Abstract
Reading speed in peripheral vision improves with practice, but the cortical site of this improvement is not understood. Using psychophysics and fMRI, we investigated the potential training-related functional changes in retinotopic and non-retinotopic cortical areas. Ten young normally sighted subjects were trained (1hour/day over 4days) to read sentences displayed in the lower visual field (10º eccentricity) using the Rapid Serial Visual Presentation (RSVP) paradigm. Pre- and post-training psychophysical tests included RSVP reading speed, visual span and orientation discrimination (Gabor patch) measurements in both the trained (lower) and untrained (upper) visual fields. Functional MRI measurements (BOLD) were recorded before and after training for eccentric RSVP reading (at four presentation rates) and grating orientation discrimination. The fMRI measurements used a rapid event-related design, with analysis focusing on three cortical regions: the primary visual cortex, Broca’s area and the visual word form area (VWFA). Training resulted in a significant gain (60% ±25%) in RSVP reading speed in the trained visual field, and partial transfer of this improvement to the untrained upper visual field. The fMRI results showed that the activity level in VWFA was dependent on the presentation rate and in turn was positively correlated with the percentage of words accurately recognized. More specifically, before training, BOLD activity in VWFA was significantly weaker (p<0.01) for the fastest (hardest) reading condition than for the slowest (easiest) one, but this difference was significantly reduced after training. A weaker but similar trend was observed in retinotopic cortex as well. Our results show that VWFA response during reading in peripheral vision is affected by a training protocol that enhances reading speed. The more uniform VWFA responses at the four RSVP rates following training may be associated with higher word recognition accuracy for the faster rates which in turn yield shallower behavioral psychometric functions.
Meeting abstract presented at VSS 2013