[Smt-talk] Audio disability question

Sun Oct 5 12:56:20 PDT 2014

Amy,

I get the sense you're most interested in practical evidence, but I found
myself intrigued with your question and thought I'd send you some slightly
more theoretical thoughts. In short, I would say that while differences can
be found in processing styles found in the left and right hemispheres
(specifically for auditory processing), the differences are not
black-and-white. I've grouped these thoughts into anatomical
considerations, neuropsychological considerations, and music-specific
neuro-cognitive considerations.

I suppose I should mention that I'm not an MD, so anything that piques your
interest you should verify with someone who is.

*Anatomical Considerations*
One thing you mention having read is that "we use our left ears almost
exclusively for" the purpose of "reproducing and recognizing pitch height."
I don't have proof that this isn't true, but I personally would shy away
from accepting it without further investigation (and I'd love to take a
look at the article you mention). It is clear that, if you look at neural
pathways from each ear to each side of the brain, you will find a favoring
for contralateral information flow: i.e., a slight tendency for sounds
coming in through the left ear to be processed by the right side of the
brain, and vice versa. I say "favoring" and "slight," however, since the
percentage ratio is not 100%-0% (as it is for vision), but is more like
60%-40% (at least to the best of my knowledge). There is, in addition, a
significant amount of "cross-talk" across the hemispheres, at brainstem
levels and via the corpus callosum in the neocortex. If you take a look at this
figure
<http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/figures/3035F10.gif>,
which traces the path of information flow from the left cochlea up the
brainstem to the auditory cortex, you can see that most of the connections
go to the contralateral side but that some do stay on the ipsilateral side.
Thus, in theory at least, sound entering the right ear should be processed
at least somewhat in the right auditory cortex.

It is worth noting that if your student is "deaf in her left ear," the
deafness could conceivably be the result of damage at any one of these
multiple points—ear drum, cochlea, auditory nerve, cochlear nucleus,
inferior colliculus, auditory cortex, etc. It might be worth a visit to a
neurologist or otolaryngologist to determine where origin of the deficit
is. That visit could give you some clues on how to deal with her musical
issues.

*Neuropsychological **Considerations*
There is much debate regarding how music-specific the right hemisphere is,
and how speech-specific the left hemisphere is. It seems that most
researchers agree with a hypothesis advanced by Robert Zatorre and
colleagues in around 2002 <http://www.ncbi.nlm.nih.gov/pubmed/11849614>
(dating at least back to Penhune et al. 1996
<http://www.ncbi.nlm.nih.gov/pubmed/8921202>) that the left hemisphere is
not specialized for the processing speech *per se*, but rather is
specialized for the processing of *rapid information flow*. Music *can* be
fast, but speech virtually *always is*. Similarly, distinctions in speech
tend to be simple binaries, such as "was that /b/ or /p/?" The left side of
the (auditory) brain thus appears to be specialized for *rapidly resolving
yes-no binaries*, the right for indulging in the contemplation of spectral
complexity. There is anatomical support for this as well: the left Heschl's
gyrus (primary auditory cortex) has more white matter than gray, relative
to the right HG—white matter translating to more myelination and hence
faster transmission in neurons, but fewer neurons altogether. A recent
study from Stefan Koelsch's lab
<http://www.pnas.org/content/107/10/4758.short> reports that music-specific
processing is biased toward the right hemisphere as early as a few hours
after birth.

>From the above it should be clear that there's a general acknowledgement in
the scientific community that the right and left sides of the brain (at
least auditory cortices) do have different *processing styles*.
Nevertheless, this does not translate directly to speech-perception on the
left and music-perception on the right. In primates as well as humans, regions
in *both* the right and left sides of the brain
<http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3398142/> are specially
sensitive to the vocal sounds of conspecifics. We process both speech and
music simultaneously along *multiple parallel channels*, some subserved
more by left-side networks, some more by right-side networks. Moreover,
there's significant redundancy, such that whenever a right-side region
shows activation for a given task, at least some activation (if less) is
seen on the left as well. I don't have a paper I can cite on this, but
that's my sense from my familiarity with the literature.

In sum, the right and left auditory cortices do seem to have different
strengths, and hence different processing styles. But there's redundancy as
well, with right side activations tending to be mirrored by left-side
activations as well. The right and left auditory cortices are probably
better thought to differ in *degree rather than in kind. *

*Musico-Neurological **Considerations*
You wrote specifically with concerns about your student's ability to
"reproduce and recognize pitch height." In neuroscience, this faculty has
been broken up into two sub-faculties—assessing height generally, and
assessing membership in a pitch class or scale degree. The former, in the
neuroscience literature, is called *height*, the latter *chroma*. E.g., C4
and C5 differ in height but not in chroma.

