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  • Addiction, Drugs
  • Information from Lay-Language Summaries is Embargoed Until the Conclusion of the Scientific Presentation

    245—Speech, Language, and Signaling in Autism

    Sunday, November 10, 2013, 1:00 pm - 5:00 pm

    245.10: Auditory cortex speech sound processing impairments in a rat model of autism

    Location: Halls B-H

    Behavioral and Brain Sci., The Univ. of Texas at Dallas, Richardson, TX

    Abstract Body: Although individuals with autism are known to have significant communication problems, the neural mechanisms responsible for impaired communication are poorly understood. This study documents speech sound coding in the valproic acid (VPA) animal model of autism, and quantifies the beneficial effects of a common autism therapy, auditory training. Valproic acid is an anticonvulsant that is a known risk factor for autism in children who are prenatally exposed to it. Prenatal exposure to VPA in rats causes symptoms that mimic autism. Multiunit responses to speech sounds were collected from primary auditory cortex, anterior auditory field, ventral auditory field, and posterior auditory field in VPA exposed and control rats. Speech sounds evoke precise spatiotemporal activity patterns in the auditory cortex of control rats. Our results indicate that in utero VPA exposure severely degrades the precise spatiotemporal patterns evoked by speech sounds in anterior auditory field and ventral auditory field, but not primary auditory cortex or posterior auditory field. We next tested the hypothesis that speech sound discrimination would be impaired in VPA exposed rats. Groups of VPA exposed and control rats were trained to discriminate consonants, vowels, and tones, and were tested on their ability to generalize to novel sounds. VPA exposed rats are impaired in their ability to discriminate between some consonant sounds. Multiunit responses to speech sounds were then collected from auditory cortex of VPA exposed rats that were speech trained. Our preliminary results indicate that training enhances both speech discrimination ability and anterior auditory field responses to speech sounds. Insights derived from these studies may influence the development of new behavioral and sensory techniques to treat the communication impairments in autism that result in part from a degraded representation of speech sounds.

    Lay Language Summary: Our experiments demonstrate that the ability to discriminate speech sounds is impaired in a model of autism and the manner in which the brain responds to the sounds is disrupted. Extensive training enhanced discrimination ability and normalized auditory cortical responses to the speech sounds.
    Approximately 1 in 88 children in the United States is diagnosed with autism spectrum disorder. Although autistic individuals have significant communication problems, the responsible neural mechanisms behind the deficits are poorly understood. We found brain responses to speech sounds were weaker and slower in the auditory cortex of our autistic model compared to the non-autistic controls. Additionally, the autistic model was impaired at discriminating speech sounds.
    We evaluated speech processing using the in utero valproic acid model of autism. Prenatal exposure to the anticonvulsant valproic acid is a risk factor for autism - approximately 10% of valproic acid exposed children develop autism compared to 1% in the general population. Rats prenatally exposed to valproic acid exhibit many of the classic neural abnormalities and behavioral deficits observed in autism.
    Neural responses were obtained in four areas of the auditory cortex in valproic acid exposed and control rats. Rats exposed to valproic acid had severely degraded responses to speech sounds in anterior and ventral auditory fields, but not primary auditory cortex or posterior auditory field. Interestingly, autistic children have also demonstrated impaired responses to speech in non-primary auditory cortex.
    Animal models of autism can be used to better understand how treatments work. Normal rats are able to distinguish between the basic speech sounds as well as people. Valproic acid exposed rats were impaired at discriminating many consonant sounds compared to control animals, but performed normally on tone and vowel discrimination tasks. Months of speech training enhanced the consonant discrimination ability in the valproic acid exposed rats to control levels and improved their anterior auditory field responses to speech sounds.
    Behavioral intervention in children with autism, such as the Early Start Denver model, has been shown to improve IQ scores and reduce the severity of the diagnosis. Our results are consistent with human results demonstrating that aspects of autism may be effectively treated with behavioral therapy. This model of impaired speech processing in autism provides a novel resource for the development of new behavioral and sensory techniques to treat the communication impairments in autism.