Event Abstract Back to Event Obtaining auditory M100 responses in children: Success rates Sarah Y. Khan1*, Christopher J. Edgar1, Justin F. Monroe1, Kate M. Cannon1, Lisa Blaskey1, Saba Qasmieh1, Sue E. Levy1 and Timothy P. Roberts1 1 The Children's Hospital of Philadelphia, United States Electrophysiological research demonstrates auditory abnormalities in children with autism spectrum disorders (ASD) and in children with language impairment. Although MEG electrophysiological measures are potential biomarkers [1], no studies have examined whether these measures can be reliably obtained in children. Success obtaining 100 ms (M100) auditory responses in control and patient children was examined. Whole-cortex MEG data were examined in 103 children: controls (N=37), ASD without language impairment (N=36), ASD with language impairment (N=22), and specific language impairment (N=8). Subjects were split into young (N=70, range 6-10 years, mean = 8.63 years) and older groups (N=33, range 11-15 years, mean=13.28 years). Binaural 200, 300, 500 and 1000 Hz tones were presented, and left and right M100 superior temporal gyrus evoked activity was modeled. In each hemisphere, a M100 response was considered present when observed for at least 2 of the 4 tones, with source strength significantly above background, and with a latency between 80 and 180 ms. Chi-squared analyses examined the presence or absence of M100 activity as function of gender, hemisphere, age, and diagnosis. No gender differences were observed. M100 responses were observed less often in the left (68.0%) than right hemisphere (87.4%, χ2 = 11.2, p < 0.01), and less often in young (72.1%) than older participants (89.4%, χ2 = 7.7, p < 0.01). M100 responses were also observed less often in patients than controls in the left (χ2 = 8.97, p = 0.03) and right hemisphere (χ2 = 8.67, p = 0.03). Simple-effect analyses indicated that patient and control differences were due to less frequent M100 responses in the young and older language impaired children (p's< 0.05). M100 responses were more difficult to obtain in young subjects, as well as in young and older subjects with language impairment. A lack of M100 activity in these two groups may reflect less fully matured auditory pathways.