Approximately one out of every fifteen children
entering elementary school in the U.S. has a significant developmental
language impairment of unknown origin.
Detailed studies of speech acoustics have significantly improved
understanding and treatment of language impairments. These studies also provide the foundation
needed to investigate the neural representation of speech. While peripheral representations have been
extensively studied, relatively little is known about the cortical mechanisms
that contribute to speech processing.
The objective of this proposal is to define the distributed response of
mammalian auditory cortex neurons to human speech sounds and to determine what
experience-dependent changes in the neural representation of speech are
possible. The first aim of the project
will be to precisely document the distributed response of auditory cortex
neurons to speech sounds. Our results
(from awake and anesthetized recordings in two distinct auditory fields)
indicate that frequency bandwidth and forward masking time course can account
for speech responses of most auditory cortex neurons. The second aim is to determine how well
cortical responses can predict the ability of rats to discriminate particular
phonemes (i.e. /D/ vs. /T/ and /R/ vs. /L/).
The third aim is to document how cortical neurons are modified by
training on speech sound discrimination.
The results of these studies will add to our understanding of neural
mechanisms that could contribute to speech processing and learning in human
auditory cortex. Insights derived from
these studies will influence the use and development of behavioral and sensory
rehabilitation of language impairments.