Assessment of pitch height has been found to be a product of activity in a
region just *posterior* to primary auditory cortex (on both sides of the
brain), called the *planum polare* (PP). Assessment of pitch chroma has
been found to be a product of activity in a region just *anterior* to
primary auditory cortex, called the *planum temporale* (PT).

My guess is that pitch chroma identification is the issue your student is
having the most trouble with, and thus that there might be an issue either
with the functioning of the PT or with getting information *to* the PT. I
also would not at all be surprised if the right-side PT were more important
for this task than the left-side PT, and this could explain why your
student's left-ear deafness might be an issue. *But*... I don't see any
evidence for the right-side PT being more integral to this task than the
left-side PT. Warren et al. (2003)
<http://www.pnas.org/content/100/17/10038.short> were the first (to my
knowledge) to dissociate the functioning of PT and PP, and to attribute
chroma identification to PP.  In their paper, I don't see a significantly
stronger involvement of the right PT than the left PT (but I may be missing
something). You might consider sending them a note and seeing what they
have to say about this. I also looked for more recent evidence about PP and
pitch chroma but didn't turn up much (at least nothing that challenges the
original theory or says anything new about lateralization). Here's a more
up-to-date review <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3098378/> of
the the literature on the neurology of pitch perception generally, however,
and these authors do indicate that many aspects of pitch perception are
straightforwardly lateralized to the right hemisphere predominantly. I
think a close read of that article could turn up some new leads.

Here's my summary.

1) I would say the neurology of the situation is relevant. I think it's
great that your student showed you that study (please send it to me by the
way!), and I also think any problem solving you continue to do can be
usefully informed by understanding the neuroscience underlying pitch
perception, chroma identification, and the connections between auditory
cortex and the ears. As I said, I'm not an MD, but I'm more than happy to
keep exchanging thoughts and be available for idea-bouncing-off.

2) I think a neurological and/or otolaryngological assessment would be a
good investment in the student's musical future, given that it might help
diagnose the problem better, and thus help you guide her education better.

3) Brian Wilson was deaf in one ear—his right—and seems to have had no
problem understanding speech. Reciprocally, I would be somewhat surprised
if deafness in the left ear *necessarily* meant difficulty resolving and
reproducing pitch. But it is clear that the right brain has some privileged
involvement in music cognition, and the right brain gets its input
predominantly (but not exclusively) from the left ear. All of this just
means that a medical exam would be worthwhile. If you get one, let me know,
and I'll try to help sort out further issues.

I hope this helps!

David

On Thu, Oct 2, 2014 at 2:34 PM, Amy Bauer <abauer at uci.edu> wrote:

>  Dear colleagues,
>
> We have a very hard-working, gifted young pianist who cannot pass her
> aural skills sequence. She has bronchial pulmonary dispasia (which affects
> her ability to sight-sing). But her primary issue is almost total deafness
> in her left ear. She struggled for a long while to understand why she had
> absolutely no problems with speech or understanding speech, but had
> difficulty reproducing and recognizing pitch height. According to a recent
> research paper she shared with me, we use our left ears almost exclusively
> for that purpose, while using the right ear to decipher speech and
> syntactical relationships.
>
> Has anyone dealt with a similar situation, or has anyone dealt with a
> situation where a student simply could not complete their aural skills
> requirement for medical reasons?
>
> Thank you very much for any replies.
> --
>
> Amy Bauer
> Associate Professor of Music Theory
> 3043 Contemporary Arts Center
> Claire Trevor School of the Arts
> University of California, Irvine
> Irvine, CA 92697-2775
>
>  Tel: 949-824-6615
> Fax: 949-824-4914
> e-mail: abauer at uci.ed
> Department website <http://music.arts.uci.edu/content/amy-bauer>
> Ligeti's Laments: Nostalgia, Exoticism and the Absolute
> <http://www.ashgate.com/isbn/9781409400417>
>
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>
>

-- 
*David Bashwiner*
Assistant Professor of Music Theory
University of New Mexico
Center for the Arts, Rm 2103
MSC04 2570
1 University of New Mexico
Albuquerque, NM  87131-0001
(505) 277-4449
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