Cortical localization of reading in normal children - An fMRI language study

Background: fMRI provides a noninvasive means of identifying the location a nd organization of neural networks that underlie cognitive functions. Objec tive: To identify, using fMRI, brain regions involved in processing written text in children. Methods: The authors studied nine normal right-handed na tive English-speaking children, aged 10.2 years (range 7.9 to 13.3 years), with two paradigms: reading Aesop's Fables and "Read Response Naming" tread ing a description of an object that was then silently named). Data were acq uired using blood oxygen level-dependent fMRI. Group data were analyzed wit h statistical parametric mapping; individual data sets were analyzed with a region-of-interest approach from individual study t maps. The number of ac tivated pixels was determined in brain regions and an asymmetry index (AI = [L - R]/[L + R]) calculated for each region. Results: The authors found st rong activation in the left, middle temporal gyrus and left midfrontal gyru s and variable activation in left inferior frontal gyrus for both reading t asks in the group analysis (z > 5.5 to 9.1). All subjects had strong left-s ided lateralization for both tasks in middle/superior temporal gyrus, infer ior frontal gyrus, and middle frontal gyrus (AI = 0.76 to 1.0 for t = 4). R eading Fables activated twice as many pixels in temporal cortex as the Read Response Naming task; activation in dorsolateral prefrontal cortex was sim ilar for both tasks. Small homologous right middle temporal region activati on was seen with reading a fable. Conclusions: The neural networks that pro cess reading appear to be lateralized and localized by middle to late child hood. Reading text paradigms may prove useful for identifying frontal and t emporal language-processing areas and for determining language dominance in children experiencing epilepsy or undergoing tumor surgery.