Abstracts

Rationale: fMRI is used to identify language areas in planning for surgery. Most fMRI studies of language have focused on anterior expressive language. We aimed to determine receptive language patterns in the superior temporal Gyrus (STG) assessed by fMRI in normal, healthy children in order to provide a basis for future evaluation in children with epilepsy. Methods: We studied 64 typically developing right-handed children (age 4-12) who all had normal MRI and normal neurologic exam. Functional imaging was conducted using whole brain 3T fMRI (EPI BOLD) with an auditory description decision task employing a box car design (with reverse speech control condition). Data were analyzed using SPM2 and with a region of interest mask (Wake Forrest PICK Atlas) that encompassed Brodmann's areas 22, 23, and 39, and includes the superior temporal gyrus. Laterality Index (LI)was calculated using LI Toolbox with both weighting and clustering (LI = [L - R]/[L + R]). LI ≥ 0.20 was defined as left dominant, LI ≤ -0.20 as right dominant, and |LI| < 0.20 as bilateral. Activation was analyzed at 2x the adaptive threshold for each patient, and activation was then compared for each age group. There were 15 children aged 4-6, 22 children aged 7-9, and 27 children aged 10-12. Results: Mean T-score was 2.10 (range: 1.068 - 3.9). Mean |LI| was 0.73. 55 children (84.4%) were lateralized to the left (mean LI =0.84), 3 (4.6%) were lateralized to the right (mean LI = -0.3), and 7 ( 10.8%) had bilateral activation (mean LI =|0.11|). When compared for age, 11 (73.3%) of 4-6 year olds were left lateralized (mean LI = 0.84) and 4 (26.7%) of 4-6 year olds had bilateral activation (mean LI = |0.10|). In the 7-9 year olds, 19 (86.4%) were lateralized to the left (mean LI =0.86) and 3 (13.6%) had bilateral activation (mean LI = |0.11|). Among the 10-12 year olds, 100 % were lateralized, with 24 (88.9%) lateralized to the left (mean LI = 0.81), and 3 (11.1 %) lateralized to the right (mean LI = -0.3). Conclusions: We identified strongly left temporal receptive language lateralization using an auditory-based word definition decision task. However, we found left dominance for receptive language in 84.4% of right-handed children, which is less than reported in older populations. This may be due to delayed maturation of receptive language dominance.