Филологические науки/9. Этно-,
социо- и психолингвистика.
к.филол.н.
Вандышева А.В., Иванченко Т.Ю.
Академия
маркетинга и социально-информационных технологий г.Краснодар
Sound effect upon brain
The present study examines
neurological processes in brain caused by words and sounds. In this paper we
make a survey of some research results that have
identified certain mechanisms for interpreting sounds and speech in
human brain.
There are certain words
which seem to attract a certain blessing in life. Some attract power, some
bring release from difficulties, and some give courage and strength.
What makes a word powerful? Is it the meaning,
the vibration, the way it is used, or the knowledge of the teacher who teaches
the pupil to repeat it? The answer to such questions is that some words have
power because of their meaning, others because of the vibration they produce, others for their
influence upon the various centers.
Words have power to vibrate through different
parts of man's body. There are words that echo in the heart, and there are
others that do so in the head, and again others that have power over the body.
By certain words definite emotions can be quickened or calmed. There is also a science of syllables,
which has its own particular effect.
So, the question arises: How does our brain
perceive words? The study of neurological affect of the sound
showed that human brain reacts upon the clear sounds in a certain way.
Positron-electron tomography measuring the level of glucose absorption revealed
that sounds initiate cellular hyperactivity in the right-brain.
Psychoacoustics, a newly emerging field of human
potential technology, promises to radically affect human behavior through its
study of sound, language, and music and their effects on the brain/mind. Only
recently have we begun to understand the physiological effects of sound and
music on the brain.
Tom Kenyon claims that acoustic stimulation of the brain is accomplished
via the auditory pathways which are routed into the auditory cortex. The
Reticular Activating System (RAS) is also activated through the spinoreticular
fibers located in laminae of the spinal gray matter. While the RAS is not
equipped to deal with specific sensory information, it is well suited for
controlling arousal. Any strong stimulation, such as sound, activates the RAS,
thereby diffusely activating the entire cerebral cortex, the seat of “higher”
thought.
The human brain is hard-wired to find combinations of integer harmonic
frequencies pleasing. Combined integer harmonic sounds are two or more separate
tones, heard at the same time, where their frequencies are related by a simple
integer ratio. For instance, the two frequencies 1000 Hz and 2000 Hz heard
together would be a combined integer harmonic because 2000 Hz is exactly twice 1000
Hz. Human speech uses such simple harmonic tones to construct the sounds in
words. In speech the harmonic ratios are typically numbers like 2/5 , 1/2, 1/3
etc. These tones heard together are called formants (M. Townsend). Formants are discrete sounds
within a word, equating to phonemes in phonetics. Instead of hearing the two
tones combined a single musical note, our brain interprets the sound as a
discrete sound within a word instead. So, for instance, the 'O' sound might
typically consist of a 500 Hz and 1000 Hz frequency combination.
The only information we get from our ears is the amplitude, frequency and
time of arrival of sounds. It is left entirely to our brains to interpret what
the sounds are, relying mainly on experience, context and expectation. Townsend
insists that the brain generally interprets sounds in one of three 'modes'. In
one mode it interprets a sound as random noise. In another mode the same sound
appears to be music. In the third mode, the same sound becomes speech.
Interpretation of a sound by brain is largely a
matter of expectation. If we hear tones from a musical scale, particularly set
to a fixed rhythm, we are likely to hear it is as music. If we hear sounds with
the typical frequency range and rhythms of speech we will probably try to
interpret the sound as words. If we do not hear a sound as music or speech, we will hear
it in its raw state, as a mixture of frequencies.
If we are listening to someone in a noisy situation we may not hear all the
words. Our brains will 'fill in' the gaps with likely words, sometimes wrong,
based on expectation. We will actually hear and remember 'filled in' words even
if they are wrong. The words we hear are produced in our brains, not our ears.
In the phoneme restoration effect, someone is played a recording of a
spoken sentence where one word is replaced by white noise of the same duration.
And yet, people still 'hear' the missing word. Their brain has inserted it
using context and expectation. In the verbal transformation effect, someone is
played a word repeatedly. After many repeats, the word turns into another with
a similar sound structure ('truce' may transform to 'truth', for instance).
These effects, together with other scientific evidence, demonstrate that the
brain decides what it hears based on experience, context and expectation.
Experiments have revealed that almost any simple
noise, like white noise, can sound like speech if the person listening to it is
in 'speech mode'. The more voice-like features in the noise (such as frequencies
and rhythm), the more people will interpret it as words. If there are peaks in
the frequency spectrum of the noise that happen, by chance, to form a harmonic
ratio, as in formants, there is a much higher chance it will sound like speech.
If there are variations in the overall amplitude of the sound giving a rhythm,
similar to words in human speech, that will also greatly increase the chances
of its being interpreted as a voice. Also, if the spectrum envelope of the
sound (the overall frequency range) is restricted to that typical of a human
voice, the illusion of speech is increased. The actual frequencies of the
harmonics and the spectrum envelope don't have to be identical to normal human
speech. Research has shown that people still understand speech even when it has been
frequently shifted.
Noise
with these sort of characteristics is called by Townsend 'formant noise'. Though the apparent formants may make
no sense (as they are noise, not words), our brains will work hard to turn the
result into recognizable words. That's because they use a 'top-down' process to
processing speech, trying to fit likely words to the apparent formants present.
It explains why, with formant noise, you never 'hear' partial words. The words
come from your brain, not the sound, and are made to fit the noise. In the same
way, whole phrases can emerge. You may need to listen to formant noise several
times to fix the phrase as your brain tries various likely alternatives. If
someone tells you beforehand what the 'words' are meant to be, you will
often hear it straight away.
