Includes the following articles: (1) Hearing with Both
Hemispheres of the Brain (2) The Right/Left Hemisphere
Concept and Human Auditory PerceptionQuestions may be
submitted online to the "contact us" section of this
website or sent directly to: DigiCare Hearing Research &
Rehabilitation, P.O. Box 706, Rye, CO 81069, or faxed to
(719) 66-6882. Your name, address, and telephone number
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a reply from the Digicare team.
"HEARING WITH BOTH HEMISPHERES OF THE BRAIN"
By Max Stanley Chartrand, Director of Research
Human hearing, language perception, and hemispheric
function share an intricately entwined relationship.
Understanding this relationship is crucial to a properly
developed aural rehabilitation program.
From a perceptive standpoint, the ”learning process” of
language (or the symbols we come to know as language)
becomes markedly lateralized or specialized to various
and specific parts of the brain where the information is
processed and responded to. In other words, language
comprehension is actually composed of essentially two
different “mental viewpoints,” verbal and non-verbal.
The verbal viewpoint is primarily processed in the left
hemisphere of the temporal lobe in humans as evidenced
by the physical location of Wernicke’s area where
language communication is expressed.(1) Both of these
vital language processing areas reside in the left
hemisphere.
The left hemisphere, therefore involves mainly abstract,
logical, and technical interpretation of language, the
“what and whereof.”(2) Since the right ear primarily
lateratlizes to the left hemisphere, we often refer to
the phenomena of better speech utilization and retention
in the right ear as the right ear advantage.(3) The
right ear advantage aspect is particularly important in
the rehabilitative process, in terms of fitting
parameters and other considerations such as monaural vs.
binaural applications.
The right hemisphere, via the left ear primarily,
performs a different, yet vitally important, function in
speech communication, albeit more subtly. From the right
hemisphere, humans obtain spatial, holistic, contextual,
and aesthetic interpretation of speech, The “non-verbal”
meaning of communication.(4) The right hemisphere is
then more attuned to the emotions and is able to “read
into” language communication how a message was meant to
be received, not getting lost in the logic (or lack of
logic) of it all.(5) This ability, being the strong suit
of the female of our species, is often referred to as
“intuition.”(6) In actuality, it appears to be more an
innate ability to listen with both sides of the
brain.(7) (Remember the larger corpus callosum in
females?)
MENTAL TUG-OF-WAR
Another way to look at interrelationship of the two
hemispheres is: To be verbally debating Einstein’s
Theory of Relativity vs. Newtonian Physical Laws in
one’s left hemisphere, while hanging by fingertips onto
the edge of a sheer cliff, would come across as rather
odd to the right side of the brain which keeps and eye
out for the “big picture” of events around us. Taking
into consideration the “context” of the situation, the
right (holistic) side of the brain then forces the left
(abstract) side to take a momentary backseat while it
sizes up the situation.
The right hemisphere, once its wits are collected, may
“dole out” portions of the problem to be solved by the
left hemisphere. As the adrenaline and the other
powerful “fight or flight” reactions come rushing to the
rescue, however, the right brain will (in most cases) be
fully in charge during the crisis! Once safely back upon
solid terra firma, then the left side of the brain tends
to take charge in taking remedial action to the (now
past)crisis.
A more anecdotal illustration of the right/left brain
relationship was humorously stated by Williams (8):
“The hemispheres do not ignore each other or act
independently, like the fictional Dr. Jekyll and Mr.
Hyde. Our strong left brain doesn’t drag our weaker
right brain around by his gray matter – it wouldn’t dare
– the right brain would kick the heck out of him while
he’s sleeping. No, our hemispheres, although they are
functionally biased, work together through many inner
cerebral roads and connections. Each plays a special
part in the reception, selection and perception of the
uncountable stimuli that bombards us each millisecond of
our lives. Life without one hemisphere, or without full
function of the other, would be hazardous and dull
indeed, and we would miss a lot of incoming stimuli.
Now, can you think of a better argument for wearing
hearing aids on both ears?”
IMPORTANCE OF BINAURAL HEARING AIDS
Since much of the acoustic information to the right
hemisphere of the human brain is encoded and supplied
form the left (contralateral) ear, we certainly cannot
discount the importance of information from that ear.
Together, the normal function of the right and left
ears, primarily contralateral to the opposing brain
hemispheres, are needed for normal development of verbal
and non-verbal language communication. Hence, the most
successful rehabilitation program in bilateral hearing
loss, at the most symbolic level of hearing, would
depend significantly upon binaural correction of the
defective system.
Other binaural auditory functions, such as binaural
summation, binaural squelch, binaural integration,
spatial mapping and localization are also vital
bi-hemispheric functions.(9) However, these auditory
skills do not come genetically, but are developed
through time exposure and maturation in the ongoing
process of hearing, listening and communicating. In
short, these are learned skills.
