Interhemispheric Transfer of Visual Sensory Information in Autism Spectrum Disorder: A High-Density Electrical Mapping Study
Background: There is limited research on the rate of interhemispheric transfer in the ASD population. Behavioral studies indicate that interhemispheric transfer time (IHTT) is ~4 ms, although event related potentials (ERPs) derived IHTT estimates range from 15 - 30 ms. Aim 1) To demonstrate that the current paradigm can provide an estimate of IHTT, 2) to investigate current source dipoles and white matter integrity related to IHTT, 3) to investigate the developmental trajectory of IHTT, and 4) to show that IHTT is prolonged in ASD patients. Exploratory analysis in the frequency domain was completed to better understand underlying IHTT mechanisms. Methods: Checkerboard stimuli were presented either 4° from fixation in the left visual field (LVF), right visual field (RVF), or bilaterally (BVF) with left or right-hand reaction times recorded along with continuous electroencephalogram. ERPs were analyzed using multilevel linear modeling with interest in the P1 and N2 latency and amplitude measures. Study 1 also included dipole source modeling and probabilistic tractography. A fast Fourier transform was applied to the ERP data to look at the associated frequency components. Participants in Study 1 ( n = 24) were typically developed (TD) adults, while Study 2 participants (n = 31) were TD children. Study 3 focused on clinical differences between age and sex-matched TD children (n = 18) and children with ASD (n = 19). Results: ERP latencies were earlier for the BVF condition, which also elicited greater power in the frequency domain. Peak ERP latencies for the directly stimulated hemisphere occurred earlier (IHTT range of 7 - 15 ms). Dipole models show that 131 source originates in Brodmann Area 18 (extrastriate cortex) and white matter integrity does not correlate with IHTT. In Study 2, age did not correlate with IHTT or ERP latencies, but negatively correlated with P1 amplitude, and positively correlated with N2 amplitude. In Study 3, no significant group interactions emerged. Symptom severity did not correlate with IHTT. Conclusion: Our paradigm elicits IHTTs on the order of ~7-15 ms. We do not see an effect of age on IHTT. Finally, we did not obtain longer IHTT estimates in ASD children.
Source: Dissertation Abstracts International, Volume: 79-02(E), Section: B.;Advisors: Vance Zeman.