In conversation,
humans recognize words primarily from the sounds they hear. However, scientists
have long known that what humans perceive goes beyond the sounds and even the
sights of speech. The brain actually constructs its own unique interpretation,
factoring in both the sights and sounds of speech.
For example, when combining
the acoustic patterns of speech with the visual images of the speaker's mouth
moving, humans sometimes reconstruct a syllable that is not physically present
in either sight or sound. Although this illusion suggests spoken syllables are
represented in the brain in a way that is more abstract than the physical
patterns of speech, scientists haven't understood how the brain
generates abstractions of this sort.
Researchers at the University of Chicago have
identified brain areas responsible for this perception. One of these areas,
known as Broca's region, is typically thought of as an area of the brain used
for talking rather than listening.
Uri Hasson, lead author of the
study and a post-doctoral scholar at the university's Human Neuroscience
Laboratory, explains that when the speech sounds do not correspond exactly to
the words that are mouthed, the brain often conjures a third sound as an
experience -- and this experience may often vary from what was actually spoken.
He gives an example with the syllable “pa” pronounced by person’s voice. The experiment
has shown that the person's lips mouth the word 'ka"' One would think you
might hear 'pa' because that is what was said. But in fact, with the
conflicting verbal and visual signals, the brain is far more likely to hear
'ta,' an entirely new sound.
This demonstration is called the McGurk effect (named
after Harry McGurk, a developmental psychologist from England who first noticed
this phenomenon in the 1970s). In the current study, scientists used functional
magnetic resonance imaging (graphic depiction of brain activity) to demonstrate
that Broca's region is responsible for the type of abstract speech processing
that underlies this effect.
Although we experience speech as a series of words
like print on a page, the speech signal is not as clear as print, and must be
interpreted rather than simply recognized, Hasson explains.
He says this paper provides a glimpse into how such
interpretations are carried out in the brain. These types of interpretations
might be particularly important, when the speech sounds are unclear, such as
when conversing in a crowded bar, listening to an unfamiliar accent, or coping
with hearing loss.
In all these cases, understanding what is said
requires interpreting the physical speech signal to determine what is said. And
scientists now know the Broca's region is plays a major role in this process.
R. Näätänen from University of
Helsinki, states the contribution of the mismatch negativity (MMN), and its
magnetic equivalent MMNm, to our understanding of the perception of speech
sounds in the human brain. MMN data indicate that each sound, both speech and
nonspeech, develops its neural representation corresponding to the percept of
this sound in the neurophysiological substrate of auditory sensory memory. The
accuracy of this representation, determining the accuracy of the discrimination
between different sounds, can be probed with MMN separately for any auditory
feature (e.g., frequency or duration) or stimulus type such as phonemes.
Furthermore, MMN data show that the perception of phonemes, and probably also
of larger linguistic units (syllables and words), is based on language-specific
phonetic traces developed in the posterior part of the left-hemisphere auditory
cortex. These traces serve as recognition models for the corresponding speech
sounds in listening to speech. MMN studies further suggest that these language-specific
traces for the mother tongue develop during the first few months of life.
Moreover, MMN can also index the development of such traces for a foreign
language learned later in life. MMN data have also revealed the existence of
such neuronal populations in the human brain that can encode acoustic
invariances specific to each speech sound, which could explain correct speech
perception irrespective of the acoustic variation between the
different speakers and word context.
Scientists
at the University of Rochester have discovered that the hormone estrogen plays
a pivotal role in how the brain processes sounds.
Raphael
Pinaud, assistant professor of brain and cognitive sciences at the University
of Rochester and lead author of the study said they had discovered estrogen
“doing something totally unexpected”. The findings of this study indicate that
estrogen plays a central role in how the brain extracts and interprets auditory
information. It does this on a scale of milliseconds in neurons, as opposed to
days, months or even years in which estrogen is more commonly known to affect
an organism. Pinaud, along with Lisa Tremere, a research assistant professor of
brain and cognitive sciences, and Jin Jeong, a postdoctoral fellow in Pinaud's
laboratory, demonstrated that increasing estrogen levels in brain regions that
process auditory information caused heightened sensitivity of sound-processing
neurons, which encoded more complex and subtle features of the sound stimulus.
Pinaud's team also shows that estrogen is required to activate genes that
instruct the brain
to lay down memories of those sounds.
Pinaud’s research revealed a dual role played by
estrogen. It was discovered that estrogen modulates the gain of auditory
neurons instantaneously, and it initiates cellular processes that activate genes that are involved
in learning and memory formation.
Pinaud’s theory opens prospects for investigating how neurons adapt their
functionality when encountering new sensory information and how these changes
may ultimately enable the formation of memories; and for exploring the specific
mechanisms by which estrogen might impact these processes.
Литература:
2. Estrogen controls how the brain processes sound. [Electronic
resource]. – Mode access: http://www.physorg.com/news160765483.html
.- May 5, 2009.
3. Kenyon, T. Theoretical Constructs of ABR Technology. [Electronic
resource]. – Mode access: http://tomkenyon.com/theoretical-constructs-of-abr-technology
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4. Näätänen , R. The perception of speech sounds by the
human brain as reflected by the mismatch negativity and its magnetic equivalent
[Text] / R. Näätänen
// Psychophysiology.
- #38 . – 2001.
– pp. 1–21.- Cambridge University Press. - Society for Psychophysiological
Research.
Townsend M. EVP formant noise
theory electronic voice fenomena. [Electronic resource]. – Mode access: http://www.assap.org/newsite/htmlfiles/Articles.html