Research Description

Highlights of Major Accomplishments

• Successful application of functional MRI to children with learning disabilities and matched controls to study cerebral functional localization of timing functions and impairments thereof.

• Demonstration that the supplementary motor area and right superior temporal gyrus participate in a network needed for internally timed paced finger tapping in children.

• Delineation of deficits in information processing in children with developmental dyslexia.

Major Results

Our initial studies in the area of learning disabilities have addressed issues of timing in affected and matched control children. Paced finger tapping (PFT) is a classic paradigm for studying timing in humans. The subject taps fingers in time to a regular auditory signal and continues at the same rate after the signal is stopped. Adult studies show that both supplementary motor area and superior temporal gyrus act in network retrieval of stored auditory information. Disturbances of PFT have been noted in children with developmental dyslexia. We used fMRI to study PFT in children who are poor readers compared to good readers. Children were selected based on WIAT Basic Reading test and a tapping composite score. Good readers/Good tappers (GG, n=8, mean age=12.2y) and Poor readers/Poor tappers (PP, n=7, mean age=11.3y) performed an activation paradigm comprising 8 units of 5 epochs each in boxcar-format. Children either tapped by alternating index finger movements or rested. When tapping, they either tapped to the auditory signal (metronome tapping, MT) or without a signal (self-tapping, ST), trying to reproduce the rhythm of the antecedent MT epoch. Resting epochs (no tone/no tapping) followed MT (RMT) and ST (RST) epochs. Epoch order in each unit was: MT-ST-RST-MT-RMT. A 1.5T GE LX MRI scanner with EPIBOLD contrast acquisition was used. High-resolution T2-EPI and SPGR neuroanatomic images were obtained. Individual/group data sets were analyzed with SPM software. The results were striking. There were no group differences in primary motor cortex activation. However, MT + ST vs. RMT + RST revealed greater activation in supplementary motor area in the GG than the PP group. There was strong bilateral activation in posterior superior temporal gyrus in the GG group but little in the PP group. MT vs. RMT revealed robust bilateral supplementary motor area and posterior superior temporal gyrus activation in the GG group, but no activation of supplementary motor area and minimal activation of superior temporal gyrus in the PP group. Finally, in the GG group, ST vs. RST revealed activation in right hemisphere posterior superior temporal gyrus and greater supplementary motor area activation than during MT. In the PP group, some supplementary motor area but no superior temporal gyrus activation was found.