Physiological bases of altered multisensory temporal-order-judgments in dyslexia
Poster Presentation

W. David Hairston
Neurobiology and Anatomy, WFU School of Medicine

*Jonathan Burdette
Radiology, WFU School of Medicine

*D. Lynn Flowers
Neuropsychology, WFU School of Medicine

*Frank Wood
Neuropsychology, WFU School of Medicine

Mark Wallace
Neurobiology and Anatomy

     Abstract ID Number: 143
     Full text: PDF
     Last modified: June 24, 2005

Abstract
Recent research in our lab suggests that dyslexia may be associated with abnormal multisensory temporal interactions, as shown by differences in the influence of a non-relevant auditory cue during the performance of a visual temporal-order-judgment (TOJ) task. To examine the physiological underpinnings of these altered multisensory interactions, fMRI is currently being done while subjects perform TOJ tasks. During initial testing, subjects perform both visual and auditory TOJ tasks in order to determine subject-specific thresholds (stimulus onset asynchronies – SOAs). Following this, subjects perform the visual TOJ with task-irrelevant auditory cues (multisensory TOJ). The first sound is always synchronous with the first light, and the second sound is either synchronous or lagged behind the second light by a variable delay. Although both control (i.e., normal reading) and dyslexic subjects show performance improvements (i.e., lower thresholds) with the addition of the auditory stimulus, dyslexic subjects show a larger gain over a wider range of temporal delays. To take advantage of these differences, during a subsequent event-related fMRI paradigm, subjects perform the multisensory TOJ task both with the visual SOA at their own subject-dependent visual threshold and at an SOA that is constant for all subjects, while sounds are presented with both short and long delays. Preliminary data suggests differences in activation between control and dyslexic subjects in multisensory cortical areas interposed between occipital, temporal and parietal cortices.

Supported by NIH grant MH63861 and the WFU Center for Investigative Neuroscience