Hearing. Canada: John Wiley & Sons,
p.111.
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