OBJECTIVE: The cortical magnification factor characterizes the area of human primary visual cortex activated by a stimulus as a function of angular distance from an observer's line of sight. This study estimates human cortical magnification using an electrophysiological method with excellent temporal resolution: visual evoked potential (VEP) dipole source localization. METHODS: For each of 60 independently modulated checkerboard patches within the central 18 deg of the visual field, location, orientation, magnitude, and time-course of the dipole current source that best described the VEP distribution across a multi-electrode array was obtained. At numerous eccentricities, cortical magnification was determined using two different techniques: (1) the distance between each pair of adjacent stimulus patches was matched to the corresponding distance between adjacent cortical sources; and (2) the area of each stimulus patch was matched to the magnitude of the corresponding cortical source (which was assumed to be proportional to cortical area). RESULTS: The estimates of human cortical magnification using our electrophysiological method were similar to previous estimates from psychophysics, cortical stimulation, and functional magnetic resonance imaging. CONCLUSIONS: The concordance of results provided by these disparate technologies, with differing spatial and temporal limitations, supports their combination in studying the spatio-temporal dynamics of human brain function.
OBJECTIVE: The cortical magnification factor characterizes the area of human primary visual cortex activated by a stimulus as a function of angular distance from an observer's line of sight. This study estimates human cortical magnification using an electrophysiological method with excellent temporal resolution: visual evoked potential (VEP) dipole source localization. METHODS: For each of 60 independently modulated checkerboard patches within the central 18 deg of the visual field, location, orientation, magnitude, and time-course of the dipole current source that best described the VEP distribution across a multi-electrode array was obtained. At numerous eccentricities, cortical magnification was determined using two different techniques: (1) the distance between each pair of adjacent stimulus patches was matched to the corresponding distance between adjacent cortical sources; and (2) the area of each stimulus patch was matched to the magnitude of the corresponding cortical source (which was assumed to be proportional to cortical area). RESULTS: The estimates of human cortical magnification using our electrophysiological method were similar to previous estimates from psychophysics, cortical stimulation, and functional magnetic resonance imaging. CONCLUSIONS: The concordance of results provided by these disparate technologies, with differing spatial and temporal limitations, supports their combination in studying the spatio-temporal dynamics of human brain function.
Authors: Sanja Josef Golubic; Ana Susac; Veljko Grilj; Douglas Ranken; Ralph Huonker; Jens Haueisen; Selma Supek Journal: Med Biol Eng Comput Date: 2011-04-08 Impact factor: 2.602
Authors: J Benjamin Hutchinson; Melina R Uncapher; Kevin S Weiner; David W Bressler; Michael A Silver; Alison R Preston; Anthony D Wagner Journal: Cereb Cortex Date: 2012-09-26 Impact factor: 5.357