For instance, as an adjunct skill to developing language
communication ability, it is often not until the age of
six or seven years that most normally developing
children acquire sufficient attention and auditory
focusing skills to function well in challenging
listening situations such as in classroom settings.(10)
The ability to direct attention and to screen-out
unrelated or unneeded sounds (or speech-in-noise
ability) is developed as a result of continuous
bilateral exposure to the aural environment.
Likewise, deprivation of hearing acuity (after language
is attained) may cause a temporary central auditory
processing condition called phonemic regression.(11)
Phonemic regression is a speech understanding problem
that is either out of proportion to the degree of
hearing loss, or which persists for a period of time
after amplification is first applied.(12) Resolution of
this condition is dependent upon a carefully structured
“wearing schedule” for the new hearing instrument user,
whereas it may require up to 12 weeks of acclimatization
to the new acoustic signal before optimum speech
understanding is realized.”(13)
CONCLUSION
Components of complete auditory communication involve
both verbal and non-verbal viewpoints, which, in the
binaural format, are manifest by specialization of each
hemisphere via its contralateral ear. So, not only are
we looking at time and spectral differences by virtue of
dichotic listening., but also interpretative and
conceptual differences as well. This is probably the
most persuasive argument for binaural amplification
correction in cases of bilateral hearing loss.
Human hearing, language perception, and hemispheric
function share an intricately entwined relationship. A
better understanding of this relationship is crucial to
a properly developed aural rehabilitation program. By
utilization of this concept, patients understand the
importance of maintaining optimum hearing health and its
indispensable connection to more effective language
communication and meaningful social interaction.
REFERENCES
1. Graham R: Physiological Psychology, Belmont, CA:
Wadsworth Publishing Co., 1990
2. Chartrand M: Hearing Instrument Counseling; Practical
Applications for Counseling the Hearing Impaired,
Livonia, MI. National Institute for Instruments Studies,
1990.
3. Hellige J: Hemispheric Asymmetry: What’s Right and
What’s Left. Cambridge, MA University Press, 1993:
285-293.
4. Springer S and Duetsch G: Left Brain, Right Brain.
New York, WH Freeman and Co., 1989.
5. Ley R and Bryden M: Hemispheric Differences in
Recognizing Faces and Emotions, Brain and Languages
1979; 7:127-138.
6. Johnson G: Machinery of the Mind, Redmon, WA, Tempura
Books, 1986:254-56.
7. Pool R: Eve’s Rib: Searching for the Biological Roots
of Sex Differences, New York, Crown Publishers, 1994.
8. Williams H: Thinking about our thinkers. Hear Instum,
1993; 44:4, 50.
9. Libby R: In Search of the Two-Eared Man, Binaural
Hear and Amp, Vol 1, E. Robert Libby, editor. Chicago,
Zenetron, Inc, 1980: 1- 36.
10. Phillips P: Speech and Hearing Problems in the
Classroom. Lincoln, NE, Cliff Notes, 1975.
11. Delk J: Comprehensive Dictionary of Audiology,
Maynard, MA, Laux Co. 1991.
12. Palmer C: Deprivation, Acclimatization, Adaption:
What Do They Mean For Your Hearing Aid Fittings?. Hear J
1995; 47(5): 10, 41-45.
13. Gatehouse S and Killion M: HABRAT: Hearing Aid Brain
Rewiring Accommodation Time, Hear Instrum 1993; 44(10):
29-32.
"THE RIGHT/LEFT HEMISPHERE CONCEPTS & HUMAN AUDITORY
PERCEPTION"
By Max Stanley Chartrand, Ph.D.
One of the most persuasive arguments for the validity,
indeed, the necessity, of binaural hearing aid fittings
lies in how humans use the two hemispheres of the brain.
Within this context we find process specialization in
the various symbols of language to form whole
communication.
Many years ago this author attended a course on
rehabilitative speech pathology where a most amazing
“theory” was being presented. It was proposed that the
left hemisphere provided the technical backdrop in
psychological processing of communication, while the
right hemisphere provided the aesthetic mode. It was
then hypothesized that the two hemispheres together
provide the brain with an enormous capacity for
cognizance of the aesthetic qualities of life while
simultaneously interpreting abstract “meaning”. Since
that long ago hypothesis, virtually thousands of studies
have proven the validity of such speculation.
Hence, we will cite only a few of those, along with
their powerful implications that binaural hearing is
much more preferable to monaural. In the fields of
psychology (Corvallis and Beale, 1976), art (Arnheim,
1954), music (Critchley, 1977), education (Bruner,
1962), speech (Paivio, 1971), and others this principle
has long been a major consideration in matters of
curriculum and therapy. Aspiring artists (Arguelles,
1975) have long trained in the concept that they can
intentionally develop cognitive shifts in their artistic
skills. A cognitive shift is described as the ability to
transform from one mental state to another, e.g., from
L-mode to R-mode, or vice versa. In this way one could
develop both abstract and expressive abilities in their
artwork.
