How Poverty Molds the Brain: Poor Neural Processing of Sound Linked to Lower Maternal Education Background
Now new research conducted at Northwestern University has taken that
finding in a neuroscientific direction: linking poor processing of
auditory information in the adolescent brain to a lower maternal
educational background.
"These adolescents had noisier neural activity than their classmates,
even when no sound was presented," said Nina Kraus, the Hugh Knowles
Professor of Neurobiology, Physiology and Communication Sciences at
Northwestern and corresponding author of the study.
In addition, the neural response to speech for the adolescents from a
lower maternal educational background was erratic over repeated
stimulation, with lower fidelity to the incoming sound.
"Think about the neural noise like static in a radio -- with the announcer's voice coming in faintly," Kraus said.
Maternal education acted as a proxy for socioeconomic status for the
study. Adolescents were divided into two groups, according to whether
their mothers had a high school education or less or had completed some
post-secondary schooling.
Not only did the adolescents from a lower maternal educational
background have neural responses to speech sounds that were nosier, more
variable and represented the input signal weakly, but their
performances on tests of reading and working memory also were poorer.
"The impoverished brain: Disparities in maternal education affect the
neural response to sound" will be published Oct. 30 in the Journal of Neuroscience.
Its authors are Erika Skoe, assistant professor of speech, language and
hearing sciences at the University of Connecticut; Jennifer Krizman, a
doctoral student in Northwestern's Auditory Neuroscience Laboratory; and
Kraus, also the director of the Auditory Neuroscience Lab.
This study builds on evidence that children from low-income families
experience a type of auditory impoverishment. The landmark study by Hart
and Risley (1995) revealed that children in high-income families are
exposed to 30 million more words than children from families on welfare.
This reduction in the quality and quantity of language input, along
with greater exposure to unstructured sound such as ambient noise, may
be affecting how the brain represents auditory information.
In urban populations, income and amount of noise exposure are known
to be correlated. Consistent with the idea that noisy auditory
environments increase neural noise, the new Journal of Neuroscience
study found that the adolescents from the lower maternal educational
group have increased neural activity in the absence of sound input.
According to the study, "Neural models indicate that when the input
to a neuron is noisier, the firing rate becomes more variable,
ultimately limiting the amount of sensory information that can be
transmitted."
"If your brain is creating a different signal each time you hear a
sound, you might be losing some of the details of the sound," said Skoe,
lead author of the study. "Losing these details may create challenges
in the classroom and other noisy settings."
The new research conducted at Northwestern contributes to a recent
wave of neuroscientific research demonstrating that sociocultural
factors influence brain structure and function.
Another recently published study from the Kraus lab showed that
inconsistent neural responses to sounds relate to poor reading but that
by acoustically augmenting the classroom, neural responses became more
stable.
"Modifying the auditory world for a particular student, even if just
for a portion of the day, may improve academic performance and fine-tune
how sound is automatically encoded in the brain," Skoe said.
Ongoing work in Northwestern's Auditory Neuroscience Laboratory is
investigating whether auditory enrichment in the form of music education
and other school-based activities can offset the negative impact of an
impoverished acoustic environment.
For the new study, brain activity of Chicago Public School
adolescents, almost all ninth-graders, was assessed both in response to
and in the absence of auditory input. The nervous system's responses to
speech sounds were observed through passive electrophysiological
recordings, with students grouped according to the highest educational
level achieved by their mothers.
The responses reflect activity from a communication hub within the
central nervous system that provides a snapshot of sensory, cognitive
and reward circuits that are engaged to process sound. These
fundamental, automatic responses to sound reflect past and ongoing
sensory experiences and relate to linguistic and cognitive function.
The collection protocol for "the impoverished auditory brain" lasted
roughly 20 minutes, during which participants sat comfortably watching a
self-selected subtitled movie, while the brain response to speech
syllables was passively collected.
The syllables were presented at a rapid rate to the right ear through
an earphone placed in the ear canal. The left ear remained unblocked,
making the movie sound track audible yet not intense enough to mask the
stimulus.
The syllables chosen are common to many languages of the world, and their acoustic characteristics are perceptually challenging.
In addition, IQ assessments for the students were collected, and they
were administered a standardized, age-normed test battery of reading
ability and executive function (working memory). Previous work has
revealed that the neurobiological systems mediating higher order
functions such as language, memory and executive function are especially
sensitive to disparities in socioeconomic status.
"By studying socioeconomic status within a neuroscientific framework,
we have the potential to expand our understanding of the biological
signatures of poverty," Kraus concluded. "And a better understanding of
how experiences shape the brain could inform educational efforts aimed
at closing the socioeconomic achievement gap."
Story Source:
The above story is based on materials provided by Northwestern University. The original article was written by Pat Vaughan Tremmel.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
- Skoe E, Krizman J, Kraus N. The impoverished brain: Disparities in maternal education affect the neural response to sound. Journal of Neuroscience, 2013
By Michael Snyder, on October 13th, 2015
