Project Summary
Endocrine disrupting chemicals (EDCs) are known hazards which are still prevalent in
the environment and in the human home. Bisphenol A (BPA) is a known EDC found in common
items from plastic to paper receipts. Recent evidence suggests that BPA is present in
Americans at levels high enough to cause detrimental effects on language acquisition in male,
human children. Though such levels are considered safe for acute, adult exposure, the impact
of long-term, low-dose exposure to EDCs during development is an understudied phenomenon
with potentially serious impacts on human health.
The aims of this study are to: 1) To track the impact of low-dose BPA exposure across
development into adulthood, and 2) To identify the mechanisms underlying vocal deficits caused
by endocrine disruption. The proposed studies include in vivo analyses of juvenile development
and behavior as they transition into adult vocal behavior patterns. The in vivo work is
complemented with in vitro analysis of the larynx and the neural structures within the brain that
drive vocalization.
These studies utilize the South African clawed frog, Xenopus laevis, as a model
organism. The mechanisms driving X. laevis vocalization patterns are well-studied, and their
vocal behaviors are varied but not complex. X. laevis produce at least seven different types of
vocalization; some are male-specific, some are female-specific, and all are used in specific
social contexts. The variation is vocal patterns is balanced by the fact that the calls are innate
and do not need to be learned.
Xenopus vocal behavior is easily quantified. Calls have distinct features which make
them easily counted as distinct units. Each call is also composed of sounds that have distinct
temporal and spectral features which can also be quantified for comparisons. The temporal and
spectral components of vocalizations are generated by the vocal pattern generator in the brain
and the resonance structures within the larynx (respectively,) and both structures have robust in
vitro preparations that allow for mechanistic study. Thus, the X. laevis vocal system is well
suited for studies of language disruption by EDCs like BPA, because aberrations are easily
identified and proximal causes can be directly investigated. This investigation will provide insight
how BPA impacts language development, allowing us to identify potential targets for speech
therapy as well as highlighting the potential hazards of long-term, low-dose exposure to EDCs.