Bi-hemispheric principles adapted from the psychology
field are particularly useful in the area of auditory
rehabilitation. In the literature we find that the
language-mediation areas of the superior temporal lobes
of the human brain are significantly larger on the left
side than on the right (Gerchwind and Levitsky,
1968)(Witelson and Pallie, 1973). This would make
improvements in speech discrimination more critical for
the right ear, which lateralizes primarily to the left
hemisphere. This concept provides neurophysiological
credence to the long-held “right ear advantage” (Hellige,
1993). The left ear, favoring the right hemisphere, on
the other hand fulfills a more holistic, aesthetic
purpose in its perception of auditory stimulus (Ley and
Bryden, 1979).
Furthermore, while the differences in processing general
sensory information between the two hemispheres of the
brain are often small, there are astonishing differences
in perceiving music and speech/language communication
(von Bonin, 1962). This and other research would
indicate that communication, especially language---both
expressive and receptive---dominates in the left brain,
received primarily by the right ear. The left ear,
therefore, would provide mostly emotional and conceptual
interpretation, an important component of intimate
communication and in bonding in human relationships.
In the hearing health field, there are numerous examples
that might be applied as evidence of this principle in
action Fig. 1). In other words, the right ear (left
brain) tells us what another person is saying. Is the
message logical? Is the syntax and grammar correct? What
is the “abstract” meaning of the message?
Likewise, the left ear may receive information helping
one to perceive how another means what they are saying.
Are they being cheerful? Sad? Sarcastic? Sincere?
Deceitful? The left ear (e.g., right brain) is more
likely to know the answer to those questions. Some might
describe the information discerned by the left ear
(right brain) as “intuition.” Actually, this
information---often described as “non-verbal” is an
essential part of human communication, relying more upon
voice stress, inflection, and psychosocial elements (Chartrand,
1999).
By combining both hemispheric interpretations of a
single communication, or several connected symbolic
subsets, we are capable of extracting significantly
greater meaning out of everyday communication. Whereas,
written communication can only convey essentially
abstract communication, verbal communication brings
immensely enhanced meaning to human communication.
These observations are particularly helpful in helping
prospective hearing aid patients who may not yet
appreciate or understand advantages of binaural hearing.
For instance, after explaining the two separate
functions of the ears, hearing professionals might ask,
“Which is more important to you, to understand what a
person says to you, or how they mean it?” Of course, put
this way, any rational person would insist on binaural
hearing. Hence, we have a reasoned and persuasive
approach to justify the recommendation for binaural
hearing aids, any subsequent contraindications
notwithstanding.
Another application of the right/left concept: If one
were to go to an orchestra concert, they would notice
that the passage being listened to is, say, a Mozart
Concerto, with a solo by the cello. The woodwinds and
brass instruments provide the chordal background to the
melody, while the tympani is quietly and gradually
building in tempo and dynamic variations.
Emotional aspects of the music are being discerned via
the right ear (toward the left hemisphere of the brain).
We relax, allowing memories and imagination roam freely;
emotions stirring with growing excitement and
anticipation.
Technical aspects, such as form and analysis of the
musical opus itself, including the realization that the
violins carry the lead, supported in 6ths from the
violas with the underlying fundamentals played by the
bass violin section are all functions performed
primarily through the right ear (toward the right
hemisphere).
The combination of interpretations-from both
hemispheres-allow us to enjoy the beauty and sparkle of
music and the more abstract details of its writing,
conduction, and performance. Without both messages,
music loses more than half of its potential appeal. The
same logic, therefore, may also carry over into human
communication.
There are exceptions, of course, to recommending
binaural correction in cases of bilateral deficits,
though most of these can only be determined clinically,
and rarely through the usual audiometric battery. Such
exceptions would include Meniere’s cases, post-stroke
aphasia, hemiplegia, apraxia, and chemical/acoustic
trauma of the cochlea.
Further, it should be noted that the right/left concept
is not a cut and dried process, for though most
neurological innervation of the central auditory system
routes information contralaterally, a good deal of
information is still routed ipsilaterally. However, the
interpretive areas of the brain are still “wired” for
specialization, while dichotic (two-eared hearing)
comprises the normal human sensory configuration.
REFERENCES
Arnheim, 1954
Arguelles, 1975
Bruner, 1962
Chartrand, M.S., 1993
Corvallis and Beale, 1976
Critchley, 1977
Gerchwind and Levitsky, 1968
Hellige, 1993
Ley and Bryden, 1979
Paivio, 1971
von Bonin, 1962
Witelson and Pallie, 1973 |
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