Visually evoked BOLD responses in human cortex modulated by gaze direction
Poster Presentation

Michela Tosetti
Stella Maris Scientific Institute, Pisa, Italy

Giovanni D'Avossa
Washington University School of Medicine, St. Louis, USA

Sofia Crespi
Università Vita-Salute S Raffaele ,Milan, Italy

Laura Biagi
Stella Maris Scientific Institute, Pisa, Italy

Maria Concetta Morrone
Università Vita-Salute S Raffaele ,Milan, Italy

David Burr
Università Degli Studi di Firenze, Florence, Italy

     Abstract ID Number: 114
     Full text: Not available
     Last modified: April 11, 2007
     Presentation date: 07/05/2007 10:00 AM in Quad Maclauren Hall
     (View Schedule)

Abstract
Gaze direction affects responses to visual stimuli in many cortical areas of the monkey, and in humans there is good psychophysical evidence for spatiotopic integration of motion stimuli. Here we demonstrate that human middle temporal cortex encodes motion in a spatiotopic fashion and therefore could mediate the spatiotopic integration of motion signals, converting retinotopic information into a spatiotopic reference frame. We first isolated the “retinotopic” portion of hMT complex in each subject then selected those voxels within this portion that responded to flow against speed-matched random motion. We then measured fMRI BOLD responses to coherent motion in four screen positions and for three different gaze directions. In V1 gaze did not alter the retinotopicity of the responses: the response curves for the three different fixations were almost identical when plotted in retinal coordinates, but widely spaced in screen coordinates. MT showed the opposite, with the curves were displaced in retinal coordinates, but aligned in spatial coordinates, showing that retinotopic selectivity changes with eye position to produce a clear spatiotopicity.